PLATELET-DERIVED GROWTH-FACTOR BLOCKS THE CELL-CYCLE TRANSITION FROM THE G(0) TO G(1) 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 (increas ing the cell numbers) at the progression phase. These changes in the r esponses to PDGF-BB were due to the phenotype-dependent expression of PDGF beta-receptor (PDGFR-beta) on EC because PDGFR-beta-like immunore activity was observed in the angiogenic EC forming a tube-like structu re in 35-day culture with 10% fetal bovine serum, but not in the proli ferative EC in 5-day culture. To elucidate the functional role of PDGF R-beta 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 G(0) to G(1) phase in the 35-day cultured EC, although no effect was observed on a ny phases of the cell cycle in 5-day culture. We conclude that 1) PDGF R-beta 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.