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Diederichs EV, Mondal D, Patil H, Gorbet M, Willett TL. The effect of triglycerol diacrylate on the printability and properties of UV curable, bio-based nanohydroxyapatite composites. J Mech Behav Biomed Mater 2024; 153:106499. [PMID: 38490049 DOI: 10.1016/j.jmbbm.2024.106499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Revised: 02/29/2024] [Accepted: 03/07/2024] [Indexed: 03/17/2024]
Abstract
3D printable biopolymer nanocomposites composed of hydroxyapatite nanoparticles and functionalized plant-based monomers demonstrate potential as sustainable and structural biomaterials. To increase this potential, their printability and performance must be improved. For extrusion-based 3D printing, such as Direct Ink Writing (DIW), printability is important for print fidelity. In this work, triglycerol diacrylate (TGDA) was added to an acrylated epoxidized soybean oil:polyethylene glycol diacrylate resin to increase hydrogen bonding. Greater hydrogen bonding was hypothesized to improve printability by increasing the ink's shear yield strength, and therefore shape holding after deposition. The effects of this additive on material and mechanical properties were quantified. Increased hydrogen bonding due to TGDA content increased the ink's shear yield stress and viscosity by 916% and 27.6%, respectively. This resulted in improved printability, with best performance at 3 vol% TGDA. This composition achieved an ultimate tensile strength (UTS) of 32.4 ± 2.1 MPa and elastic modulus of 1.15 ± 0.21 GPa. These were increased from the 0 vol% TGDA composite, which had an UTS of 24.8 ± 1.8 MPa and a modulus of 0.88 ± 0.06 GPa. This study demonstrates the development of bio-based additive manufacturing feedstocks for potential uses in sustainable manufacturing, rapid prototyping, and biomaterial applications.
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Affiliation(s)
- Elizabeth V Diederichs
- Composite Biomaterial Systems Laboratory, Department of Systems Design, University of Waterloo, Douglas Wright Engineering Building, 200 University Avenue West, Waterloo, Canada
| | - Dibakar Mondal
- Composite Biomaterial Systems Laboratory, Department of Systems Design, University of Waterloo, Douglas Wright Engineering Building, 200 University Avenue West, Waterloo, Canada
| | - Haresh Patil
- Composite Biomaterial Systems Laboratory, Department of Systems Design, University of Waterloo, Douglas Wright Engineering Building, 200 University Avenue West, Waterloo, Canada
| | - Maud Gorbet
- Material Interaction with Biological Systems Laboratory, Department of Systems Design, University of Waterloo, Carl A. Pollock Hall, 200 University Avenue West, Waterloo, Canada
| | - Thomas L Willett
- Composite Biomaterial Systems Laboratory, Department of Systems Design, University of Waterloo, Douglas Wright Engineering Building, 200 University Avenue West, Waterloo, Canada.
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Unal M, Uppuganti S, Dapaah DY, Ahmed R, Pennings JS, Willett TL, Voziyan P, Nyman JS. Effect of ribose incubation on physical, chemical, and mechanical properties of human cortical bone. J Mech Behav Biomed Mater 2023; 140:105731. [PMID: 36827936 PMCID: PMC10068591 DOI: 10.1016/j.jmbbm.2023.105731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 01/27/2023] [Accepted: 02/11/2023] [Indexed: 02/22/2023]
Abstract
Raman spectroscopy (RS) is sensitive to the accumulation of advanced glycation end-products (AGEs), and it measures matrix-sensitive properties that correlate with the fracture toughness of human cortical bone. However, it is unclear whether sugar-mediated accumulation of AGEs affects the fracture toughness of human cortical bone in a manner that is consistent with the negative correlations between amide I sub-peak ratios and fracture toughness. Upon machining 64 single-edge notched beam (SENB) specimens from cadaveric femurs (8 male and 7 female donors between 46 years and 61 years of age), pairs of SENB specimens were incubated in 15 mL of phosphate buffered saline with or without 0.1 M ribose for 4 weeks at 37 °C. After acquiring 10 Raman spectra per bone specimen (n = 32 per incubation group), paired SENB specimens were loaded in three-point bending at a quasi-static or a high loading rate approximating 10-4 s-1 or 10-2 s-1, respectively (n = 16 per incubation group per loading rate). While 2 amide I sub-peak ratios, I1670/I1640 and I1670/I1610, decreased by 3-5% with a 100% increase in AGE content, as confirmed by fluorescence measurements, the ribose incubation to accumulate AGEs in bone did not affect linear elastic (KIc) nor non-linear elastic (KJc) measurements of bone's ability to resist crack growth. Moreover, AGE accumulation did not affect the change in these properties when the loading rate changed. Increasing the loading rate increased KIc but decreased KJc. Ribose incubation did not affect mineral-related RS properties such as mineral-to-matrix ratios, Type B carbonate substitutions, and crystallinity. It did however increase the thermal stability of demineralized bone (differential scanning calorimetry), without affecting the network connectivity of the organic matrix (i.e., maximum slope during a hydrothermal isometric tension test of demineralized bone). In conclusion, RS is sensitive to AGE accumulation via the amide I band (plus the hydroxyproline-to-proline ratio), but the increase in AGE content due to ribose incubation was not sufficient to affect the fracture toughness of human cortical bone.
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Affiliation(s)
- Mustafa Unal
- Department of Bioengineering, Karamanoglu Mehmetbey University, Karaman, 70200, Turkey; Department of Biophysics, Faculty of Medicine, Karamanoglu Mehmetbey University, Karaman, 70200, Turkey
| | - Sasidhar Uppuganti
- Department of Orthopaedic Surgery, Vanderbilt University Medical Center, 1215 21st Ave. S, Suite 4200, Nashville, TN, 37232, USA; Vanderbilt Center for Bone Biology, Vanderbilt University Medical Center, 2215B Garland Ave, Nashville, TN, 37212, USA
| | - Daniel Y Dapaah
- Biomedical Engineering Program, Systems Design Engineering, University of Waterloo, Waterloo, Ontario, Canada
| | - Rafay Ahmed
- Department of Orthopaedic Surgery, Vanderbilt University Medical Center, 1215 21st Ave. S, Suite 4200, Nashville, TN, 37232, USA; Vanderbilt Center for Bone Biology, Vanderbilt University Medical Center, 2215B Garland Ave, Nashville, TN, 37212, USA
| | - Jacquelyn S Pennings
- Department of Orthopaedic Surgery, Vanderbilt University Medical Center, 1215 21st Ave. S, Suite 4200, Nashville, TN, 37232, USA; Vanderbilt Center for Musculoskeletal Research, Vanderbilt University Medical Center, 2525 West End Avenue, Suite 1200, Nashville, TN, 37203, USA
| | - Thomas L Willett
- Biomedical Engineering Program, Systems Design Engineering, University of Waterloo, Waterloo, Ontario, Canada
| | - Paul Voziyan
- Department of Orthopaedic Surgery, Vanderbilt University Medical Center, 1215 21st Ave. S, Suite 4200, Nashville, TN, 37232, USA; Vanderbilt Center for Matrix Biology, Vanderbilt University Medical Center, 1611 21st Ave. S, Nashville, TN, 37212, USA
| | - Jeffry S Nyman
- Department of Orthopaedic Surgery, Vanderbilt University Medical Center, 1215 21st Ave. S, Suite 4200, Nashville, TN, 37232, USA; Vanderbilt Center for Bone Biology, Vanderbilt University Medical Center, 2215B Garland Ave, Nashville, TN, 37212, USA; Department of Veterans Affairs, Tennessee Valley Healthcare System, 1310 24th Ave. S, Nashville, TN, 37212, USA; Vanderbilt Center for Musculoskeletal Research, Vanderbilt University Medical Center, 2525 West End Avenue, Suite 1200, Nashville, TN, 37203, USA.
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Willett TL, Voziyan P, Nyman JS. Causative or associative: A critical review of the role of advanced glycation end-products in bone fragility. Bone 2022; 163:116485. [PMID: 35798196 PMCID: PMC10062699 DOI: 10.1016/j.bone.2022.116485] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 06/27/2022] [Accepted: 06/29/2022] [Indexed: 11/02/2022]
Abstract
The accumulation of advanced glycation end-products (AGEs) in the organic matrix of bone with aging and chronic disease such as diabetes is thought to increase fracture risk independently of bone mass. However, to date, there has not been a clinical trial to determine whether inhibiting the accumulation of AGEs is effective in preventing low-energy, fragility fractures. Moreover, unlike with cardiovascular or kidney disease, there are also no pre-clinical studies demonstrating that AGE inhibitors or breakers can prevent the age- or diabetes-related decrease in the ability of bone to resist fracture. In this review, we critically examine the case for a long-standing hypothesis that AGE accumulation in bone tissue degrades the toughening mechanisms by which bone resists fracture. Prior research into the role of AGEs in bone has primarily measured pentosidine, an AGE crosslink, or bulk fluorescence of hydrolysates of bone. While significant correlations exist between these measurements and mechanical properties of bone, multiple AGEs are both non-fluorescent and non-crosslinking. Since clinical studies are equivocal on whether circulating pentosidine is an indicator of elevated fracture risk, there needs to be a more complete understanding of the different types of AGEs including non-crosslinking adducts and multiple non-enzymatic crosslinks in bone extracellular matrix and their specific contributions to hindering fracture resistance (biophysical and biological). By doing so, effective strategies to target AGE accumulation in bone with minimal side effects could be investigated in pre-clinical and clinical studies that aim to prevent fragility fractures in conditions that bone mass is not the underlying culprit.
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Affiliation(s)
- Thomas L Willett
- Biomedical Engineering Program, Systems Design Engineering, University of Waterloo, Waterloo, Ontario, Canada.
| | - Paul Voziyan
- Department of Orthopaedic Surgery, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Jeffry S Nyman
- Department of Orthopaedic Surgery, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Department of Veterans Affairs, Tennessee Valley Healthcare System, Nashville, TN 37212, USA.
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Mondal D, Willett TL. Enhanced mechanical performance of mSLA-printed biopolymer nanocomposites due to phase functionalization. J Mech Behav Biomed Mater 2022; 135:105450. [PMID: 36115176 DOI: 10.1016/j.jmbbm.2022.105450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 08/30/2022] [Accepted: 09/02/2022] [Indexed: 10/31/2022]
Abstract
Functionalized phases can effectively increase the mechanical properties of nanocomposites through interfacial bonding. This work demonstrates masked stereolithography (mSLA) of biopolymer-based nanocomposites and the improvement of their mechanical properties by the functionalization of both polymer matrix and nanoparticles with methacrylate groups. 3D printable nanocomposite inks were prepared from plant-derived acrylated epoxidized soybean oil (AESO), polyethylene glycol diacrylate (PEGDA), and nano-hydroxyapatite (nHA). Both AESO and nHA were further functionalized with additional methacrylate groups. We hypothesized that the additional functionalization of AESO and surface functionalization of nHA would improve the tensile strength and fracture toughness of these nanocomposites by increasing the degree of crosslinking and the strength of the interface between the matrix and nanoparticles. Curing efficiency, rheology, and print-fidelity of the nanocomposites were evaluated. Mechanical test specimens were prepared by mSLA-based 3D printing. Tensile mechanical properties, Poisson's ratio, and Mode-I fracture toughness were measured by following ASTM standards. Fracture surfaces of the tested specimens were studied using scanning electron microscopy. Thermomechanical behavior, especially glass transition temperature (Tg), was studied using dynamic mechanical analysis (DMA). Functionalized AESO (mAESO) improved rheological, tensile, and fracture mechanical properties. For instance, by replacing AESO with mAESO, tensile strength, Young's modulus, fracture toughness (K1c), and Tg increased by 33%, 53%, 40%, and 38% respectively. In addition, the combination of both functionalized nHA and mAESO improved the fracture toughness of the 10% volume fraction nHA nanocomposites but made them less extensible presumably due to reduced chain mobility due to greater crosslinking.
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Affiliation(s)
- Dibakar Mondal
- Composite Biomaterial Systems Laboratory, Department of Systems Design Engineering, University of Waterloo, 200 University Ave. West, Waterloo, N2L 3G1, Canada
| | - Thomas L Willett
- Composite Biomaterial Systems Laboratory, Department of Systems Design Engineering, University of Waterloo, 200 University Ave. West, Waterloo, N2L 3G1, Canada.
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Dapaah D, Martel DR, Laing AC, Willett TL. The impact of fall-related loading rate on the formation of micro-damage in human cortical bone fracture. J Biomech 2022; 142:111254. [PMID: 35986951 DOI: 10.1016/j.jbiomech.2022.111254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 06/23/2022] [Accepted: 08/05/2022] [Indexed: 11/18/2022]
Abstract
The quest for better predictive tools as well as new preventative and therapeutic measures for bone fragility and fracture has highlighted the need for greater mechanistic understanding of the bone fracture process. Cortical bone, the major load bearing part of the bone, employs different toughening mechanisms to either inhibit or slow down crack growth which leads to fracture. Among these toughening mechanisms, is the formation of a micro-damage process zone (MDPZ) around the region of the propagating crack. Investigations into the MDPZ to date have primarily been based on quasi-static or cyclic loading rate experiments which do not necessarily replicate physiological fracture rates. Consequently, the impact of fall-related loading rates on the formation of the micro-damage process zone was investigated comparing these to quasi-static loading rate equivalents. The size of MDPZ was found to be 42% smaller in the high-rate group compared to the quasi-static rate group. The smaller MDPZ size was associated with a brittle, unstable fracture behaviour and an overall smaller fracture resistance measure (Jmax). This result points to the possibility of a strain rate hardening mechanism at the heart of micro-damage formation, which is hampered under high loading rates, resulting in lower overall fracture resistance.
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Affiliation(s)
- Daniel Dapaah
- University of Waterloo, Department of Systems Design Engineering, Canada
| | - Daniel R Martel
- University of Waterloo, Department of Kinesiology and Health Sciences, Canada
| | - Andrew C Laing
- University of Waterloo, Department of Kinesiology and Health Sciences, Canada
| | - Thomas L Willett
- University of Waterloo, Department of Systems Design Engineering, Canada.
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Iranmanesh F, Willett TL. A linear systems model of the hydrothermal isometric tension test for assessing collagenous tissue quality. J Mech Behav Biomed Mater 2021; 125:104916. [PMID: 34717118 DOI: 10.1016/j.jmbbm.2021.104916] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 10/14/2021] [Accepted: 10/16/2021] [Indexed: 11/30/2022]
Abstract
Collagen is the most abundant structural protein in the animal kingdom. Its thermal and thermomechanical properties are often measured using differential scanning calorimetry (DSC) and hydrothermal isometric tension (HIT) tests, respectively. In living tissues, not all collagenous structures (molecules, fibrils, etc.) have the same "quality," and the heterogeneity among these structures in specific tissues increases with remodeling, aging, and/or disease states. In this paper, first, a peak-fitting analysis is carried out to separate and distinguish the sequential denaturation events in a DSC endotherm, which presumably stem from heterogeneity in the collagen fibrils. The fitting analysis uses one of two functions: a Gaussian function or a function proposed by Miles. The individual endotherms were then convolved with a physics-based parametric function, J(T), proposed by the authors, to model the development of the isometric tension in two stages: 1) tension development due to a sudden increase in conformational entropy as each collagen packet denatures, and 2) additional isometric tension development due to increasing temperature, consistent with rubber thermo-elasticity. The proposed function parameters were then found by fitting to actual HIT curves using a global optimization technique. This model provides a decoupling of the effects of denaturation kinetics and collagen network connectivity and therefore an improved interpretation of HIT test results during the temperature ramp from ambient temperature to 90 °C. The simple model outputs are two parameters, α and β, that have physical meaning and aid in assessing collagenous tissue quality in terms of connectivity and integrity.
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Affiliation(s)
- Faezeh Iranmanesh
- Composite Biomaterial Systems Laboratory, Systems Design Engineering, University of Waterloo, Ontario, Canada
| | - Thomas L Willett
- Composite Biomaterial Systems Laboratory, Systems Design Engineering, University of Waterloo, Ontario, Canada.
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Rizwan M, Chan SW, Comeau PA, Willett TL, Yim EK. Effect of sterilization treatment on mechanical properties, biodegradation, bioactivity and printability of GelMA hydrogels. Biomed Mater 2020; 15:065017. [PMID: 32640427 PMCID: PMC7733554 DOI: 10.1088/1748-605x/aba40c] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Gelatin methacryloyl (GelMA) hydrogel scaffolds and GelMA-based bioinks are widely used in tissue engineering and bioprinting due to their ability to support cellular functions and new tissue development. Unfortunately, while terminal sterilization of the GelMA is a critical step for translational tissue engineering applications, it can potentially cause thermal or chemical modifications of GelMA. Thus, understanding the effect of terminal sterilization on GelMA properties is an important, though often overlooked, aspect of material design for translational tissue engineering applications. To this end, we characterized the effects of FDA-approved terminal sterilization methods (autoclaving, ethylene oxide treatment, and gamma (γ)-irradiation) on GelMA prepolymer (bioink) and GelMA hydrogels in terms of the relevant properties for biomedical applications, including mechanical strength, biodegradation rate, cell culture in 2D and 3D, and printability. Autoclaving and ethylene oxide treatment of the GelMA decreased the stiffness of the hydrogel, but the treatments did not modify the biodegradation rate of the hydrogel; meanwhile, γ-irradiation increased the stiffness, reduced the pore size and significantly slowed the biodegradation rate. None of the terminal sterilization methods changed the 2D fibroblast or endothelial cell adhesion and spreading. However, ethylene oxide treatment significantly lowered the fibroblast viability in 3D cell culture. Strikingly, γ-irradiation led to significantly reduced ability of the GelMA prepolymer to undergo sol-gel transition. Furthermore, printability studies showed that the bioinks prepared from γ-irradiated GelMA had significantly reduced printability as compared to the GelMA bioinks prepared from autoclaved or ethylene oxide treated GelMA. These results reveal that the choice of the terminal sterilization method can strongly influence important properties of GelMA bioink and hydrogel. Overall, this study provides further insight into GelMA-based material design with consideration of the effect of terminal sterilization.
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Affiliation(s)
- Muhammad Rizwan
- Department of Chemical Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada N2L 3G1
| | - Sarah W. Chan
- Department of Chemical Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada N2L 3G1
| | - Patricia A. Comeau
- Systems Design Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada N2L 3G1
| | - Thomas L. Willett
- Systems Design Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada N2L 3G1
- Centre for Biotechnology and Bioengineering, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada N2L 3G1
| | - Evelyn K.F. Yim
- Department of Chemical Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada N2L 3G1
- Centre for Biotechnology and Bioengineering, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada N2L 3G1
- Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada N2L 3G1
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Mondal D, Srinivasan A, Comeau P, Toh YC, Willett TL. Acrylated epoxidized soybean oil/hydroxyapatite-based nanocomposite scaffolds prepared by additive manufacturing for bone tissue engineering. Mater Sci Eng C Mater Biol Appl 2020; 118:111400. [PMID: 33255003 DOI: 10.1016/j.msec.2020.111400] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 08/07/2020] [Accepted: 08/12/2020] [Indexed: 12/13/2022]
Abstract
The mechanical properties and biocompatibility of nanocomposites composed of Acrylated Epoxidized Soybean Oil (AESO), nano-Hydroxyapatite (nHA) rods and either 2-Hydroxyethyl Acrylate (HEA) or Polyethylene Glycol Diacrylate (PEGDA) and 3D printed using extrusion-based additive manufacturing methods were investigated. The effects of addition of HEA or PEGDA on the rheological, mechanical properties and cell-biomaterial interactions were studied. AESO, PEGDA (or HEA), and nHA were composited using an ultrasonic homogenizer and scaffolds were 3D printed using a metal syringe on an extrusion-based 3D printer while simultaneously UV cured during layer-by-layer deposition. Nanocomposite inks were characterized for their viscosity before curing, and dispersion of the nHA particles and tensile mechanical properties after curing. Proliferation and differentiation of human bone marrow-derived mesenchymal stem cells (BM-MSCs) were studied by seeding cells onto the scaffolds and culturing in osteogenic differentiation medium for 7, 14 and 21 days. Overall, each of the scaffolds types demonstrated controlled morphology resulting from the printability of nanocomposite inks, well-dispersed nHA particles within the polymer matrices, and were shown to support cell proliferation and osteogenic differentiation after 14 and 21 days of culture. However, the nature of the functional groups present in each ink detectably affected the mechanical properties and cytocompatibility of the scaffolds. For example, while the incorporation of HEA reduced nHA dispersion and tensile strength of the final nanocomposite, it successfully enhanced shear yield strength, and printability, as well as cell adhesion, proliferation and osteogenic differentiation, establishing a positive effect perhaps due to additional hydrogen bonding.
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Affiliation(s)
- Dibakar Mondal
- Composite Biomaterial Systems Laboratory, Department of Systems Design Engineering, University of Waterloo, 200 University Ave. West, Waterloo N2L 3G1, Canada
| | - Akshaya Srinivasan
- Department of Biomedical Engineering, National University of Singapore, 4 Engineering Drive 3, #04-10, 117583, Singapore
| | - Patricia Comeau
- Composite Biomaterial Systems Laboratory, Department of Systems Design Engineering, University of Waterloo, 200 University Ave. West, Waterloo N2L 3G1, Canada
| | - Yi-Chin Toh
- Department of Biomedical Engineering, National University of Singapore, 4 Engineering Drive 3, #04-10, 117583, Singapore
| | - Thomas L Willett
- Composite Biomaterial Systems Laboratory, Department of Systems Design Engineering, University of Waterloo, 200 University Ave. West, Waterloo N2L 3G1, Canada.
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Comeau PA, Willett TL. Triethyleneglycol dimethacrylate addition improves the 3D-printability and construct properties of a GelMA-nHA composite system towards tissue engineering applications. Materials Science and Engineering: C 2020; 112:110937. [PMID: 32409083 DOI: 10.1016/j.msec.2020.110937] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2020] [Revised: 03/30/2020] [Accepted: 04/05/2020] [Indexed: 12/26/2022]
Abstract
In tissue engineering, there is a growing interest in the development of 3D printable bone tissue-inspired nanocomposites. However, most such nanocomposites have poor mechanical properties, owing to poor dispersion of the mineral phase (e.g. nano-hydroxyapatite, nHA) within the organic phase (e.g. methacrylated gelatin, GelMA) and low volume fractions of each phase. Triethyleneglycol dimethacrylate (TEGDMA) is commonly added to dental resin-based composites to improve the properties of the dental resin. Here, the effects of substituting a portion of the water phase in a GelMA-nHA composite with TEGDMA were evaluated. TEGDMA improved the dispersion of nHA within the highly-concentrated GelMA-based composite ink, as well as increased the ink's shear yield strength and reduced the critical energy for ink cure. As a result, the printability of the composite ink was greatly improved upon TEGDMA inclusion. Lastly, while the swelling of the cast composite in 37 °C water increased slightly, the mechanical properties (tensile strength, toughness, and stiffness) of the cast composite increased by at least an order of magnitude upon TEGDMA addition, and all composites demonstrated MSC cytocompatibility after 24 h. Overall, TEGDMA shows promise as an additive to tune properties of the GelMA-nHA system towards use in tissue engineering applications.
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Affiliation(s)
- P A Comeau
- 200 University Avenue West, Systems Design Engineering, University of Waterloo, Waterloo N2L 3G1, Ontario, Canada
| | - T L Willett
- 200 University Avenue West, Systems Design Engineering, University of Waterloo, Waterloo N2L 3G1, Ontario, Canada.
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Mondal D, Willett TL. Mechanical properties of nanocomposite biomaterials improved by extrusion during direct ink writing. J Mech Behav Biomed Mater 2020; 104:103653. [PMID: 32174411 DOI: 10.1016/j.jmbbm.2020.103653] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 01/17/2020] [Accepted: 01/23/2020] [Indexed: 11/16/2022]
Abstract
In this study, single filaments of acrylated epoxidized soybean oil (AESO)/polyethylene glycol diacrylate (PEGDA)/nanohydroxyapatite (nHA)-based nanocomposites intended for bone defect repair have displayed significant improvement of their mechanical properties when extruded through smaller needle gauges before UV curing. These nanocomposite inks can be deposited layer-by-layer during direct ink writing (DIW) - a form of additive manufacturing. Single filaments were prepared by extruding the nanocomposite ink through needles with varying diameters from 0.21 mm to 0.84 mm and then UV cured. Filaments and cast specimens were tensile tested to determine elastic modulus, strength and toughness. The cured nanocomposite filaments were further characterized using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). SEM confirmed that the hydroxyapatite nanoparticles were well dispersed in the polymer matrices. The ultimate tensile strength and moduli increased as the diameter of the extrusion needle was decreased. These correlated with increased matrix crystallinity and fewer defects. For instance, filaments extruded through 0.84 mm diameter needles had ultimate tensile stress and modulus of 26.3 ± 2.8 MPa and 885 ± 100 MPa, respectively, whereas, filaments extruded through 0.21 mm needles had ultimate tensile stress and modulus of 48.9 ± 4.0 MPa and 1696 ± 172 MPa, respectively. This study has demonstrated enhanced mechanical properties resulting from extrusion-based direct ink writing of a new AESO-PEGDA-nHA nanocomposite biomaterial intended for biomedical applications. These enhanced properties are the result of fewer defects and increased crystallinity. A means of achieving mechanical properties suitable for repairing bone defects is apparent.
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Affiliation(s)
- Dibakar Mondal
- Composite Biomaterial Systems Laboratory, Department of Systems Design Engineering, University of Waterloo, 200 University Ave. West, Waterloo, N2L 3G1, Canada
| | - Thomas L Willett
- Composite Biomaterial Systems Laboratory, Department of Systems Design Engineering, University of Waterloo, 200 University Ave. West, Waterloo, N2L 3G1, Canada.
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Willett TL, Dapaah DY, Uppuganti S, Granke M, Nyman JS. Bone collagen network integrity and transverse fracture toughness of human cortical bone. Bone 2019; 120:187-193. [PMID: 30394355 PMCID: PMC6360115 DOI: 10.1016/j.bone.2018.10.024] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 10/09/2018] [Accepted: 10/25/2018] [Indexed: 12/15/2022]
Abstract
Greater understanding of the determinants of skeletal fragility is highly sought due to the great burden that bone affecting diseases and fractures have on economies, societies and health care systems. Being a complex, hierarchical composite of collagen type-I and non-stoichiometric substituted hydroxyapatite, bone derives toughness from its organic phase. In this study, we tested whether early observations that a strong correlation between bone collagen integrity measured by thermomechanical methods and work to fracture exist in a more general and heterogeneous sampling of the population. Neighboring uniform specimens from an established, highly characterized and previously published collection of human cortical bone samples (femur mid-shaft) were decalcified in EDTA. Fifty-four of the original 62 donors were included (26 male and 28 females; ages 21-101 years; aging, osteoporosis, diabetes and cancer). Following decalcification, bone collagen was tested using hydrothermal isometric tension (HIT) testing in order to measure the collagen's thermal stability (denaturation temperature, Td) and network connectivity (maximum rate of isometric tension generation; Max.Slope). We used linear regression and general linear models (GLMs) with several explanatory variables to determine whether relationships between HIT parameters and generally accepted bone quality factors (e.g., cortical porosity, pentosidine content [pen], pyridinoline content [pyd]), age, and measures of fracture toughness (crack initiation fracture toughness, Kinit, and total energy release/dissipation rate evaluated at the point of unstable fast fracture, J-int) were significant. Bone collagen connectivity (Max.Slope) correlated well with the measures of fracture toughness (R2 = 24-35%), and to a lesser degree with bound water fraction (BW; R2 = 7.9%) and pore water fraction (PW; R2 = 9.1%). Significant correlations with age, apparent volumetric bone mineral density (vBMD), and mature enzymatic [pyd] and non-enzymatic collagen crosslinks [pen] were not detected. GLMs found that Max.Slope and vBMD (or BW), with or without age as additional covariate, all significantly explained the variance in Kinit (adjusted-R2 = 36.7-49.0%). Also, the best-fit model for J-int (adjusted-R2 = 35.7%) included only age and Max.Slope as explanatory variables with Max.Slope contributing twice as much as age. Max.Slope and BW without age were also significant predictors of J-int (adjusted-R2 = 35.5%). In conclusion, bone collagen integrity as measured by thermomechanical methods is a key factor in cortical bone fracture toughness. This study further demonstrates that greater attention should be paid to degradation of the overall organic phase, rather than a specific biomarker (e.g. [pen]), when seeking to understand elevated fracture rates in aging and disease.
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Affiliation(s)
- Thomas L Willett
- Biomedical Engineering Program, Systems Design Engineering, University of Waterloo, Waterloo, Ontario, Canada
| | - Daniel Y Dapaah
- Biomedical Engineering Program, Systems Design Engineering, University of Waterloo, Waterloo, Ontario, Canada
| | - Sasidhar Uppuganti
- Vanderbilt University Medical Center, Nashville, TN, United States of America
| | - Mathilde Granke
- Vanderbilt University Medical Center, Nashville, TN, United States of America
| | - Jeffry S Nyman
- Vanderbilt University Medical Center, Nashville, TN, United States of America.
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12
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Attia T, Woodside M, Minhas G, Lu XZ, Josey DS, Burrow T, Grynpas M, Willett TL. Development of a novel method for the strengthening and toughening of irradiation-sterilized bone allografts. Cell Tissue Bank 2017; 18:323-334. [PMID: 28560495 DOI: 10.1007/s10561-017-9634-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 05/26/2017] [Indexed: 01/22/2023]
Abstract
Reconstruction of large skeletal defects is a significant and challenging issue. Bone allografts are often used for such reconstructions. However, sterilizing bone allografts by using γ-irradiation, damages collagen and causes the bone to become weak, brittle and less fatigue resistant. In a previous study, we successfully protected the mechanical properties of human cortical bone by conducting a pre-treatment with ribose, a natural and biocompatible agent. This study focuses on examining possible mechanisms by which ribose might protect the bone. We examined the mechanical properties, crosslinking, connectivity and free radical scavenging potentials of the ribose treatment. Human cortical bone beams were treated with varying concentration of ribose (0.06-1.2 M) and γ-irradiation before testing them in 3-point bending. The connectivity and amounts of crosslinking were determined with Hydrothermal-Isometric-Tension testing and High-Performance-Liquid-Chromatography, respectively. The free radical content was measured using Electron Paramagnetic Resonance. Ribose pre-treatment improved the mechanical properties of irradiation sterilized human bone in a pre-treatment concentration-dependent manner. The 1.2 M pre-treatment provided >100% of ultimate strength of normal controls and protected 76% of the work-to-fracture (toughness) lost in the irradiated controls. Similarly, the ribose pre-treatment improved the thermo-mechanical properties of irradiation-sterilized human bone collagen in a concentration-dependent manner. Greater free radical content and pentosidine content were modified in the ribose treated bone. This study shows that the mechanical properties of irradiation-sterilized cortical bone allografts can be protected by incubating the bone in a ribose solution prior to irradiation.
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Affiliation(s)
- Tarik Attia
- Musculoskeletal Research Laboratory, Mount Sinai Hospital - Lunenfeld Tanenbaum Research Institute, Toronto, ON, Canada.,Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada
| | - Mitchell Woodside
- Musculoskeletal Research Laboratory, Mount Sinai Hospital - Lunenfeld Tanenbaum Research Institute, Toronto, ON, Canada
| | - Gagan Minhas
- Musculoskeletal Research Laboratory, Mount Sinai Hospital - Lunenfeld Tanenbaum Research Institute, Toronto, ON, Canada
| | - Xing Ze Lu
- Musculoskeletal Research Laboratory, Mount Sinai Hospital - Lunenfeld Tanenbaum Research Institute, Toronto, ON, Canada
| | - David S Josey
- Musculoskeletal Research Laboratory, Mount Sinai Hospital - Lunenfeld Tanenbaum Research Institute, Toronto, ON, Canada
| | - Timothy Burrow
- Department of Chemistry, University of Toronto, Toronto, ON, Canada
| | - Marc Grynpas
- Musculoskeletal Research Laboratory, Mount Sinai Hospital - Lunenfeld Tanenbaum Research Institute, Toronto, ON, Canada.,Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada
| | - Thomas L Willett
- Biomedical Engineering Program, Department of Systems Design Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada.
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13
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Burke MV, Atkins A, Akens M, Willett TL, Whyne CM. Osteolytic and mixed cancer metastasis modulates collagen and mineral parameters within rat vertebral bone matrix. J Orthop Res 2016; 34:2126-2136. [PMID: 27027407 DOI: 10.1002/jor.23248] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Accepted: 03/23/2016] [Indexed: 02/04/2023]
Abstract
Metastatic involvement in vertebral bone diminishes the mechanical integrity of the spine; however minimal data exist on the potential impact of metastases on the intrinsic material characteristics of the bone matrix. Thirty-four (34) female athymic rats were inoculated with HeLa (N = 17) or Ace-1 (N = 17) cancer cells lines producing osteolytic or mixed (osteolytic and osteoblastic) metastases, respectively. A maximum of 21 days was allowed between inoculation and rat sacrifice for vertebrae extraction. High performance liquid chromatography (HPLC) was utilized to determine modifications in collagen-I parameters such as proline hydroxylation and the formation of specific enzymatic and non-enzymatic (pentosidine) cross-links. Raman spectroscopy was used to determine relative changes in mineral crystallinity, mineral carbonation, mineral/collagen matrix ratio, collagen quality ratio, and proline hydroxylation. HPLC results showed significant increase in the formation of pentosidine and decrease in the formation of the enzymatic cross-link deoxy-pryridinoline within osteolytic bone compared to mixed bone. Raman results showed decreased crystallinity, increased carbonation, and collagen quality (aka 1660/1690 sub-band) ratio with osteolytic bone compared to mixed bone and healthy controls along with an observed increase in proline hydroxylation with metastatic involvement. The mineral/matrix ratio decreased in both osteolytic and mixed bone compared to healthy controls. Quantifying modifications within the intrinsic characteristics of bone tissue will provide a foundation to assess the impact of current therapies on the material behavior of bone tissue in the metastatic spine and highlight targets for the development of new therapeutics and approaches for treatment. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2126-2136, 2016.
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Affiliation(s)
- Mikhail V Burke
- Orthopaedics Biomechanics Laboratory, Sunnybrook Research Institute, 2075 Bayview Ave., Room S620, Toronto, Ontario, M4N 3M5, Canada.,Institute of Biomaterials and Biomedical Engineering, Toronto, Ontario, Canada
| | - Ayelet Atkins
- Orthopaedics Biomechanics Laboratory, Sunnybrook Research Institute, 2075 Bayview Ave., Room S620, Toronto, Ontario, M4N 3M5, Canada
| | - Margarete Akens
- Department of Surgery, University of Toronto, Toronto, Ontario, Canada.,Techna, University Health Network, Toronto, Ontario, Canada
| | - Thomas L Willett
- Institute of Biomaterials and Biomedical Engineering, Toronto, Ontario, Canada.,Department of Surgery, University of Toronto, Toronto, Ontario, Canada
| | - Cari M Whyne
- Orthopaedics Biomechanics Laboratory, Sunnybrook Research Institute, 2075 Bayview Ave., Room S620, Toronto, Ontario, M4N 3M5, Canada.,Institute of Biomaterials and Biomedical Engineering, Toronto, Ontario, Canada.,Department of Surgery, University of Toronto, Toronto, Ontario, Canada
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14
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Woodside M, Willett TL. Elastic-plastic fracture toughness and rising JR-curve behavior of cortical bone is partially protected from irradiation-sterilization-induced degradation by ribose protectant. J Mech Behav Biomed Mater 2016; 64:53-64. [PMID: 27479894 DOI: 10.1016/j.jmbbm.2016.07.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Revised: 06/24/2016] [Accepted: 07/03/2016] [Indexed: 12/12/2022]
Abstract
OBJECTIVE This study tested the hypothesis that pre-treating cortical bone with ribose would protect the rising fracture resistance curve behavior and crack initiation fracture toughness of both bovine and human cortical bone from the degrading effects of γ-irradiation sterilization. MATERIALS AND METHODS A ribose pre-treatment (1.8 M for bovine, and 1.2 M for human, in PBS at 60 °C for 24 h) was applied to single-edge notched bending fracture specimens prior to sterilization with a 33 kGy dose of γ-irradiation. Fracture resistance curves were generated with a single specimen method using an optical crack length measurement technique. The effect of the treatment on overall fracture resistance behavior, crack initiation fracture toughness, and tearing modulus was compared with non-irradiated and conventionally irradiation sterilized controls. Hydrothermal isometric tension testing was used to examine collagen network connectivity and thermal stability to explore relationships between collagen network quality and fracture resistance. RESULTS The ribose pre-treatment successfully protected the crack growth initiation fracture toughness of bovine and human bone by 32% and 63%, respectively. The rising JR-curve behavior was also partially protected. Furthermore, collagen connectivity and thermal stability followed similar patterns to those displayed by fracture toughness. CONCLUSIONS This paper demonstrates that the fracture toughness of irradiation-sterilized bone tissue can be partially protected with a ribose pre-treatment. This new approach shows potential for the production and clinical application of sterilized allografts with improved mechanical performance and durability.
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Affiliation(s)
- Mitchell Woodside
- Materials Science and Engineering, University of Toronto, Toronto, ON, Canada; Musculoskeletal Research Laboratory, Mount Sinai Hospital - Lunenfeld-Tanenbaum Research Institute, Toronto, ON, Canada
| | - Thomas L Willett
- Materials Science and Engineering, University of Toronto, Toronto, ON, Canada; Musculoskeletal Research Laboratory, Mount Sinai Hospital - Lunenfeld-Tanenbaum Research Institute, Toronto, ON, Canada; Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada; Division of Orthopaedic Surgery, Mount Sinai Hospital, Toronto, ON, Canada; Division of Orthopaedic Surgery, Department of Surgery, University of Toronto, ON, Canada.
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15
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Girardi BL, Attia T, Backstein D, Safir O, Willett TL, Kuzyk PR. Biomechanical comparison of the human cadaveric pelvis with a fourth generation composite model. J Biomech 2016; 49:537-42. [DOI: 10.1016/j.jbiomech.2015.12.050] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Revised: 11/18/2015] [Accepted: 12/28/2015] [Indexed: 10/22/2022]
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16
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Dwyer T, Willett TL, Dold AP, Petrera M, Wasserstein D, Whelan DB, Theodoropoulos JS. Maximum load to failure and tensile displacement of an all-suture glenoid anchor compared with a screw-in glenoid anchor. Knee Surg Sports Traumatol Arthrosc 2016; 24:357-64. [PMID: 24201901 DOI: 10.1007/s00167-013-2760-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Accepted: 10/28/2013] [Indexed: 01/02/2023]
Abstract
PURPOSE The purpose of this study was to evaluate the biomechanical behavior of an all-suture glenoid anchor in comparison with a more conventional screw-in glenoid anchor, with regard to maximum load to failure and tensile displacement. METHODS All mechanical testing was performed using an Instron ElectroPuls E1000 mechanical machine, with a 10 N pre-load and displacement rate of 10 mm/min. Force-displacement curves were generated, with calculation of maximum load, maximum displacement, displacement at 50 N and stiffness. Pretesting of handset Y-Knots in bone analog models revealed low force displacement below 60 N of force. Subsequently, three groups of anchors were tested for pull out strength in bovine bone and cadaver glenoid bone: a bioabsorbable screw-in anchor (Bio Mini-Revo, ConMed Linvatec), a handset all-suture anchor (Y-Knot, ConMed Linvatec) and a 60 N pre-tensioned all-suture anchor (Y-Knot). A total of 8 anchors from each group was tested in proximal tibia of bovine bone and human glenoids (age range 50-90). RESULTS In bovine bone, the Bio Mini-Revo displayed greater maximum load to failure (206 ± 77 N) than both the handset (140 ± 51 N; P = 0.01) and the pre-tensioned Y-Knot (135 ± 46 N; P = 0.001); no significant difference was seen between the three anchor groups in glenoid bone. Compared to the screw-in anchors, the handset all-suture anchor displayed inferior fixation, early displacement and greater laxity in the bovine bone and cadaveric bone (P < 0.05). Pre-tensioning the all-suture anchor to 60 N eliminated this behavior in all bone models. CONCLUSIONS Handset Y-Knots display low force anchor displacement, which is likely due to slippage in the pilot hole. Pre-tensioning the Y-Knot to 60 N eliminates this behavior. LEVEL OF EVIDENCE I.
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Affiliation(s)
- Tim Dwyer
- Women's College, Toronto Western Hospital, University of Toronto Orthopaedic Sports Medicine, 76 Grenville St, Toronto, ON, M5S 1B1, Canada.
| | - Thomas L Willett
- Musculoskeletal Research Laboratory, Division of Orthopaedic Surgery, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 25 Orde Street, Room 416, Toronto, ON, M5T 3H7, Canada
| | | | | | - David Wasserstein
- University of Toronto Orthopaedic Sports Medicine, Toronto, ON, Canada
| | - Danny B Whelan
- Women's College Hospital, Toronto, ON, Canada.,St. Michael's Hospital, University of Toronto Orthopaedic Sports Medicine, Toronto, ON, Canada
| | - John S Theodoropoulos
- Women's College Hospital, Toronto, ON, Canada.,Mt. Sinai Hospital, University of Toronto Orthopaedic Sports Medicine, Toronto, ON, Canada
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17
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Ng AH, Omelon S, Variola F, Allo B, Willett TL, Alman BA, Grynpas MD. Adynamic Bone Decreases Bone Toughness During Aging by Affecting Mineral and Matrix. J Bone Miner Res 2016; 31:369-79. [PMID: 26332924 DOI: 10.1002/jbmr.2702] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Revised: 08/16/2015] [Accepted: 08/29/2015] [Indexed: 01/22/2023]
Abstract
Adynamic bone is the most frequent type of bone lesion in patients with chronic kidney disease; long-term use of antiresorptive therapy may also lead to the adynamic bone condition. The hallmark of adynamic bone is a loss of bone turnover, and a major clinical concern of adynamic bone is diminished bone quality and an increase in fracture risk. Our current study aims to investigate how bone quality changes with age in our previously established mouse model of adynamic bone. Young and old mice (4 months old and 16 months old, respectively) were used in this study. Col2.3Δtk (DTK) mice were treated with ganciclovir and pamidronate to create the adynamic bone condition. Bone quality was evaluated using established techniques including bone histomorphometry, microcomputed tomography, quantitative backscattered electron imaging, and biomechanical testing. Changes in mineral and matrix properties were examined by powder X-ray diffraction and Raman spectroscopy. Aging controls had a natural decline in bone formation and resorption with a corresponding deterioration in trabecular bone structure. Bone turnover was severely blunted at all ages in adynamic animals, which preserved trabecular bone loss normally associated with aging. However, the preservation of trabecular bone mass and structure in old adynamic mice did not rescue deterioration of bone mechanical properties. There was also a decrease in cortical bone toughness in old adynamic mice that was accompanied by a more mature collagen matrix and longer bone crystals. Little is known about the effects of metabolic bone disease on bone fracture resistance. We observed an age-related decrease in bone toughness that was worsened by the adynamic condition, and this decrease may be due to material level changes at the tissue level. Our mouse model may be useful in the investigation of the mechanisms involved in fractures occurring in elderly patients on antiresorptive therapy who have very low bone turnover.
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Affiliation(s)
- Adeline H Ng
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.,Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada
| | - Sidney Omelon
- Department of Chemical and Biological Engineering, University of Ottawa, Ottawa, Canada
| | - Fabio Variola
- Department of Mechanical Engineering, University of Ottawa, Ottawa, Canada.,Department of Physics, University of Ottawa, Ottawa, Canada
| | - Bedilu Allo
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada
| | - Thomas L Willett
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada.,Department of Surgery, University of Toronto, Toronto, Canada
| | - Benjamin A Alman
- Program in Developmental and Stem Cell Biology, Hospital for Sick Children, Toronto, Canada.,Department of Orthopaedic Surgery, Duke University, Durham, NC, USA
| | - Marc D Grynpas
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.,Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada
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18
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Willett TL, Burton B, Woodside M, Wang Z, Gaspar A, Attia T. γ-Irradiation sterilized bone strengthened and toughened by ribose pre-treatment. J Mech Behav Biomed Mater 2015; 44:147-55. [PMID: 25637825 DOI: 10.1016/j.jmbbm.2015.01.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Revised: 12/22/2014] [Accepted: 01/03/2015] [Indexed: 01/22/2023]
Abstract
OBJECTIVE This study tested the hypothesis that a ribose-based pre-treatment would protect the strength, ductility and toughness of γ-irradiation sterilized cortical bone. METHODS Experiment 1: The effects of ribose pre-treatment (1.8M in PBS at 60°C for 24h) prior to 33 kGy of irradiation on strength, ductility and toughness (beams in three-point bending) and fracture toughness (J-integral at instability in single edge notched (bending)) were tested against matched non-irradiated and irradiated controls from bovine tibiae. Experiment 2: Three-point bending tests were conducted using beams from human femora (males, 59-67 years). Bone collagen thermal stability and network connectivity were examined using hydrothermal isometric tension testing. RESULTS Ribose pre-treatment protected the strength, ductility and toughness of irradiation sterilized bovine and human specimens to differing degrees. Their ultimate strength was not detectably different from non-irradiated control levels; toughness in bovine and human specimens was protected by 57 and 76%, respectively. Untreated human bone was less affected by irradiation and ribose pre-treatment was more effective in human bone than bovine bone. CONCLUSIONS This paper presents the first proof-of-principle that irradiation-sterilized bone with improved mechanical properties can be produced through the application of a ribose pre-irradiation treatment, which provides a more stable and connected collagen network than found in conventionally irradiated controls.
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Affiliation(s)
- Thomas L Willett
- Musculoskeletal Research Laboratory, Mount Sinai Hospital-Lunenfeld Tanenbaum Research Institute, Toronto, ON, Canada; Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada; Department of Materials Science and Engineering, University of Toronto, Toronto, ON, Canada; Division of Orthopaedic Surgery, Mount Sinai Hospital, Toronto, ON, Canada; Department of Surgery, University of Toronto, Toronto, ON, Canada.
| | - Brianne Burton
- Musculoskeletal Research Laboratory, Mount Sinai Hospital-Lunenfeld Tanenbaum Research Institute, Toronto, ON, Canada; Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada
| | - Mitchell Woodside
- Musculoskeletal Research Laboratory, Mount Sinai Hospital-Lunenfeld Tanenbaum Research Institute, Toronto, ON, Canada; Department of Materials Science and Engineering, University of Toronto, Toronto, ON, Canada
| | - Zhirui Wang
- Department of Materials Science and Engineering, University of Toronto, Toronto, ON, Canada
| | - Anne Gaspar
- Musculoskeletal Research Laboratory, Mount Sinai Hospital-Lunenfeld Tanenbaum Research Institute, Toronto, ON, Canada; Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada
| | - Tarik Attia
- Musculoskeletal Research Laboratory, Mount Sinai Hospital-Lunenfeld Tanenbaum Research Institute, Toronto, ON, Canada; Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada
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Ng AH, Willett TL, Alman BA, Grynpas MD. Development, validation and characterization of a novel mouse model of Adynamic Bone Disease (ABD). Bone 2014; 68:57-66. [PMID: 25111968 DOI: 10.1016/j.bone.2014.07.037] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Revised: 07/29/2014] [Accepted: 07/31/2014] [Indexed: 11/29/2022]
Abstract
The etiology of Adynamic Bone Disease (ABD) is poorly understood but the hallmark of ABD is a lack of bone turnover. ABD occurs in renal osteodystrophy (ROD) and is suspected to occur in elderly patients on long-term anti-resorptive therapy. A major clinical concern of ABD is diminished bone quality and an increased fracture risk. To our knowledge, experimental animal models for ABD other than ROD-ABD have not been developed or studied. The objectives of this study were to develop a mouse model of ABD without the complications of renal ablation, and to characterize changes in bone quality in ABD relative to controls. To re-create the adynamic bone condition, 4-month old female Col2.3Δtk mice were treated with ganciclovir to specifically ablate osteoblasts, and pamidronate was used to inhibit osteoclastic resorption. Four groups of animals were used to characterize bone quality in ABD: Normal bone controls, No Formation controls, No Resorption controls, and an Adynamic group. After a 6-week treatment period, the animals were sacrificed and the bones were harvested for analyses. Bone quality assessments were conducted using established techniques including bone histology, quantitative backscattered electron imaging (qBEI), dual energy X-ray absorptiometry (DXA), microcomputed tomography (microCT), and biomechanical testing. Histomorphometry confirmed osteoblast-related hallmarks of ABD in our mouse model. Bone formation was near complete suppression in the No Formation and Adynamic specimens. Inhibition of bone resorption in the Adynamic group was confirmed by tartrate-resistant acid phosphatase (TRAP) stain. Normal bone mineral density and architecture were maintained in the Adynamic group, whereas the No Formation group showed a reduction in bone mineral content and trabecular thickness relative to the Adynamic group. As expected, the No Formation group had a more hypomineralized profile and the Adynamic group had a higher mean mineralization profile that is similar to suppressed bone turnover in human. This data confirms successful replication of the adynamic bone condition in a mouse without the complication of renal ablation. Our approach is the first model of ABD that uses pharmacological manipulation in a transgenic mouse to mimic the bone cellular dynamics observed in the human ABD condition. We plan to use our mouse model to investigate the adynamic bone condition in aging and to study changes to bone quality and fracture risk as a consequence of over-suppressed bone turnover.
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Affiliation(s)
- Adeline H Ng
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada; Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
| | - Thomas L Willett
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada; Department of Surgery, University of Toronto, Toronto, Ontario, Canada
| | - Benjamin A Alman
- Program in Developmental and Stem Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada; Department of Orthopaedic Surgery, Duke University, Durham, NC, USA
| | - Marc D Grynpas
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada; Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada.
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Willett TL, Pasquale J, Grynpas MD. Collagen modifications in postmenopausal osteoporosis: advanced glycation endproducts may affect bone volume, structure and quality. Curr Osteoporos Rep 2014; 12:329-37. [PMID: 24880722 DOI: 10.1007/s11914-014-0214-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The classic model of postmenopausal osteoporosis (PM-OP) starts with the depletion of estrogen, which in turn stimulates imbalanced bone remodeling, resulting in loss of bone mass/volume. Clinically, this leads to fractures because of structural weakness. Recent work has begun to provide a more complete picture of the mechanisms of PM-OP involving oxidative stress and collagen modifications known as advanced glycation endproducts (AGEs). On one hand, AGEs may drive imbalanced bone remodeling through signaling mediated by the receptor for AGEs (RAGE), stimulating resorption and inhibiting formation. On the other hand, AGEs are associated with degraded bone material quality. Oxidative stress promotes the formation of AGEs, inhibits normal enzymatically derived crosslinking and can degrade collagen structure, thereby reducing fracture resistance. Notably, there are multiple positive feedback loops that can exacerbate the mechanisms of PM-OP associated with oxidative stress and AGEs. Anti-oxidant therapies may have the potential to inhibit the oxidative stress based mechanisms of this disease.
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Affiliation(s)
- Thomas L Willett
- Musculoskeletal Research Laboratory, Lunenfeld-Tanenbaum Research Institute at Mount Sinai Hospital, 60 Murray Street, Box 42, Toronto, Ontario, Canada, M5T 3L9,
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21
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Burton B, Gaspar A, Josey D, Tupy J, Grynpas MD, Willett TL. Bone embrittlement and collagen modifications due to high-dose gamma-irradiation sterilization. Bone 2014; 61:71-81. [PMID: 24440514 DOI: 10.1016/j.bone.2014.01.006] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Revised: 12/23/2013] [Accepted: 01/10/2014] [Indexed: 12/11/2022]
Abstract
Bone allografts are often used in orthopedic reconstruction of skeletal defects resulting from trauma, bone cancer or revision of joint arthroplasty. γ-Irradiation sterilization is a widely-used biological safety measure; however it is known to embrittle bone. Irradiation has been shown to affect the post-yield properties, which are attributed to the collagen component of bone. In order to find a solution to the loss of toughness in irradiated bone allografts, it is important to fully understand the effects of irradiation on bone collagen. The objective of this study was to evaluate changes in the structure and integrity of bone collagen as a result of γ-irradiation, with the hypothesis that irradiation fragments collagen molecules leading to a loss of collagen network connectivity and therefore loss of toughness. Using cortical bone from bovine tibiae, sample beams irradiated at 33kGy on dry ice were compared to native bone beams (paired controls). All beams were subjected to three-point bend testing to failure followed by characterization of the decalcified bone collagen, using differential scanning calorimetry (DSC), hydrothermal isometric tension testing (HIT), high performance liquid chromatography (HPLC) and gel electrophoresis (SDS-PAGE). The carbonyl content of demineralized bone collagen was also measured chemically to assess oxidative damage. Barium sulfate staining after single edge notch bending (SEN(B)) fracture testing was also performed on bovine tibia bone beams with a machined and sharpened notch to evaluate the fracture toughness and ability of irradiated bone to form micro-damage during fracture. Irradiation resulted in a 62% loss of work-to-fracture (p≤0.001). There was significantly less micro-damage formed during fracture propagation in the irradiated bone. HPLC showed no significant effect on pentosidine, pyridinoline, or hydroxypyridinoline levels suggesting that the loss of toughness is not due to changes in these stable crosslinks. For DSC, there was a 20% decrease in thermal stability (p<0.001) with a 100% increase (p<0.001) in enthalpy of denaturation (melting). HIT testing also showed a decrease in thermal stability (20% lower denaturation temperature, p<0.001) and greatly reduced measures of collagen network connectivity (p<0.001). Interestingly, the increase in enthalpy of denaturation suggests that irradiated collagen requires more energy to denature (melt), perhaps a result of alterations in the hydrogen bonding sites (increased carbonyl content detected in the insoluble collagen) on the irradiated bone collagen. Altogether, this new data strongly indicates that a large loss of overall collagen connectivity due to collagen fragmentation resulting from γ-irradiation sterilization leads to inferior cortical bone toughness. In addition, notable changes in the thermal denaturation of the bone collagen along with chemical indicators of oxidative modification of the bone collagen indicate that the embrittlement may be a function not only of collagen fragmentation but also of changes in bonding.
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Affiliation(s)
- Brianne Burton
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 Collagen Street, Toronto, ON M5S 3G9, Canada; Musculoskeletal Research Laboratory, Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 25 Orde Street, Room 417, Toronto, ON M5T 3H7, Canada
| | - Anne Gaspar
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 Collagen Street, Toronto, ON M5S 3G9, Canada; Musculoskeletal Research Laboratory, Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 25 Orde Street, Room 417, Toronto, ON M5T 3H7, Canada
| | - David Josey
- Musculoskeletal Research Laboratory, Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 25 Orde Street, Room 417, Toronto, ON M5T 3H7, Canada
| | - Jindra Tupy
- Musculoskeletal Research Laboratory, Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 25 Orde Street, Room 417, Toronto, ON M5T 3H7, Canada
| | - Marc D Grynpas
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 Collagen Street, Toronto, ON M5S 3G9, Canada; Musculoskeletal Research Laboratory, Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 25 Orde Street, Room 417, Toronto, ON M5T 3H7, Canada; Department of Material Science, University of Toronto, 184 College Street, Toronto, ON M5S 3E4, Canada
| | - Thomas L Willett
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 Collagen Street, Toronto, ON M5S 3G9, Canada; Musculoskeletal Research Laboratory, Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 25 Orde Street, Room 417, Toronto, ON M5T 3H7, Canada; Department of Material Science, University of Toronto, 184 College Street, Toronto, ON M5S 3E4, Canada; Department of Surgery, University of Toronto, 149 College Street, Toronto, ON M5T 1P5, Canada; Division of Orthopaedic Surgery, Mount Sinai Hospital, 600 University Avenue, Toronto, ON M5G 1X5, Canada.
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Abstract
Non-enzymatic glycation (NEG) and advanced glycation endproducts (AGEs) may contribute to bone fragility in various diseases, ageing, and other conditions by modifying bone collagen and causing degraded mechanical properties. In this study, we sought to further understand how collagen modification in an in vitro non-enzymatic ribation model leads to loss of cortical bone toughness. Previous in vitro studies using non-enzymatic ribation reported loss of ductility in the cortical bone. Increased crosslinking is most commonly blamed for these changes; however, some studies report positive correlations between measures of total collagen crosslinking and work-to-fracture/toughness measurements whilst correlations between general NEG and measures of ductility are often negative. Fifteen bone beam triplets were cut from bovine metatarsi. Each provided one native non-incubated control, one incubated control and one ribated specimen. Incubation involved simulated body fluid±ribose for fourteen days at 37°C. Pentosidine and pyridinoline crosslinks were measured using HPLC. Three-point bending tests quantified mechanical properties. Fracture surfaces were examined using scanning electron microscopy. The effects of ribation on bone collagen molecular stability and intermolecular connectivity were investigated using differential scanning calorimetry and hydrothermal isometric tension testing. Ribation caused increased non-enzymatic collagen modification and pentosidine content (16mmol/mol collagen) and inferior post-yield mechanical behaviour, especially post-yield strain and flexural toughness. Fracture surfaces were smoother with less collagen fibril deformation or tearing than observed in controls. In the ribated group only, pentosidine content and thermomechanical measures of crosslinking were positively correlated with measures of strain accommodation and energy absorption before failure. Non-enzymatic ribation and the resulting modifications reduce cortical bone pseudo-plasticity through a reduced capacity for post-yield strain accommodation. However, the positive correlations we have found suggest that increased crosslinking may not provide a complete explanation for this embrittlement.
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Affiliation(s)
- Thomas L Willett
- Division of Orthopaedic Surgery, Department of Surgery, University of Toronto, 100 College Street, Toronto, Ontario, Canada M5G 1L5.
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Willett TL, Kandel R, De Croos JNA, Avery NC, Grynpas MD. Enhanced levels of non-enzymatic glycation and pentosidine crosslinking in spontaneous osteoarthritis progression. Osteoarthritis Cartilage 2012; 20:736-44. [PMID: 22469851 DOI: 10.1016/j.joca.2012.03.012] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Revised: 02/21/2012] [Accepted: 03/22/2012] [Indexed: 02/08/2023]
Abstract
OBJECTIVE To test the hypothesis that heightened advanced glycation endproducts (AGEs) content in cartilage accelerates the progression of spontaneous osteoarthritis (OA) in the Hartley guinea pig (HGP) model. METHODS Twenty-eight male, 3-month-old HGPs were used. Eight were left untreated as a baseline control group and sacrificed at 3 months of age (n = 4) and 9 months of age (n = 4; age-matched controls). The other 20 HGPs received intra-articular knee injections in the right knee whereas the left knees acted as contra-lateral non-injected controls. Injections consisted of 100 μl phosphate buffered saline (PBS; n = 10) or PBS+2.0 M D-(-)-Ribose (n = 10). Injections were given once weekly for 24 weeks. At the end of the treatment period, the tibiae were fixed with formalin, scanned with microCT for sub-chondral bone mineral density, and then histological slides were prepared, stained with Safranin-O with Fast Green counter stain and scored using the OARSI-HISTOgp scheme. Cartilage pentosidine (established biomarker for AGEs) content, collagen content (% dry mass), glucosaminoglycan GAG-to-collagen ratio (μg/μg), GAG-to-DNA ratio and DNA-to-collagen ratio were measured. RESULTS Pentosidine content increased greatly due to PBS + Ribose injection (P < 0.0001) and reached levels found in cartilage from 80-year-old humans. Surprisingly, mean OARSI-HISTOgp scores for both the injected and contra-lateral controls in the PBS + Ribose group were not detectably different, nor were they different from the mean score for the age-matched control group. CONCLUSION AGEs accumulation due to intra-articular ribose-containing injections in the HGP model of spontaneous knee OA did not enhance disease progression.
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Affiliation(s)
- T L Willett
- Division of Orthopaedic Surgery, Department of Surgery, University of Toronto, Ontario, Canada.
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Abstract
OBJECTIVE Rosiglitazone (RSG) is an insulin-sensitizing drug used to treat type 2 diabetes mellitus. The A Diabetes Outcome Progression Trial (ADOPT) shows that women taking RSG experienced more fractures than patients taking other type 2 diabetes drugs. These were not osteoporotic vertebral fractures but, rather, occurred in the limbs. The purpose of this study was to investigate how RSG treatment alters bone quality, which leads to fracture risk, using the Zucker fatty rat as a model. RESEARCH DESIGN AND METHODS A total of 61 female 4-month-old rats were divided into six groups. One Sham group was a control and another was administered oral RSG 10 mg/kg/day. Four ovariectomized (OVX) groups were dosed as follows: controls, RSG 10 mg/kg, alendronate (ALN, injected at 0.7 mg/kg/week), and RSG 10 mg/kg plus ALN. After 12 weeks of treatment, bone quality was evaluated by mechanical testing. Microarchitecture, bone mineral density (BMD), cortical bone porosity, and bone remodeling were also measured. RESULTS OVX RSG 10 mg/kg rats had lower vertebral BMD and compromised trabecular architecture versus OVX controls. Increased cortical bone porosity and decreased mechanical properties occurred in these rats. ALN treatment prevented decreased BMD and architectural and mechanical properties in the OVX model. Reduced bone formation, increased marrow adiposity, and excess bone resorption were observed in RSG-treated rats. CONCLUSIONS RSG decreases bone quality. An unusual finding was an increase in cortical bone porosity induced by RSG, consistent with its effect on long bones of women. ALN, an inhibitor of bone resorption, enhanced mechanical strength and may provide an approach to partially counter the deleterious skeletal effects of RSG.
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Affiliation(s)
- Laura D. Sardone
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
| | - Richard Renlund
- Department of Surgery, University of Toronto, Toronto, Ontario, Canada
| | - Thomas L. Willett
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
- Department of Surgery, University of Toronto, Toronto, Ontario, Canada
| | - Ivan G. Fantus
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
- Department of Medicine, Mount Sinai Hospital, University of Toronto, Ontario, Canada
| | - Marc D. Grynpas
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
- Corresponding author: Marc D. Grynpas,
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Levaot N, Simoncic PD, Dimitriou ID, Scotter A, La Rose J, Ng AHM, Willett TL, Wang CJ, Janmohamed S, Grynpas M, Reichenberger E, Rottapel R. 3BP2-deficient mice are osteoporotic with impaired osteoblast and osteoclast functions. J Clin Invest 2011; 121:3244-57. [PMID: 21765218 DOI: 10.1172/jci45843] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2010] [Accepted: 06/01/2011] [Indexed: 12/29/2022] Open
Abstract
A fine balance between bone resorption by osteoclasts and bone formation by osteoblasts maintains bone homeostasis. In patients with cherubism, gain-of-function mutations in 3BP2, which is encoded by SH3-domain binding protein 2 (SH3BP2), cause cystic lesions with activated osteoclasts that lead to craniofacial abnormalities. However, little is known about the function of wild-type 3BP2 in regulating bone homeostasis. Here we have shown that 3BP2 is required for the normal function of both osteoblasts and osteoclasts. Initial analysis showed that Sh3bp2-/-mice developed osteoporosis as a result of reduced bone formation despite the fact that bone resorption was impaired. We demonstrated using reciprocal bone marrow chimeras, a cell-intrinsic defect of the osteoblast and osteoclast compartments in vivo. Further, Sh3bp2-/- osteoblasts failed to mature and form mineralized nodules in vitro, while Sh3bp2-/- osteoclasts spread poorly and were unable to effectively degrade dentine matrix in vitro. Finally, we showed that 3BP2 was required for Abl activation in osteoblasts and Src activation in osteoclasts, and demonstrated that the in vitro defect of each cell type was restored by the respective expression of activated forms of these kinases. These findings reveal an unanticipated role for the 3BP2 adapter protein in osteoblast function and in coordinating bone homeostatic signals in both osteoclast and osteoblast lineages.
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Affiliation(s)
- Noam Levaot
- Campbell Family Cancer Research Institute, Ontario Cancer Institute, Princess Margaret Hospital, University Health Network, Department of Medicine, University of Toronto, Toronto, Ontario, Canada
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26
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Yan D, Willett TL, Gu XM, Martinez-Mier EA, Sardone L, McShane L, Grynpas M, Everett ET. Phenotypic variation of fluoride responses between inbred strains of mice. Cells Tissues Organs 2011; 194:261-7. [PMID: 21555858 DOI: 10.1159/000324224] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Excessive systemic exposure to fluoride (F) can lead to disturbances in bone homeostasis and dental enamel development. We have previously shown strain-specific responses to F in the development of dental fluorosis (DF) and in bone formation/mineralization. The current study was undertaken to further investigate F responsive variations in bone metabolism and to determine possible relationships with DF susceptibility. Seven-week-old male mice from FVB/NJ, C57BL/6J, C3H/HeJ, A/J, 129S1/SvImJ, AKR/J, DBA/2J, and BALB/cByJ inbred strains were exposed to NaF (0 or 50 ppm as F(-)) in drinking water for 60 days. Sera were collected for F, Ca, Mg, PO(4), iPTH, sRANKL, and ALP levels. Bone marrow cells were subjected to ex vivo cell culture for osteoclast potential and CFU colony assays (CFU-fibroblast, CFU-osteoblast, CFU-erythrocyte/granulocyte/macrophage/megakaryocyte, CFU-granulocyte/macrophage, CFU-macrophage, and CFU-granulocyte). Femurs and vertebrae were subjected to micro-CT analyses, biomechanical testing, and F, Mg, and Ca content assays. DF was evaluated using quantitative fluorescence and clinical criteria. Strain-specific responses to F were observed for DF, serum studies, ex vivo cell culture studies, and bone quality. Among the strains, there were no patterns or significant correlations between DF severity and the actions of F on bone homeostasis (serum studies, ex vivo assays, or bone quality parameters). The genetic background continues to play a role in the actions of F on tooth enamel development and bone homeostasis. F exposure led to variable phenotypic responses between strains involving dental enamel development and bone metabolism.
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Affiliation(s)
- Dong Yan
- Dental Research, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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27
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Magalhaes JKRS, Grynpas MD, Willett TL, Glogauer M. Deleting Rac1 improves vertebral bone quality and resistance to fracture in a murine ovariectomy model. Osteoporos Int 2011; 22:1481-92. [PMID: 20683708 DOI: 10.1007/s00198-010-1355-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Accepted: 07/06/2010] [Indexed: 12/19/2022]
Abstract
SUMMARY The roles of Rac1 and Rac2 in regulating osteoclast-mediated bone quality in postmenopausal osteoporosis were evaluated using an ovariectomized murine model. Animals' bone composition and architecture were evaluated. Our results demonstrate that the deletion of Rac1 increases vertebral bone quality compared to wild-type bones in an ovariectomized model. INTRODUCTION To determine the roles of the Rho family small GTPases Rac1 and Rac2 in regulating osteoclast-mediated bone quality in a model of postmenopausal osteoporosis. METHODS Twelve-month-old female mice from three genotypes-wild type (WT), Rac1 null (LysM.Rac1 KO), and Rac2 null (Rac2KO)--were studied in control and ovariectomized groups (mice previously ovariectomized at 4 months of age). Animals were sacrificed at 12 months of age, and the femora and vertebrae were harvested for mechanical testing, bone densitometry, micro-computed tomography, and histomorphometric analyses to evaluate bone mineralization and architecture. The results were compared between groups using ANOVA and LSD post-hoc tests. RESULTS We observed that LysM.Rac1 KO mice showed higher vertebral bone mineral density compared to WT in both control and ovariectomized groups. Consistent with this finding, LysM.Rac1 KO vertebrae showed increased resistance to fracture and increased trabecular connectivity compared to WT in both groups. Micro-CT analysis revealed that Rac2KO ovariectomized vertebrae have more trabecular bone compared to WT and LysM.Rac1 KO, but this did not translate into increased fracture resistance. CONCLUSION Our results demonstrate that the deletion of Rac1 increases vertebral bone quality compared to WT bones in a postmenopausal osteoporosis model.
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Affiliation(s)
- J K R S Magalhaes
- CIHR Group in Matrix Dynamics, Faculty of Dentistry, University of Toronto, Fitzgerald Building-150 College Street, Room 221, Toronto, ON, Canada M5S 3E2
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Willett TL, Wynnyckyj C, Wang J, Grynpas MD. The fatigue resistance of rabbit tibiae varies with age from youth to middle age. Osteoporos Int 2011; 22:1157-65. [PMID: 20495904 DOI: 10.1007/s00198-010-1282-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2009] [Accepted: 03/30/2010] [Indexed: 12/27/2022]
Abstract
UNLABELLED Young adults are at risk of stress fractures. Risk is higher in younger and female individuals. Stress fractures occur due to repeated loading of the bone (fatigue). We modeled this with rabbit tibiae. Age increased fatigue resistance which correlated with bone mineral density. A sex difference was not detected. INTRODUCTION Younger adults who engage in intense physical activity with a sudden increase in intensity level (military recruits/college athletes) are at risk of bone stress fractures. Risk is greater in females and diminishes with aging. Stress fractures may be the result of fatigue damage, which is not repaired rapidly enough to avoid fracture. It was hypothesized that the fatigue resistance of whole rabbit tibiae would be less in female specimens but greater as animal age increased. METHODS Rabbit tibiae were harvested from three age groups (4, 7, and ≥ 12 months (females only)). The tibiae were scanned with dual energy X-ray absorptiometry to determine bone mineral density (BMD), computed tomography to quantify geometry, and then fatigue tested in three-point bending. RESULTS In the ≥ 12-month group, BMD was approximately 20% higher, while the fatigue resistance was found to be approximately ten times higher than the other age groups. Sex was not a factor in the 4- and 7-month groups. Multiple linear regression revealed that fatigue life was negatively correlated with applied stress range and positively correlated with BMD (adjusted r (2) = 0.69). CONCLUSIONS A difference in fatigue behavior due to sex was not detected, but there was a large increase in fatigue resistance with age. This correlated with increased BMD and parallels a reduced risk of stress fracture due to age in military recruits. Skeletal "maturation" may play an important role in determining stress fracture risk. Increased risk in females may be due to mechanisms other than those that determine material behavior.
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Affiliation(s)
- T L Willett
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
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Kyle KA, Willett TL, Baggio LL, Drucker DJ, Grynpas MD. Differential effects of PPAR-{gamma} activation versus chemical or genetic reduction of DPP-4 activity on bone quality in mice. Endocrinology 2011; 152:457-67. [PMID: 21177828 PMCID: PMC3084690 DOI: 10.1210/en.2010-1098] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Patients with type 2 diabetes mellitus have an increased risk of fracture that can be further exacerbated by thiazolidinediones. A new class of antidiabetic agents control glucose through reduction of dipeptidyl peptidase-4 (DPP-4) activity; however the importance of DPP-4 for the control of bone quality has not been extensively characterized. We compared the effects of the thiazolidinedione pioglitazone and the DPP-4 inhibitor sitagliptin on bone quality in high-fat diet (HFD)-fed wild-type mice. In complementary studies, we examined bone quality in Dpp4(+/+) vs. Dpp4(-/-) mice. Pioglitazone produced yellow bones with greater bone marrow adiposity and significantly reduced vertebral bone mechanics in male, female, and ovariectomized (OVX) HFD fed female mice. Pioglitazone negatively affected vertebral volumetric bone mineral density, trabecular architecture, and mineral apposition rate in male mice. Sitagliptin treatment of HFD-fed wild-type mice significantly improved vertebral volumetric bone mineral density and trabecular architecture in female mice, but these improvements were lost in females after OVX. Genetic inactivation of Dpp4 did not produce a major bone phenotype in male and female Dpp4(-/-) mice; however, OVX Dpp4(-/-) mice exhibited significantly reduced femoral size and mechanics. These findings delineate the skeletal consequences of pharmacological and genetic reduction of DPP-4 activity and reveal significant differences in the effects of pioglitazone vs. sitagliptin vs. genetic Dpp4 inactivation on bone mechanics in mice.
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Wynnyckyj C, Willett TL, Omelon S, Wang J, Wang Z, Grynpas MD. Changes in bone fatigue resistance due to collagen degradation. J Orthop Res 2011; 29:197-203. [PMID: 20803484 DOI: 10.1002/jor.21228] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2010] [Accepted: 06/28/2010] [Indexed: 02/04/2023]
Abstract
Clinical tools for evaluating fracture risk, such as dual energy X-ray absorptiometry (DXA) and quantitative ultrasound (QUS), focus on bone mineral and cannot detect changes in the collagen matrix that affect bone mechanical properties. However, the mechanical response tissue analyzer (MRTA) directly measures a whole bone mechanical property. The aims of our study were to investigate the changes in fatigue resistance after collagen degradation and to determine if clinical tools can detect changes in bone mechanical properties due to fatigue. Male and female emu tibiae were endocortically treated with 1 M KOH for 1-14 days and then either fatigued to failure or fatigued to induce stiffness loss without fracture. Partial fatigue testing caused a decrease in modulus measured by mechanical testing even when not treated with KOH, which was detected by MRTA. At high stresses, only KOH-treated samples had a lower fatigue resistance compared to untreated bones for both sexes. No differences were observed in fatigue behavior at low stresses for all groups. KOH treatment is hypothesized to have changed the collagen structure in situ and adversely affected the bone. Cyclic creep may be an important mechanism in the fast deterioration rate of KOH-treated bones, as creep is the major cause of fatigue failure for bones loaded at high stresses. Therefore, collagen degradation caused by KOH treatment may be responsible for the observed altered fatigue behavior at high stresses, since collagen is responsible for the creep behavior in bone.
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Affiliation(s)
- Chrystia Wynnyckyj
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Room 840, Toronto, Ontario, Canada M5G 1X5
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31
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Abstract
Municipal water fluoridation has notably reduced the incidence of dental caries and is widely considered a public health success. However, ingested fluoride is sequestered into bone, as well as teeth, and data on the long-term effect of exposure to these very low doses of fluoride remain inconclusive. Epidemiological studies suggest that effects of fluoride on bone are minimal. We hypothesized that the direct measurement of bone tissue from individuals residing in municipalities with and without fluoridated water would reveal a relationship between fluoride content and structural or mechanical properties of bone. However, consonant with the epidemiological data, only a weak relationship among fluoride exposure, accumulated fluoride, and the physical characteristics of bone was observed. Analysis of our data suggests that the variability in heterogenous urban populations may be too high for the effects, if any, of low-level fluoride administration on skeletal tissue to be discerned.
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Affiliation(s)
- D Chachra
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, ON, Canada
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Willett TL, Labow RS, Aldous IG, Avery NC, Lee JM. Changes in Collagen With Aging Maintain Molecular Stability After Overload: Evidence From an In Vitro Tendon Model. J Biomech Eng 2010; 132:031002. [DOI: 10.1115/1.4000933] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Soft tissue injuries are poorly understood at the molecular level. Previous work using differential scanning calorimetry (DSC) has shown that tendon collagen becomes less thermally stable with rupture. However, most soft tissue injuries do not result in complete tissue rupture but in damaging fiber overextension. Covalent crosslinking, which increases with animal maturity and age, plays an important role in collagenous fiber mechanics. It is also a determinant of tissue strength and is hypothesized to inhibit the loss of thermal stability of collagen due to mechanical damage. Controlled overextension without rupture was investigated to determine if overextension was sufficient to reduce the thermal stability of collagen in the bovine tail tendon (BTT) model and to examine the effects of aging on the phenomenon. Baseline data from DSC and hydrothermal isometric tension (HIT) techniques were compared between two groups: steers aged 24–30 months (young group), and skeletally mature bulls and oxen aged greater than five years (old group). Covalent crosslinks were quantified by ion exchange chromatography. Overextension resulted in reduced collagen thermal stability in the BTT model. The Young specimens, showing detectably lower tissue thermomechanical competence, lost more thermal stability with overextension than did the old specimens. The effect on old specimens, while smaller, was detectable. Multiple overextension cycles increased the loss of stability in the young group. Compositional differences in covalent crosslinking corresponded with tissue thermomechanical competence and therefore inversely with the loss of thermal stability. HIT testing gave thermal denaturation temperatures similar to those measured with DSC. The thermal stability of collagen was reduced by overextension of the tendon—without tissue rupture—and this effect was amplified by increased cycles of overextension. Increased tissue thermomechanical competence with aging seemed to mitigate the loss of collagen stability due to mechanical overextension. Surprisingly, the higher tissue thermomechanical competence did not directly correlate with the concentration of endogenous enzymatically derived covalent crosslinking on a mole per mole of collagen basis. It did, however, correlate with the percentage of mature and thermally stable crosslinks. Compositional changes in fibrous collagens that occur with aging affect fibrous collagen mechanics and partially determine the nature of mechanical damage at the intermolecular level. As techniques develop and improve, this new information may lead to important future studies concerning improved detection, prediction, and modeling of mechanical damage at much finer levels of tissue hierarchy than currently possible.
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Affiliation(s)
- Thomas L. Willett
- Bone Biology Laboratory, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, ON, M5G 1X5, Canada
| | - Rosalind S. Labow
- Department of Biochemistry, Microbiology and Immunology, Division of Cardiac Surgery, University of Ottawa Heart Institute, University of Ottawa, Ottawa, ON, K1Y 4W7, Canada
| | - Ian G. Aldous
- School of Biomedical Engineering, Dalhousie University, Halifax, NS, B3M 3J5, Canada
| | - Nick C. Avery
- Matrix Biology Research Group, School of Clinical Veterinary Medicine, University of Bristol, Bristol BS40 5DU, UK
| | - J. Michael Lee
- Department of Applied Oral Sciences, School of Biomedical Engineering, Dalhousie University, Halifax, NS, B3H 3J5, Canada
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Abstract
Musculoskeletal soft tissue injuries are very common, yet poorly understood. We investigated molecular-level changes in collagen caused by tensile overload of bovine tail tendons in vitro. Previous investigators concluded that tensile tendon rupture resulted in collagen denaturation, but our study suggests otherwise. Based on contemporary collagen biophysics, we hypothesized that tensile overload would lead to reduced thermal stability without change in the nativity of the molecular conformation. The thermal behavior of collagen from tail tendons ruptured in vitro at two strain rates (0.01 s(-1) and 10 s(-1)) was measured by differential scanning calorimetry (DSC). The 1,000-fold difference in strain rate was used since molecular mechanisms that determine mechanical behavior are thought to be strain rate-dependent. DSC revealed that the collagen in tensile overloaded tendons was less thermally stable by 3 degrees to 5 degrees C relative to undamaged controls and was not denatured since there was no change in enthalpy of denaturation. The decrease in thermal stability occurred throughout the overloaded regions, independent of rupture site, and was greater in specimens ruptured at the lower strain rate. The deformation mechanism apparently involves disruption of the lattice structure of the collagen fibrils and greatly increases the molecular freedom of the collagen molecules, leading to reduced thermal molecular stability and the previously reported increased proteolysis. This has important implications for understanding soft tissue injuries, disease etiology and treatment, and for developing tissue engineered products with improved durability.
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Affiliation(s)
- Thomas L Willett
- School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia B3M 3J5, Canada.
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Willett TL, Labow RS, Avery NC, Lee JM. Increased Proteolysis of Collagen in an In Vitro Tensile Overload Tendon Model. Ann Biomed Eng 2007; 35:1961-72. [PMID: 17763961 DOI: 10.1007/s10439-007-9375-x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2007] [Accepted: 08/20/2007] [Indexed: 10/22/2022]
Abstract
Presently, there is a lack of fundamental understanding regarding changes in collagen's molecular state due to mechanical damage. The bovine tail tendon (BTT; steers approximately 30 months) was characterized and used as an in vitro model for investigating the effect of tensile mechanical overload on collagen susceptibility to proteolysis by acetyltrypsin and alpha-chymotrypsin. Two strain rates with a 1000-fold difference (0.01 and 10 s(-1)) were used, since molecular mechanisms that determine mechanical behavior were presumed to be strain rate dependent. First, it was determined that the BTTs were normal but immature tendons. Water content and collagen content (approx. 60% of wet weight and 80% of dry weight, respectively) and mechanical properties were all within the expected range. The collagen crosslinking was dominated by the intermediate crosslink hydroxylysinonorleucine. Second, tensile overload damage significantly enhanced proteolysis by acetyltrypsin and, to a lesser degree, by alpha-chymotrypsin. Interestingly, proteolysis by acetyltrypsin was greatest for specimens ruptured at 0.01 s(-1) and seemed to occur throughout the specimen. Understanding damage is important for insight into injuries (as in sports and trauma) and for better understanding of collagen fiber stability, durability, and damage mechanisms, aiding in the development of durable tissue-based products for mechanically demanding surgical applications.
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Affiliation(s)
- Thomas L Willett
- School of Biomedical Engineering, Dalhousie University, Halifax, NS, Canada, B3M 3J5.
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Willett TL, Whiteside R, Wild PM, Wyss UP, Anastassiades T. Artefacts in the mechanical characterization of porcine articular cartilage due to freezing. Proc Inst Mech Eng H 2006; 219:23-9. [PMID: 15777054 DOI: 10.1243/095441105x9200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Many experimental protocols for investigating articular cartilage mechanics have involved the use of a freeze-thaw cycle for storage or tissue manipulation. It was hypothesized that mechanical properties are altered due to freeze-thaw cycling. The aim of this study, therefore, was to examine the possibility of protocol-induced artefacts in the mechanical properties of porcine articular cartilage specimens related specifically to freeze-thaw events. Twenty-eight osteochondral specimens [14 from the femoral condyles (FCs) and 14 from the patella-femoral (PF) groove] were tested in confined compression before and after being frozen at -20°C for 7 days. The fluid-independent and fluid-dependent mechanical properties (aggregate modulus of the solid phase and the half-life of stress relaxation respectively) were determined and compared. The aggregate modulus decreased by 13.5 per cent and 20.1 per cent for the PF and FC regions respectively ( p = 0.002) and the half-life of the stress relaxation at 10 per cent strain decreased by 6.4 per cent and 12.6 per cent for the PF and FC specimens respectively ( p = 0.0341). In conclusion, it has been shown that the protocol used, which involved freezing to -20°C and thawing after 7 days, caused artefacts in the mechanical properties of porcine osteochondral specimens. It is suggested that protocols requiring freezing must be critically reviewed to eliminate such artefacts.
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Affiliation(s)
- T L Willett
- Human Mobility Research Centre, Queen's University, Kingston, Canada.
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