Having reached epidemic proportions in the United States and globally, diabetes and the associated wound healing impairment is a significant and growing clinical problem. In 2014, more than 70,000 lower extremity amputations disabled diabetic patients, of which nearly 85% were preceded by a diabetic wound. Despite the enormous impact of these wounds on both individuals and society, effective therapies are lacking. Thus, the improving/accelerating the healing of cutaneous wound in diabetics has the potential to significantly improve patient outcomes and reduce healthcare expenditures. The long-term goal of our research is to develop therapies to effectively promote healing of diabetic wounds. The defects in wound healing in diabetics is multifactorial. A central feature of diabetic wounds is the persistence of chronic inflammation, partly due to the prolonged presence of proinflammatory (M1) macrophages. The presence of the M1 macrophage phenotype and failure to transition to the regenerative or pro-remodeling (M2) macrophage phenotype have been shown to play a role in the pathogenesis of the diabetic wounds; however, the mechanism underlying this relationship remains unclear. Dysregulated expression of long non-coding RNAs (lncRNAs) has recently been implicated in wound healing, and it is thought that dysregulated expression or function of lncRNAs might contribute to poor wound healing. The lncRNA, growth arrest specific 5 (GAS5), has been widely studied in numerous human diseases, although a role in wound healing had not been observed. We recently found evidence that GAS5 does, in fact, play a role in wound healing. Our recent observations reveal abnormal GAS5 levels in impaired healing of diabetic wounds: 1) The expression of GAS5 is significantly increased in diabetic wounds and in cells isolated from diabetic wounds when compared to non-diabetic tissues; 2) Hyperglycemia induces GAS5 expression in macrophages in vitro; 3) Overexpression of GAS5 in vitro promotes macrophage polarization towards an M1 phenotype by upregulating STAT1; 4) GAS5 expression is significantly elevated in undamaged human diabetic skin relative to non-diabetic skin; and 5) Most importantly, GAS5 loss-of-function enhances diabetic wound healing. Given the compelling evidence that GAS5 is involved in wound healing, it becomes essential to determine the mechanisms of GAS5 action. Filling this gap in knowledge holds promise to overcome a heretofore impenetrable hurdle preventing development of novel therapeutic strategies to address the rising morbidity associated with diabetic wounds. Our objective here is to elucidate the mechanisms through which GAS5 impairs diabetic wound healing, and to assess GAS5 as a therapeutic target for improving diabetic wound healing. Our central hypothesis is that elevated GAS5 expression in diabetic wounds causes persistence of the M1 macrophage phenotype, increased inflammation, and delayed wound healing. The rationale for this work is that through understanding how GAS5 is regulated and how GAS5 regulates macrophage polarization, we will be positioned to manipulate GAS5 for therapeutic purposes. We will test our central hypothesis in the following three specific aims:
Aim 1 : Determine the impact of altered GAS5 levels on wound macrophage polarization and inflammatory signaling in diabetic wounds.
Aim 2 : Elucidate the molecular mechanisms underlying GAS5 dysregulation in macrophage and diabetic wounds.
Aim 3 : Assess the functional consequences of inhibition of GAS5 on macrophage polarization and diabetic wound healing. It is likely that completion of these studies will provide a comprehensive understanding of the role lncRNA GAS5 in diabetic wounds, allowing the identification of novel therapeutic targets and enabling the design of novel interventions aimed at improving healing of diabetic wounds.
Non-healing wounds in diabetic patients represent a challenging clinical problem that often results in amputation. To date, there is no good way to treat these wounds because of the complicated disorders in diabetes. Our overall goal is to determine the mechanisms involved in impairment of diabetic wounds, in particular, the role of long non-coding RNA, GAS5 in regulation of macrophage polarization and inflammatory response, to develop a better understanding of chronic inflammation for potential modification of the diabetic wounds at lncRNA level.