Transforming growth factor beta 1 mediates the low-frequency vertical vibration enhanced production of tenomodulin and type I collagen in rat Achilles tendon

Vertical vibration (VV) is a whole-body vibration with mechanical loading that commonly used in rehabilitation and sports training to increase athlete muscle strength. Our previous study showed that low-magnitude, low-frequency VV at 8 Hz and 10 Hz increased myoblast myogenesis. Herein, we investigated whether a VV frequency at low-frequency 5-10 Hz has anabolic effects on tenocytes and improves tendon stiffness. In primary tenocytes, 10 Hz VV treatment increased the tenogenic marker gene expression of tenomodulin and extracellular matrix type I collagen but decreased decorin expression. qPCR and Enzyme-Linked Immunosorbent Assay (ELISA) results showed that TGF-β1 expression was increased in tenocytes after 3 days of 10 Hz VV treatment in vitro and in Achilles tendons after 3 weeks in vivo. Tenomodulin expression and Achilles tendon stiffness were significantly increased in Achilles tendons after 3 weeks in vivo. We also showed that the TGF-β1 receptor inhibitor SB431542 (10 μM) decreased the expression of tenomodulin and type I collagen but increased the decorin expression in tenocytes. These results indicated that the 10 Hz VV stimulated anabolic effects in tenocytes by increasing TGF-β1 expression that subsequently increases the expression of tenomodulin and type I collagen, and increased the Achilles tendon stiffness. This study provides insight into the low-frequency 10 Hz VV treatment improves tendon properties and can minimizes the risk of ligament/tendon reinjure during rehabilitation.