Induction of fat regeneration in skin wounds by hair follicle signaling

University Of California-Irvine, Irvine CA

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Abstract

DESCRIPTION (provided by applicant): The process of wound healing is critical to restoring integrity and homeostasis after significant skin injuries. Although embryonic skin can heal by regenerating itself completely, adult skin is only capable of partial repair, altering the skin's integrity at the site of injury. Cutaneous adipose tissue is thought to poorly regenerate during wound healing, and because scars lack adipose tissue, they often assume debilitating hypertrophic, keloid, or atrophic characteristics. Lack of adipose regeneration is also a major cause of long term morbidity following extensive soft tissue trauma or surgical resection, such as tumor removal. We have identified the previously unknown phenomenon of adipose tissue neogenesis in large cutaneous wounds that occurs under the instructive signaling of de novo hair follicles. This application will focus on identifying permissive epigenetic changes and novel signaling cues generated by neogenic hair follicles in the wound environment that guide de novo regeneration of cutaneous fat. Our recent lineage analyses show that instead of recruiting already committed adipose precursors from the wound's edges and simply stimulating their differentiation to lipid-laden adipocytes, neogenic hair follicles guide de novo adipogenic cell fae acquisition by otherwise non-adipogenic wound myofibroblasts. Our studies demonstrate that acquisition of adipose identity by wound myofibroblasts critically depends on reactivation of Zfp423 signaling, the lead adipogenic commitment pathway in embryogenesis. Our studies also implicate hair follicle-derived BMP signaling inputs as the critical regulators of adipogenic fate commitment in wound scar tissue. The first goal of the proposed research is to establish the epigenetic changes in wound myofibroblasts that permit their adipogenic competence. Specifically, we will focus on epigenetic changes in Zfp423, the developmental master-regulator gene characterized by an exceptionally CpG-dense promoter. The second goal is to establish the mechanism by which BMP signaling events generated in the wound around neogenic hair follicles promote de novo fat formation. Ultimately, we want to be able to replicate these signaling events in hairless wounds for the purposes of inducing cutaneous fat regeneration. We anticipate that the proposed studies will help uncover new mechanisms that allow adult skin to expand lineage plasticity during wound repair. They could also have applicability to the development of new scarless wound healing strategies.