To investigate osteoclastogenesis in bone marrow cells from patients with various pathogenic backgrounds known to induce osteoporosis, to identify specific factors that may cause generalized osteoporosis in patients with rheumatoid arthritis (RA).
Bone marrow blood was obtained from 59 women, 36 with RA and 23 without RA. Patients with RA were classified as severe (26) and mild RA (10: 5 patients with and 5 without corticosteroid therapy). The non-RA subjects were divided into 3 groups, premenopausal (7), menopausal (8), and elderly (8). As a marker of bone resorption, the pyridinoline crosslinked telopeptide domain of type I collagen (ICTP) concentration in the bone marrow supernatant was measured by radioimmunoassay. The bone marrow cells were cultured 14 days in the presence or absence of autologous bone marrow supernatant; then the number of tartrate resistant acid phosphatase positive multinucleated cells (TRAP positive MNC) was counted as an indicator of osteoclastogenesis.
ICTP concentration of the bone marrow supernatant and the number of TRAP positive MNC showed remarkable enhancement in some patients with severe RA, but these features were not observed in the 3 control groups.
Increased bone resorption and enhanced osteoclastogenesis were specifically observed in the iliac bone marrow of patients with RA, especially those with severe RA. These phenomena can be considered to accompany generalized osteoporosis in RA.