OBJECTIVES The active form of vitamin D₃, 1α,25 dihydroxyvitamin D₃(1,25D₃), through its interaction with vitamin D receptors (VDR), is reported to effect a variety of anabolic and catabolic events, especially in bone and cartilage tissues. As cartilage degradation and tissue remodelling are characteristic features of the rheumatoid lesion, the distribution and expression of VDR at sites of cartilage erosion was examined.

RESULTS VDR was demonstrated in 15 of 18 cartilage-pannus junctions either at the interface (8 of 18), within the pannus tissue (12 of 18), and by chondrocytes often close to the erosive lesion (10 of 18). All the rheumatoid synovial tissue and 5 of 10 cartilage specimens showed cells with positive staining, but the extent of this was variable. Negligible VDR staining was observed for normal cartilage. Primary cultures of RSC also showed variability in both the numbers and proportions of macrophages or synovial fibroblasts stained for VDR (range 10–50%), this being more common in cultures with a high proportion of macrophages.

CONCLUSIONS VDR expression has been demonstrated by most specimens of cartilage-pannus junction; was associated with various cell types, including chondrocytes, but not exclusively with CD68⁺ macrophages. The focal nature of VDR expression within the rheumatoid lesion suggests a contributory role for 1α,25D₃ in the pathophysiological processes of rheumatoid arthritis.