Efeitos da fotobiomodulação associado ao própolis verde na angiogênese, produção e reorganização do colágeno em feridas cutâneas de ratos diabéticos

Abstract

In diabetes mellitus (DM) the accumulation of advanced glycation end products promotes structural and biochemical changes in the tissues, contributing to the development of clinical complications, especially delayed skin wound repair. The aim of this study was to evaluate the effect of the combination of laser therapy and topical application of green propolis extract on cutaneous wound healing in rats with DM induced by streptozotocin. Male Wistar rats (n = 90) were divided into five groups according to whether or not the DM Induction and the therapy employed in surgically produced cutaneous wounds: (N) normoglycemic without therapy; (C) diabetic control without therapy; (L) laser therapy (660 nm, 30 mW, 4 J/cm²); (P) topical administration of green propolis (30% alcohol extract); and (LP) combined laser and propolis therapy. The treatments were performed at the immediate postoperative moment and daily for six days. At intervals of 7, 14 and 21 days, wound closure was assessed by digital image of the surgical site and the animals were then submited to euthanasia. Histological sections of the healing area were stained with Picrosirius Red for quantitative analysis of the occupied area and the organization pattern of the collagen under polarized light microscopy and fluorescence; and with Toluidine Blue for counting of intact and degranulating mast cell. The microvessel density and the number of myofibroblasts were evaluated by immunohistochemical expression of CD105 and α-smooth muscle actin (α-SMA), respectively. Data show that the treated groups (L, P and LP) exhibited an accelerated contraction of the surgical wound (p<0.05) and a higher collagenation index, both in polarized and fluorescence light microscopy (p<0.05). These two methods of evaluation had a strong correlation index in healthy tissue (r=0.7559; p<0.0001), and moderate in the wound bed (r=0.5446; p<0.0001). The treated groups showed a more random morphological organization (p <0.05) by collagen orientation index and a progressive replacement of fine fibers by a thick collagen fibers. A higher number of myofibroblasts was evident in the wounds treated with P, LP and L, on days 7, 14 and 21, respectively. A smaller amount of degranulating mast cells was observed in the treated groups (p <0.05), with an even greater reduction in LP group. The vascular microdensity remained higher in the treated groups, with a better neovascularization index in the P groups on days 7 and 21, and in LP on day 14. It is concluded that the association of laser and propolis promotes a faster repair of wounds in diabetic rats by lower degranulation of mast cells, increase in vascular density, and greater production and organization of collagen through the higher density of myofibroblasts.