EFFECT OF LOW INTENSITY LASER COMBINED WITH TOPICAL APPLICATION OF GREEN PROPOLIS ON CUTANEOUS WOUND CONTRACTION IN STREPTOZOTOCIN-INDUCED DIABETIC RATS
Diabetes mellitus; tissue repair; collagen; laser; propolis.
In diabetes mellitus (DM) the accumulation of advanced glycation end products promotes structural and biochemical changes in the tissues, contributing to the appearance of clinical complications, especially delayed healing of skin wounds. Low intensity laser and propolis represent two therapeutic options that have been studied for the treatment of cutaneous lesions; however, there are still controversies regarding the best individual therapeutic protocol and there are no studies analyzing the effects of their combined use in DM models. The aim of the project is to evaluate the effect of the combination of laser therapy and topical application of green propolis extract on the contraction of cutaneous wounds in diabetic rats. Wistar male rats (n=90) were allocated into five experimental groups according to the induction or not of DM and the therapy used on surgically produced cutaneous wounds: (N) normoglycemic without complementary therapy; (C) diabetic control without therapy; (L) low intensity laser therapy (660 nm, 30 mW, 4 J/cm2; (P) topical administration of green propolis (30% alcoholic extract); and (LP) combined laser and propolis therapy. The induction of DM was performed by intraperitoneal administration of streptozotocin, confirmed by serum glucose levels at the fifth day post-induction and monitored during the experiment. The therapeutic applications were performed at the immediate postoperative moment and daily for six days. The wound closure was evaluated through digital images of the surgical area, obtained up to the 21st day. At intervals of 7, 14 and 21 days, the animals were submitted to euthanasia and the healing areas were removed, fixed, and processed for microscopic evaluation. Histological sections were stained with Picrosirius red for quantitative and qualitative analysis of the organization pattern of collagen under polarized light and fluorescence microscopy. The expression of metalloproteinases (MMP-2 and MMP-9) and the α-smooth muscle actin marker for quantification of myofibroblasts will also be evaluated. Partial data demonstrate that the treated groups (L, P, and LP) showed a more rapid closure of the surgical wound area, with a positive correlation to the collagenation index. Initial analyzes of the tissue organization pattern indicate that the LP group has longer and thicker collagen fibers, suggesting that the therapeutic association may promote a better quality of tissue repair in the model studied.