CHONDROITIN SULFATE PROTEOGLYCAN MODULATES THE PERMEABILITY OF HYALURONAN-CONTAINING COATS AROUND NORMAL HUMAN MESOTHELIAL CELLS

The composition and permeability of the pericellular coat surrounding normal human mesothelial (NHM) cells have been studied in vitro. NHM c ells were grown in the presence of H-3-glucosamine and the amount of l abel recovered in hyaluronan and chondroitin sulfate was determined af ter selective enzymatic digestion of the polysaccharides in medium, pe ricellular, and intracellular pools. For comparison a similar analysis was carried out on mesothelioma cells (Mero-14). Of the labeled polys accharides in the medium and pericellular pools of NHM cells about 80- 90% could be ascribed to hyaluronan and only 3-5% to chondroitin sulfa te. In contrast, Mero-14 synthesized only minute amounts of hyaluronan whereas chondroitin sulfate corresponded to 61% of the total glycosam inoglycans in the culture. The results exclude a structure of the peri cellular layer of NHM cells similar to the hyaluronan-proteoglycan agg regates found in cartilage. The permeability of the pericellular layer was tested by the exclusion of polystyrene microspheres acid bacteria of diameter 0.1-3.0 mu m, as well as erythrocytes of diameter 7 mu m. While the erythrocytes were excluded the smaller particles penetrated the coat. By adding 0.5 mg/ml of aggregating cartilage proteoglycan t o the medium particles of 0.3 mu m or larger were also excluded. Thus exogenous proteoglycans can reinforce the structure of the pericellula r layer. (C) 1995 Wiley-Liss, Inc.