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

Abstract

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.

Tail-Suspended Mice Lacking Calponin H1 Experience Decreased Bone Loss

“…According to Harmey et al (2004), Rho-Rho-kinase inhibitors stimulate osteoblast differentiation and bone nodule formation correlating with increased BMP-2 and BMP-4 expression. Yoshikawa et al (2009), also reported that Y-27632 enhanced ectopic bone formation induced by rhBMP-2 impregnated into an atelocollagen carrier in mice and also enhanced the osteoblastic differentiation of cultured murine neonatal calvarial cells, associated with increased expression of BMP-4 gene. A constitutively active mutant of Rho kinase attenuated osteoblastic differentiation and the Rho kinase inhibitor reversed this phenotype.…”

“…A constitutively active mutant of Rho kinase attenuated osteoblastic differentiation and the Rho kinase inhibitor reversed this phenotype. Thus, Rho kinase inhibits osteogenesis, and a Rho kinase inhibitor in combination with the local delivery of rhBMP/collagen composite may be clinically applicable for stimulating bone formation (Yoshikawa et al 2009). In our experiment, ALP was significantly suppressed by CNh1 transfection, but was partially rescued by treatment with Y27632, a Rho kinase inhibitor.…”

Hyaluronan inhibits BMP‐induced osteoblast differentiation

“…In addition, recent findings indicate that the RhoA signaling pathway has important roles in bone remodeling. For example, in osteoblast survival [26], the integrity of the actin cytoskeleton as well as migration [27] and differentiation [28][29][30] are regulated by RhoA signaling. We examined the effects of HA on RhoA activation in cells.…”

Simvastatin enhances Rho/actin/cell rigidity pathway contributing to mesenchymal stem cells’ osteogenic differentiation

“…43,44 Y-27632 has been reported as increasing mineralization in mouse calvarial osteoblasts 43,44 and inducing ectopic bone formation in response to rhBMP-2. 45 However, ROCK activation has …”