Effect of high- and low- frequency transcutaneous electrical nerve stimulation (TENS) on angiogenesis and wound contraction in acute excisional wounds in rat skin / Efeito da estimulação elétrica nervosa transcutânea (TENS) de alta e de baixa frequências na angiogênese e na contração da ferida excisional aguda em pele de ratos

Abstract Introduction: Transcutaneous electrical nerve stimulation (TENS) can alter the local temperature, increase skin blood flow and induce the release of vasodilator neuropeptides and growth factors. These changes may be related to the effects of TENS on the tissue repair process. Objective: To assess the effect of high- and low-frequency TENS on angiogenesis and the contraction of acute excisional wounds in rat skin. Methods: Fifty-four young adult male EPM1-Wistar rats were used in the study. An excisional wound was performed on the back of each animal using an 8mm punch. The animals were randomly assigned to three groups: the High-frequency Group (HG: 80 Hz), Low-frequency Group (LG: 5 Hz), and Sham Group (SG: TENS turned off). TENS was delivered on three days consecutives. Pulse duration and current intensity were 200 µs and 15 mA. The length of each TENS session was 60 minutes. Microscopic and macroscopic assessments were performed on 3, 7 and 14 postoperative (PO) days. Hematoxylin-eosin staining was utilized to quantify the neoformed blood vessels. Photographs were taken to determine the percentage of wound contraction. After assessment, the animals were painlessly sacrificed. Results: There were increases in angiogenesis in the HG on the 3 PO day, and in the LG on the 14 PO day. No significant differences in wound contraction were found between the groups on the different PO days. Conclusion: High frequency TENS improved angiogenesis, and neither frequency of TENS had any influence on the contraction of acute excisional wounds in rat skin.

Resumo Introdução: A TENS pode promover alteração da temperatura local, aumento do fluxo sanguíneo cutâneo, liberação de neuropeptídeos vasodilatadores e de fatores de crescimento. Tais eventos podem estar relacionados aos efeitos da TENS no processo de reparo tecidual. Objetivo: Avaliar o efeito da TENS de alta e de baixa frequências na angiogênese e na contração da ferida excisional aguda em pele de ratos. Materiais e Métodos: Foram utilizados 54 ratos (Wistar-EPM1), machos e adultos jovens. Realizou-se uma ferida excisional na região dorsal do animal com um punch medindo 8 milímetros. Os animais foram randomizados em três grupos: Grupo Alta frequência (HG:80 Hz), Grupo Baixa frequência (LG:5 Hz) e Grupo Simulado (SG, TENS desligada). A TENS foi aplicada por 3 dias consecutivos. A duração do pulso e intensidade da corrente foram 200 µs e 15 mA. O tempo de cada aplicação foi de 60 minutos. As análises microscópicas e macroscópicas foram feitas nos POI, 3, 7 e 14 dias de pós-operatório (PO). Utilizou-se a hematoxilina-eosina para quantificação dos vasos neoformados. Foram feitas imagens fotográficas para determinação da porcentagem de contração da ferida. Após as avaliações, os animais foram sacrificados. Resultados: Observou-se aumento na quantidade de vasos sanguíneos no HG, aos 3 dias de PO; e no LG, aos 14 dias de PO. Não houve alterações na contração da ferida entre os grupos. Conclusão: A TENS de alta frequência estimulou a angiogênese e ambas as frequências não influenciaram na contração da ferida excisional aguda em pele de ratos.

What is better in TRAM flap survival: LLLT single or multi-irradiation?

Low-level laser therapy (LLLT) has been used with the aim of improving vascular perfusion of the skin and musculocutaneous flaps. This study evaluated the effect of LLLT on transverse rectus abdominis musculocutaneous flap (TRAM) viability, vascular angiogenesis, and VEGF release. Eighty-four Wistar rats were randomly divided into seven groups with 12 rats in each group. Group 1 received sham laser treatment; group 2, 3 J/cm(2) at 1 point; group 3, 3 J/cm(2) at 24 points; group 4, 72 J/cm(2) at 1 point; group 5, 6 J/cm(2) at 1 point; group 6, 6 J/cm(2) at 24 points; and group 7, 144 J/cm(2) at 1 point. All experimental groups underwent LLLT immediately after the TRAM operation and on the following 2 days; thus, animals underwent 3 days of treatment. The percentage of skin flap necrosis area was calculated on the fourth postoperative day using the paper template method, and two skin samples were collected using a 1-cm(2) punch to evaluate alpha smooth muscle actin (1A4) and VEGF levels in blood vessels. Significant differences were found in necrosis percentage, and higher values were seen in group 1 than in the other groups. Statistically significant differences were not found among groups 3 to 7 (p<0.292). Groups 5 and 7 showed significantly higher VEGF levels compared to other groups. Groups 3 and 5 had an increase in levels of blood vessels compared to other groups. LLLT at energy densities of 6 to 144 J/cm(2) was efficient to increase angiogenesis and VEGF levels and promote viability in TRAM flaps in rats.

Different power settings of LLLT on the repair of the calcaneal tendon.

OBJECTIVE: The purpose of this study was to evaluate the effect of an 830-nm GaAlAs diode laser operating at output powers of 40, 60, 80, and 100 mW and energy density of 30 J/cm(2) on the repair of partial calcaneal tendon ruptures in rats. METHODS: A partial tendon rupture was induced in all animals, which were treated with laser irradiation for 5 consecutive days. Six days after injury, the injured tendons were removed and examined by polarized light microscopy. Collagen fiber organization was evaluated by birefringence measurements, and collagen content was determined by Picrosirius Red staining. RESULTS: It was observed that the higher the output power (60-100 mW) the greater the amount of type III collagen (p<0.01). The amount of type I collagen was significantly greater (p=0.05) in the 80 mW group than in the control group (sham stimulation). A non-statistically significant improvement in the realignment of collagen fibers was observed in the irradiated groups. CONCLUSIONS: Low-level laser therapy resulted in significantly greater amounts of type III collagen (output powers of 60 mW or more) and type I collagen (output power of 80 mW), however, no significant differences between groups were found in the realignment of collagen fibers.