Photobiomodulation therapy on collagen type I and III, vascular endothelial growth factor, and metalloproteinase in experimentally induced tendinopathy in aged rats.

This study investigates the effect of photobiomodulation therapy (PBMT) on collagen type I and III, matrix metalloproteinase (MMP), and vascular endothelial growth factor (VEGF) in experimentally induced tendinopathy in female aged rats. Tendinopathy was induced by the Achilles tendoncollagenase peritendinous. Forty-two Wistar rats (Norvegicus albinus) were used; groups consisted of 36 aged animals (18 months old; mean body weight, 517.7 ± 27.54 g) and 6 adult animals (12 weeks old; mean body weight, 266± 19.30 g). The animals were divided into three groups: control, aged tendinopathy, and aged tendinopathy PBMT; the aged groups were subdivided based on time to euthanasia: 7, 14, and 21 days. PBMT involved a gallium-arsenide-aluminum laser (Theralaser, DMC®) with active medium operating at wavelength 830 ± 10 nm, 50 mW power, 0.028 cm2 laser beam, 107 J/cm2 energy density, 1.8 W/cm2 power density, and an energy of 3 J per point. The laser was applied by direct contact with the left Achilles tendon during 60 s per point at a frequency of three times per week, until the euthanasia date (7, 14, and 21 days). VEGF, MMP-3, and MMP-9 were analyzed by immunohistochemistry, and collagen type I and III by Sirius red. PBMT increased the deposition of collagen type I and III in a gradual manner, with significant differences relative to the group aged tendonitis (p < 0.001), and in relation to VEGF (p < 0.001); decreased expression of MMP-3 and 9 were observed in group aged tendinopathy (p < 0.001). PBMT, therefore, increased the production of collagen type I and III, downregulated the expression of MMP-3 and MMP-9, and upregulated that of VEGF, with age and age-induced hormonal deficiency.