Figure 2: Critical cytokines implicated in vasculogenesis. Signaling molecules such as vascular endothelial growth factor (VEGF), stromal derived factor-1 (SDF-1), fibroblast growth factor (FGF), sphingosine-1-phosphate (S1P), endothelial nitric oxide synthase (eNOS), matrix metalloproteinase-9 (MMP9), and transforming growth factor (TGF ) regulate the function of EPCs during vasculogenesis. Pericyte activity during vasculogenesis appears to be modulated by platelet-derived growth factor (PDGF), TGF , and possibly S1P.