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McDonnell EE, Wilson N, Barcellona MN, Ní Néill T, Bagnall J, Brama PAJ, Cunniffe GM, Darwish SL, Butler JS, Buckley CT. Preclinical to clinical translation for intervertebral disc repair: Effects of species-specific scale, metabolism, and matrix synthesis rates on cell-based regeneration. JOR Spine 2023; 6:e1279. [PMID: 37780829 PMCID: PMC10540833 DOI: 10.1002/jsp2.1279] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 06/15/2023] [Accepted: 08/24/2023] [Indexed: 10/03/2023] Open
Abstract
Background A significant hurdle for potential cell-based therapies is the subsequent survival and regenerative capacity of implanted cells. While many exciting developments have demonstrated promise preclinically, cell-based therapies for intervertebral disc (IVD) degeneration fail to translate equivalent clinical efficacy. Aims This work aims to ascertain the clinical relevance of both a small and large animal model by experimentally investigating and comparing these animal models to human from the perspective of anatomical scale and their cellular metabolic and regenerative potential. Materials and Methods First, this work experimentally investigated species-specific geometrical scale, native cell density, nutrient metabolism, and matrix synthesis rates for rat, goat, and human disc cells in a 3D microspheroid configuration. Second, these parameters were employed in silico to elucidate species-specific nutrient microenvironments and predict differences in temporal regeneration between animal models. Results This work presents in silico models which correlate favorably to preclinical literature in terms of the capabilities of animal regeneration and predict that compromised nutrition is not a significant challenge in small animal discs. On the contrary, it highlights a very fine clinical balance between an adequate cell dose for sufficient repair, through de novo matrix deposition, without exacerbating the human microenvironmental niche. Discussion Overall, this work aims to provide a path towards understanding the effect of cell injection number on the nutrient microenvironment and the "time to regeneration" between preclinical animal models and the large human IVD. While these findings help to explain failed translation of promising preclinical data and the limited results emerging from clinical trials at present, they also enable the research field and clinicians to manage expectations on cell-based regeneration. Conclusion Ultimately, this work provides a platform to inform the design of clinical trials, and as computing power and software capabilities increase in the future, it is conceivable that generation of patient-specific models could be used for patient assessment, as well as pre- and intraoperative planning.
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Affiliation(s)
- Emily E. McDonnell
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College DublinThe University of DublinDublinIreland
- Discipline of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College DublinThe University of DublinDublinIreland
| | - Niamh Wilson
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College DublinThe University of DublinDublinIreland
- Discipline of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College DublinThe University of DublinDublinIreland
| | - Marcos N. Barcellona
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College DublinThe University of DublinDublinIreland
- Discipline of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College DublinThe University of DublinDublinIreland
| | - Tara Ní Néill
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College DublinThe University of DublinDublinIreland
- Discipline of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College DublinThe University of DublinDublinIreland
| | - Jessica Bagnall
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College DublinThe University of DublinDublinIreland
- Discipline of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College DublinThe University of DublinDublinIreland
| | - Pieter A. J. Brama
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College DublinThe University of DublinDublinIreland
- School of Veterinary MedicineUniversity College DublinDublinIreland
| | - Gráinne M. Cunniffe
- National Spinal Injuries UnitMater Misericordiae University HospitalDublinIreland
- School of MedicineUniversity College DublinDublinIreland
| | - Stacey L. Darwish
- National Spinal Injuries UnitMater Misericordiae University HospitalDublinIreland
- School of MedicineUniversity College DublinDublinIreland
- National Orthopaedic HospitalDublinIreland
- St Vincent's University HospitalDublinIreland
| | - Joseph S. Butler
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College DublinThe University of DublinDublinIreland
- National Spinal Injuries UnitMater Misericordiae University HospitalDublinIreland
- School of MedicineUniversity College DublinDublinIreland
| | - Conor T. Buckley
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College DublinThe University of DublinDublinIreland
- Discipline of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College DublinThe University of DublinDublinIreland
- Advanced Materials and Bioengineering Research (AMBER) Centre, Royal College of Surgeons in Ireland & Trinity College DublinThe University of DublinDublinIreland
- Tissue Engineering Research Group, Department of Anatomy and Regenerative MedicineRoyal College of Surgeons in IrelandDublinIreland
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McDonnell EE, Buckley CT. Consolidating and re-evaluating the human disc nutrient microenvironment. JOR Spine 2022; 5:e1192. [PMID: 35386756 PMCID: PMC8966889 DOI: 10.1002/jsp2.1192] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2021] [Revised: 12/14/2021] [Accepted: 01/07/2022] [Indexed: 12/19/2022] Open
Abstract
Background Despite exciting advances in regenerative medicine, cell‐based strategies for treating degenerative disc disease remain in their infancy. To maximize the potential for successful clinical translation, a more thorough understanding of the in vivo microenvironment is needed to better determine and predict how cell therapies will respond when administered in vivo. Aims This work aims to reflect on the in vivo nutrient microenvironment of the degenerating IVD through consolidating what has already been measured together with investigative in silico models. Materials and Methods This work uses in silico modeling, underpinned by more recent experimentally determined parameters of degeneration and nutrient transport from the literature, to re‐evaluate the current knowledge in terms of grade‐specific stages of degeneration. Results Through modeling only the metabolically active cell population, this work predicts slightly higher glucose concentrations compared to previous in silico models, while the predicted results show good agreement with previous intradiscal pH and oxygen measurements. Increasing calcification with degeneration limits nutrient transport into the IVD and initiates a build‐up of acidity; however, its effect is compensated somewhat by a reduction in diffusional distance due to decreasing disc height. Discussion This work advances in silico modeling through a strong foundation of experimentally determined grade‐specific input parameters. Taken together, pre‐existing measurements and predicted results suggest that metabolite concentrations may not be as critically low as commonly believed, with calcification not appearing to have a detrimental effect at stages of degeneration when cell therapies are an appropriate intervention. Conclusion Overall, our initiative is to provoke greater deliberation and consideration of the nutrient microenvironment when performing in vitro cell culture and cell therapy development. This work highlights urgency for robust experimental glucose measurements in healthy and degenerating IVDs, not only to validate in silico models but to significantly advance the field in fully elucidating the nutrient microenvironment and refining in vitro techniques to accelerate clinical translation.
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Affiliation(s)
- Emily E McDonnell
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College Dublin The University of Dublin Dublin Ireland.,Discipline of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College Dublin The University of Dublin Dublin Ireland
| | - Conor T Buckley
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College Dublin The University of Dublin Dublin Ireland.,Discipline of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College Dublin The University of Dublin Dublin Ireland.,Advanced Materials and Bioengineering Research (AMBER) Centre, Royal College of Surgeons in Ireland & Trinity College Dublin The University of Dublin Dublin Ireland.,Tissue Engineering Research Group, Department of Anatomy and Regenerative Medicine Royal College of Surgeons in Ireland Dublin Ireland
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Shalash W, Ahrens SR, Bardonova LA, Byvaltsev VA, Giers MB. Patient-specific apparent diffusion maps used to model nutrient availability in degenerated intervertebral discs. JOR Spine 2021; 4:e1179. [PMID: 35005445 PMCID: PMC8717112 DOI: 10.1002/jsp2.1179] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 09/29/2021] [Accepted: 10/25/2021] [Indexed: 01/07/2023] Open
Abstract
INTRODUCTION In this study, magnetic resonance imaging data was used to (1) model IVD-specific gradients of glucose, oxygen, lactate, and pH; and (2) investigate possible effects of covariate factors (i.e., disc geometry, and mean apparent diffusion coefficient values) on the IVD's microenvironment. Mathematical modeling of the patient's specific IVD microenvironment could be important when selecting patients for stem cell therapy due to the increased nutrient demand created by that treatment. MATERIALS AND METHODS Disc geometry and water diffusion coefficients were extracted from MRIs of 37 patients using sagittal T1-weighted images, T2-weighted images, and ADC Maps. A 2-D steady state finite element mathematical model was developed in COMSOL Multiphysics® 5.4 to compute concentration maps of glucose, oxygen, lactate and pH. RESULTS Concentration of nutrients (i.e., glucose, and oxygen) dropped with increasing distance from the cartilaginous endplates (CEP), whereas acidity levels increased. Most discs experienced poor nutrient levels along with high acidity values in the inner annulus fibrosus (AF). The disc's physiological microenvironment became more deficient as degeneration progressed. For example, minimum glucose concentration in grade 4 dropped by 31.1% compared to grade 3 (p < 0.0001). The model further suggested a strong effect of the following parameters: disc size, AF and CEP diffusivities, metabolic reactions, and cell density on solute concentrations in the disc (p < 0.05). CONCLUSION The significance of this work implies that the individual morphology and physiological conditions of each disc, even among discs of the same Pfirrmann grade, should be evaluated when modeling IVD solute concentrations.
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Affiliation(s)
- Ward Shalash
- School of Chemical, Biological and Environmental EngineeringOregon State UniversityCorvallisOregonUSA
| | - Sonia R. Ahrens
- School of Chemical, Biological and Environmental EngineeringOregon State UniversityCorvallisOregonUSA
| | - Liudmila A. Bardonova
- School of Chemical, Biological and Environmental EngineeringOregon State UniversityCorvallisOregonUSA
- Irkutsk State Medical UniversityIrkutskRussia
| | - Vadim A. Byvaltsev
- Irkutsk State Medical UniversityIrkutskRussia
- Railway Clinical Hospital at the Irkutsk‐Passazhirsky StationIrkutskRussia
| | - Morgan B. Giers
- School of Chemical, Biological and Environmental EngineeringOregon State UniversityCorvallisOregonUSA
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Jackson AR, Eismont A, Yu L, Li N, Gu W, Eismont F, Brown MD. Diffusion of antibiotics in intervertebral disc. J Biomech 2018; 76:259-262. [PMID: 29941209 DOI: 10.1016/j.jbiomech.2018.06.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 05/22/2018] [Accepted: 06/09/2018] [Indexed: 10/14/2022]
Abstract
Delivering charged antibiotics to the intervertebral disc is challenging because of the avascular, negatively charged extracellular matrix (ECM) of the tissue. The purpose of this study was to measure the apparent diffusion coefficient of two clinically relevant, charged antibiotics, vancomycin (positively charged) and oxacillin (negatively charged) in IVD. A one-dimensional steady state diffusion experiment was employed to measure the apparent diffusion coefficient of the two antibiotics in bovine coccygeal annulus fibrosus (AF) tissue. The averaged apparent diffusion coefficient for vancomycin under 20% compressive strain was 7.94 ± 2.00 × 10-12 m2/s (n = 10), while that of oxacillin was 2.26 ± 0.68 × 10-10 m2/s (n = 10). A student's t-test showed that the diffusivity of vancomycin was significantly lower than that of oxacillin. This finding may be attributed to two factors: solute size and possible binding effects. Vancomycin is approximately 3 times larger in molecular weight than oxacillin, meaning that steric hindrance likely plays a role in the slower transport. Reversible binding between positive vancomycin and the negative ECM could also slow down the rate of diffusion. Therefore, more investigation is necessary to determine the specific relationship between net charge on antibiotic and diffusion coefficients in IVD. This study provides essential quantitative information regarding the transport rates of antibiotics in the IVD, which is critical in using computational modeling to design effective strategies to treat disc infection.
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Affiliation(s)
- Alicia R Jackson
- Department of Biomedical Engineering, University of Miami, Coral Gables, FL, USA
| | - Adam Eismont
- Department of Biomedical Engineering, University of Miami, Coral Gables, FL, USA
| | - Lu Yu
- Department of Mechanical and Aerospace Engineering, University of Miami, Coral Gables, FL, USA
| | - Na Li
- Department of Mechanical and Aerospace Engineering, University of Miami, Coral Gables, FL, USA
| | - Weiyong Gu
- Department of Mechanical and Aerospace Engineering, University of Miami, Coral Gables, FL, USA.
| | - Frank Eismont
- Department of Orthopaedics, Miller School of Medicine, University of Miami, Miami, FL, USA
| | - Mark D Brown
- Department of Orthopaedics, Miller School of Medicine, University of Miami, Miami, FL, USA
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Bowden JA, Bowden AE, Wang H, Hager RL, LeCheminant JD, Mitchell UH. In vivo correlates between daily physical activity and intervertebral disc health. J Orthop Res 2018; 36:1313-1323. [PMID: 28976592 DOI: 10.1002/jor.23765] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Accepted: 09/27/2017] [Indexed: 02/04/2023]
Abstract
Physical activity impacts health and disease in multiple body tissues including the intervertebral discs. Fluid flow within the disc is an indicator of disc health that can be observed using diffusion weighted magnetic resonance imaging. We monitored activity levels of 26 participants, age 35-55 yrs, using Actigraph accelerometers for 4 days to evaluate vigorous-intensity activity, moderate to vigorous intensity activity, and sedentary time. Participants underwent structural and diffusion weighted magnetic resonance imaging to evaluate intervertebral disc health and fluid flow. They also underwent bone density scans, carotid artery ultrasounds, a treadmill test, and a physical exam for pain, range of motion, and instability. These measures were used to correlate MRI indicators of intervertebral disc health with participant activity levels. Participants with any vigorous-intensity physical activity compared with no vigorous-intensity activity had significantly greater L5/S1 apparent diffusion coefficient values (p = 0.002), corresponding to higher freedom of diffusive movement for cellular nutrients and metabolic waste. Sagittal T2 values in the L5/S1 were also higher (p = 0.004), corresponding to a higher water content in the discs. Higher apparent diffusion coefficients were also found in participants with more than 30 min compared with less than 30 min of daily moderate to vigorous physical activity (p = 0.03), and in participants with less than 67% awake time as sedentary time compared with more than 67% sedentary time (p = 0.03). Increased dynamic loading through physical activity and decreased static loading from sedentary time benefit intervertebral disc health. Physical activity, particularly vigorous activity, is beneficial in helping maintain intervertebral disc health. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1313-1323, 2018.
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Affiliation(s)
- Jennifer A Bowden
- Department of Exercise Sciences, Brigham Young University, Provo, Utah, 84602
| | - Anton E Bowden
- Department of Mechanical Engineering, Brigham Young University, Provo, Utah, 84602
| | - Haonan Wang
- Department of Electrical and Computer Engineering, Brigham Young University, Provo, Utah, 84602
| | - Ron L Hager
- Department of Exercise Sciences, Brigham Young University, Provo, Utah, 84602
| | - James D LeCheminant
- Department of Exercise Sciences, Brigham Young University, Provo, Utah, 84602
| | - Ulrike H Mitchell
- Department of Exercise Sciences, Brigham Young University, Provo, Utah, 84602
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Cherubini C, Filippi S, Gizzi A, Ruiz-Baier R. A note on stress-driven anisotropic diffusion and its role in active deformable media. J Theor Biol 2017; 430:221-228. [PMID: 28755956 DOI: 10.1016/j.jtbi.2017.07.013] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Revised: 07/10/2017] [Accepted: 07/13/2017] [Indexed: 12/13/2022]
Abstract
We introduce a new model to describe diffusion processes within active deformable media. Our general theoretical framework is based on physical and mathematical considerations, and it suggests to employ diffusion tensors directly influenced by the coupling with mechanical stress. The proposed generalised reaction-diffusion-mechanics model reveals that initially isotropic and homogeneous diffusion tensors turn into inhomogeneous and anisotropic quantities due to the intrinsic structure of the nonlinear coupling. We study the physical properties leading to these effects, and investigate mathematical conditions for its occurrence. Together, the mathematical model and the numerical results obtained using a mixed-primal finite element method, clearly support relevant consequences of stress-driven diffusion into anisotropy patterns, drifting, and conduction velocity of the resulting excitation waves. Our findings also indicate the applicability of this novel approach in the description of mechano-electric feedback in actively deforming bio-materials such as the cardiac tissue.
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Affiliation(s)
- Christian Cherubini
- Unit of Nonlinear Physics and Mathematical Modeling, Department of Engineering, University Campus Bio-Medico of Rome, Via A. del Portillo 21, 00128 Rome, Italy; International Center for Relativistic Astrophysics, I.C.R.A., University Campus Bio-Medico of Rome, Via A. del Portillo 21, 00128 Rome, Italy.
| | - Simonetta Filippi
- Unit of Nonlinear Physics and Mathematical Modeling, Department of Engineering, University Campus Bio-Medico of Rome, Via A. del Portillo 21, 00128 Rome, Italy; International Center for Relativistic Astrophysics, I.C.R.A., University Campus Bio-Medico of Rome, Via A. del Portillo 21, 00128 Rome, Italy.
| | - Alessio Gizzi
- Unit of Nonlinear Physics and Mathematical Modeling, Department of Engineering, University Campus Bio-Medico of Rome, Via A. del Portillo 21, 00128 Rome, Italy.
| | - Ricardo Ruiz-Baier
- Mathematical Institute, University of Oxford, A. Wiles Building, Radcliffe Observatory Quarter, Woodstock Road, Oxford OX2 6GG, United Kingdom.
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Wang YF, Barrera CM, Dauer EA, Gu W, Andreopoulos F, Huang CYC. Systematic characterization of porosity and mass transport and mechanical properties of porous polyurethane scaffolds. J Mech Behav Biomed Mater 2017; 65:657-664. [DOI: 10.1016/j.jmbbm.2016.09.029] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Revised: 09/12/2016] [Accepted: 09/22/2016] [Indexed: 01/23/2023]
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Elmasry S, Asfour S, de Rivero Vaccari JP, Travascio F. A computational model for investigating the effects of changes in bioavailability of insulin-like growth factor-1 on the homeostasis of the intervertebral disc. Comput Biol Med 2016; 78:126-137. [PMID: 27697672 DOI: 10.1016/j.compbiomed.2016.09.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 09/08/2016] [Accepted: 09/21/2016] [Indexed: 01/04/2023]
Abstract
Insulin-like growth factor-1 (IGF-1) is well-known for upregulating cell proliferation and biosynthesis of the extracellular matrix in the intervertebral disc (IVD). Pathological conditions, such as obesity or chronic kidney disease cause IGF-1 deficiency in plasma. How this deficiency impacts disc homeostasis remains unknown. Pro-anabolic approaches for the treatment of disc degeneration based on enhancing IGF-1 bioavailability to tissue-cells are considered, but knowledge of their effectiveness in enhancing cellular anabolism of a degenerated disc is limited. In this study, we developed a computational model for disc homeostasis specifically addressing the role of IGF-1 in modulating both extracellular matrix biosynthesis and cellularity in the IVD. This model was applied to investigate how changes in IGF-1 bioavailability, namely deficiency or enhancement of growth factor, affect disc health. In this study, it was found that IGF-1 deficiency mainly affects the biosynthesis of ECM components, especially in the most external regions of the IVD such as the cartilage endplates and the outer portion of annulus fibrosus. Also, a total of three approaches for increasing IGF-1 bioavailability as a therapy for degenerated IVDs were investigated. It was found that all these strategies are only beneficial to those disc regions receiving sufficient nutritional supply (i.e., the outmost IVD regions), while they exacerbate tissue degradation in malnourished regions (i.e., inner portion of the disc). This suggests that pro-anabolic growth factor-based therapies are limited in that their success strongly depends on an adequate nutritional supply to the IVD tissue, which is not guaranteed in degenerated discs.
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Affiliation(s)
- Shady Elmasry
- Department of Industrial Engineering, University of Miami, Coral Gables, FL, USA
| | - Shihab Asfour
- Department of Industrial Engineering, University of Miami, Coral Gables, FL, USA
| | | | - Francesco Travascio
- Department of Industrial Engineering, University of Miami, Coral Gables, FL, USA.
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Kleinhans KL, McMahan JB, Jackson AR. Electrical conductivity and ion diffusion in porcine meniscus: effects of strain, anisotropy, and tissue region. J Biomech 2016; 49:3041-3046. [DOI: 10.1016/j.jbiomech.2016.06.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 06/02/2016] [Accepted: 06/07/2016] [Indexed: 10/21/2022]
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Diffusion characteristics of human annulus fibrosus-a study documenting the dependence of annulus fibrosus on end plate for diffusion. Spine J 2016; 16:1007-14. [PMID: 27060711 DOI: 10.1016/j.spinee.2016.03.046] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 03/10/2016] [Accepted: 03/31/2016] [Indexed: 02/03/2023]
Abstract
BACKGROUND Intervertebral disc being avascular depends on nutrition from either the end plate or the annulus fibrosus (AF). The role of the end plate on disc diffusion had been extensively studied. However, diffusion of human AF remains poorly understood because of the lack of reliable techniques to study AF in vivo and non-invasively. The present study for the first time evaluates the 24-hour diffusion characteristics of AF in radial, axial, and circumferential directions. PURPOSE The study aimed to document the 24-hour diffusion characteristics of human AF. STUDY DESIGN This is an in vivo human serial post-contrast magnetic resonance image study. METHODS Twenty-five discs from five healthy volunteers (age <20 years) were studied. Diffusion over 24 hours following intravenous gadodiamide injection (0.3 mmol/kg) was studied at 10 minutes, and at 2, 4, 6, 12, and 24 hours. Axial images of the cranial, middle, and caudal zones of the discs were obtained. The vertebral body and end plate signal intensities were measured in sagittal sections. Thirty-nine regions of interest (24 in AF, 15 in nucleus pulposus) in each disc were analyzed. The peak enhancement percentage (EPmax) and the time to attain EPmax (Tmax) were calculated. Radial (outer vs. inner AF), axial (cranial vs. caudal vs. middle zone), and circumferential diffusions were analyzed. (The study received research grant from AOSpine India for US$6,000). RESULTS Annulus fibrosus showed a biphasic pattern of diffusion with a characteristic "double peak." Early peak was seen at 10 minutes (coinciding with Tmax of the vertebral body) and delayed peak was seen at 6 hours (coinciding with Tmax of the nucleus pulposus), and characteristically noted after Tmax of the end plate (2 hours). The inner AF showed significant regional differences both at the early and delayed peaks, but the outer AF had no regional differences in the early peak. In axial direction, both outer and inner AF showed maximum enhancement percentage in the middle zone, followed by the caudal zone and least in the cranial zone. CONCLUSIONS Annulus fibrosus characteristically showed a "double-peak" pattern of diffusion. Both the peaks had different characteristics, confirming two different sources of nutrition. The initial peak was contributed by periannular vascularity and the delayed one via the end plate from the vertebral body. The fact that even AF depends on the end plate for nutrition helps us better understand the complex nutritional pathways of intervertebral discs.
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Kleinhans KL, Jaworski LM, Schneiderbauer MM, Jackson AR. Effect of Static Compressive Strain, Anisotropy, and Tissue Region on the Diffusion of Glucose in Meniscus Fibrocartilage. J Biomech Eng 2015. [DOI: 10.1115/1.4031118] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Osteoarthritis (OA) is a significant socio-economic concern, affecting millions of individuals each year. Degeneration of the meniscus of the knee is often associated with OA, yet the relationship between the two is not well understood. As a nearly avascular tissue, the meniscus must rely on diffusive transport for nutritional supply to cells. Therefore, quantifying structure–function relations for transport properties in meniscus fibrocartilage is an important task. The purpose of the present study was to determine how mechanical loading, tissue anisotropy, and tissue region affect glucose diffusion in meniscus fibrocartilage. A one-dimensional (1D) diffusion experiment was used to measure the diffusion coefficient of glucose in porcine meniscus tissues. Results show that glucose diffusion is strain-dependent, decreasing significantly with increased levels of compression. It was also determined that glucose diffusion in meniscus tissues is anisotropic, with the diffusion coefficient in the circumferential direction being significantly higher than that in the axial direction. Finally, the effect of tissue region was not statistically significant, comparing axial diffusion in the central and horn regions of the tissue. This study is important for better understanding the transport and nutrition-related mechanisms of meniscal degeneration and related OA in the knee.
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Affiliation(s)
- Kelsey L. Kleinhans
- Orthopaedic Biomechanics Laboratory, Department of Biomedical Engineering, University of Miami, 1251 Memorial Drive, MEA 219, Coral Gables, FL 33146 e-mail:
| | - Lukas M. Jaworski
- Orthopaedic Biomechanics Laboratory, Department of Biomedical Engineering, University of Miami, 1251 Memorial Drive, MEA 219, Coral Gables, FL 33146 e-mail:
| | - Michaela M. Schneiderbauer
- Department of Orthopaedics, University of Miami Miller School of Medicine, 1400 NW 12th Avenue, Room 4056, Miami, FL 33136 e-mail:
| | - Alicia R. Jackson
- Orthopaedic Biomechanics Laboratory, Department of Biomedical Engineering, University of Miami, 1251 Memorial Drive, MEA 219, Coral Gables, FL 33146 e-mail:
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Wright GJ, Kuo J, Shi C, Bacro TRH, Slate EH, Yao H. Effect of mechanical strain on solute diffusion in human TMJ discs: an electrical conductivity study. Ann Biomed Eng 2013; 41:2349-57. [PMID: 23771300 DOI: 10.1007/s10439-013-0840-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Accepted: 06/04/2013] [Indexed: 11/26/2022]
Abstract
This study investigated the effect of mechanical strain on solute diffusion in human TMJ discs (mean cadaver age 77.8) using the electrical conductivity method. The electrical conductivity, as well as small ion diffusivity, of male and female TMJ discs was determined under three compressive strains. In the male group, the average disc electrical conductivity (mean ± SD) at 0% strain was 5.14 ± 0.97 mS/cm, decreased to 4.50 ± 0.91 mS/cm (-12.3%) at 10% strain, and 3.93 ± 0.81 mS/cm (-23.5%) at 20% compressive strain. Correspondingly, the average disc relative ion diffusivity at 0% strain was 0.44 ± 0.08, decreased to 0.40 ± 0.08 (-8.9%) at 10% strain, and 0.36 ± 0.08 (-16.7%) at 20% compressive strain. In the female group, the average disc electrical conductivity at 0% strain was 5.84 ± 0.59 mS/cm, decreased to 5.01 ± 0.50 mS/cm (-14.2%) at 10% strain, and 4.33 ± 0.46 mS/cm (-25.8%) at 20% compressive strain. Correspondingly, the average disc relative ion diffusivity at 0% strain was 0.49 ± 0.05, decreased to 0.43 ± 0.04 (-11.3%) at 10% strain, and 0.39 ± 0.04 (-19.9%) at 20% compressive strain. The results indicated that mechanical strain significantly impeded solute diffusion through the disc. This mechanical strain effect was larger in the female than in the male human TMJ disc. This study may provide new insights into TMJ pathophysiology.
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Affiliation(s)
- Gregory J Wright
- Clemson-MUSC Bioengineering Program, Department of Bioengineering, Clemson University, 173 Ashley Avenue, P.O. Box 250508, Charleston, SC, 29425, USA
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Zhu Q, Jackson AR, Gu WY. Cell viability in intervertebral disc under various nutritional and dynamic loading conditions: 3d finite element analysis. J Biomech 2012; 45:2769-77. [PMID: 23040882 PMCID: PMC3593676 DOI: 10.1016/j.jbiomech.2012.08.044] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 07/30/2012] [Accepted: 08/31/2012] [Indexed: 12/23/2022]
Abstract
In this study, a new cell density model was developed and incorporated into the formulation of the mechano-electrochemical mixture theory to investigate the effects of deprivation of nutrition supply at boundary source, degeneration, and dynamic loading on the cell viability of intervertebral disc (IVD) using finite element methods. The deprivation of nutrition supply at boundary source was simulated by reduction in nutrition level at CEP and AF boundaries. Cases with 100%, 75%, 60%, 50% and 30% of normal nutrition level at both CEP and AF boundaries were modeled. Unconfined axial sinusoidal dynamic compressions with different combinations of amplitude (u=10%± 2.5%, ± 5%) and frequency (f=1, 10, 20 cycle/day) were applied. Degenerated IVD was modeled with altered material properties. Cell density decreased substantially with reduction of nutrition level at boundaries. Cell death was initiated primarily near the NP-AF interface on the mid-plane. Dynamic loading did not result in a change in the cell density in non-degenerated IVD, since glucose levels did not fall below the minimum value for cell survival; in degenerated IVDs, we found that increasing frequency and amplitude both resulted in higher cell density, because dynamic compression facilitates the diffusion of nutrients and thus increases the nutrition level around IVD cells. The novel computational model can be used to quantitatively predict both when and where cells start to die within the IVD under various kinds of nutritional and mechanical conditions.
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Affiliation(s)
- Qiaoqiao Zhu
- Tissue Biomechanics Laboratory, Department of Mechanical and Aerospace Engineering, College of Engineering, University of Miami, P.O. Box 248294, Coral Gables, FL 33124-0624, USA
| | - Alicia R. Jackson
- Orthopaedic Biomechanics Laboratory, Department of Biomedical Engineering, University of Miami, Coral Gables, FL, USA
| | - Wei Yong Gu
- Tissue Biomechanics Laboratory, Department of Mechanical and Aerospace Engineering, College of Engineering, University of Miami, P.O. Box 248294, Coral Gables, FL 33124-0624, USA
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Jackson AR, Yuan TY, Huang CY, Brown MD, Gu WY. Nutrient transport in human annulus fibrosus is affected by compressive strain and anisotropy. Ann Biomed Eng 2012; 40:2551-8. [PMID: 22669503 DOI: 10.1007/s10439-012-0606-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Accepted: 05/25/2012] [Indexed: 11/24/2022]
Abstract
The avascular intervertebral disc (IVD) receives nutrition via transport from surrounding vasculature; poor nutrition is believed to be a main cause of disc degeneration. In this study, we investigated the effects of mechanical deformation and anisotropy on the transport of two important nutrients--oxygen and glucose--in human annulus fibrosus (AF). The diffusivities of oxygen and glucose were measured under three levels of uniaxial confined compression--0, 10, and 20%--and in three directions--axial, circumferential, and radial. The glucose partition coefficient was also measured at three compression levels. Results for glucose and oxygen diffusivity in AF ranged from 4.46 × 10(-7) to 9.77 × 10(-6) cm(2)/s and were comparable to previous studies; the glucose partition coefficient ranged from 0.71 to 0.82 and was also similar to previous results. Transport properties were found to decrease with increasing deformation, likely caused by fluid exudation during tissue compression and reduction in pore size. Furthermore, diffusivity in the radial direction was lower than in the axial or circumferential directions, indicating that nutrient transport in human AF is anisotropic. This behavior is likely a consequence of the layered structure and unique collagen architecture of AF tissue. These findings are important for better understanding nutritional supply in IVD and related disc degeneration.
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Affiliation(s)
- Alicia R Jackson
- Orthopaedic Biomechanics Lab, Department of Biomedical Engineering, University of Miami, Coral Gables, FL, USA
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Mavrogonatou E, Kletsas D. Differential response of nucleus pulposus intervertebral disc cells to high salt, sorbitol, and urea. J Cell Physiol 2011; 227:1179-87. [DOI: 10.1002/jcp.22840] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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16
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Kuo J, Wright GJ, Bach DE, Slate EH, Yao H. Effect of mechanical loading on electrical conductivity in porcine TMJ discs. J Dent Res 2011; 90:1216-20. [PMID: 21743033 DOI: 10.1177/0022034511415275] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The objective of this study was to examine the impact of mechanical loading on solute transport in porcine temporomandibular joint (TMJ) discs using the electrical conductivity method. The electrical conductivity, as well as ion diffusivity, of TMJ discs was determined under confined compression with 3 strains in 5 disc regions. The average electrical conductivity over the 5 regions (mean ± SD) at 0% strain was 3.10 ± 0.68 mS/cm, decreased to 2.76 ± 0.58 mS/cm (-11.0%) at 10% strain, and 2.38 ± 0.55 mS/cm (-22.2%) at 20% compressive strain. Correspondingly, the average relative ion diffusivity (mean ± SD) at 0% strain was 0.273 ± 0.055, decreased to 0.253 ± 0.048 (-7.3%) at 10% strain, and 0.231 ± 0.048 (-15.4%) at 20% compressive strain. These results indicated that compressive strain impeded solute transport in the TMJ disc. Furthermore, our results showed that the transport properties of TMJ discs were region-dependent. The electrical conductivity and ion diffusivity in the anterior region were significantly higher than in the posterior region. This regional difference is likely due to the significant differences of tissue hydration between these 2 regions. This study provides important insight into the electrical and solute transport behaviors in TMJ discs under mechanical loading and aids in the understanding of TMJ pathophysiology related to tissue nutrition.
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Affiliation(s)
- J Kuo
- Department of Bioengineering, Clemson University, Clemson, SC, USA
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Difference in Energy Metabolism of Annulus Fibrosus and Nucleus Pulposus Cells of the Intervertebral Disc. Cell Mol Bioeng 2011; 4:302-310. [PMID: 21625336 DOI: 10.1007/s12195-011-0164-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Low back pain is associated with intervertebral disc degeneration. One of the main signs of degeneration is the inability to maintain extracellular matrix integrity. Extracellular matrix synthesis is closely related to production of adenosine triphosphate (i.e. energy) of the cells. The intervertebral disc is composed of two major anatomical regions: annulus fibrosus and nucleus pulposus, which are structurally and compositionally different, indicating that their cellular metabolisms may also be distinct. The objective of this study was to investigate energy metabolism of annulus fibrosus and nucleus pulposus cells with and without dynamic compression, and examine differences between the two cell types. Porcine annulus and nucleus tissues were harvested and enzymatically digested. Cells were isolated and embedded into agarose constructs. Dynamically loaded samples were subjected to a sinusoidal displacement at 2 Hz and 15% strain for 4 h. Energy metabolism of cells was analyzed by measuring adenosine triphosphate content and release, glucose consumption, and lactate/nitric oxide production. A comparison of those measurements between annulus and nucleus cells was conducted. Annulus and nucleus cells exhibited different metabolic pathways. Nucleus cells had higher adenosine triphosphate content with and without dynamic loading, while annulus cells had higher lactate production and glucose consumption. Compression increased adenosine triphosphate release from both cell types and increased energy production of annulus cells. Dynamic loading affected energy metabolism of intervertebral disc cells, with the effect being greater in annulus cells.
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Travascio F, Jackson AR, Brown MD, Gu WY. Relationship between solute transport properties and tissue morphology in human annulus fibrosus. J Orthop Res 2009; 27:1625-30. [PMID: 19489044 PMCID: PMC2798905 DOI: 10.1002/jor.20927] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Poor nutritional supply to the intervertebral disc is believed to be an important factor leading to disc degeneration. However, little is known regarding nutritional transport in human annulus fibrosus (AF) and its relation to tissue morphology. We hypothesized that solute diffusivity in human AF is anisotropic and inhomogeneous, and that transport behaviors are associated with tissue composition and structure. To test these hypotheses, we measured the direction-dependent diffusivity of a fluorescent molecule (fluorescein, 332 Da) in three regions of AF using a fluorescence recovery after photobleaching (FRAP) technique, and associated transport results to the regional variation in water content and collagen architecture in the tissue. Diffusivity in AF was anisotropic, with higher values in the axial direction than in the radial direction for all regions investigated. The values of the diffusion coefficient ranged from 0.38 +/- 0.25 x 10(-6) cm(2)/s (radial diffusivity in outer AF) to 2.68 +/- 0.84 x 10(-6) cm(2)/s (axial diffusivity in inner AF). In both directions, diffusivity decreased moving from inner to outer AF. Tissue structure was investigated using both scanning electron microscopy and environmental scanning electron microscopy. A unique arrangement of microtubes was found in human AF. Furthermore, we also found that the density of these microtubes varied moving from inner to outer AF. A similar trend of regional variation was found for water content, with the highest value also measured in inner AF. Therefore, we concluded that a relationship exists among the anisotropic and inhomogeneous diffusion in human AF and the structure and composition of the tissue.
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Affiliation(s)
- Francesco Travascio
- Tissue Biomechanics Lab, Dept. of Biomedical Engineering, University of Miami, Coral Gables, FL
| | - Alicia R. Jackson
- Tissue Biomechanics Lab, Dept. of Biomedical Engineering, University of Miami, Coral Gables, FL
| | - Mark D. Brown
- Dept. of Orthopaedics, Miller School of Medicine, University of Miami, Miami, FL
| | - Wei Yong Gu
- Tissue Biomechanics Lab, Dept. of Biomedical Engineering, University of Miami, Coral Gables, FL,Corresponding author: WY Gu, Ph.D. Department of Biomedical Engineering College of Engineering University of Miami P.O. Box 248294 Coral Gables, Fl 33124-0621 USA Telephone: (305) 284-5434 Fax: (305)284-6494
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Jackson AR, Travascio F, Gu WY. Effect of mechanical loading on electrical conductivity in human intervertebral disk. J Biomech Eng 2009; 131:054505. [PMID: 19388789 DOI: 10.1115/1.3116152] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The intervertebral disk (IVD), characterized as a charged, hydrated soft tissue, is the largest avascular structure in the body. Mechanical loading to the disk results in electromechanical transduction phenomenon as well as altered transport properties. Electrical conductivity is a material property of tissue depending on ion concentrations and diffusivities, which are in turn functions of tissue composition and structure. The aim of this study was to investigate the effect of mechanical loading on electrical behavior in human IVD tissues. We hypothesized that electrical conductivity in human IVD is strain-dependent, due to change in tissue composition caused by compression, and inhomogeneous, due to tissue structure and composition. We also hypothesized that conductivity in human annulus fibrosus (AF) is anisotropic, due to the layered structure of the tissue. Three lumbar IVDs were harvested from three human spines. From each disk, four AF specimens were prepared in each of the three principal directions (axial, circumferential, and radial), and four axial nucleus pulposus (NP) specimens were prepared. Conductivity was determined using a four-wire sense-current method and a custom-designed apparatus by measuring the resistance across the sample. Resistance measurements were taken at three levels of compression (0%, 10%, and 20%). Scanning electron microscopy (SEM) images of the human AF tissue were obtained in order to correlate tissue structure with conductivity results. Increasing compressive strain significantly decreased conductivity for all groups (p<0.05, analysis of variance (ANOVA)). Additionally, specimen orientation significantly affected electrical conductivity in the AF tissue, with conductivity in the radial direction being significantly lower than that in the axial or circumferential directions at all levels of compressive strain (p<0.05, ANOVA). Finally, conductivity in the NP tissue was significantly higher than that in the AF tissue (p<0.05, ANOVA). SEM images of the AF tissues showed evidence of microtubes orientated in the axial and circumferential directions, but not in the radial direction. This may suggest a relationship between tissue morphology and the anisotropic behavior of conductivity in the AF. The results of this investigation demonstrate that electrical conductivity in human IVD is strain-dependent and inhomogeneous, and that conductivity in the human AF tissue is anisotropic (i.e., direction-dependent). This anisotropic behavior is correlated with tissue structure shown in SEM images. This study provides important information regarding the effects of mechanical loading on solute transport and electrical behavior in IVD tissues.
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Affiliation(s)
- Alicia R Jackson
- Department of Biomedical Engineering, Tissue Biomechanics Laboratory, University of Miami, Coral Gables, FL 33146, USA
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