Supportive angiogenic and osteogenic differentiation of mesenchymal stromal cells and endothelial cells in monolayer and co-cultures

Sites of implantation with compromised biology may be unable to achieve the required level of angiogenic and osteogenic regeneration. The specific function and contribution of different cell types to the formation of prevascularized, osteogenic networks in co-culture remains unclear. To determine how bone marrow-derived mesenchymal stromal cells (BMSCs) and endothelial cells (ECs) contribute to cellular proangiogenic differentiation, we analysed the differentiation of BMSCs and ECs in standardized monolayer, Transwell and co-cultures. BMSCs were derived from the iliac bone marrow of five patients, characterized and differentiated in standardized monolayers, permeable Transwells and co-cultures with human umbilical vein ECs (HUVECs). The expression levels of CD31, von Willebrand factor, osteonectin (ON) and Runx2 were assessed by quantitative reverse transcriptase polymerase chain reaction. The protein expression of alkaline phosphatase, ON and CD31 was demonstrated via histochemical and immunofluorescence analysis. The results showed that BMSCs and HUVECs were able to retain their lineage-specific osteogenic and angiogenic differentiation in direct and indirect co-cultures. In addition, BMSCs demonstrated a supportive expression of angiogenic function in co-culture, while HUVEC was able to improve the expression of osteogenic marker molecules in BMSCs. Interaction between developing blood vessel and bone marrow cells may improve the quality of engineered bone grafts. Florian Böhrnsen and Henning Schliephake at Germany’s University of Göttingen cultured bone marrow stem cells and cells from blood vessels together and separately, and analyzed how they differentiated. Even when grown together, cells retained their ability to differentiate into bone marrow and blood vessels, respectively. The expression of differentiation markers was increased in the co-cultures, suggesting that the two cell types reinforce each other’s differentiation. Furthermore, the presence of bone marrow cells encouraged structured growth of the blood vessels. Understanding the beneficial interactions between these two cell types is important in efforts to engineer bone grafts with a blood vessel network, and will improve our ability to successfully engineer and implant bone tissue.