Changes in proteoglycan and collagen in cartilage in rheumatoid arthritis.

Articular cartilage from thirteen patients with rheumatoid arthritis was studied by both light and electron microscopy using recently developed staining techniques for proteoglycan. Normally proteoglycan is concentrated about active chondrocytes, but in the cartilage from these patients it was found to be diminished about most of the chondrocytes while it was increased around a few. Fragmentation of collagen and phagocytosis of the fragments by chondrocytes were also noted. This dissolution of collagen was associated with loss of proteoglycan in the matrix. These findings are consistent with the variable nature of the rheumatoid destructive process and appear to be morphological reflections of biochemical changes which formerly were thought to occur in this disease only at the cartilage-pannus junction.