PANNOCYTES - DISTINCTIVE CELLS FOUND IN RHEUMATOID-ARTHRITIS ARTICULAR-CARTILAGE EROSIONS

A distinctive cell was identified front sites of rheumatoid arthritis cartilage injury. Similar cells are not found in lesions of osteoarthr itis cartilage. We have designated them as pannocytes (PCs). Their rho mboid morphology differs front the bipolar shape of fibroblast-like sy noviocytes or the spherical configuration of primary human articular c hondrocytes. Chondrocytes are short-lived, whereas the original PC lin e grew for 25 passages before becoming senescent. Features in common w ith cultured primary chondrocytes include maximal proliferation in res ponse to transforming growth factor-beta a catabolic response to inter leukin-1 beta, collagenase production, and mRNA for the induced lympho cyte antigen and inducible nitric oxine synthase. Despite the presence of the inducible nitric oxide synthase message, PCs no not produce NO either constitutively or when cytokine stimulated. Each of the mesenc hymal cells, fibroblast-like synoviocytes, primary chondrocytes, and P Cs have the gene for type I collagen, but the type II collagen gene is detected only in primary chondrocytes. PCs can be distinguished from fibroblast-like synoviocytes and primary chondrocytes by their morphol ogy, bright VCAM-1 staining, and growth response to cytokines and grow th factors. Their prolonged life span in vitro suggests that PCs might represent an earlier stage of mesenchymal cell differentiation, and t hey could have a heretofore unrecognized role in rheumatoid arthritis joint destruction.