Cell surface changes in senescent and Werner's syndrome fibroblasts: their role in cell proliferation.

Abstract

Cell surface is known to participate in the regulation of cell proliferation through interaction with adjacent cell surfaces or the extracellular matrix, or both. A clinical survey of the Werner syndrome suggests some disorders in glycosaminoglycan metabolism. Also, the skin fibroblasts derived from the patients with WS have a reduced proliferation capacity. We here examined, in vitro and in vivo, alterations of the cell-surface properties of WS cells and aging human fibroblasts. Cell-surface negative charges, examined by electrophoretic mobility of dispersed single cells in buffer, were seen to decline steadily as a function of cumulative population doublings. A strict linear relationship was found between electrophoretic mobility (micron/sec/V/cm) and number of cells harvested at each passage in all cell lines examined. The slope of this line in cells from donors of different ages indicated that WS fibroblasts resemble cells from much older normal controls. The same conclusion was drawn from our previous study of Con A-mediated red cell adsorption, which was confirmed as reflecting an alteration of cell-surface coat negative charge. Electrophoretic mobility after treatment of cell surface with degradative enzymes showed that the cell-surface negative charges were attributable to sialic acid, chondroitin sulphates, hyaluronic acid, and heparan sulphate. Two-dimensional electrophoresis of 3H-glucosamine incorporated glycosaminoglycans (GAGs) revealed that heparan sulphate was the main component of GAGs on the fibroblast cell surface and that the relative amount of heparan sulphate among GAGs on the cell surface increased in vitro with the number of passages. Growth kinetics of fibroblasts on sheets of fixed cells treated with a fixative (glutaraldehyde) and degradative enzymes were examined to elucidate the role of cell-surface GAGs in the regulation of cell proliferation. Cell growth was inhibited 40% when the fibroblasts were cultured on the fixed sheets of late passage cells. Treatment of the fixed cell sheets with heparitinase or nitrous acid resulted in complete recovery from the growth inhibition. Cell growth on sheets of fixed cells derived from young, middle, and senescent fibroblasts showed that the surface of the senescent cells had the greatest inhibitory effect. These inhibitory effects of fixed cell sheets correlated well with both the amount of heparan sulphate relative to the total GAGs on the surface and to the saturation density of cell growth at each passage. These findings strongly suggest that heparan sulphate, or its complex, on the cell surface is involved in the regulation of cell proliferation.(ABSTRACT TRUNCATED AT 400 WORDS)