Coculture of vascular endothelial cells and adipose-derived stem cells as a source for bone engineering

The interaction between vascular endothelial cells (VECs) and osteoblasts (OBs) is the focus of this recent research. Vascular endothelial cells secrete bone morphogenetic protein, which promotes OB differentiation and stimulates OBs and their precursor cells to secrete vascular endothelial growth factor. Vascular endothelial growth factor is important in angiogenesis and angiopoiesis. Cloning studies have shown that adipose-derived stem cells (ADSCs) have the potential to differentiate into fat, bone, cartilage, and skeletal and smooth muscle cells, among others. Adipose-derived stem cells can express multiple growth factors, including vascular endothelial growth factor and hepatocyte growth factor. Our study examined the influence of coculturing VECs and ADSCs on osteogenic differentiation. Cord blood-derived VECs and ADSCs were isolated from rats and characterized with immunofluorescence staining and morphological observation. Coculture of third-generation ADSCs and VECs was induced for 6 weeks. Cell growth was analyzed using a modified MTT assay. Alkaline phosphatase (ALP) and osteocalcin (OC) was analyzed using immunofluorescence staining. When ADSCs and VECs were cocultured, the absorbance of cells gradually increased, reaching a peak on day 12. The highest absorbance was seen in a coculture system with a ratio of ADSCs and VECs of 1:1. The secretion of ALP and OC gradually increased in these cells and was significantly higher than controls (P < 0.01). Coculturing of ADSCs and VECs at a 1:1 ratio gave the highest secretion of ALP and OC at every time point, and was significantly higher than other groups (P < 0.01). Our results indicated that ADSCs can be induced to osteogenic differentiation by VECs in vitro, suggesting a coculture system of VECs and ADSC as a novel source of cells for bone engineering.