Physical shock wave mediates membrane hyperpolarization and ras activationfor osteogenesis in human bone marrow stromal cells

Physical shock wave (SW) has shown effectiveness on promotion of bone growt h. We have recently demonstrated that SW could promote bone marrow stromal cell differentiation toward osteoprogenitor associated with induction of TG F-beta1. We have further demonstrated that SW-induced membrane hyperpolariz ation and Ras activation acted an early signal for the osteogenesis in huma n bone marrow stromal cells. An optimal dose of SW treatment at 0.16 mj/mm( 2) for 500 impulses induced a rapid membrane hyperpolarization in 5 min, ac tivation of Ras in 30 min, and cell proliferation in 2 days. The SW-promote d cell growth was related to osteogenesis as demonstrated by increase of bo ne alkaline phosphatase activity in 6 days and osteocalcin mRNA expression in 12 days. In support that SW-induced Ras activation mediated osteogenesis of human bone marrow stromal cells, we further demonstrated that transfect ion of bone marrow stromal cells with a dominant negative Ras mutant (Asn-1 7 ras(H)) abrogated the SW enhancement of osteogenic transcription factor ( CBFA1) activation, osteocalcin mRNA expression, and bone nodule formations These results suggest that physical SW promotes bone marrow stromal cell di fferentiation toward osteogenic lineage via membrane hyperpolarization, fol lowed by Ras activation and specific osteogenic transcription factor CBFA1 expression. A link between physical SW and biomembrane perturbation-mediate d Ras activation may highlight how noninvasive physical agents could be use d to promote fracture healing and to rescue patients with osteoporosis and osteopenic disorders in the future. (C) 2001 Academic Press.