Overexpression of p21Waf-1 in Vascular Smooth Muscle Cells: Regulation of Proliferation, Differentiation, and Cell Size

Abstract

Cyclin-dependent kinase inhibitor p21Waf-1 is recognized as a negative regulator of cell cycle progression, and it possibly mediates cell differentiation and apoptosis. To understand the role of p21Waf-1 in phenotypic modulation of vascular smooth muscle cells (SMC), we induced the overexpression of p21Waf-1 in cultured rat SMC. The recombinant adenovirus vector encoding p21Waf-1 (AdvCMVp21) was constructed by homologous recombination and the vector encoding β-galactosidase (AdvCMVLacZ) was used as an experimental control. Administration of AdvCMVp21 suppressed serum-induced proliferation and cell cycle progression; however, the number of quiescent cells and the population of TUNEL-positive cells were not altered. Overexpression of p21Waf-1 did not affect the expression of contractile proteins and the availability of an endogenous growth factor signal p21Waf-1 may regulate cell cycle progression in SMC without affecting the apoptotic process and cell differentiation. Furthermore, the longitudinal diameter of AdvCMVp21 infected cells was increased compared with that of AdvCMVLacZ infected cells. Total protein content was also increased in AdvCMVp21 infected cells. Responses to the serum stimulation, proliferation and total protein synthesis may be independently regulated. Thus, the suppression of cell cycle progression by p21Waf-1 resulted in cellular hypertrophy of SMC.