Gene Expression for Extracellular Matrix Proteins in Shockwave-Induced Osteogenesis in Rats

Abstract

To clarify the mechanisms underlying shockwave-induced osteogenesis, we applied shockwave to rat femoral shafts from the ventral side. We assessed bone mineral content (BMC) and bone mineral density (BMD), and analyzed the spatial and temporal gene expression for pro-alpha1 (I) collagen (COL1A1), pro-alpha1 (II) collagen (COL2A1), pro-alpha1 (X) collagen (COL10A1), osteocalcin (OC) and osteopontin (OPN) using in situ hybridization. On the 21st day post-exposure, BMC and BMD in the exposed femur were elevated by 8.46% and 5.80%, respectively, relative to the unexposed femur. Immediately following exposure, there was evidence of scraping of the cortex and periosteal separation with hemorrhage. On day 4, new periosteal bone formation could be seen on the ventral and dorsal side of the femur. In the newly formed bone, COL1A1, OC and OPN were expressed in osteoblastic cells underlying the periosteum. On day 7, there was progression of periosteal bone and trabeculae formation. COL1A1 and OC were expressed in mature osteoblasts lining the trabeculae, whereas OPN was expressed in immature osteoblastic cells, osteocytes and osteoclasts. On day 14, bone remodeling commenced in the periosteal bone. COL1A1, OC and OPN were still expressed at this stage, however, signals were much weaker. Between 4-7 days, chondrocyte clusters were distributed multi-focally near the exposed site, and there was expression of COL2A1 but not of COL10A1. The results demonstrate that gene expression patterns of shockwave-induced osteogenesis are similar to those of periosteal hard callus formation during fracture healing. Shockwaves can yield dramatic activation of cells in normal long bones, and drive the cells to express genes for osteogenesis.

Dose-Dependent New Bone Formation by Extracorporeal Shock Wave Application on the Intact Femur of Rabbits

“…In line with previous reports of extracorporeal shock wave therapy in animal models [5,11,13,14,40] , the present study shows shock wave mediated new bone formation. In recent publications a dose-dependent effect has been assumed; however, this was based on only 1 low-dose group receiving 2,000 shock wave impulses with EFD 0.18 mJ/mm 2 and 1 highdose group receiving 4,000 shock wave impulses with EFD of 0.47 mJ/mm 2 in a fracture model [33] .…”

“…It has been used, with varying success rates, for conditions such as tendinopathies, delayed bone healing, pseudarthrosis and aseptic femoral head necrosis [1][2][3] . When shock waves were found to be effective for the treatment of nonunions in 1991 [4] , numerous groups investigated the effects of shock waves in animal models [5][6][7][8][9][10][11][12][13][14] and clinical-experimental applications [15][16][17][18] . Unfortunately, the application of extracorporeal shock wave therapy was not very standardized in terms of the strength and number of the impulses used, making comparisons between studies difficult.…”

VEGF Modulates Angiogenesis and Osteogenesis in Shockwave-Promoted Fracture Healing in Rabbits

“…ESWT was shown to affect local blood flow and metabolism of normal bone [4]. ESWT was also shown to activate extracellular signal-regulated kinase (ERK) and p38 kinase in fracture callus [20], and trigger the cascades of osteogenic transcriptions including collagen I, bone alkaline phosphatase, osteocalcin, and Cbfal/Runx2, and the production of VEGF [21]. These findings suggest that bone tissue converts physical shockwave stimulation into differentiation for subsequent chondrogenesis and osteogenesis in bone repair.…”

The Use of Extracorporeal Shock Wave-Stimulated Periosteal Cells for Orthotopic Bone Generation

“…The ability of ESWs to stimulate periosteal cell proliferation has previously been shown by our group 19 as well as others. 21,22 To our knowledge, to date, however, ESWSP (or ESW-stimulated tissue from any region) has not been combined with scaffolds in a tissue-engineering approach. The advantage of adding a scaffold is three-fold: It contours the new bone, helps maintain bone at the implant site, and creates a space that allows the periosteal cells to further proliferate and fill the scaffold.…”