Low-Level Laser Irradiation Promotes Cell Proliferation and mRNA Expression of Type I Collagen and Decorin in Porcine Achilles Tendon Fibroblasts In Vitro

Achilles tendon problems are commonly encountered in sports medicine and low-level laser therapy (LLLT) is widely used in rehabilitative applications to decrease pain, reduce inflammatory processes, and promote tissue healing. This study examined the effects on the proliferation of porcine Achilles tendon fibroblasts and gene expression, using different doses of low-level laser irradiation (LLLI). Four groups of identically cultured fibroblasts were exposed to LLLI and harvested after 24 h. The control group (Group 1) was subjected to no LLLI. Other groups received 1 J/cm(2) (Group 2), 2 J/cm(2) (Group 3), and 3 J/cm(2) (Group 4), respectively. Cell proliferation and mRNA expressions of type I collagen and decorin were then measured. When compared to the control group, the cell proliferation of irradiated Achilles tendon fibroblasts in the other three groups increased significantly by 13% +/- 0.8% (Group 2), 30% +/- 0.4% (Group 3), and 12% +/- 0.6% (Group 4) respectively. But progressively higher laser intensity did not achieve a correspondingly higher cell proliferation effect in Achilles tendon fibroblasts. The mRNA expressions of decorin and type I collagen in fibroblasts with LLLI were significantly higher (p < 0.05). Therefore, suitable dosages of LLLI may result in more effective tissue healing by promoting type I collagen and decorin synthesis. However, these positive effects of LLLI on the repair of the Achilles tendon in humans should be further investigated in clinic. (C) 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:646-650, 2009