Effect of synthetic calcium pyrophosphate and hydroxyapatite crystals on the interaction of human blood mononuclear cells with chondrocytes, synovial cells, and fibroblasts.

Synthetic calcium pyrophosphate dihydrate crystals and, to a lesser extent, synthetic hydroxyapatite crystals increased the amount of interleukin-1/mononuclear cell factor released by human blood monocytes, as measured by collagenase and prostaglandin E2 production by rabbit chondrocytes, human dermal fibroblasts, and adherent rheumatoid synovial cells. The same crystals also directly induced collagenase and prostaglandin E2 secretion by rabbit chondrocytes, and potentiated the action of interleukin-1/mononuclear cell factor on chondrocytes. These mechanisms may be important in the pathogenesis of the destructive arthropathies associated with these crystals.