EXPRESSION OF PARATHYROID HORMONE-RELATED PEPTIDE IN HUMAN OSTEOARTHRITIS

To evaluate the involvement of the expression of parathyroid hormone-r elated peptide gene in human articular cartilage pathology, we perform ed immunohistochemical staining and in situ hybridization on specimens of femoral head cartilage obtained from 15 patients with osteoarthrit is, 11 with rheumatoid arthritis, and 12 control subjects. Parathyroid hormone-related peptide-positive chondrocytes were observed predomina ntly in degenerated lesions of osteoarthritic tissue and were less evi dent in rheumatoid arthritic samples, while the normal cartilage expre ssed little parathyroid hormone-related peptide. In addition, the leve l of parathyroid hormone-related peptide expression was clearly depend ent on the degree of cartilage degeneration; cartilage tissues with mo derate degenerative changes contained more positive chondrocytes compa red with mildly or severely degenerated cartilage. In situ hybridizati on confirmed the localization of parathyroid hormone-related peptide p rotein and demonstrated intense expression of mRNA of the peptide in o steoarthritic samples. This is the first demonstration of parathyroid hormone-related peptide expression in chondrocytes from pathologic art icular cartilage of humans. Our results suggest that parathyroid hormo ne-related peptide may be involved in the pathophysiology of osteoarth ritis.