Postnatal vasculogenesis: identification, growth, and function of endothelial progenitors cells from peripheral blood mononuclear cells

To identify best growth conditions for the in vitro differentiation of human peripheral blood mono-nuclear cells (PBMNCs) into endothelial progenitor cells (EPCs), PBMNCs of healthy volunteers were cultured on fibronectin as follows: M199 with VEGF, bFGF, and IGF-I; M199 with bovine retina-derived growth supplement (RDGS); human umbilical vein endothelial cell (HUVEC) conditioned medium; DiI-stained PBMNCs with HUVECs (1:4 ratio) in M199 with RDGS (cocultures system); PHA burst (10μL/106 cells) for 24 h and culture in M199 with RDGF. EPCs were identified by FACS using mAbs for endothelial markers. EPCs migration was determined using a modified Boyden chamber assay and VEGF as chemoattractant. Matrigel was used to assess in vitro angiogenesis capability. Spindle-shaped and attached cells sprouted with growth factors, differentiating in EPCs within 2 weeks and forming cobblestone-like monolayers within 3 weeks. With RDGS, numerous large cell clusters appeared within 1 week but the number of clusters decreased during culture. After stimulation with PHA, many cells clusters and some adherent EC-like cells were observed within 7 days; their number and size increased within 14 days. With HUVEC conditioned medium, spindle-shaped cells were observed after 10 days. FACS confirmed the endothelial phenotype. Cocultures induced the appearance of double-labeled EPCs expressing endothelial antigens starting from 7 days. EPCs were able to migrate in response to VEGF and to incorporate in capillary-like structures formed by HUVECs on Matrigel. PBMNCs are able to differentiate in EPCs when stimulated with appropriate culture conditions. The contact with mature endothelial cells (ECs) makes this process quicker