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Mousavizadeh R, West VC, Inguito KL, Elliott DM, Parreno J. The application of mechanical load onto mouse tendons by magnetic restraining represses Mmp-3 expression. BMC Res Notes 2023; 16:127. [PMID: 37391824 PMCID: PMC10314558 DOI: 10.1186/s13104-023-06413-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2022] [Accepted: 06/20/2023] [Indexed: 07/02/2023] Open
Abstract
OBJECTIVES Mechanical loading is crucial for tendon matrix homeostasis. Under-stimulation of tendon tissue promotes matrix degradation and ultimately tendon failure. In this study, we examined the expression of tendon matrix molecules and matrix-degrading enzymes (matrix metalloproteinases) in stress-deprived tail tendons and compared to tendons that were mechanically loaded by a simple restraining method. DATA DESCRIPTION Isolated mouse tail fascicles were either floated or restrained by magnets in cell culture media for 24 h. The gene expression of tendon matrix molecules and matrix metalloproteinases in the tendon fascicles of mouse tails were examined by real-time RT-PCR. Stress deprivation of tail tendons increase Mmp3 mRNA levels. Restraining tendons represses these increases in Mmp3. The gene expression response to restraining was specific to Mmp3 at 24 h as we did not observe mRNA level changes in other matrix related genes that we examined (Col1, Col3, Tnc, Acan, and Mmp13). To elucidate, the mechanisms that may regulate load transmission in tendon tissue, we examined filamentous (F-)actin staining and nuclear morphology. As compared to stress deprived tendons, restrained tendons had greater staining for F-actin. The nuclei of restrained tendons are smaller and more elongated. These results indicate that mechanical loading regulates specific gene expression potentially through F-actin regulation of nuclear morphology. A further understanding on the mechanisms involved in regulating Mmp3 gene expression may lead to new strategies to prevent tendon degeneration.
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Affiliation(s)
- Rouhollah Mousavizadeh
- Department of Physical Therapy, Faculty of Medicine, The University of British Columbia, Vancouver, Canada
| | - Valerie C West
- Department of Biomedical Engineering, University of Delaware, Newark, DE, USA
| | - Kameron L Inguito
- Department of Biological Sciences, University of Delaware, Newark, DE, USA
| | - Dawn M Elliott
- Department of Biomedical Engineering, University of Delaware, Newark, DE, USA
| | - Justin Parreno
- Department of Biomedical Engineering, University of Delaware, Newark, DE, USA.
- Department of Biological Sciences, University of Delaware, Newark, DE, USA.
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2
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Inguito KL, Schofield MM, Faghri AD, Bloom ET, Heino M, West VC, Ebron KMM, Elliott DM, Parreno J. Stress deprivation of tendon explants or Tpm3.1 inhibition in tendon cells reduces F-actin to promote a tendinosis-like phenotype. Mol Biol Cell 2022; 33:ar141. [PMID: 36129771 PMCID: PMC9727789 DOI: 10.1091/mbc.e22-02-0067] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Actin is a central mediator between mechanical force and cellular phenotype. In tendons, it is speculated that mechanical stress deprivation regulates gene expression by reducing filamentous (F)-actin. However, the mechanisms regulating tenocyte F-actin remain unclear. Tropomyosins (Tpms) are master regulators of F-actin. There are more than 40 Tpm isoforms, each having the unique capability to stabilize F-actin subpopulations. We investigated F-actin polymerization in stress-deprived tendons and tested the hypothesis that stress fiber-associated Tpm(s) stabilize F-actin to regulate cellular phenotype. Stress deprivation of mouse tail tendon down-regulated tenogenic and up-regulated protease (matrix metalloproteinase-3) mRNA levels. Concomitant with mRNA modulation were increases in G/F-actin, confirming reduced F-actin by tendon stress deprivation. To investigate the molecular regulation of F-actin, we identified that tail, Achilles, and plantaris tendons express three isoforms in common: Tpm1.6, 3.1, and 4.2. Tpm3.1 associates with F-actin in native and primary tenocytes. Tpm3.1 inhibition reduces F-actin, leading to decreases in tenogenic expression, increases in chondrogenic expression, and enhancement of protease expression in mouse and human tenocytes. These expression changes by Tpm3.1 inhibition are consistent with tendinosis progression. A further understanding of F-actin regulation in musculoskeletal cells could lead to new therapeutic interventions to prevent alterations in cellular phenotype during disease progression.
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Affiliation(s)
- Kameron L. Inguito
- Departments of Biological Sciences, University of Delaware, Newark, DE 19716
| | - Mandy M. Schofield
- Departments of Biological Sciences, University of Delaware, Newark, DE 19716
| | - Arya D. Faghri
- Departments of Biological Sciences, University of Delaware, Newark, DE 19716
| | - Ellen T. Bloom
- Biomedical Engineering, University of Delaware, Newark, DE 19716
| | - Marissa Heino
- Departments of Biological Sciences, University of Delaware, Newark, DE 19716,Biomedical Engineering, University of Delaware, Newark, DE 19716
| | - Valerie C. West
- Biomedical Engineering, University of Delaware, Newark, DE 19716
| | | | - Dawn M. Elliott
- Biomedical Engineering, University of Delaware, Newark, DE 19716
| | - Justin Parreno
- Departments of Biological Sciences, University of Delaware, Newark, DE 19716,Biomedical Engineering, University of Delaware, Newark, DE 19716,*Address correspondence to: Justin Parreno ()
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Quantification of cell contractile behavior based on non-destructive macroscopic measurement of tension forces on bioprinted hydrogel. J Mech Behav Biomed Mater 2022; 134:105365. [PMID: 35863297 DOI: 10.1016/j.jmbbm.2022.105365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 07/01/2022] [Accepted: 07/09/2022] [Indexed: 11/24/2022]
Abstract
Contraction assay based on surface measurement have been widely used to evaluate cell contractility in 3D models. This method is straightforward and requires no specific equipment, but it does not provide quantitative data about contraction forces generated by cells. We expanded this method with a new biomechanical model, based on the work-energy theorem, to provide non-destructive longitudinal monitoring of contraction forces generated by cells in 3D. We applied this method on hydrogels seeded with either fibroblasts or osteoblasts. Hydrogel mechanical characteristics were modulated to enhance (condition HCAHigh: hydrogel contraction assay high contraction) or limit (condition HCALow: hydrogel contraction assay low contraction) cell contractile behaviors. Macroscopic measures were further correlated with cell contractile behavior and descriptive analysis of their physiology in response to different mechanical environments. Fibroblasts and osteoblasts contracted their matrix up to 47% and 77% respectively. Contraction stress peaked at day 5 with 1.1 10-14 Pa for fibroblasts and 3.5 10-14 Pa for osteoblasts, which correlated with cell attachment and spreading. Negligible contraction was seen in HCALow. Both fibroblasts and osteoblasts expressed α-SMA contractile fibers in HCAHigh and HCALow. Failure to contract HCALow was attributed to increased cross-linking and resistance to proteolytic degradation of the hydrogel.
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Vogel S, Ullm F, Damaris Müller C, Pompe T, Hempel U. Remodeling of Three-Dimensional Collagen I Matrices by Human Bone Marrow Stromal Cells during Osteogenic Differentiation In Vitro. ACS APPLIED BIO MATERIALS 2020; 3:6967-6978. [DOI: 10.1021/acsabm.0c00856] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Sarah Vogel
- Institute of Physiological Chemistry, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Fiedlerstrasse 42, Dresden 01307, Germany
| | - Franziska Ullm
- Institute of Biochemistry, Faculty of Life Sciences, Leipzig University, Johannisallee 21-23, Leipzig 04103, Germany
| | - Claudia Damaris Müller
- Institute of Physiological Chemistry, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Fiedlerstrasse 42, Dresden 01307, Germany
| | - Tilo Pompe
- Institute of Biochemistry, Faculty of Life Sciences, Leipzig University, Johannisallee 21-23, Leipzig 04103, Germany
| | - Ute Hempel
- Institute of Physiological Chemistry, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Fiedlerstrasse 42, Dresden 01307, Germany
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Kihara T, Umezu C, Sawada K, Furutani Y. Osteogenic cells form mineralized particles, a few μm in size, in a 3D collagen gel culture. PeerJ 2019; 7:e7889. [PMID: 31660270 PMCID: PMC6815190 DOI: 10.7717/peerj.7889] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 09/13/2019] [Indexed: 02/03/2023] Open
Abstract
Osteogenic cells form mineralized matrices in vitro, as well as in vivo. The formation and shape of the mineralized matrices are highly regulated by the cells. In vitro formation of mineralized matrices by osteogenic cells can be a model for in vivo osteogenesis. In this study, using a three-dimensional (3D) collagen gel culture system, we developed a new in vitro model for the formation of mineralized particles, a few µm in size, by the osteogenic cells. Human osteosarcoma (HOS) cells formed spherical mineralized matrices (about 12 µm) at approximately 7 days when cultured with β-glycerophosphate (β-GP)-containing culture media on 2D tissue culture plates. Alternately, when they were cultured in a 3D collagen gel containing β-GP, they formed mineralized particles with about 1.7 µm in the gel at approximately 3 days. Calcium precipitation in the gel was evaluated by measuring the gel turbidity. This type of mineralization of HOS cells, which formed mineralized particles inside the gel, was also observed in a peptide-based hydrogel culture. The mineralized particles were completely diminished by inhibiting the activity of Pit-1, phosphate cotransporter, of the HOS cells. When mouse osteoblast-like MC3T3-E1 cells, which form large and flat mineralized matrices in 2D osteogenic conditions at approximately 3 weeks of culture, were cultured in a 3D collagen gel, they also formed mineralized particles in the gel, similar to those in HOS cells, at approximately 18 days. Thus, osteogenic cells cultured in the 3D collagen gel form mineralized particles over a shorter period, and the mineralization could be easily determined by gel turbidity. This 3D gel culture system of osteogenic cells acts as a useful model for cells forming particle-type mineralized matrices, and we assume that the mineralized particles in the 3D hydrogel are calcospherulites, which are derived from matrix vesicles secreted by osteogenic cells.
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Affiliation(s)
- Takanori Kihara
- Department of Life and Environment Engineering, Faculty of Environmental Engineering, The University of Kitakyushu, Kitakyushu, Fukuoka, Japan
| | - Chiya Umezu
- Department of Life and Environment Engineering, Faculty of Environmental Engineering, The University of Kitakyushu, Kitakyushu, Fukuoka, Japan
| | - Karin Sawada
- Department of Life and Environment Engineering, Faculty of Environmental Engineering, The University of Kitakyushu, Kitakyushu, Fukuoka, Japan
| | - Yukari Furutani
- Department of Life and Environment Engineering, Faculty of Environmental Engineering, The University of Kitakyushu, Kitakyushu, Fukuoka, Japan
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Parreno J, Bianchi VJ, Sermer C, Regmi SC, Backstein D, Schmidt TA, Kandel RA. Adherent agarose mold cultures: An in vitro platform for multi-factorial assessment of passaged chondrocyte redifferentiation. J Orthop Res 2018; 36:2392-2405. [PMID: 29575101 DOI: 10.1002/jor.23896] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Accepted: 03/14/2018] [Indexed: 02/04/2023]
Abstract
Generating the best possible bioengineered cartilage from passaged chondrocytes requires culture condition optimization. In this study, the use of adherent agarose mold (adAM) cultures to support redifferentiation of passaged twice (P2) chondrocytes and serve as a scalable platform to assess the effect of growth factor combinations on proteoglycan accumulation by cells was examined. By 2 days in adAM culture, bovine P2 cells were partially redifferentiated as demonstrated by regression of actin-based dedifferentiation signalling and fibroblast matrix and contractile gene expression. By day 10, aggrecan and type II collagen gene expression were significantly increased in adAM cultured cells. At day 20, a continuous layer of cartilage tissue was observed. There was no evidence of tissue contraction by P2 cells in adAM cultures. The matrix properties of the resultant tissue as well as proteoglycan 4 (PRG4) secreted by the cells were dependent on the initial cell seeding density. AdAM cultures were scalable and culture within small 3 mm diameter adAM allowed for multi-factorial assessment of growth factors on proteoglycan accumulation by human P2 chondrocytes. Although there was a patient specific response in proteoglycan accumulation to the various cocktail combinations, the cocktail consisting of 2 ng/ml TGFβ1, 10 ng/ml FGF2, and 250 ng/ml FGF18 resulted in a consistent increase in alcian blue tissue staining. Additional studies will be required to identify the optimal conditions to bioengineer articular cartilage tissue for clinical use. However, the results to date suggest that adAM cultures may be suitable to use for high throughput assessment. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2392-2405, 2018.
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Affiliation(s)
- Justin Parreno
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada.,Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California
| | - Vanessa J Bianchi
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada.,Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada
| | - Corey Sermer
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada
| | - Suresh C Regmi
- Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
| | - David Backstein
- Division of Orthopaedics, Mount Sinai Hospital, Toronto, ON, Canada
| | - Tannin A Schmidt
- Biomedical Engineering Department, University of Connecticut Health Center, Farmington, Connecticut
| | - Rita A Kandel
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada.,Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada.,Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada.,Pathology and Laboratory Medicine, Mount Sinai Hospital, Toronto, ON, Canada
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7
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Budyn E, Gaci N, Sanders S, Bensidhoum M, Schmidt E, Cinquin B, Tauc P, Petite H. Human Stem Cell Derived Osteocytes in Bone-on-Chip. ACTA ACUST UNITED AC 2018. [DOI: 10.1557/adv.2018.278] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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8
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Plasma assisted surface treatments of biomaterials. Biophys Chem 2017; 229:151-164. [DOI: 10.1016/j.bpc.2017.07.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Revised: 07/06/2017] [Accepted: 07/06/2017] [Indexed: 02/02/2023]
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9
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Bosetti M, Borrone A, Leigheb M, Shastri VP, Cannas M. * Injectable Graft Substitute Active on Bone Tissue Regeneration. Tissue Eng Part A 2017; 23:1413-1422. [PMID: 28530130 DOI: 10.1089/ten.tea.2016.0554] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
With the aim to obtain an injectable bioactive scaffold that can accelerate bone formation in sinus lift augmentation, in bony void and fracture repair, we have developed a three-dimensional (3D) jelly collagen containing lysophosphatidic acid (LPA) and 1α,25-dihydroxyvitamin D3 (1,25D3). Using an in vitro 3D culture model of bone fracture, we show that the contraction of the collagen gel is mediated by Rho-kinase activation in osteoblasts. The gel contraction showed dependence on cell concentration and was increased by LPA, which favored apposition and fastening of bone fragments approach. LPA was shown to act through actin cytoskeleton reorganization and myosin light chain phosphorylation of human primary osteoblasts (hOB). Moreover, LPA conferred osteoconductive properties as evidenced by the induction of proliferation, differentiation, and migration of hOB. The addition of 1,25D3 did not enhance cell-mediated gel contraction, but stimulated the maturation of hOB in vitro through the production of extracellular matrix of higher quality. On the basis of these observations, the collagen gel enriched with LPA and 1,25D3 described herein can be considered an injectable natural scaffold that allows the migration of cells from the side of bone defect and a promising candidate to accelerate bone growth and fracture healing.
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Affiliation(s)
- Michela Bosetti
- 1 Dipartimento di Scienze del Farmaco, Università del Piemonte Orientale , Novara, Italy
| | - Alessia Borrone
- 1 Dipartimento di Scienze del Farmaco, Università del Piemonte Orientale , Novara, Italy
| | - Massimiliano Leigheb
- 2 Department of Orthopaedics and Traumatology, Azienda Ospedaliero-Universitaria Maggiore della Carità , Novara, Italy
| | - V Prasad Shastri
- 3 Institute for Macromolecular Chemistry, University of Freiburg , Freiburg, Germany
| | - Mario Cannas
- 4 Dipartimento di Scienze della Salute, Università del Piemonte Orientale , Novara, Italy
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10
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Wittkowske C, Reilly GC, Lacroix D, Perrault CM. In Vitro Bone Cell Models: Impact of Fluid Shear Stress on Bone Formation. Front Bioeng Biotechnol 2016; 4:87. [PMID: 27896266 PMCID: PMC5108781 DOI: 10.3389/fbioe.2016.00087] [Citation(s) in RCA: 162] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2016] [Accepted: 10/25/2016] [Indexed: 01/06/2023] Open
Abstract
This review describes the role of bone cells and their surrounding matrix in maintaining bone strength through the process of bone remodeling. Subsequently, this work focusses on how bone formation is guided by mechanical forces and fluid shear stress in particular. It has been demonstrated that mechanical stimulation is an important regulator of bone metabolism. Shear stress generated by interstitial fluid flow in the lacunar-canalicular network influences maintenance and healing of bone tissue. Fluid flow is primarily caused by compressive loading of bone as a result of physical activity. Changes in loading, e.g., due to extended periods of bed rest or microgravity in space are associated with altered bone remodeling and formation in vivo. In vitro, it has been reported that bone cells respond to fluid shear stress by releasing osteogenic signaling factors, such as nitric oxide, and prostaglandins. This work focusses on the application of in vitro models to study the effects of fluid flow on bone cell signaling, collagen deposition, and matrix mineralization. Particular attention is given to in vitro set-ups, which allow long-term cell culture and the application of low fluid shear stress. In addition, this review explores what mechanisms influence the orientation of collagen fibers, which determine the anisotropic properties of bone. A better understanding of these mechanisms could facilitate the design of improved tissue-engineered bone implants or more effective bone disease models.
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Affiliation(s)
- Claudia Wittkowske
- Department of Mechanical Engineering, University of Sheffield, Sheffield, UK; INSIGNEO Institute for in silico Medicine, University of Sheffield, Sheffield, UK
| | - Gwendolen C Reilly
- INSIGNEO Institute for in silico Medicine, University of Sheffield, Sheffield, UK; Department of Material Science, University of Sheffield, Sheffield, UK
| | - Damien Lacroix
- Department of Mechanical Engineering, University of Sheffield, Sheffield, UK; INSIGNEO Institute for in silico Medicine, University of Sheffield, Sheffield, UK
| | - Cecile M Perrault
- Department of Mechanical Engineering, University of Sheffield, Sheffield, UK; INSIGNEO Institute for in silico Medicine, University of Sheffield, Sheffield, UK
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11
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MRTF-A signaling regulates the acquisition of the contractile phenotype in dedifferentiated chondrocytes. Matrix Biol 2016; 62:3-14. [PMID: 27751947 DOI: 10.1016/j.matbio.2016.10.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 10/09/2016] [Accepted: 10/10/2016] [Indexed: 11/22/2022]
Abstract
Chondrocyte culture as a monolayer for cell number expansion results in dedifferentiation whereby expanded cells acquire contractile features and increased actin polymerization status. This study determined whether the actin polymerization based signaling pathway, myocardin-related transcription factor-a (MRTF-A) is involved in regulating this contractile phenotype. Serial passaging of chondrocytes in monolayer culture to passage 2 resulted in increased gene and protein expression of the contractile molecules alpha-smooth muscle actin, transgelin and vinculin compared to non-passaged, primary cells. This resulted in a functional change as passaged 2, but not primary, chondrocytes were capable of contracting type I collagen gels in a stress-relaxed contraction assay. These changes were associated with increased actin polymerization and MRTF-A nuclear localization. The involvement of actin was demonstrated by latrunculin B depolymerization of actin which reversed these changes. Alternatively cytochalasin D which activates MRTF-A increased gene and protein expression of α-smooth muscle actin, transgelin and vinculin, whereas CCG1423 which deactivates MRTF-A decreased these molecules. The involvement of MRTF-A signaling was confirmed by gene silencing of MRTF or its co-factor serum response factor. Knockdown experiments revealed downregulation of α-smooth muscle actin and transgelin gene and protein expression, and inhibition of gel contraction. These findings demonstrate that passaged chondrocytes acquire a contractile phenotype and that this change is modulated by the actin-MRTF-A-serum response factor signaling pathway.
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12
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An easy-to-use and versatile method for building cell-laden microfibres. Sci Rep 2016; 6:33328. [PMID: 27616467 PMCID: PMC5018858 DOI: 10.1038/srep33328] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 07/26/2016] [Indexed: 02/06/2023] Open
Abstract
Fibre-shaped materials are useful for creating different functional three-dimensional (3D) structures that could mimic complex tissues. Several methods (e.g. extrusion, laminar flow or electrospinning) have been proposed for building hydrogel microfibres, with distinctive cell types and with different degrees of complexity. However, these methods require numerous protocol adaptations in order to achieve fibre fabricating and lack the ability to control microfibre alignment. Here, we present a simple method for the production of microfibers, based on a core shell approach, composed of calcium alginate and type I collagen. The process presented here allows the removal of the calcium alginate shell, after only 24 hours of culture, leading to stable and reproducible fibre shaped cellular constructs. With time of culture cells show to distribute preferentially to the surface of the fibre and display a uniform cellular orientation. Moreover, when cultured inside the fibres, murine bone marrow mesenchymal stem cells show the capacity to differentiate towards the osteoblastic lineage, under non-osteoinductive culture conditions. This work establishes a novel method for cellular fibre fabrication that due to its inherent simplicity can be easily upscaled and applied to other cell types.
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Włodarczyk-Biegun MK, Farbod K, Werten MWT, Slingerland CJ, de Wolf FA, van den Beucken JJJP, Leeuwenburgh SCG, Cohen Stuart MA, Kamperman M. Fibrous Hydrogels for Cell Encapsulation: A Modular and Supramolecular Approach. PLoS One 2016; 11:e0155625. [PMID: 27223105 PMCID: PMC4880210 DOI: 10.1371/journal.pone.0155625] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Accepted: 05/01/2016] [Indexed: 12/25/2022] Open
Abstract
Artificial 3-dimensional (3D) cell culture systems, which mimic the extracellular matrix (ECM), hold great potential as models to study cellular processes under controlled conditions. The natural ECM is a 3D structure composed of a fibrous hydrogel that provides both mechanical and biochemical cues to instruct cell behavior. Here we present an ECM-mimicking genetically engineered protein-based hydrogel as a 3D cell culture system that combines several key features: (1) Mild and straightforward encapsulation meters (1) ease of ut I am not so sure.encapsulation of the cells, without the need of an external crosslinker. (2) Supramolecular assembly resulting in a fibrous architecture that recapitulates some of the unique mechanical characteristics of the ECM, i.e. strain-stiffening and self-healing behavior. (3) A modular approach allowing controlled incorporation of the biochemical cue density (integrin binding RGD domains). We tested the gels by encapsulating MG-63 osteoblastic cells and found that encapsulated cells not only respond to higher RGD density, but also to overall gel concentration. Cells in 1% and 2% (weight fraction) protein gels showed spreading and proliferation, provided a relative RGD density of at least 50%. In contrast, in 4% gels very little spreading and proliferation occurred, even for a relative RGD density of 100%. The independent control over both mechanical and biochemical cues obtained in this modular approach renders our hydrogels suitable to study cellular responses under highly defined conditions.
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Affiliation(s)
| | - Kambiz Farbod
- Department of Biomaterials, Radboud University Medical Center, Nijmegen, The Netherlands
| | | | - Cornelis J. Slingerland
- Physical Chemistry and Soft Matter, Wageningen University & Research, Wageningen, The Netherlands
| | - Frits A. de Wolf
- Wageningen UR Food & Biobased Research, Wageningen, The Netherlands
| | | | | | - Martien A. Cohen Stuart
- Physical Chemistry and Soft Matter, Wageningen University & Research, Wageningen, The Netherlands
| | - Marleen Kamperman
- Physical Chemistry and Soft Matter, Wageningen University & Research, Wageningen, The Netherlands
- * E-mail:
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14
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Price JC, Roach P, El Haj AJ. Liquid Crystalline Ordered Collagen Substrates for Applications in Tissue Engineering. ACS Biomater Sci Eng 2016; 2:625-633. [DOI: 10.1021/acsbiomaterials.6b00030] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Joshua C Price
- ISTM
Guy Hilton Research Centre, Keele University, Thornburrow Drive, Stoke on Trent ST4 7QB, United Kingdom
| | - Paul Roach
- ISTM
Guy Hilton Research Centre, Keele University, Thornburrow Drive, Stoke on Trent ST4 7QB, United Kingdom
| | - Alicia J El Haj
- ISTM
Guy Hilton Research Centre, Keele University, Thornburrow Drive, Stoke on Trent ST4 7QB, United Kingdom
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15
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Zhang M, Manchanda PK, Wu D, Wang Q, Kirschner LS. Knockdown of PRKAR1A, the gene responsible for Carney complex, interferes with differentiation in osteoblastic cells. Mol Endocrinol 2014; 28:295-307. [PMID: 24506536 DOI: 10.1210/me.2013-1152] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
PRKAR1A is the gene encoding the type 1A regulatory subunit of protein kinase A, and it is the cause of the inherited human tumor syndrome Carney complex. Data from our laboratory has demonstrated that Prkar1a loss causes tumors in multiple cell lineages, including neural crest cells and osteoblasts. We have proposed that one mechanism by which tumorigenesis occurs is through the failure of terminal differentiation. In the present study, we directly test the effects of Prkar1a reduction on osteogenic differentiation in mouse and human cells in vitro. We found that Prkar1a levels noticeably increased during osteoblastic differentiation, indicating a positive correlation between the expression of Prkar1a and osteogenic potential. To validate this hypothesis, we generated stable Prkar1a knockdown in both mouse and human cells. These cells displayed significantly suppressed bone nodule formation and decreased expression of osteoblast markers such as osteocalcin and osteopontin. These observations imply that the antiosteogenic effect of Prkar1a ablation is not species or cell line specific. Furthermore, because Runt-related transcription factor-2 (Runx2) is a key mediator of osteoblast differentiation, we reasoned that the function of this transcription factor may be inhibited by Prkar1a knockdown. Chromatin immunoprecipitation and luciferase assays demonstrated that Prkar1a ablation repressed DNA binding and function of Runx2 at its target genes. Additionally, we determined that this effect is likely due to reductions in the Runx2-cooperating transcription factors forkhead box O1 and activating transcription factor 4. Taken together, this study provides direct evidence that ablation of Prkar1a interferes with signaling pathways necessary for osteoblast differentiation.
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Affiliation(s)
- Mei Zhang
- Departments of Molecular, Virology, Immunology, and Medical Genetics (M.Z., P.K.M., L.S.K.) and Molecular and Cellular Biochemistry (D.W., Q.W.) and Division of Endocrinology, Diabetes, and Metabolism (L.S.K.), The Ohio State University, Columbus, Ohio 43210
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Fong G, Backman LJ, Hart DA, Danielson P, McCormack B, Scott A. Substance P enhances collagen remodeling and MMP-3 expression by human tenocytes. J Orthop Res 2013; 31:91-8. [PMID: 22836729 PMCID: PMC3959169 DOI: 10.1002/jor.22191] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Accepted: 06/25/2012] [Indexed: 02/06/2023]
Abstract
The loss of collagen organization is considered a hallmark histopathologic feature of tendinosis. At the cellular level, tenocytes have been shown to produce signal substances that were once thought to be restricted to neurons. One of the main neuropeptides implicated in tendinosis, substance P (SP), is known to influence collagen organization, particularly after injury. The aim of this study was to examine the influence of SP on collagen remodeling by primary human tendon cells cultured in vitro in three-dimensional collagen lattices. We found that SP stimulation led to an increased rate of collagen remodeling mediated via the neurokinin-1 receptor (NK-1 R), the preferred cell receptor for SP. Gene expression analysis showed that SP stimulation resulted in significant increases in MMP3, COL3A1 and ACTA2 mRNA levels in the collagen lattices. Furthermore, cyclic tensile loading of tendon cell cultures along with the administration of exogenous SP had an additive effect on MMP3 expression. Immunoblotting confirmed that SP increased MMP3 protein levels via the NK-1 R. This study indicates that SP, mediated via NK-1 R, increases collagen remodeling and leads to increased MMP3 mRNA and protein expression that is further enhanced by cyclic mechanical loading.
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Affiliation(s)
- Gloria Fong
- Dept. of Physical Therapy, University of British Columbia, Vancouver, BC, Canada,Dept. of Integrative Medical Biology, Anatomy, Umeå University, Umeå, Sweden,Centre for Hip Health and Mobility, Vancouver Coastal Health and Research Institute, Vancouver, BC, Canada
| | - Ludvig J. Backman
- Dept. of Integrative Medical Biology, Anatomy, Umeå University, Umeå, Sweden
| | - David A. Hart
- Centre for Hip Health and Mobility, Vancouver Coastal Health and Research Institute, Vancouver, BC, Canada,McCaig Institute for Bone and Joint Health, University of Calgary, Calgary, AB, Canada
| | - Patrik Danielson
- Dept. of Integrative Medical Biology, Anatomy, Umeå University, Umeå, Sweden
| | - Bob McCormack
- Centre for Hip Health and Mobility, Vancouver Coastal Health and Research Institute, Vancouver, BC, Canada
| | - Alex Scott
- Dept. of Physical Therapy, University of British Columbia, Vancouver, BC, Canada,Centre for Hip Health and Mobility, Vancouver Coastal Health and Research Institute, Vancouver, BC, Canada,Correspondence to: Alex Scott, PhD, Dept. of Physical Therapy, University of British Columbia, Vancouver, BC, Canada, , phone: +1 604 875 4111 Ext. 21810, fax: +1 604 675 2576
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Achari Y, Reno CR, Frank CB, Hart DA. Carrageenan-induced transient inflammation in a rabbit knee model: molecular changes consistent with an early osteoarthritis phenotype. Inflamm Res 2012; 61:907-14. [DOI: 10.1007/s00011-012-0483-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Revised: 04/18/2012] [Accepted: 04/20/2012] [Indexed: 01/12/2023] Open
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Bone biomimetic microenvironment induces osteogenic differentiation of adipose tissue-derived mesenchymal stem cells. NANOMEDICINE-NANOTECHNOLOGY BIOLOGY AND MEDICINE 2012; 8:507-15. [DOI: 10.1016/j.nano.2011.07.012] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Accepted: 07/23/2011] [Indexed: 01/21/2023]
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19
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Barthelemi S, Robinet J, Garnotel R, Antonicelli F, Schittly E, Hornebeck W, Lorimier S. Mechanical forces-induced human osteoblasts differentiation involves MMP-2/MMP-13/MT1-MMP proteolytic cascade. J Cell Biochem 2012; 113:760-72. [DOI: 10.1002/jcb.23401] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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Monument MJ, Hart DA, Befus AD, Salo PT, Zhang M, Hildebrand KA. The mast cell stabilizer ketotifen reduces joint capsule fibrosis in a rabbit model of post-traumatic joint contractures. Inflamm Res 2011; 61:285-92. [PMID: 22173279 DOI: 10.1007/s00011-011-0409-3] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2011] [Revised: 11/22/2011] [Accepted: 11/28/2011] [Indexed: 10/14/2022] Open
Abstract
OBJECTIVES Using a rabbit model of post-traumatic joint contractures, we investigated whether treatment with a mast cell stabilizer after joint injury would lessen the molecular manifestations of joint capsule fibrosis. METHODS Surgical joint injury was used to create stable post-traumatic contractures of the knee in skeletally mature New Zealand white rabbits. Four groups of animals were studied: a non-operated control group (n = 8), an operated contracture group (n = 13) and two operated groups treated with the mast cell stabilizer, ketotifen, at doses of 0.5 mg/kg (n = 9) and 1.0 mg/kg (n = 9) twice daily. Joint capsule fibrosis was assessed by quantifying the mRNA and protein levels of α-SMA, tryptase, TGF-β1, collagen I and collagen III. Significance was tested using an ANOVA analysis of variance. RESULTS The protein and mRNA levels of α-SMA, TGF-β1, tryptase and collagen I and III were significantly elevated in the operated contracture group compared to control (p < 0.01). In both ketotifen-treated groups, protein and mRNA levels of α-SMA, TGF-β1 and collagen I were significantly reduced compared to the operated contracture group (p < 0.01). CONCLUSIONS These data suggest an inflammatory pathway mediated by mast cell activation is involved in joint capsule fibrosis after traumatic injury.
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Affiliation(s)
- Michael J Monument
- Division of Orthopaedic Surgery, Faculty of Medicine, McCaig Institute for Bone and Joint Health, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada.
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21
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Huebner KD, O'Brien EJO, Heard BJ, Chung M, Achari Y, Shrive NG, Frank CB. Post-natal molecular adaptations in anteromedial and posterolateral bundles of the ovine anterior cruciate ligament: one structure with two parts or two distinct ligaments? Connect Tissue Res 2011; 53:277-84. [PMID: 22148917 DOI: 10.3109/03008207.2011.637652] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The human anterior cruciate ligament (ACL) is a composite structure of two anatomically distinct bundles: an anteromedial (AM) and posterolateral (PL) bundles. Tendons are often used as autografts for surgical reconstruction of ACL following severe injury. However, despite successful surgical reconstruction, some people experience re-rupture and later development of osteoarthritis. Understanding the structure and molecular makeup of normal ACL is essential for its optimal replacement. Reportedly the two bundles display different tensions throughout joint motion and may be fundamentally different. This study assessed the similarities and differences in ultrastructure and molecular composition of the AM and PL bundles to test the hypothesis that the two bundles of the ACL develop unique characteristics with maturation. ACLs from nine mature and six immature sheep were compared. The bundles were examined for mRNA and protein levels of collagen types I, III, V, and VI, and two proteoglycans. The fibril diameter composition of the two bundles was examined with transmission electron microscopy. Maturation does alter the molecular and structural composition of the two bundles of ACL. Although the PL band appears to mature slower than the AM band, no significant differences were detected between the bundles in the mature animals. We thus reject our hypothesis that the two ACL bundles are distinct. The two anatomically distinct bundles of the sheep ACL can be considered as two parts of one structure at maturity and material that would result in a structure of similar functionality can be used to replace each ACL bundle in the sheep.
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Affiliation(s)
- Kyla D Huebner
- McCaig Institute for Bone & Joint Health, Faculty of Medicine, University of Calgary, Calgary, AL, Canada
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22
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Chicatun F, Pedraza CE, Ghezzi CE, Marelli B, Kaartinen MT, McKee MD, Nazhat SN. Osteoid-mimicking dense collagen/chitosan hybrid gels. Biomacromolecules 2011; 12:2946-56. [PMID: 21661759 DOI: 10.1021/bm200528z] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Bone extracellular matrix (ECM) is a 3D network, composed of collagen type I and a number of other macromolecules, including glycosaminoglycans (GAGs), which stimulate signaling pathways that regulate osteoblast growth and differentiation. To model the ECM of bone for tissue regenerative approaches, dense collagen/chitosan (Coll/CTS) hybrid hydrogels were developed using different proportions of CTS to mimic GAG components of the ECM. MC3T3-E1 mouse calvaria preosteoblasts were seeded within plastically compressed Coll/CTS hydrogels with solid content approaching that of native bone osteoid. Dense, cellular Coll/CTS hybrids were maintained for up to 8 weeks under either basal or osteogenic conditions. Higher CTS content significantly increased gel resistance to collagenase degradation. The incorporation of CTS to collagen gels decreased the apparent tensile modulus from 1.82 to 0.33 MPa. In contrast, the compressive modulus of Coll/CTS hybrids increased in direct proportion to CTS content exhibiting an increase from 23.50 to 55.25 kPa. CTS incorporation also led to an increase in scaffold resistance to cell-induced contraction. MC3T3-E1 viability, proliferation, and matrix remodeling capability (via matrix metalloproteinase expression) were maintained. Alkaline phosphatase activity was increased up to two-fold, and quantification of phosphate mineral deposition was significantly increased with CTS incorporation. Thus, dense Coll/CTS scaffolds provide osteoid-like models for the study of osteoblast differentiation and bone tissue engineering.
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Affiliation(s)
- Florencia Chicatun
- Department of Mining and Materials Engineering, Faculty of Engineering, McGill University, Montreal, Quebec, Canada H3A 2B2
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Niinaka Y, Harada K, Fujimuro M, Oda M, Haga A, Hosoki M, Uzawa N, Arai N, Yamaguchi S, Yamashiro M, Raz A. Silencing of autocrine motility factor induces mesenchymal-to-epithelial transition and suppression of osteosarcoma pulmonary metastasis. Cancer Res 2010; 70:9483-93. [PMID: 20978190 DOI: 10.1158/0008-5472.can-09-3880] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Phosphoglucose isomerase (PGI) is a multifunctional enzyme that functions in glucose metabolism as a glycolytic enzyme catalyzing an interconversion between glucose and fructose inside the cell, while it acts as cytokine outside the cell, with properties that include autocrine motility factor (AMF)-regulating tumor cell motility. Overexpression of AMF/PGI induces epithelial-to-mesenchymal transition with enhanced malignancy. Recent studies have revealed that silencing of AMF/PGI resulted in mesenchymal-to-epithelial transition (MET) of human lung fibrosarcoma cells and breast cancer cells with reduced malignancy. Here, we constructed a hammerhead ribozyme specific against GUC triplet at the position G390 in the human, mouse, and rat AMF/PGI mRNA sequence. Mesenchymal human osteosarcoma MG-63, HS-Os-1, and murine LM8 cells were stably transfected with the ribozyme specific for AMF/PGI. The stable transfectant cells showed effective downregulation of AMF/PGI expression and subsequent abrogation of AMF/PGI secretion, which resulted in morphologic change with reduced growth, motility, and invasion. Silencing of AMF/PGI induced MET, in which upregulation of E-cadherin and cytokeratins, as well as downregulation of vimentin, were noted. The MET guided by AMF/PGI gene silencing induced osteosarcoma MG-63 to terminally differentiate into mature osteoblasts. Furthermore, MET completely suppressed the tumor growth and pulmonary metastasis of LM8 cells in nude mice. Thus, acquisition of malignancy might be completed in part by upregulation of AMF/PGI, and waiver of malignancy might also be controlled by downregulation of AMF/PGI.
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Affiliation(s)
- Yasufumi Niinaka
- Department of Oral and Maxillofacial Surgery, Faculty of Medicine, University of Yamanashi, Chuo, Japan.
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Beta-tricalcium phosphate exerts osteoconductivity through α2β1 integrin and down-stream MAPK/ERK signaling pathway. Biochem Biophys Res Commun 2010; 394:323-9. [DOI: 10.1016/j.bbrc.2010.02.178] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2010] [Accepted: 02/27/2010] [Indexed: 11/19/2022]
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Parreno J, Hart DA. Molecular and mechano-biology of collagen gel contraction mediated by human MG-63 cells: involvement of specific intracellular signaling pathways and the cytoskeleton. Biochem Cell Biol 2010; 87:895-904. [PMID: 19935875 DOI: 10.1139/o09-052] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Culture of human osteoblast-like MG-63 cells within collagen gels results in the generation of intrinsic stress. Release of such collagen gels from attachment results in gel contraction and enhanced MMP-1, MMP-3, and alpha2 integrin mRNA levels. To understand the potential role of microtubules and signaling pathways involved in MG-63 cell-mediated contraction and gene expression, cells were cultured in collagen gels. After 24 h collagen gels were released, then immediately treated with nocodazole or specific protein kinase inhibitors. Contraction was assessed, RNA isolated, and real-time PCR analysis performed. Treatment with high concentrations of a microtubule depolymerization agent, nocodazole, enhanced early contraction and led to elevated mRNA levels for MMP-3, whereas low concentrations inhibited contraction at later time points and did not affect mRNA levels. ROCK inhibitor treatment (Y27632) inhibited collagen gel contraction and led to depressed mRNA levels. The ERK1/2 inhibitor U0126 did not affect contraction, but treatment led to depressed MMP-1, MMP-3, and alpha2 mRNA levels. The p38MAPK inhibitor SB203580 modestly affected contraction, but did not affect mRNA levels. These results suggest the potential role of cytoskeletal integrity and multiple kinase signaling pathways in specific bone-remodeling events.
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Affiliation(s)
- Justin Parreno
- Department of Laboratory Medicine and Pathobiology, Mount Sinai Hospital, University of Toronto, 600 University Ave., Toronto ON M5X 1G5, Canada
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Polewski MD, Johnson KA, Foster M, Millán JL, Terkeltaub R. Inorganic pyrophosphatase induces type I collagen in osteoblasts. Bone 2010; 46:81-90. [PMID: 19733704 PMCID: PMC2818162 DOI: 10.1016/j.bone.2009.08.055] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/21/2009] [Revised: 08/25/2009] [Accepted: 08/27/2009] [Indexed: 12/11/2022]
Abstract
INTRODUCTION The physiologic selectivity of calcification in bone tissue reflects selective co-expression by osteoblasts of fibrillar collagen I and of tissue nonspecific alkaline phosphatase (TNAP), which hydrolyzes the calcification inhibitor pyrophosphate (PP(i)) and generates phosphate (P(i)). Humans and mice deficient in the PP(i)-generating ecto-enzyme NPP1 demonstrate soft tissue calcification, occurring at sites of extracellular matrix expansion. Significantly, the function in osteoblasts of cytosolic inorganic pyrophosphatase (abbreviated iPP(i)ase), which generates P(i) via PP(i) hydrolysis with neutral pH optimum, remains unknown. We assessed iPP(i)ase in Enpp1(-/-) and wild type (WT) mouse osteoblasts and we tested the hypothesis that iPP(i)ase regulates collagen I expression. METHODS We treated mouse calvarial osteoblasts with ascorbate and beta-glycerol phosphate to promote calcification, and we assessed cytosolic P(i) and PP(i) levels, sodium-dependent P(i) uptake, Pit-1 P(i) co-transporter expression, and iPP(i)ase and TNAP activity and expression. We also assessed the function of transfected Ppa1 in osteoblasts. RESULTS Inorganic pyrophosphatase but not TNAP was elevated in Enpp1(-/-) calvariae in situ. Cultured primary Enpp1(-/-) calvarial osteoblasts demonstrated increased calcification despite flat TNAP activity rather than physiologic TNAP up-regulation seen in WT osteoblasts. Despite decreased cytosolic PP(i) in early culture, Enpp1(-/-) osteoblasts maintained cytosolic P(i) levels comparable to WT osteoblasts, in association with increased iPP(i)ase, enhanced sodium-dependent P(i) uptake and expression of Pit-1, and markedly increased collagen I synthesis. Suppression of collagen synthesis in Enpp1(-/-) osteoblasts using 3,4-dehydroproline markedly suppressed calcification. Last, transfection of Ppa1 in WT osteoblasts increased cytosolic P(i) and decreased cytosolic but not extracellular PP(i), and induced both collagen I synthesis and calcification. CONCLUSIONS Increased iPP(i)ase is associated with "P(i) hunger" and increased calcification by NPP1-deficient osteoblasts. Furthermore, iPP(i)ase induces collagen I at the levels of mRNA expression and synthesis and, unlike TNAP, stimulates calcification by osteoblasts without reducing the extracellular concentration of the hydroxyapatite crystal inhibitor PP(i).
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Affiliation(s)
- Monika D Polewski
- Department of Medicine, Rheumatology Section, VA Health Care System/UCSD, San Diego, CA 92161, USA.
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