Usefullness of stem cell-produced extracellular matrix as a scaffold

Objectives: To achieve new regenerative therapy with mesenchymal stem cells (MSCs) , it is necessary to regulate the function of MSCs. The transplanted MSCs for tissue regeneration are interacting with its surrounding microenvironment such as extracellular matrix (ECM) or cytokines. ECM may have a potential to induce cell proliferation and differentiation of MSCs. In this study, we evaluated regenerative effect of ECM which MSCs due to be transplanted produce as a scaffold for MSCs in rat bone defect model. Methods: MSCs were isolated from rat femur bone marrows, expanded and characterized for the MSC specific markers by flow cytometry. MSCs were cultured in DMEM containing 10% FBS and 50 µg/ml ascorbic acid to use abundant ECM as a scaffold for the MSCs transplantation. The complex of the MSCs with the ECM (MSCs/ECM group) was transplanted into the rat experimentally created calvarial bone defect. The ECM alone (ECM group) and the MSCs mixed with atelocollagen (MSCs/atelocollagen group) also were implanted into the defects. Calvarial bone formation was evaluated by histological analyses four weeks after the transplantation. Results: Isolated MSCs were positive for STRO-1, p75NGFR and CD105, and negative for CD34 and CD45, suggesting the isolated cells contained a higher percentage of MSCs. One week after surgery, the most blood capillaries were observed in the MSCs/ECM group among the groups tested. Four weeks after surgery, histological analyses showed that the percentage of newly formed bone was significantly increased in the MSCs/ECM group than the MSCs/atelocollagen group and the ECM group. Between the ECM group and MSCs/atelocollagen group, there was no difference of newly formed bone area. Conclusion: The complex between ECM and MSCs promotes new bone formation, which may result from enhanced blood vessel formation. ECM produced by MSCs is suggested to be an adequate scaffold for the MSC transplantation.