Platelet-derived growth factor blocks the cell-cycle transition from the G₀ to G₁ phase in subcultured angiogenic endothelial cells in rat thoracic aorta

Platelet-derived growth factor (PDGF)-BB induces tube formation by the differentiating (tube-forming) endothelial cells (EC) of rat thoracic aorta, although PDGF-BB does not affect the proliferative EC (increasing the cell numbers) at the progression phase. These changes in the responses to PDGF-BB were due to the phenotype-dependent expression of PDGF β-receptor (PDGFR-β) on EC because PDGFR-β-like immunoreactivity was observed in the angiogenic EC forming a tube-like structure in 35-day culture with 10% fetal bovine serum, but not in the proliferative EC in 5-day culture. To elucidate the functional role of PDGFR-β in the alteration of EC phenotype, the influence of PDGF-BB on the cell cycle of EC was investigated by flow cytometry. This analysis demonstrates that PDGF-BB blocks the transition from the G₀ to G₁ phase in the 35-day cultured EC, although no effect was observed on any phases of the cell cycle in 5-day culture. We conclude that 1. PDGFR-β is expressed in mature angiogenic EC of rat aorta, and 2. PDGF-BB may contribute to promotion of the EC differentiation with tubular morphogenesis by inhibiting cell growth.