Immunohistochemical assessment of myofibroblasts and lymphoid cells during wound healing in rats subjected to laser photobiomodulation at 660 nm.

OBJECTIVE: The goal of this study was to assess the biomodulatory effect of low-level laser therapy (LLLT) on myofibroblasts and T and B cells during wound healing. BACKGROUND DATA: Phtotobiomodulation using LLLT has been extensively applied to improve wound healing. MATERIALS AND METHODS: Standardized artificial surgical wounds were made on the backs of 24 male rats. Half of them underwent LLLT (20 J/cm(2)) at 660 nm delivered for 7 d. At 8 and 14 d post-surgery the healing wounds were removed and immunohistochemical analysis of myofibroblasts, T cells, and B cells was carried out. The mean of each cell subset was calculated and compared to one another using two-way analysis of variance (ANOVA) and Tukey's test. RESULTS: The average number of myofibroblasts was statistically significantly higher in the irradiated group than in the non-irradiated group on the eighth (p = 0.001) but not the 14th (p = 0.555) day. B and T cells were significantly more conspicuous in the irradiated group on both the eighth (p = 0.004 and 0.02, respectively) and 14th days (p = 0.04 and 0.03, respectively). CONCLUSIONS: Our results suggest that LLLT facilitates myofibroblastic differentiation during the early stages of the cicatricial repair process. Furthermore, LLLT also appears to modulate the inflammatory response by downregulating lymphocytic proliferation during the wound healing process.

Effect of laser therapy on bone tissue submitted to radiotherapy: experimental study in rats.

OBJECTIVE: The aim of this study was to investigate the effect of laser therapy (lambda = 780 nm) on bone tissue submitted to ionizing radiation. BACKGROUND DATA: The biostimulation effect of laser in normal bone tissue has already been demonstrated successfully; however its effect on bone tissue submitted to radiotherapy has not yet been studied. METHODS: Twenty-two Wistar rats were randomly divided into four groups: group I, control (n = 4), submitted only to radiotherapy; group II, laser starting 1 day prior to radiotherapy (n = 6); group III, laser started immediately after radiotherapy (n = 6); group IV, laser 4 weeks after radiotherapy (n = 6). The source of ionizing radiation used was Cobalt 60, which was applied in a single dose of 3000 cGy on the femur. The laser groups received seven applications with a 48-h interval in four points per session of DE = 4 J/cm(2), P = 40 mW, t = 100 sec, and beam diameter of 0.04 cm(2). All animals were killed 6 weeks after radiotherapy. RESULTS: Clinical examination revealed cutaneous erosions on experimental groups (II, III, and IV) starting at the 6th week after radiotherapy. The radiographic findings showed higher bone density in groups II and IV (p < 0.05) compared to the control group. The results further showed an increase of bone marrow cells, and number of osteocytes and Haversian canals in experimental groups II and IV (p < 0.05). It was also found an increase of osteoblastic activity, in groups II, III, and IV (p < 0.05). CONCLUSION: Laser therapy on bone tissue in rats presented a positive biostimulative effect, especially when applied before or 4 weeks after radiotherapy. However, the use of laser in the parameters above should be used with caution due to epithelial erosions.