Smooth muscle cell growth in monolayer and aortic organ culture is promoted by a nonheparin binding endothelial cell-derived soluble factor/s.

Objective: To characterize endothelial derived soluble factor(s) that regulate neointimal formation in porcine aortic organ cultures.

Methods And Results: Endothelial cell (EC) conditioned medium, collected in preconfluent EC cultures at 4 days after plating, stimulates vascular smooth muscle cell (SMC) growth in cell culture and in the intima of porcine aortic organ cultures. EC conditioned medium was fractionated consecutively by salt precipitation, ion exchange chromatography and affinity chromatography on a heparin column. Heparin column nonbound fraction (HNBF) contains an endothelial cell-derived soluble factor/s (ECDSF) that promotes neointimal formation by increasing intimal SMC (iSMC) proliferation, as detected by BrdU labeling and inhibiting iSMC apoptosis, as shown by TUNEL. Trypsin digestion of HNBF resulted in loss of mitogenic activity. HNBF show a prominent 70-kDa band in SDS-NuPAGE.

Conclusions: Endothelial-derived soluble factor(s) has a molecular weight higher than other growth factors, does not have affinity to heparin, is a protein, at least in the active part of the molecule and increases iSMC number due to increased proliferation and suppression of apoptosis leading to neointimal formation.