The Role of Rac1 and Rac2 in Determining Bone Quality in Aged and Osteoporotic Female Mouse Models

The osteoclasts, the bone cells responsible for bone degradation, have a crucial role in the age-related bone loss and post-menopause osteoporosis. Rac1 and Rac2, members of the Rho-family of small GTPases, are known for having a key role in osteoclast formation and activity, which could be translated to bone quality. In this study, we characterize the roles of Rac1 and Rac2 on bone quality using an aged and osteoporotic mouse model. Bones from wild type, Rac1KO and Rac2KO mice were harvested for mechanical tests, bone densitometry, micro-computed tomography and histomorphometric analyses to evaluate bone mineralization and architecture.

We observed that the deletion of Rac1 or Rac2 in pre-osteoclasts minimized bone loss in both age-related and post-menopause osteoporosis. These results highlight the importance of the two small GTPases in bone remodeling and identify Rac1 and Rac2 as potential targets for the development of new therapies for the treatment of osteoporosis.

Year	Entry
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Year

Entry

2002

Halloran BP, Ferguson VL, Simske SJ, Burghardt A, Venton LL, Majumdar S. Changes in bone structure and mass with advancing age in the male C57BL/6J mouse. J Bone Miner Res. June 2002;17(6):1044-1050.

2005

Raisz LG. Pathogenesis of osteoporosis: concepts, conflicts, and prospects. J Clin Invest. December 2005;115(12):3318-3325.

1999

Center JR, Nguyen TV, Schneider D, Sambrook PN, Eisman JA. Mortality after all major types of osteoporotic fracture in men and women: an observational study. Lancet. March 13, 1999;353(9156):878-882.

1998

Lacey DL, Timms E, Tan H-L, Kelley MJ, Dunstan CR, Burgess T, Elliott R, Colombero A, Elliott G, Scully S, Hsu H, Sullivan J, Hawkins N, Davy E, Capparelli C, Eli A, Qian Y-X, Kaufman S, Sarosi I, Shalhoub V, Senaldi G, Guo J, Delaney J, Boyle WJ. Osteoprotegerin ligand is a cytokine that regulates osteoclast differentiation and activation. Cell. April 17, 1998;93(2):165-176.

1993

Grynpas M. Age and disease-related changes in the mineral of bone. Calcif Tiss Int. February 1993;53(suppl 1):S57-S64.