Pericytes contribute to the stability of the vascular network of osteogenic tissue formed from cell sheet-based constructs

Despite the increased use of cell sheets for tissue engineering, the appli- cation of this new technology for thick tissue reconstruction is being limited by old barriers such as the need to create a pre-vascular net- work to ensure proper nutrient and oxygen supply in vivo. In the pres- ent work, we created a cell sheet-based construct by co-culturing bone marrow-derived osteogenic and pericyte-like cells with human umbili- cal vein endothelial cells (HUVECs) with the purpose of enhancing the in vivo vascularization of newly formed osteogenic tissue. Human bone marrow mesenchymal stromal cells (hBMSCs) were isolated and cul- tured in medium supplemented with osteogenic factors or TGF-b1 to obtain either osteogenic or CD146+ pericyte-like cells. Immunocyto- chemistry analysis of the co-cultures showed organized structures formed by CD146+ hBMSCs and HUVECs over the osteogenic cell sheet, suggesting the existence of cross-talk between the co-cultured cell types. Nude mice were used to test the ability of those constructs to form functional and vascularized osteogenic tissue. Immunohisto- chemistry analysis of cell sheet-based constructs after 1 and 3 weeks of transplantation revealed the integration of HUVECs with neighboring host’s vessels. Additionally, the analysis of the diameter of the blood vessels showed a higher mean diameter for the condition that com- bined pericyte-like cells and HUVECs, reinforcing the advantage of the proposed model regarding blood vessels maturation and stability.