Static pressure regulates connective tissue growth factor expression in human mesangial cells

Abstract

Connective tissue growth factor (CTGF) is overexpressed in a variety of fibrotic disorders such as renal fibrosis and atherosclerosis. Fibrosis is a common final pathway of renal diseases of diverse etiology, including inflammation, hemodynamics, and metabolic injury. Mechanical strains such as stretch, shear stress, and static pressure are possible regulatory elements in CTGF expression. In this study, we examined the ability of static pressure to modulate CTGF gene expression in cultured human mesangial cells. Low static pressure (40-80 mm Hg) stimulated cell proliferation via a protein kinase C-dependent pathway. In contrast, high static pressure (100-180 mm Hg) induced apoptosis in human mesangial cells. This effect was reversed by treatment with CTGF antisense oligonucleotide but not with transforming growth factor beta1-neutralizing antibody or protein kinase C inhibitor. High static pressure not only up-regulated the expression of CTGF, but also the expression of extracellular matrix proteins (collagen I and IV, laminin). This up-regulation of extracellular matrix proteins was also reversed by treatment with CTGF antisense oligonucleotide. As judged by mRNA expression of a total of 1100 genes, including apoptosis-associated genes using DNA microarray techniques, recombinant CTGF protein induced apoptosis by down-regulation of a number of anti-apoptotic genes. Overexpression of CTGF in mesangial cells by transient transfection had similar effects. Taken together, these results suggest that high blood pressure up-regulates CTGF expression in mesangial cells. High levels of CTGF in turn enhance extracellular matrix production and induce apoptosis in mesangial cells, and may contribute to remodeling of mesangium and ultimately glomerulosclerosis.