Large scars are a serious health concern; they inhibit mobility, are painful, and are a source of psychological trauma. In the United States, treatment for burn victims alone amounts to $7.5 billion annually, the total market for scar treatment is estimated to be around $12 billion. There are also several clinical conditions associated with scarring, such as, scleroderma, diabetic ulcers, psoriasis and fibrotic keloid scarring. Consequently, understanding how to regenerate skin has the potential to impact anyone who undergoes surgery, but also individuals with clinical conditions associated with scarring. Adult skin wounds heal with scars, but embryonic skin can regenerate without scarring. However, not knowing how to reproduce the regeneration abilities of embryonic skin in adult skin remains a gap in knowledge. Thus, the long term goal of our research is to establish methods to induce fibroblasts in adult skin to have the same regenerative potential as their embryonic skin counterparts. The particular objective of this application is to induce adult fibroblasts with embryonic transcription factors to reprogram skin to support regeneration. Embryonic skin has Papillary Fibroblasts (PFs) and Reticular Fibroblasts (RFs), which are established during skin development. PFs reside beneath the epidermis, can differentiate into fibroblasts that support hair follicle formation, and express the canonical Wnt transcription factor, Lef1. In contrast, RFs reside in the reticular dermis, secrete the bulk of dermal extracellular matrix, differentiate into adipocytes, and do not express Lef1. Importantly, RFs cannot differentiate into PFs in wounds to support regeneration. Interestingly, a hallmark of skin maturation and aging is the molecular and structural degradation of PFs and the loss of Lef1 expression. Our central hypothesis is that Lef1 is the master regulator of PF function in fibroblasts that induces scar-less skin regeneration in wounds and will restore PF identity in aged skin. Guided by our exciting preliminary data we will use novel transgenic mouse models and next generation sequencing technologies to investigate this hypothesis by the following specific aims:
In aim 1 we will test the hypothesis that Lef1 is the master regulator of PF function and that its induction in RFs supports skin regeneration. Here we will use novel transgenic model systems to test if Lef1 activation in RFs supports regeneration in wounds and chamber grafting assays.
In aim 2, we will define the downstream pathways that Lef1 regulates to specify PF functions. To do this we will perform ChIPSeq and Single-Cell-RNA-Seq with our regenerative transgenic model systems. Finally, in aim 3 we will determine if Lef1 can restore PF identity and function in aged skin. We will analyze ?old? transgenic mice with reprogrammed RFs and test their ability to regenerate skin and inhibit ?aging?. This proposal is innovative because of our novel approach of manipulating embryonic transcription factors in fibroblasts in vivo. The proposed research is significant because our findings will influence clinical and in vitro approaches utilizing fibroblasts to induce human hair follicle regeneration as well as scar-less healing.
The proposed research is relevant to public health because understanding how to regenerate skin without scarring has the potential to impact anyone who undergoes surgery, but also individuals with clinical conditions associated with scarring. The proposed research is relevant to NIH's mission because inducing embryonic transcriptional profiles in adult fibroblasts has the potential to increase our current understanding of fibroblast biology and skin regeneration.
