VEGF - Supplemented extracellular matrix is sufficient to induce endothelial differentiation of human iPSC.

Extracellular matrix (ECM) provides a scaffold for cells and tissues, but also supports organogenesis and tissue remodeling. The required instructive properties of the ECM to interact with cells depend on matrix architecture, structural proteins and functional matrix components such as growth factors, providing spatial, chemical and functional cues. Decellularized ECM (dECM) has been proposed as an instructive material that promotes tissue regeneration. We investigated the instructive ECM elements preserved in dECM and necessary to promote endothelial differentiation of human induced pluripotent stem cells (hiPSC). We show that detergent-decellularized human kidney ECM remains structurally intact and carries a number of heparin-binding growth factors, including FGF2, VEGF, BMP2, HGF, EGF, PDGF-BB and TGFβ, albeit at reduced levels compared to native tissues. Clearance of these heparin-binding factors, or heparan-sulfate proteoclycans from ECM resulted in massively reduced differentiation of hiPSC, suggesting that remaining structural dECM proteins such as laminin, collagen or fibronectin alone are not instructive. In contrast, replenishing dECM with VEGF replaced medium-supplemented VEGF and resulted in more efficient differentiation of hiPSC into endothelial cells, and even in the absence of other culture-supplemented differentiation factors dECM alone was superior to geltrex. In conclusion, conditioning of dECM with specific growth factors acting as functional cues may allow to generate functional niches by selective promotion of cell attachment, survival and differentiation.