Atsushi Tanida1, Yuji Kishimoto, Toru Okano, Hiroshi Hagino. 1. Division of Orthopedic Surgery, Department of Medicine of Sensory and Motor Organs, School of Medicine, Tottori University Faculty of Medicine, Yonago 683-8504, Japan.
Abstract
BACKGROUND: Various clinical reports suggest etanercept (ETN) has some efficacy in bone formation in rheumatoid arthritis (RA). To examine this effect, we investigated the gene expression of cytokines relevant to osteoblast/osteoclast differentiation, and evaluated histomorphometric findings in mature rats with collagen-induced arthritis (CIA). METHODS: Total RNA was extracted from knee joints with CIA after ETN or placebo administration. Subsequently, realtime-PCR was carried out to quantify the mRNAs encoding Wnt-1, Dickkopf-1 (DKK-1), receptor activator of nuclear factor kappa-B ligand (RANKL), osteoprotegelin (OPG) and TNF (tumor necrosis factor)-alpha. In histomorphometric analysis, the infiltrating pannus volume and pannus surface, and the following items in contact with pannus surface were measured: osteoclast number, osteoid surface, osteoid volume and labeling surface. These were evaluated in the distal femur with CIA with or without ETN administration. RESULTS: TNF-alpha, RANKL and OPG mRNA expressions, linked to osteoclastogenesis, were not significantly different with or without ETN administration. ETN administration significantly increased Wnt-1 mRNA expression, the osteoblast promoter, and decreased DKK-1 mRNA expression, the Wnt signal inhibitor. In histomorphometric analysis, pannus volume, pannus surface and osteoclast number, parameters of bone destruction, were not significantly different among groups. Osteoid volume, osteoid surface and labeling surface, parameters of bone formation, increased significantly with ETN administration. CONCLUSION: Our results suggest that ETN suppresses DDK-1 expression, and, as a result, Wnt expression is promoted and osteoblastogenesis becomes more active, independent of the regulation of osteoclast activity. Marked bone formation is attributed to the fact that ETN directly promotes osteoblastogenesis, not as a result of suppressing osteoclastogenesis.
BACKGROUND: Various clinical reports suggest etanercept (ETN) has some efficacy in bone formation in rheumatoid arthritis (RA). To examine this effect, we investigated the gene expression of cytokines relevant to osteoblast/osteoclast differentiation, and evaluated histomorphometric findings in mature rats with collagen-induced arthritis (CIA). METHODS: Total RNA was extracted from knee joints with CIA after ETN or placebo administration. Subsequently, realtime-PCR was carried out to quantify the mRNAs encoding Wnt-1, Dickkopf-1 (DKK-1), receptor activator of nuclear factor kappa-B ligand (RANKL), osteoprotegelin (OPG) and TNF (tumor necrosis factor)-alpha. In histomorphometric analysis, the infiltrating pannus volume and pannus surface, and the following items in contact with pannus surface were measured: osteoclast number, osteoid surface, osteoid volume and labeling surface. These were evaluated in the distal femur with CIA with or without ETN administration. RESULTS:TNF-alpha, RANKL and OPG mRNA expressions, linked to osteoclastogenesis, were not significantly different with or without ETN administration. ETN administration significantly increased Wnt-1 mRNA expression, the osteoblast promoter, and decreased DKK-1 mRNA expression, the Wnt signal inhibitor. In histomorphometric analysis, pannus volume, pannus surface and osteoclast number, parameters of bone destruction, were not significantly different among groups. Osteoid volume, osteoid surface and labeling surface, parameters of bone formation, increased significantly with ETN administration. CONCLUSION: Our results suggest that ETN suppresses DDK-1 expression, and, as a result, Wnt expression is promoted and osteoblastogenesis becomes more active, independent of the regulation of osteoclast activity. Marked bone formation is attributed to the fact that ETN directly promotes osteoblastogenesis, not as a result of suppressing osteoclastogenesis.
Entities:
Keywords:
Dickkopf-1; Wnt; bone formation; etanercept; rheumatoid arthritis
Authors: Mark C Genovese; Joan M Bathon; Roy M Fleischmann; Larry W Moreland; Richard W Martin; James B Whitmore; Wayne H Tsuji; Jonathan A Leff Journal: J Rheumatol Date: 2005-07 Impact factor: 4.666
Authors: Ping Li; Edward M Schwarz; Regis J O'Keefe; Lin Ma; R John Looney; Christopher T Ritchlin; Brendan F Boyce; Lianping Xing Journal: Arthritis Rheum Date: 2004-01