IRF6 in the Inflammatory Phase of Cutaneous Wound Healing

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DESCRIPTION (provided by applicant): The innate immune system is of critical importance in the initiation of the inflammation and proper wound healing. Amongst molecules modulating the immune response are the transcription factors of the interferon regulatory factor (IRF) family. Of particular interest is IRF6, a unique member of this family and a transcriptional regulator of wound healing. Indeed, patients with Van der Woude syndrome (VWS), an autosomal dominant orofacial clefting syndrome caused by IRF6 haploinsufficiency, are more likely to have wound complications following corrective surgery than patients with a non-syndromic form of orofacial clefting. Loss of Irf6 results in craniofacial, limb and epidermal anomalies in the mouse, leading to neonatal mortality. We recently identified the presence of strong Irf6 signal in the granulation tissue of excisional wounds, particularly in macrophages and neutrophils. Preliminary data show that neutrophils from patients with VWS have impaired chemotaxis in vitro compared to controls. Furthermore, conditional removal of Irf6 in neutrophils and macrophages in a unique murine model results in a three fold reduction of cellular influx in a simple model of inflammation. Finally, cutaneous wound healing was severely impaired seven days post-wounding. Although the function of other IRF family members in innate immunity is well described, nothing is known about the function of IRF6 in innate immune cells and how it affects the inflammatory phase of cutaneous wound healing. The central hypothesis of this proposal is that Irf6 is required for proper macrophages and neutrophils function in vitro and in vivo in the context of wound healing. In specific aim #1, we will test the hypothesis that Irf6 regulates the secretion and migration of macrophages and neutrophils using luminex assay and live imaging of migration assays. In specific aim #2, we will directly test the hypothesis that expression of Irf6 in innate immune cells is necessary for the proper inflammatory phase of wound healing using our Irf6-conditional knockout mouse crossed with a lysosyme-driven Cre-recombinase mouse model. This proposal is innovative in that it extends the recently discovered role of Irf6 in epidermal morphogenesis and biology to innate immunity and cutaneous wound healing-a process that is highly significant from a clinical perspective, and a major cause of rising health-related costs. A the completion of these studies, we will have a better understanding of the contribution of Irf6 to the inflammatory process during cutaneous wound healing. Because continuous inflammation is a phenomenon leading to chronic wounds, chronic obstructive pulmonary disease, and is also implicated in cancer, new information will be obtained about a potential pathophysiological mechanism for these other common health concerns.