| IntroductionLigaments and tendons are frequently injured during sports and other rigorous physical activities, and often fail to heal optimally. Due to the limited regenerative capacity of ligaments and tendons, healing is often accompanied with fibrotic scar tissue formation. Currently, autografts, allografts, xenografts and ligament prostheses have been used for repairing ligament and tendon injuries. However, these graft reconstructive techniques have various drawbacks such as donor site morbidity, disease transmission, immunological rejection, and poor graft integration. Hence, more appropriate reconstructive techniques for tendon and ligament repair need to be developed.Transplanted cells (teddon-derived fibroblasts, skin-derived fibroblast, BMSCs, ESCs and IPSs) are a crucial component of tissue engineering and should ideally be able to influence the regeneration of injured tendons by enhancing cell proliferation and deposition of appropriate extracellular matrix. Tendon-derived tendon stem/progenitor cells (TSPCs) have great potential for the repair and regeneration of tendon injuries. Another key issue of tendon tissue engineering is cytokine. Previous study showed that TSPCs not only had the character of stem cell, but also owned the high expression of tendon-related genes and protein. More research are needed to explore the feasibility of exogenous TSPCs transplantation. In other hand, how to mobilize the autogeneic cell is another problem in the research of tendon repair.Stromal cell-derived factor-1 (SDF-1), as a major cytokine that regulates stem cell homing, may be potential to initiate in situ regeneration by recruiting host stem cells. The TSPCs/SDF-1 modified scaffold fomed a novel tendon tissue engineering product. We further investigated the role of modified scaffolds in promoting tendon regeneration in animal models. Our study will bring a new approach for treatment of tendon injuries.In recent years, tissue engineering constructs have been developed to aid the regeneration of tendon injury, which combines biodegradable biomaterials, cell, growth factors/cytokines. Collagen sponges were incorporated into knitted silk to form a practical composite scaffold for ligament and tendon tissue engineering in our group. The silk fibers provided sufficient mechanical strength, while collagen sponges encouraged in-growth of surrounding tissues and enhanced neo-tendon regeneration by promoting extracellular matrix gene expression and collagen fibril assembly. Although this scaffold could improve ligament repair, the structure and function of the repaired ligament was much inferior to those of normal ligament.Our study include three stages:stage 1 to isolate and identify of TSPCs; stage 2 to investigate TSPC-seeded knitted silk-collagen sponge scaffold for tendon repair; stage 3 to fabricate a composite scaffold by rolling up a knitted silk-collagen sponge scaffold mesh with rhSDF-1 alpha and evaluate the role of composite scaffold on tendon repair.Stage 1 Isolation and identification of TSPCsAim:Tendon stem/progenitor cells (TSPCs) were recently identified within tendon tissues. The aim of this study was to investigate the isolation and identification ofTSPCs.Methods and results:The multi-differentiation and proliferation of TSPC were investigated in vitro. And the results showed that TSPCs exhibited universal stem cell characteristics (i.e. clonogenicity, high proliferative capacity and multi-differentiation potential).Conclusion:This study thus demonstrated that the TSPC exhited multi-differentiation potential. Hence, TSPC can be a clinically useful application for tendon tissue engineering.Stage 2 Allogenous tendon stem/progenitor cells (TSPCs) in silk-collagen scaffold for functional shoulder repairAim:The aim of this study was to investigate TSPC-seeded knitted silk-collagen sponge scaffold for functional shoulder repair.Methods and results:The efficacy of TSPC-seeded knitted silk-collagen sponge scaffolds in promoting rotator cuff regeneration was evaluated in vivo within a rabbit model. Implantation of allogenous TSPC-seeded scaffolds within a rabbit rotator cuff injury model did not elicit an immunological reaction, but instead increased fibroblastic cell ingrowth and reduced infiltration of inflammatory cells within the implantation sites at 4 and 8 weeks post-surgery. After 12 weeks, the allogenous TSPC-treated group exhibited increased collagen deposition and had better structural and biomechanical properties compared to the control group.Conclusion:This study thus demonstrated that the allogenous TSPC-seeded knitted silk-collagen sponge scaffold enhanced the efficacy of rotator cuff tendon regeneration by differentiating into tenocytes, and by secreting anti-inflammatory cytokines that prevent immunological rejection. Hence, allogenous TSPC-seeded knitted silk-collagen sponge scaffolds can be a clinically useful application for tendon tissue engineering.Stage 3 Incorporation of exogenous stromal cell-derived factor-1 alpha within a knitted silk-collagen sponge scaffold enhances tendon regenerationAim:This study developed a bioactive knitted silk-collagen sponge scaffold by incorporation of exogenous SDF-1 alpha, to enable selective migration and homing of cells for in situ tendon regeneration.Methods and results:With in vitro studies, it was observed that CXCR4 gene expression and migration of bone mesenchymal stromal cells and hypodermal fibroblasts were more sensitive to exogenous SDF-1 alpha, while expression of tendon repair gene markers by hypodermal fibroblasts and Achilles tendon fibroblasts were more sensitive to exogenous SDF-1 alpha. With a rat Achilles tendon injury model, exogenous SDF-1 alpha was shown to reduce infiltration of inflammatory cells and enhance migration of fibroblast-like cells into the scaffold at 4 days and 1 week post-surgery. After 4 weeks, SDF-1 alpha treated tendon had increased expression of tendon repair gene markers and endogenous SDF-1 alpha, exhibited more physiological microstructures with larger diameter collagen fibrils, and had better biomechanical properties than the control group.Conclusion:Hence, our bioactive scaffold improved efficacy of tendon regeneration by increasing the recruitment of fibroblast-like cells, enhancing local endogenous SDF-1 alpha and tendon extracellular matrix production, and decreasing accumulation of inflammatory cells. Incorporation of SDF-1 alpha within a knitted silk-collagen sponge scaffold can therefore be a practical application for tendon tissue engineering. |
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