Extracorporeal Shock Wave-Mediated Changes in Proliferation, Differentiation, and Gene Expression of Human Osteoblasts

Background., The goal of this study was to determine whether cell proliferation, differentiation, and gene expression of primary human osteoblasts (hOB) are influenced by shock wave application (SWA). Methods: Osteoblast cultures were isolated from cancellous bone fragments and treated with 500 impulses of energy flux densities of 0.06 mJ/mm(2), 0.18 mJ/mm(2), 0.36 mJ/mm(2), and 0.50 mJ/mm(2). Twenty-four hours and 96 hours after SWA cell proliferation, alkaline phosphatase activity, and mineralization were analyzed. The global gene expression profiling was determined 96 hours after SWA employing Affymetrix HG-U133A microarrays. Results: After 24 hours, hOB showed a dose-dependent increase in cell proliferation from 68.7% (at 0.06 mJ/mm(2), P = 0.002) up to 81.6% (at 0.5 mJ/mm(2), p = 0.001), which also persisted after 96 hours. Numbers of alkaline phosphatase-positive hOB increased after SWA treatment with peak levels of response between 0.18 mJ/mm2 and 0.5 mJ/mm(2) after 24 hours. Mineralization was significantly higher in all groups compared with controls. Microarray analyses revealed SWA-induced differential expression of 94 genes involved in physiologic processes, cell homeostasis, and bone formation. Most intriguing was the up-regulation of multiple genes involved in skeletal development and osteoblast differentiation (e.g., PTHrP, prostaglandin E2-receptor EP3, BMP-2 inducible kinase, chordin, cartilage oligomeric matrix protein, matrillin). Conclusion: we showed that shock waves have direct dose-dependent stimulatory effects on proliferation and differentiation of osteoblasts from normal human cancellous bone. We demonstrated that several genes critical for osteoblast differentiation and function are regulated after SWA. Overall, data presented herein will aid further understanding of the osteogenic effect of shock waves and, in addition, will enhance current knowledge of the SWA-mediated gene expression.