Osteogenesis and angiogenesis in vitro by bidirectional induced bone marrow mesenchymal stem cells in rabbits

Abstract

Objective To study the potentials of osteogenesis and angiogenesis in vitro of the co-culture system, including endothelial cells, osteoblasts and bone marrow mesenchymal stem cells (BMSCs), by bidirectional induction. Methods BMSCs were isolated from bone marrow by density gradient centrifugation. The adhesive cells were preserved to passage in culture. The cells were divided into 4 groups: group A (pure BMSCs), group B (osteogenic induced BMSCs), group C (endothelial cells induced BMSCs) and group D (bidirectionally induced BMSCs) . The morphological changes were observed through inverted microscopy during induction. Before and after induction, the expressions of cell surface antigens were tested by flow cytometry. The cells in 4 groups were stained by Alizarin Red to observe calcium nodules. The angiogenesis in vitro by the cells in 4 groups were observed on Matrigel. Results Before induction, CD90, CD 105 and CD44 were mainly expressed on BMSCs. After BMSCs were induced in vitro into endothelial cells for 1 week, the expressions of cell surface antigens, CD90 and CD 105, reduced significantly and those of CD34 and CD 133 rose significantly ( P < 0. 05) . After BMSCs continued to be induced into osteoblasts 1 week later, the flow cytometry showed CD44 and HLA-DR were significantly higher than before (P < 0. 05). No calcium nodules could be observed in groups A and C. The calcium nodules in group D were larger than in group B. In vitro angiogenesis assay revealed that the amount and area of tubes in group B were significantly higher than in group D ( P < 0. 05). No tubes were observed in groups A and B.Conclusions Calcium nodules and vessels can be constructed by the co-culture system of endothelial cells, osteoblasts and BMSCs in vitro through bidirectional induction of BMSCs. Since the bidirectionally induced BMSCs can facilitate combined osteogenesis and angiogenesis in vitro, they may be an ideal kind of seed cells for construction of tissue engineered bone. Key words: Bone marrow cells; Neovascularization; physiologic; Bidirectional induction