ORIGINAL ARTICLE Effects of LED phototherapy on relative wound contraction and reepithelialization during tissue repair in hypothyroid rats: morphometric and histological study Gardênia Matos Paraguassú & Milena Góes da Guarda & Flávia Calo Aquino Xavier & Maria Cristina Teixeira Cangussu & Tânia Tavares Rodriguez & Maria José Pedreira Ramalho & Antônio Luis Barbosa Pinheiro & Luciana Maria Pedreira Ramalho Received: 2 March 2013 /Accepted: 7 August 2013 /Published online: 24 August 2013 # Springer-Verlag London 2013 Abstract The aim of this study was to assess morphometri- cally and histologically, the effects of light-emitting diode (LED) (λ 630±20 nm) phototherapy on reepithelialization and wound contraction during tissue repair in hypothyroid rats. Thyroid hormone deficiency has been associated with disorders of tissue repair. LED phototherapy has been studied using several healing models, but their usefulness in the improvement of hypothyroidism wound healing remains un- known. Under general anesthesia, a standard surgical wound (1 cm 2 ) was produced on the dorsum of 48 male Wistar rats divided into four groups of 12 animals each: EC—control euthyroid, ED—euthyroid + LED, HC—control hypothyroid, and HD—Hypothyroid + LED. The irradiation started imme- diately after surgery and was repeated every other day for 7 and 14 days. Photographs of the wound were taken at the day of the surgical procedure and on days 8 and 15 after surgery, when animals’ deaths occurred. The specimens were re- moved, routinely processed, and stained with hematoxylin/ eosin. Seven days after the surgery, it was possible to observe statistically significant reductions in the wound area of the irradiated euthyroid group, in comparison to hypothyroid group, irradiated and non-irradiated (ANOVA, p <0.05). The reepithelialization was significantly higher in the euthyroid and hypothyroid groups irradiated with LED than in the non- irradiated groups (Fisher’ s test, p <0.05). No significant dif- ference was found in the experimental period of 14 days among the groups. The hypothyroidism delayed wound healing and the LED phototherapy, at these specific parame- ters, improved the process of reepithelialization in the pres- ence of hypothyroidism. Keywords LED phototherapy . Wound repair . Reepithelialization . Thyroid Introduction Wound healing is a complex process that involves a series of dynamic events including coagulation, inflammation, granu- lation tissue formation, epithelialization, contraction, and tis- sue remodeling. This phenomenon still attracts the attention of many scientists, especially with regard to factors that delay tissue repair [1–6]. It is well known that some diseases or conditions such as uncontrolled diabetes, malnutrition, hypo- thyroidism, anemia, and burns, may delay wound healing [7]. Thyroid hormone is essential for optimal epidermal cell proliferation [3]. The exact pathogenesis of delayed wound healing associated with hypothyroidism is not completely G. M. Paraguassú : M. G. da Guarda : F. C. A. Xavier : M. C. T. Cangussu : A. L. B. Pinheiro : L. M. P. Ramalho (*) School of Dentistry, Federal University of Bahia, Avenida Araújo Pinho, 62. Canela, Salvador, BA CEP 40140-110, Brazil e-mail: lucianaramalho@uol.com.br T. T. Rodriguez : M. J. P. Ramalho Department of Physiology, Health Sciences Institute, Federal University of Bahia, Salvador, BA, Brazil Lasers Med Sci (2014) 29:773–779 DOI 10.1007/s10103-013-1419-x