Overexpression of α1β1 integrin directly affects rat mesangial cell behavior

Background. Glomerular mesangial cell (MC) proliferation, hypertrophy, and abnormal matrix remodeling characterized hv increased expression of fibronectin, laminin and collagen type IV, and neoexpression of collagen I and III are the main biological features of progressive glomerulonephritis (GN). Especially, persistent pathological matrix remodeling may lead to glomerular scar formation (glomerular scarring). We reported recently that alpha(1)beta(1) integrin, a major collagen receptor for MCs, may be a potential adhesion molecule for MC-mediated pathological collagen matrix remodeling in GN. Methods. To address further the direct role of alpha(1)beta(1) integrin in MC behavior, such as cell growth and matrix remodeling, alpha(1)beta(1) integrin was overexpressed in MCs by transfecting an expression vector containing a full-length rat alpha(1) integrin cDNA. Flow cytometry and immunoprecipitation analysis were applied for selection of transfectants with a stable expression of the alpha(1) integrin subunit. The effect alpha(1)beta(1) integrin overexpression on MC: biology was examined with a H-3-thymidine incorporation assay, Row cytometric analysis of cell size and DNA content, Western blot analysis of a cyclin-dependent-kinase inhibitor, p27(Kip1), alpha-smooth muscle actin expression, and a collagen gel contraction assay. Results. The oil transfectants displayed a dramatic inhibition of H-3-thymidine incorporation as compared with the mock transfectants. Increased expression of the oil subunit inversely correlated with cell cycle progression and paralleled the expression of p27(Kip1) and alpha-smooth muscle actin, as well as the cell size in MCs. In addition, the alpha(1)-transfectants were able to enhance collagen matrix reorganization effectively. Conclusion. These results indicate that MC-alpha(1)beta(1) integrin expression is a critical determinant of MC phenotypes, including cell growth, cell size, and collagen matrix remodeling ability, and thereby contributes to scar matrix remodeling (sclerosis) in GN.