Effects of shock waves on tenocyte proliferation and extracellular matrix metabolism.

The shock wave is an effective noninvasive modality for resolving various tendon pathologies. However, scientific rationale and mechanism of shock wave therapy remains limited. This study aims to investigate the effects of shock waves and their biochemical mechanisms on tenocyte proliferation and collagen synthesis. Tenocytes harvested from Achilles tendons of Sprague-Dawley rats were used in this study. Cell viability was assayed by trypan blue exclusion methods. The colorimetric assay was determined to evaluate the mitochondria activity of the tenocytes after shock wave exposure. Synthesis of collagen, nitric oxide (NO) and transforming growth factor-beta1 (TGF-beta1) were determined and their gene expression was also studied. The results showed that there was a dose-dependent impairment of cell viability observed in 0.36 mJ/mm2 and 0.68 mJ/mm2 stimulation. In the proliferation assay, low energy level with low impulses (0.36 mJ/mm2 with 50 and 100 impulses) showed positive stimulatory effects, whereas the high energy level with high impulses (0.68 mJ/mm2 with 250 and 500 impulses) had significant inhibitory effects. At 0.36 mJ/mm2, 100 impulse shock waves treatment, up-regulation of proliferating cell nuclear antigen (PCNA) (at 6 and 24 h) and collagen type I, collagen type III and TGF-beta1 gene expression (at 24 h) were observed; these were followed by the increases in NO production (at 24 h), TGF-beta1 release (at 48 and 96 h) and collagen synthesis (at the 7th day). This study revealed that shock waves can stimulate tenocyte proliferation and collagen synthesis. The associated tenocyte proliferation is mediated by early up-regulation of PCNA and TGF-beta1 gene expression, endogenous NO release and synthesis and TGF-beta1 protein and then collagen synthesis.