CHARACTERIZATION OF PROTEOGLYCANS PRODUCED BY RAT PLEURAL MESOTHELIALCELLS IN-VITRO

The mesothelial cell envelops the surface of the parietal and visceral pleura. These cells are known to synthesize most of the protein const ituents of the pleural basement membrane and interstitium. This study examined the ability of a rat pleural mesothelial cell line to synthes ize proteoglycans in vitro. Cells were labeled with inorganic (SO4)-S- 35 to label the glycosaminoglycan moiety of proteoglycans. The medium and combined cell membrane/extracellular matrix fractions contained 73 and 25% of the proteoglycan radioactivity, respectively. The medium c ontained a single chondroitin/dermatan sulfate proteoglycan of approxi mately 190 kDa, consistent with biglycan. As determined by Northern an alysis of steady-state levels of messenger RNA, the cells contained me ssage for biglycan. Stimulation of the cells with epidermal growth fac tor resulted in the appearance of a second chondroitinidermatan sulfat e proteoglycan of approximately 97 kDa, characteristic of decorin. The cell membrane/matrix contained a biglycan-like chondroitinidermatan p roteoglycan and several heparan sulfate proteoglycans. Pleural mesothe lial cells in vitro are capable of synthesizing a variety of interstit ial and basement membrane proteoglycans.