Low intensity ultrasound therapy induces angiogenesis and persistent inflammation in the chronic phase of the healing process of third degree burn wounds experimentally induced in diabetic and non-diabetic rats

PURPOSE: To evaluate the effects of low intensity ultrasound on the healing process of third degree burn wounds in experimentally induced diabetic Wistar rats. METHODS: One hundred rats were divided into: control group; non-diabetic treated group; diabetic control group; diabetic treated group. The therapy was performed with a 3MHz ultrasound application, pulsed emission at 100Hz frequency, modulated at 20% with a dosage of 0.5W/cm(2) during three minutes throughout 30 days. The surgical debridement of the wound was performed once at day 2. The wounds were morphometrically, macroscopically and microscopically evaluated at 3, 7, 14, 21 and 30 days. RESULTS: The wound contraction and collagen quantification were higher in all treated groups. Macroscopically, necrosis was higher in the diabetic control group. Granulation tissue was higher in treated groups during the proliferative and remodeling phase. Microscopically, there were greater mononuclear inflammatory infiltration, angiogenesis and fibroblast quantification in treated groups during the proliferative and remodeling phases. CONCLUSIONS: therapeutic ultrasound is beneficial in the inflammatory and proliferative phases of the healing process because it controlled the necrotic tissue, increased the granulation tissue and wound contraction. However in the remodeling phase it is not beneficial because of the continued angiogenesis and a mononuclear inflammatory infiltration.