Collagen and fibronectin expression in cardiac fibroblasts from hypertensive rats

Left ventricular hypertrophy in spontaneously hypertensive rats (SHR) is accompanied by excessive accumulation of collagen in the myocardium. The objective of this work was to examine the role of myocardial fibroblasts in this phenomenon.

Myocardial fibroblasts from SHR and control Wistar Kyoto rats (WKY) were incubated with 14C-proline; total 14C incorporation and 14C-collagen synthesis were determined by collagenase digestion assays. 14C containing proteins were further characterised by SDS gel electrophoresis. RNA was isolated from these cultures and used for northern blot hybridisation with rodent specific cDNAs for collagen types I and III and fibronectin.

Biosynthetic labelling of fibroblastic cell cultures with 14C-proline showed that 14C-proline incorporation into total protein expressed on a DNA basis was 30% higher in fibroblasts from hypertensive rats than in the corresponding sex and age matched normal rats. When the same set of cell cultures was examined for 14C-collagen synthesis there was a 50% increment in cell strains from hypertensive animals; these differences were highly significant. When the expression of collagen types I and III and fibronectin genes was analysed by northern blot analyses, 1.5- to 2-fold greater steady state levels of types I and III collagens and fibronectin transcripts were found in fibroblasts from hypertensive rats when compared to cells from normal rats.

Myocardial fibroblast cultures from hypertensive rats produce increased amounts of collagen and fibronectin associated with increased expression of the genes for types I and III collagens and also for fibronectin. Myocardial fibroblasts may participate in the increased myocardial connective tissue deposition associated with genetic hypertension.