Experimental Study Of Wnt3a Regulating The Osteogenesis Of Rat Bone Marrow Mesenchymal Stem Cells

BACKGROUND: Wnt signaling pathways have shown various biological functions in recent studies. Many studies showed that the Wnt signaling pathways , not only the canonical Wnt signaling pathway but the noncanonical pathway, play a very important role in osteogenesis of MSCs. This study observes the effects of canonical Wnt signaling pathway on differentiation of bone marrow mesenchymal stem cells (BMSCs) into osteoblasts.METHODS: 6 newborn Sprague Dawley rats were selected to prepare BMSCs, from the experimental animal center of Tongji medical college of Huazhong University of Science and Technology. Wnt3a (PeproTech, USA) was used in this study. The cytological, in vitro:The third passage of BMSCs at a density of 5×10⁷ L^-1 were incubated in 2.0 mL of osteoinductive medium, supplemented with 10^-8mol/L dexamethasone, 10 mol/Lβ-glycerophosphoric acid, and 50 mg/L vitamin C. The MSCs were divided into three groups. A Groups: Wnt3a was added with 10mg/l from the 8^th day to the 10th day. B Groups: Wnt3a was added with 10mg/l from the 18^th day to the 20^th day. C Groups: the control groups were treated with osteoinductive medium only. The following parameters were measured: surface marker expression of BMSCs; results of alkaline phosphatase staining; results from quantitative analysis of alkaline phosphatase.RESULTS: Positive rate of CD44 and CD90 were respectively 94.88% and 94.37% in BMSCs at passage 3, and the positive rate of CD45 was only 0.95%. At 11^th day, A Groups compared with the B and C Groups, showed a higher activity of alkaline phosphatase (P<0.01). However, the B Groups showed a lower activity of alkaline phosphatase (P<0.01) at 21^st days.CONCLUSION: The osteogenesis of rat mesenchymal stem cells is regulated by canonical Wnt signaling pathway, which is depends on the differentiation stage of target cells. The canonical Wnt signaling pathway enhances the osteogenic differentiation of BMSCs which have committed to osteogenic lineage and suppresses the terminal differentiation of mature osteoblasts.