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 cells were grown in the presence of 3H-glucosamine and the amount of label recovered in hyaluronan and chondroitin sulfate was determined after selective enzymatic digestion of the polysaccharides in medium, pericellular, and intracellular pools. For comparison a similar analysis was carried out on mesothelioma cells (Mero-14). Of the labeled polysaccharides in the medium and pericellular pools of NHM cells about 80-90% could be ascribed to hyaluronan and only 3-5% to chondroitin sulfate. In contrast, Mero-14 synthesized only minute amounts of hyaluronan whereas chondroitin sulfate corresponded to 61% of the total glycosaminoglycans in the culture. The results exclude a structure of the pericellular layer of NHM cells similar to the hyaluronan-proteoglycan aggregates found in cartilage. The permeability of the pericellular layer was tested by the exclusion of polystyrene microspheres and bacteria of diameter 0.1-3.0 microns, as well as erythrocytes of diameter 7 microns. While the erythrocytes were excluded the smaller particles penetrated the coat. By adding 0.5 mg/ml of aggregating cartilage proteoglycan to the medium particles of 0.3 microns or larger were also excluded. Thus exogenous proteoglycans can reinforce the structure of the pericellular layer.