, Volume 467, Issue 12, pp 3087-3095

Stimulation of Ectopic Bone Formation in Response to BMP-2 by Rho Kinase Inhibitor: A Pilot Study

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The small GTPase Rho and Rho-associated protein kinase (Rho kinase, ROCK) signal participates in a variety of biological functions including vascular contraction, tumor invasion, and penile erection. Evidence also suggests Rho-ROCK is involved in signaling for mesenchymal cellular differentiation. However, whether it is involved in osteoblastic differentiation is unknown. We therefore asked whether Rho-ROCK signaling participates in recombinant human bone morphogenetic protein (rhBMP-2)-induced osteogenesis both in vitro and in vivo. Continuous delivery of a specific ROCK inhibitor (Y-27632) enhanced ectopic bone formation induced by rhBMP-2 impregnated into an atelocollagen carrier in mice without affecting systemic bone metabolism. Treatment with Y-27632 also enhanced the osteoblastic differentiation of cultured murine neonatal calvarial cells. These effects were associated with increased expression of BMP-4 gene. Expression of a dominant negative mutant of ROCK in ST2 cells promoted osteoblastic differentiation, while a constitutively active mutant of ROCK attenuated osteoblastic differentiation and the ROCK inhibitor reversed this phenotype. Thus, ROCK inhibits osteogenesis, and a ROCK inhibitor in combination with the local delivery of rhBMP/collagen composite may be clinically applicable for stimulating bone formation.

Each author certifies that he or she has no commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangement, etc) that might pose a conflict of interest in connection with the submitted article. This work is supported in part by Grant-in-Aid for Scientific Research from the Ministry of Education, Science, Sports, Culture and Technology of Japan, as well as by research grants from the Yamanouchi Foundation for Research on Metabolic Disease.
Each author certifies that his or her institution has approved the animal protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research.
This work was performed at Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan.