Laser irradiation: a complementary treatment for wounds N N Houreld 1 and H Abrahamse Laser Research Centre, Faculty of Health Sciences, University of Johannesburg, P.O. Box 17011, Doornfontein, South Africa, 2028. Tel: +27 (0)11 559-6406 E-mail: nhoureld@uj.ac.za / habrahamse@uj.ac.za Abstract. Aim: Since the invention of the laser, its application in the health sector has been studied and in an attempt to discover effective alternative treatments, Low Level Laser Therapy (LLLT), commonly known as biostimulation or photo-biostimulation, has emerged. This therapy has been successfully used both in in vitro and in vivo studies in wound healing. Although this therapy is in use worldwide, the mechanism of action is not fully understood. Methods: Various cell culture models, such as wounded, diabetic wounded, ischemic and hypoxic have been exposed to visible and infra-red laser light and the effect on cell migration, cell survival, proliferation, cytotoxicity, mitochondrial responses, nitric oxide (NO) release, secondary messenger activation, DNA damage and pro-inflammatory cytokine expression have been studied. Results: Laser irradiation at the correct wavelength and fluence has shown to have a positive effect on stressed cells in vitro. There is an increase in migration, survival and proliferation, mitochondrial activity, NO release and secondary messenger activation. A decrease in cytotoxicity, DNA damage and pro-inflammatory cytokines is also seen. Conclusion: LLLT offers an alternative wound healing therapy. At a biochemical level there is a positive effect on cells, with stressed cells being pushed into cell survival pathways. 1. Introduction Wound healing involves a series of overlapping and intertwining events all aimed at reversing the loss of structural integrity and is controlled by a wide variety of cells, growth factors, cytokines and enzymes, all of which are released at the wound site [1]. Wound healing is divided into four main events, namely haemostasis, inflammation, proliferation and remodelling. When this sequence of events is disrupted, delayed wound healing ensues. Chronic, slow-to-heal or non-healing wounds are a common complication of diabetes mellitus (DM), particularly on the feet and lower limbs. These diabetic foot ulcers are susceptible to infection and often necessitate lower-limb amputation, which impacts heavily on patients, their families, health care departments and government. Around 20% of all patients with DM who develop foot ulcers require amputation [2]. Amputation occurs 30 times more frequently in diabetic patients than in the general population [3]. The underlying causes of these foot ulcers are thought to be due to micro- and macrovascular disease and advanced glycation end products [4] and are associated with sensory loss. The current treatment protocol is both systemic, treatment of the metabolic condition (diabetes), and local treatment of the diabetic ulcer. Common treatment of the diabetic foot involves debridement, wound care and dressing, antibiotic therapy, 1 To whom any correspondence should be addressed.