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Pardo A, Gomez-Florit M, Davidson MD, Öztürk-Öncel MÖ, Domingues RMA, Burdick JA, Gomes ME. Hierarchical Design of Tissue-Mimetic Fibrillar Hydrogel Scaffolds. Adv Healthc Mater 2024; 13:e2303167. [PMID: 38400658 PMCID: PMC11209813 DOI: 10.1002/adhm.202303167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Revised: 02/05/2024] [Indexed: 02/25/2024]
Abstract
Most tissues of the human body present hierarchical fibrillar extracellular matrices (ECMs) that have a strong influence over their physicochemical properties and biological behavior. Of great interest is the introduction of this fibrillar structure to hydrogels, particularly due to the water-rich composition, cytocompatibility, and tunable properties of this class of biomaterials. Here, the main bottom-up fabrication strategies for the design and production of hierarchical biomimetic fibrillar hydrogels and their most representative applications in the fields of tissue engineering and regenerative medicine are reviewed. For example, the controlled assembly/arrangement of peptides, polymeric micelles, cellulose nanoparticles (NPs), and magnetically responsive nanostructures, among others, into fibrillar hydrogels is discussed, as well as their potential use as fibrillar-like hydrogels (e.g., those from cellulose NPs) with key biofunctionalities such as electrical conductivity or remote stimulation. Finally, the major remaining barriers to the clinical translation of fibrillar hydrogels and potential future directions of research in this field are discussed.
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Affiliation(s)
- Alberto Pardo
- 3B’s Research Group I3Bs - Research Institute on Biomaterials, Biodegradables and Biomimetics University of Minho Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine AvePark - Parque de Ciência e Tecnologia Zona Industrial da Gandra Barco, Guimarães 4805-017, Portugal; ICVS/3B’s - PT Government Associate Laboratory Braga/Guimarães, Portugal; Colloids and Polymers Physics Group, Particle Physics Department, Materials Institute (iMATUS), and Health Research Institute (IDIS), University of Santiago de Compostela, 15782 Santiago de Compostela, Spain
| | - Manuel Gomez-Florit
- Group of Cell Therapy and Tissue Engineering (TERCIT), Research Institute on Health Sciences (IUNICS), University of the Balearic Islands (UIB), Ctra. Valldemossa km 7.5, 07122 Palma, Spain
| | - Matthew D. Davidson
- BioFrontiers Institute and Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, CO 80303, USA
| | - M. Özgen Öztürk-Öncel
- 3B’s Research Group I3Bs - Research Institute on Biomaterials, Biodegradables and Biomimetics University of Minho Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine AvePark - Parque de Ciência e Tecnologia Zona Industrial da Gandra Barco, Guimarães 4805-017, Portugal; ICVS/3B’s - PT Government Associate Laboratory Braga/Guimarães, Portugal
| | - Rui M. A. Domingues
- 3B’s Research Group I3Bs - Research Institute on Biomaterials, Biodegradables and Biomimetics University of Minho Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine AvePark - Parque de Ciência e Tecnologia Zona Industrial da Gandra Barco, Guimarães 4805-017, Portugal; ICVS/3B’s - PT Government Associate Laboratory Braga/Guimarães, Portugal
| | - Jason A. Burdick
- BioFrontiers Institute and Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, CO 80303, USA
| | - Manuela E. Gomes
- 3B’s Research Group I3Bs - Research Institute on Biomaterials, Biodegradables and Biomimetics University of Minho Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine AvePark - Parque de Ciência e Tecnologia Zona Industrial da Gandra Barco, Guimarães 4805-017, Portugal; ICVS/3B’s - PT Government Associate Laboratory Braga/Guimarães, Portugal
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Schaart JM, Kea-Te Lindert M, Roverts R, Nijhuis WH, Sommerdijk N, Akiva A. Cell-induced collagen alignment in a 3D in vitro culture during extracellular matrix production. J Struct Biol 2024; 216:108096. [PMID: 38697586 DOI: 10.1016/j.jsb.2024.108096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Revised: 04/24/2024] [Accepted: 04/27/2024] [Indexed: 05/05/2024]
Abstract
The bone extracellular matrix consists of a highly organized collagen matrix that is mineralized with carbonated hydroxyapatite. Even though the structure and composition of bone have been studied extensively, the mechanisms underlying collagen matrix organization remain elusive. In this study, we used a 3D cell culture system in which osteogenic cells deposit and orient the collagen matrix that is subsequently mineralized. Using live fluorescence imaging combined with volume electron microscopy, we visualize the organization of the cells and collagen in the cell culture. We show that the osteogenically induced cells are organizing the collagen matrix during development. Based on the observation of tunnel-like structures surrounded by aligned collagen in the center of the culture, we propose that osteoblasts organize the deposited collagen during migration through the culture. Overall, we show that cell-matrix interactions are involved in collagen alignment during early-stage osteogenic differentiation and that the matrix is organized by the osteoblasts in the absence of osteoclast activity.
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Affiliation(s)
- Judith M Schaart
- Department of Medical BioSciences, Radboud University Medical Center, Geert Grooteplein Zuid 28, 6525GA Nijmegen, The Netherlands
| | - Mariska Kea-Te Lindert
- Department of Medical BioSciences, Radboud University Medical Center, Geert Grooteplein Zuid 28, 6525GA Nijmegen, The Netherlands; Electron Microscopy Center, Radboudumc Technology Center Microscopy, Radboud University Medical Center, Geert Grooteplein Noord 29, 6525EZ Nijmegen, The Netherlands
| | - Rona Roverts
- Department of Medical BioSciences, Radboud University Medical Center, Geert Grooteplein Zuid 28, 6525GA Nijmegen, The Netherlands; Electron Microscopy Center, Radboudumc Technology Center Microscopy, Radboud University Medical Center, Geert Grooteplein Noord 29, 6525EZ Nijmegen, The Netherlands
| | - Wouter H Nijhuis
- Department of Orthopaedic Surgery, University Medical Centre Utrecht, Wilhelmina Children's Hospital, 3508GA Utrecht, The Netherlands
| | - Nico Sommerdijk
- Department of Medical BioSciences, Radboud University Medical Center, Geert Grooteplein Zuid 28, 6525GA Nijmegen, The Netherlands; Electron Microscopy Center, Radboudumc Technology Center Microscopy, Radboud University Medical Center, Geert Grooteplein Noord 29, 6525EZ Nijmegen, The Netherlands.
| | - Anat Akiva
- Department of Medical BioSciences, Radboud University Medical Center, Geert Grooteplein Zuid 28, 6525GA Nijmegen, The Netherlands; Electron Microscopy Center, Radboudumc Technology Center Microscopy, Radboud University Medical Center, Geert Grooteplein Noord 29, 6525EZ Nijmegen, The Netherlands.
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Engineering collagen fiber templates with oriented nanoarchitecture and concerns on osteoblast behaviors. Int J Biol Macromol 2021; 185:77-86. [PMID: 34139244 DOI: 10.1016/j.ijbiomac.2021.06.072] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 05/26/2021] [Accepted: 06/10/2021] [Indexed: 12/13/2022]
Abstract
Nanostructure provides a closer structural support approximation to native bone architecture for cells and further regulates cell's behavior, resulting in the formation of functional tissues. In this work, three engineering collagen templates with oriented fiber architectures were fabricated via electrospinning (Es), plastic compression and tensile (PCT), and dynamic shear stress (SS) methods. Under the observation of POM, SEM, AFM and TEM, the PCT-template and SS-template are packed with well-oriented nanofibers with the native collagen architecture of 67 nm D-periodicity, and the mechanical properties conferred to the templates are better than that of the Es-template. When mentioning the cell's behavior, MC3T3-E1 adhered to grow along the alignment of collagen fiber orientation when cultured on the PCT-template and SS-template. The SS-template with nano- and micro-ordered architecture guided cells to stretch their plasma along with the orientation of collagen fiber, produce more aligned Type I collagen fibers and promote significantly higher osteogenic differentiation of MC3T3-E1 than the PCT-template and Es-template. Overall, it is strongly argued the feasibility of hierarchical collagen fiber architectures for bone tissue regeneration.
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Sasaki JI, Abe GL, Li A, Matsumoto T, Imazato S. Large three-dimensional cell constructs for tissue engineering. SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 2021; 22:571-582. [PMID: 34408551 PMCID: PMC8366663 DOI: 10.1080/14686996.2021.1945899] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Much research has been conducted on fabricating biomimetic biomaterials in vitro. Tissue engineering approaches are often conducted by combining cells, scaffolds, and growth factors. However, the degradation rate of scaffolds is difficult to control and the degradation byproducts occasionally limit tissue regeneration. To overcome these issues, we have developed a novel system using a thermo-responsive hydrogel that forms scaffold-free, three-dimensional (3D) cell constructs with arbitrary size and morphology. 3D cell constructs prepared using bone marrow-derived stromal stem cells (BMSCs) exhibited self-organizing ability and formed bone-like tissue with endochondral ossification. Endothelial cells were then introduced into the BMSC construct and a vessel-like structure was formed within the constructs. Additionally, the bone formation ability was promoted by endothelial cells and cell constructs could be freeze-dried to improve their clinical application. A pre-treatment with specific protein protectant allowed for the fabrication of novel bone substitutes composed only of cells. This 3D cell construct technology using thermo-responsive hydrogels was then applied to other cell species. Cell constructs composed of dental pulp stem cells were fabricated, and the resulting construct regenerated pulp-like tissue within a human pulpless tooth. In this review, we demonstrate the approaches for the in vitro fabrication of bone and dental pulp-like tissue using thermo-responsive hydrogels and their potential applications.
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Affiliation(s)
- Jun-Ichi Sasaki
- Department of Biomaterials Science, Osaka University Graduate School of Dentistry, Suita, Japan
| | - Gabriela L Abe
- Department of Biomaterials Science, Osaka University Graduate School of Dentistry, Suita, Japan
| | - Aonan Li
- Department of Biomaterials Science, Osaka University Graduate School of Dentistry, Suita, Japan
| | - Takuya Matsumoto
- Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
| | - Satoshi Imazato
- Department of Biomaterials Science, Osaka University Graduate School of Dentistry, Suita, Japan
- Department of Advanced Functional Materials Science, Osaka University Graduate School of Dentistry, Suita, Japan
- CONTACT Satoshi Imazato Department of Biomaterials Science, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka, 565-0871, Japan
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Fabrication of strontium-releasable inorganic cement by incorporation of bioactive glass. Dent Mater 2019; 35:780-788. [DOI: 10.1016/j.dental.2019.02.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2018] [Accepted: 02/13/2019] [Indexed: 02/06/2023]
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Sasaki JI, Katata C, Abe GL, Matsumoto T, Imazato S. Fabricating large-scale three-dimensional constructs with living cells by processing with syringe needles. J Biomed Mater Res A 2019; 107:904-909. [PMID: 30663860 DOI: 10.1002/jbm.a.36613] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Revised: 11/30/2018] [Accepted: 12/26/2018] [Indexed: 12/13/2022]
Abstract
Three-dimensional (3D) cell constructs composed only of cells and cell-secreted extracellular matrix have been attractive biomaterials for tissue engineering technology; however, controlling construct morphology and eliminating dead cells after fabrication remain a challenge. It has been hypothesized that moderate stress could shape constructs and eliminate dead cells. The purpose of this study was to establish an easily available technology for shaping 3D cell constructs and eliminating dead cells postfabrication. To achieve these objectives, spherical cell constructs composed of L-929 fibroblasts were processed using different sized syringe needles. Our results revealed that large-scale rod-shaped cell constructs could be fabricated, and that their diameters could be controlled according to the size of the syringe needle. Additionally, cell viability assays showed that >94% of cells in the rod-shaped constructs were viable, suggesting that dead cells, which have low adhesion force, were dispersed when compressive stress was applied during passage through the needle. The technology described in this study will be promising for future tissue engineering, especially for fabricating elongated tissues such as nerves and blood vessels. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 904-909, 2019.
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Affiliation(s)
- Jun-Ichi Sasaki
- Department of Biomaterials Science, Osaka University Graduate School of Dentistry, Suita 565-0871, Japan
| | - Chihiro Katata
- Department of Biomaterials Science, Osaka University Graduate School of Dentistry, Suita 565-0871, Japan.,Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, Suita 565-0871, Japan
| | - Gabriela L Abe
- Department of Biomaterials Science, Osaka University Graduate School of Dentistry, Suita 565-0871, Japan
| | - Takuya Matsumoto
- Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8525, Japan
| | - Satoshi Imazato
- Department of Biomaterials Science, Osaka University Graduate School of Dentistry, Suita 565-0871, Japan.,Department of Advanced Functional Materials Science, Osaka University Graduate School of Dentistry, Suita 565-0871, Japan
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Noori A, Ashrafi SJ, Vaez-Ghaemi R, Hatamian-Zaremi A, Webster TJ. A review of fibrin and fibrin composites for bone tissue engineering. Int J Nanomedicine 2017; 12:4937-4961. [PMID: 28761338 PMCID: PMC5516781 DOI: 10.2147/ijn.s124671] [Citation(s) in RCA: 260] [Impact Index Per Article: 37.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Tissue engineering has emerged as a new treatment approach for bone repair and regeneration seeking to address limitations associated with current therapies, such as autologous bone grafting. While many bone tissue engineering approaches have traditionally focused on synthetic materials (such as polymers or hydrogels), there has been a lot of excitement surrounding the use of natural materials due to their biologically inspired properties. Fibrin is a natural scaffold formed following tissue injury that initiates hemostasis and provides the initial matrix useful for cell adhesion, migration, proliferation, and differentiation. Fibrin has captured the interest of bone tissue engineers due to its excellent biocompatibility, controllable biodegradability, and ability to deliver cells and biomolecules. Fibrin is particularly appealing because its precursors, fibrinogen, and thrombin, which can be derived from the patient's own blood, enable the fabrication of completely autologous scaffolds. In this article, we highlight the unique properties of fibrin as a scaffolding material to treat bone defects. Moreover, we emphasize its role in bone tissue engineering nanocomposites where approaches further emulate the natural nanostructured features of bone when using fibrin and other nanomaterials. We also review the preparation methods of fibrin glue and then discuss a wide range of fibrin applications in bone tissue engineering. These include the delivery of cells and/or biomolecules to a defect site, distributing cells, and/or growth factors throughout other pre-formed scaffolds and enhancing the physical as well as biological properties of other biomaterials. Thoughts on the future direction of fibrin research for bone tissue engineering are also presented. In the future, the development of fibrin precursors as recombinant proteins will solve problems associated with using multiple or single-donor fibrin glue, and the combination of nanomaterials that allow for the incorporation of biomolecules with fibrin will significantly improve the efficacy of fibrin for numerous bone tissue engineering applications.
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Affiliation(s)
- Alireza Noori
- Department of Tissue Engineering and Applied Cell Sciences, Faculty of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran
| | | | - Roza Vaez-Ghaemi
- Department of Chemical and Biological Engineering, Faculty of Biomedical Engineering, The University of British Columbia, Vancouver, BC, Canada
| | | | - Thomas J Webster
- Department of Chemical Engineering, Northeastern University, Boston, MA, USA
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Scaffold-Free Fabrication of Osteoinductive Cellular Constructs Using Mouse Gingiva-Derived Induced Pluripotent Stem Cells. Stem Cells Int 2016; 2016:6240794. [PMID: 27110251 PMCID: PMC4826709 DOI: 10.1155/2016/6240794] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2015] [Accepted: 02/18/2016] [Indexed: 12/14/2022] Open
Abstract
Three-dimensional (3D) cell constructs are expected to provide osteoinductive materials to develop cell-based therapies for bone regeneration. The proliferation and spontaneous aggregation capability of induced pluripotent stem cells (iPSCs) thus prompted us to fabricate a scaffold-free iPSC construct as a transplantation vehicle. Embryoid bodies of mouse gingival fibroblast-derived iPSCs (GF-iPSCs) were seeded in a cell chamber with a round-bottom well made of a thermoresponsive hydrogel. Collected ball-like cell constructs were cultured in osteogenic induction medium for 30 days with gentle shaking, resulting in significant upregulation of osteogenic marker genes. The constructs consisted of an inner region of unstructured cell mass and an outer osseous tissue region that was surrounded by osteoblast progenitor-like cells. The outer osseous tissue was robustly calcified with elemental calcium and phosphorous as well as hydroxyapatite. Subcutaneous transplantation of the GF-iPSC constructs into immunodeficient mice contributed to extensive ectopic bone formation surrounded by teratoma tissue. These results suggest that mouse GF-iPSCs could facilitate the fabrication of osteoinductive scaffold-free 3D cell constructs, in which the calcified regions and surrounding osteoblasts may function as scaffolds and drivers of osteoinduction, respectively. With incorporation of technologies to inhibit teratoma formation, this system could provide a promising strategy for bone regenerative therapies.
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Wang F, Okawa H, Kamano Y, Niibe K, Kayashima H, Osathanon T, Pavasant P, Saeki M, Yatani H, Egusa H. Controlled Osteogenic Differentiation of Mouse Mesenchymal Stem Cells by Tetracycline-Controlled Transcriptional Activation of Amelogenin. PLoS One 2015; 10:e0145677. [PMID: 26709694 PMCID: PMC4692545 DOI: 10.1371/journal.pone.0145677] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2015] [Accepted: 12/07/2015] [Indexed: 01/25/2023] Open
Abstract
Regenerative dental therapies for bone tissues rely on efficient targeting of endogenous and transplanted mesenchymal stem cells (MSCs) to guide bone formation. Amelogenin is the primary component of Emdogain, which is used to regenerate periodontal defects; however, the mechanisms underlying the therapeutic effects on alveolar bone remain unclear. The tetracycline (Tet)-dependent transcriptional regulatory system is a good candidate to investigate distinct roles of genes of interest during stem cell differentiation. Here, we investigated amelogenin-dependent regulation of osteogenesis in MSCs by establishing a Tet-controlled transcriptional activation system. Clonal mouse bone marrow-derived MSCs were lentivirally transduced with the Tet repressor (TetR) expression vector followed by drug selection to obtain MSCs constitutively expressing TetR (MSCs-TetR). Expression vectors that contained the Tet operator and amelogenin-coding (Amelx) cDNA fragments were constructed using the Gateway system and lentivirally introduced into MSCs-TetR to generate a Tet regulation system in MSCs (MSCs-TetR/Amelx). MSCs-TetR/Amelx significantly overexpressed the Amelx gene and protein in the presence of the tetracycline derivative doxycycline. Concomitant expression of osterix, bone sialoprotein (BSP), osteopontin, and osteocalcin was modulated by addition or removal of doxycycline under osteogenic guidance. During osteogenic induction, MSCs-TetR/Amelx treated with doxycycline showed significantly increased gene expression of osterix, type I collagen, BSP, and osteocalcin in addition to increased alkaline phosphatase activity and mineralized nodule formation. Enhanced extracellular matrix calcification was observed when forced Amelx expression commenced at the early stage but not at the intermediate or late stages of osteogenesis. These results suggest that a Tet-controlled Amelx gene regulation system for mouse MSCs was successfully established, in which transcriptional activation of Amelx was associated with enhanced osteogenic differentiation, especially in the early stage of biomineralization.
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Affiliation(s)
- Fangfang Wang
- Department of Fixed Prosthodontics, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan
| | - Hiroko Okawa
- Department of Fixed Prosthodontics, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan
- Division of Molecular and Regenerative Prosthodontics, Tohoku University Graduate School of Dentistry, Sendai, Miyagi, Japan
| | - Yuya Kamano
- Division of Molecular and Regenerative Prosthodontics, Tohoku University Graduate School of Dentistry, Sendai, Miyagi, Japan
| | - Kunimichi Niibe
- Division of Molecular and Regenerative Prosthodontics, Tohoku University Graduate School of Dentistry, Sendai, Miyagi, Japan
| | - Hiroki Kayashima
- Department of Fixed Prosthodontics, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan
| | - Thanaphum Osathanon
- Research Unit of Mineralized Tissue, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand
| | - Prasit Pavasant
- Research Unit of Mineralized Tissue, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand
| | - Makio Saeki
- Division of Dental Pharmacology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Hirofumi Yatani
- Department of Fixed Prosthodontics, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan
| | - Hiroshi Egusa
- Department of Fixed Prosthodontics, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan
- Division of Molecular and Regenerative Prosthodontics, Tohoku University Graduate School of Dentistry, Sendai, Miyagi, Japan
- * E-mail:
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Engineered Fibrin Gels for Parallel Stimulation of Mesenchymal Stem Cell Proangiogenic and Osteogenic Potential. Ann Biomed Eng 2014; 43:2010-21. [PMID: 25527322 DOI: 10.1007/s10439-014-1227-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 12/13/2014] [Indexed: 10/24/2022]
Abstract
Mesenchymal stem/stromal cells (MSCs) are under examination for use in cell therapies to repair bone defects resulting from trauma or disease. MSCs secrete proangiogenic cues and can be induced to differentiate into bone-forming osteoblasts, yet there is limited evidence that these events can be achieved in parallel. Manipulation of the cell delivery vehicle properties represents a candidate approach for directing MSC function in bone healing. We hypothesized that the biophysical properties of a fibrin gel could simultaneously regulate the proangiogenic and osteogenic potential of entrapped MSCs. Fibrin gels were formed by supplementation with NaCl (1.2, 2.3, and 3.9% w/v) to modulate gel biophysical properties without altering protein concentrations. MSCs entrapped in 1.2% w/v NaCl gels were the most proangiogenic in vitro, yet cells in 3.9% w/v gels exhibited the greatest osteogenic response. Compared to the other groups, MSCs entrapped in 2.3% w/v gels provided the best balance between proangiogenic potential, osteogenic potential, and gel contractility. The contribution of MSCs to bone repair was then examined when deployed in 2.3% w/v NaCl gels and implanted into an irradiated orthotopic bone defect. Compared to acellular gels after 3 weeks of implantation, defects treated with MSC-loaded fibrin gels exhibited significant increases in vessel density, early osteogenesis, superior morphology, and increased cellularity of repair tissue. Defects treated with MSC-loaded gels exhibited increased bone formation after 12 weeks compared to blank gels. These results confirm that fibrin gel properties can be modulated to simultaneously promote both the proangiogenic and osteogenic potential of MSCs, and fibrin gels modified by supplementation with NaCl are promising carriers for MSCs to stimulate bone repair in vivo.
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