Pathological wound healing is associated with ageing and many chronic diseases. It is one of the major medical burdens in the developed world, contributing towards leading causes of death and disease worldwide. The stages of wound healing normally progress in a predictable, timely manner; if they do not, healing may progress inappropriately to either a chronic wound such as diabetic ulcer or fibrotic scarring such as scleroderma. The prevalence of chronic wounds and fibrotic pathologies arrives at the number of ~80 million, which increases to >100 million if we include fibrosis associated with surgical procedures. Current treatments for chronic wounds and fibrotic scarring have limited success, so better understanding of biological mechanisms that promote healing whilst preventing scarring is urgent to achieve better therapies. Research carried out by scientists around the world as well as our own laboratory has recently discovered a crucial role for biological clocks in optimal wound healing and in curbing fibrotic scarring following injury. Biological clocks are timing mechanisms in our body that generate 24h rhythms in physiology and behavior, such as sleep/wake cycles, body temperature and hormone levels. They exist in almost all tissues and cells in our body. Their disruption due to shift work and ageing is a strong risk factor for chronic diseases. Our new pilot data using rodent models shows that there is a robust day/night variation in skin wound healing rates so that skin heals faster when injured during the night then when injured during the day. This faster healing at night is associated with increased levels of genes involved in production and organisation of matrix, a very important component for closing the wound. We have also discovered that antioxidant protection in our cells varies between day and night, and has an important role in faster night-time healing following injury. Even more, small, drug-like molecules capable of boosting antioxidant levels in our cells have a greater efficiency when used at the right time of day. These observations suggest exciting new ways to tackle pathological wound repair mechanisms. In this new project, we will answer the main question as to whether the biological clock present in key cells involved in wound healing (called fibroblasts) is critical for daily variation in repair capacity that we observed in our pilot studies. We will make use of two genetically modified rodent models 1) one in which we can visualise (by fluorescent tags) a matrix gene (called collagen) specifically activated in fibroblast cells and 2) the other in which we have genetically deleted the clock gene specifically in fibroblast cells. Using these unique rodent models, we will be able to monitor temporal changes in clock gene activity and matrix organisation within wounds. This research will uncover critical importance of robust clocks within key wound healing cells for time-of-day variation in healing rate and organisation of optimal wound repair. Furthermore, we will take advantage of advanced molecular biology tools to find out which genetic mechanisms biological clocks use to regulate matrix genes important in healing such as collagen. Using high-tech biochemical approaches, we will further find out whether biological clocks help our cells 'tell the time' when to produce the right amounts of antioxidants to fight off rises in dangerous free radicals following injury. Finally, we will test whether antioxidant-based chronotherapy (giving treatments according to one's body clock) has beneficial healing effects in chronic wound or scarring conditions such as diabetes and scleroderma. To test this, we will use rodent models of diabetes as well as skin tissue biopsies and cells from patients with Scleroderma. These new studies will provide crucial evidence to support future studies pinning down biological clocks as a new therapeutic target for the management of chronic wounds and scarring.