Growth characteristics, angiotensin II generation, and microarray-determined gene expression in vascular smooth muscle cells from young spontaneously hypertensive rats.

Abstract

We have demonstrated that vascular smooth muscle cells (VSMCs) derived from spontaneously hypertensive rats (SHR) show exaggerated growth and produce angiotensin (Ang) II and growth factors. These may reflect intrinsic abnormalities in SHR that are not caused by excessive blood pressure, and are associated with genetic abnormalities. To evaluate whether these characteristics of VSMCs from SHR are associated with hypertension or genetic factors. VSMCs were obtained by an explant method from aortas of 4-week-old male SHR/Izumo and Wistar-Kyoto (WKY)/Izumo rats. We evaluated growth characteristics by [3H]thymidine incorporation and cell number increases, immunofluorescence of alpha-smooth muscle (alpha-SM) actin, mRNA expressions of phenotype markers, Ang II-generating system components, and growth factors by reverse transcription and polymerase chain reaction analysis, and Ang II levels by radioimmunoassay in VSMCs. Expression of 850 genes in VSMCs was evaluated by microarray. VSMCs from young SHR showed increased basal DNA synthesis and higher responses of DNA synthesis and cell numbers in response to calf serum. Ang II was significantly increased in conditioned medium and cell extracts from SHR-derived VSMCs than in those from WKY rat-derived VSMCs. mRNA expression of Ang II-generating proteinases, such as cathepsin D and angiotensin-converting enzyme, was greater in VSMCs from SHRs than in cells from WKY rats. Expression of transforming growth factor-beta1, platelet-derived growth factor A-chain and basic fibroblast growth factor mRNAs was greater in VSMCs from SHRs than in cells from WKY rats. Expression of mRNAs of phenotype markers, such as matrix gamma-carboxyglutamic acid (Gla) and osteopontin, was also greater in VSMCs from SHR than in cells from WYK rats. Microarray study showed that VSMCs derived from young SHR increasingly express genes for many enzymes, adhesion molecules and cytokines. This study determined that VSMCs derived from young SHR show exaggerated growth, produce Ang II and increasingly express several enzymes, adhesion molecules and cytokines, which are independent of hypertension and possibly associated with genetic abnormalities.