Study the effect of day and night on skin wound healing

The skin is a complex structure and has three layers (epidermis, dermis and hypodermis). The skin has different cell types such as Langerhans cells, keratinocytes and etc. The skin is the first layer of the body's defense and protects the body against external factors (such as chemicals, physical damage and etc). The wound healing process begins following any damage to the skin. Wound healing consists of four stages (inflammation, debridement, proliferation and maturation). Wound healing is affected by many factors, including the circadian rhythm. In this regard, circadian rhythm is a biological process that follows a 24-hour cycle and affects the skin cells and other body organs. The aim of the present study was to compare the speed of wound healing during days and nights. Forty male Sprague-Dawley rats were prepared and kept at a constant temperature, light (12 hours light / 12 hours dark) and proper nutrition. Rats were randomly selected and divided into groups A and B. In group A, ulcers were created at 8-10 am and in group B, ulcers were created at 11-9 pm. Evaluation of results based on daily measurement of wound surface (by Digimizer program) immediately after wound creation and (3, 7, 10, 14 and 21 days after wound creation) to determine the rate of clinical healing and biochemical test (hydroxyproline assay) were performed to compare the rate of wound healing on the 10th and 21st day of the study on skin samples in both groups. Hydroxyproline level was markedly increased on day 21 in group A as compared to group B. Measurements of wound dimensions and the healing process showed a significant increase on day 21 in group A in comparison with group B. The results of the present study show that daytime wounds creation healing faster than nighttime wounds creation.