DNA synthesis and apoptosis in smooth muscle cells from a model of genetic hypertension

The present study was designed to assess vascular smooth muscle cell (VSMC) proliferation and apoptosis in primary cultured VSMCs prepared from the aortic tunica media of adult (4 to 5 months old) age- and gender-matched groups of stroke-prone spontaneously hypertensive rats (SHRSP) and the normotensive reference strain, Wistar-Kyoto (WKY) rats. In the present study, VSMC proliferation was assessed with measurement of DNA synthesis in response to stimulation of G(0)/G(1) arrested VSMCs with 10% serum, whereas apoptosis was measured in response to serum deprivation. Apoptosis in aortic VSMCs was assessed in vitro with the technique of Annexin V binding in combination with propidium iodide exclusion with bivariate flow cytometric analysis. The percentage of necrotic VSMCs in the cell populations was assessed simultaneously. The light-scattering properties of the cells were assessed to provide further information on cell shrinkage and chromatin condensation. Results of the present study have shown enhanced DNA synthesis in VSMCs from SHRSP (n=10; 5.2+/-0.9 cpmx10(3)/mg protein) compared with WKY (n=12; 2.4+/-0.7 cpmx10(3) /mg protein; P<0.05, 95% CI, -5271 to -296). In addition, the results of the present study have demonstrated the role of serum in the survival of VSMCs in vitro, because SHRSP VSMCs underwent significantly more apoptosis in response to insult by serum deprivation (n=13; 10.21+/-1.8%) than WKY VSMCs (n=7; 3.44+/-1.4%; P<0.01, 95% CI, -11.5 to -2.0). Thus, it appears that both proliferation and apoptosis are enhanced in synthetic phenotype aortic medial VSMCs from the SHRSP in vitro.