TRANCE/RANKL knockout mice are protected from bone erosion in a serum transfer model of arthritis

Allison R. Pettit, Harvard Institutes of Medicine
Hong Ji, Harvard Medical School
Dietrich von Stechow, Harvard Medical School
Ralph Muller, Harvard Medical School
Steven R. Goldring, Harvard Institutes of Medicine
Yongwon Choi, University of Pennsylvania School of Medicine
Christoph Benoist, Harvard Medical School
Ellen M. Gravallese, University of Massachusetts Medical School

At the time of publication, Ellen Gravallese was not yet affiliated with the University of Massachusetts Medical School.

Abstract

There is considerable evidence that osteoclasts are involved in the pathogenesis of focal bone erosion in rheumatoid arthritis. Tumor necrosis factor-related activation-induced cytokine, also known as receptor activator of nuclear factor-kappaB ligand (TRANCE/RANKL) is an essential factor for osteoclast differentiation. In addition to its role in osteoclast differentiation and activation, TRANCE/RANKL also functions to augment T-cell dendritic cell cooperative interactions. To further evaluate the role of osteoclasts in focal bone erosion in arthritis, we generated inflammatory arthritis in the TRANCE/RANKL knockout mouse using a serum transfer model that bypasses the requirement for T-cell activation. These animals exhibit an osteopetrotic phenotype characterized by the absence of osteoclasts. Inflammation, measured by clinical signs of arthritis and histopathological scoring, was comparable in wild-type and TRANCE/RANKL knockout mice. Microcomputed tomography and histopathological analysis demonstrated that the degree of bone erosion in TRANCE/RANKL knockout mice was dramatically reduced compared to that seen in control littermate mice. In contrast, cartilage erosion was present in both control littermate and TRANCE/RANKL knockout mice. These results confirm the central role of osteoclasts in the pathogenesis of bone erosion in arthritis and demonstrate distinct mechanisms of cartilage destruction and bone erosion in this animal model of arthritis.