Release of collagenase, neutral protease, and prostaglandins from cultured mammalian synovial cells by hydroxyapatite and calcium pyrophosphate dihydrate crystals.

Hydroxyapatite (HA) and calcium pyrophosphate dihydrate (CPPD) crystals were phagocytosed when added to cultured human rheumatoid or normal canine synovial cells. Collagenase and neutral protease secretion into the culture medium was increased 5- to 8-fold over control values in the presence of HA and increased 3-fold in the presence of CPPD crystals. HA but not CPPD crystals induced a 300-fold increase in human rheumatoid synovial cell culture fluid prostaglandin (PG) E2 levels and an 8-fold increase in PGF alpha levels. This mechanism may be important in the pathogenesis of the destructive arthropathies associated with HA and CPPD crystals.