Influence of mesenchymal stem cells with endothelial progenitor cells in co-culture on osteogenesis and angiogenesis: an in vitro study.

BACKGROUND AND AIMS: Bone is a highly vascularized tissue reliant on the close spatial and temporal connection between blood vessels and bone cells to maintain skeletal integrity. Considering the intricate connection between osteogenesis and angiogenesis, it is not surprising that communication between mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs) is one of the most important cellular interactions that orchestrates bone formation. The aim of this study was to evaluate the interaction of co-cultured bone marrow-derived endothelial progenitor cells (BM-EPCs) and mesenchymal stem cells (MSCs) in angiogenesis and osteogenesis in vitro.

METHODS: MSCs and BM-EPCs were isolated from bone marrow of dogs' iliac crest using density gradient centrifugation combined with adhesion method and identified with surface markers, cell proliferation and immunocytochemistry in vitro. We used the direct contact method of MSCs and BM-EPCs in a co-culture system. Co-cultured cells and non-co-cultured cells were examined using the alkaline phosphatase (ALP) activity assay, matrix mineralization assay, Matrigel 2D assay and gene expression.

RESULTS: ALP activity and calcification of nodules significantly increased in the co-cultured cells compared with MSCs alone after day 3, and tubulogenic activity of the co-cultured cells was also higher than BM-EPCs alone. Expression of bone and angiogenic markers were enhanced beyond expression levels of MSCs and BM-EPCs cultured alone.

CONCLUSIONS: BM-EPCs co-cultured with MSCs can promote osteogenesis and angiogenesis. This co-cultured system may be broadly useful in engineering a variety of other tissue types.