Altered acid hydrolase activities in rheumatoid synovial cells in culture.

EA R o CAL s-ruDis of normal and rheumatoid synovial membranes showed markedly increased acid phosphatase and oxidase activities in the lining cells of the rheumatoid membrane.' Acid phosphatase activity, evident in cytoplasmic granules, serves as a marker for lysosomes-subcellular organelles first described by deDuve and shown to contain numerous hydrolases active at an acid pH.2'3 Homogenates of rheumatoid synovial membranes contain a much higher content than normal of acid phosphatase, and two other lysosomal hydrolases -cathepsin4 and ,-glucosaminidase.5 Synovial cells derived from normal and rheumatoid membranes have been grown in tissue culture by a number of workers." Phase-contrast microscopy and hematoxylin and eosin stains have failed to reveal consistent differences between the normal and rheumatoid synovial cells in culture. Bartfeld8 reported multinucleated giant cells, bizarre nuclei a wide variation in cell size, and coarsely granular cytoplasm of cells in late rheumatoid cultures. It is not certain whether these changes are unique to rheumatoid cells, for they were observed in normal cells in culture by Castor and Dorstewitz.7 In an extensive study, Stanfleld and Stephens8 could detect no significant morphologic differences. It would be important to demonstrate differences between rheumatoid and normal cells in culture. We have investigated the possibility that rheumatoid synovial cells in culture maintain the increased enzymatic activities that they show in tissue sections. Cytochemical methods were used, and cells were incubated for activities of three lysosomal acid hydrolases-acid phosphatase, P-glucosaminidase, and aryl sulfatase.