Non-healing wounds in patients with Type 2 Diabetes (T2D) are a major cause of morbidity and mortality and are increasing at an alarming rate. Failure of wound healing in T2D patients represents the most common cause of amputation in the US with a 5-year mortality rate of nearly 50%. Thus, a critical need exists for understanding the wound healing defects in T2D in order to develop targeted therapies. Published data from our lab and my new preliminary data has identified that TLR4 signaling in diabetic wound macrophages upregulates the Notch ligand, DLL4, and promotes inflammation in acute wounds. Further, in diabetic wound macrophages, the TLR4/DLL4 pathway is upregulated secondary to an epigenetic mechanism whereby increased MLL1, a histone methyltransferase, on the Tlr4 promoter promotes increased TLR4 signaling. This increased TLR4 signaling (via MyD88) upregulates DLL4 in diabetic wound M?s and drives inflammation and pathologic healing in diabetes. Our proposed studies will establish that TLR4 is epigenetically upregulated via an MLL1-mediated mechanism in diabetic wound macrophages and directly regulates DLL4 expression. These results have led to our hypothesis that increased TLR4 signaling in diabetic wound macrophages increases DLL4 which promotes chronic inflammation and non-healing in diabetic wounds. Our data suggest that diabetic wound repair may be improved via locally-targeted treatment with TLR4 inhibitor(s) and/or MLL1 inhibitor(s). To test our hypotheses, we will pursue the following Aims:
Aim 1 : To examine the TLR4-dependent regulation of DLL4 in diabetic wound macrophages in acute and chronic diabetic murine wound models.
Aim 2 : To determine if local therapeutic blockade of TLR4 or MLL1 improves diabetic wound repair in acute and chronic murine wound models.
Impaired immune cell response leading to chronic inflammation is a major cause of non-healing diabetic wounds. We have identified that increased TLR4 in diabetic wound macrophages increases the Notch ligand, DLL4 and promotes chronic inflammation in diabetic wounds. This proposal will seek to understand the mechanisms responsible for the increased TLR4/DLL4 in diabetic wound macrophages and will test local therapies to restore macrophage homeostasis and healing in diabetic wounds.
