Project description:Adult mammalian skin wound healing is typically accompanied by a fibrotic scar that impairs normal skin function and regeneration of skin appendages. Interestingly, however, in adult mice, large skin injuries exhibit de novo formation of hair follicles (HFs, a phenomenon termed wound-induced HF neogenesis) in the center of the wound. Our previous analysis provides compelling evidence suggesting that regional epigenetic changes within the mesenchymal cells of the skin may underlie the divergent response to wound healing. To test this directly, we performed single-cell Assay for Transposase-Accessible Chromatin using Sequencing (sc-ATAC-Seq) on cells isolated from the center of large wounds to identify regions of the genome that are becoming differentially accessible within upper (epithelial-interfacing) fibroblasts as they transition to induce new HFs compared to their lower dermal counterparts that adopt a fibrotic phenotype. Together, our data reveals the identity and dynamics of key coding, non-coding, and regulatory regions that underlie a wound responsive fibroblasts' transition to inductive neodermal condensate cells.
Project description:We report transcriptomes of cells from large skin wounds. Dead cells were removed from post-wounding day (PWD) 12 skin wound tissue using dead cell removal kit (MACS). Remaining live cells were analyzed
Project description:Human and murine skin wounding commonly result in fibrotic scarring but the murine wounding model Wound Induced Hair Neogenesis (WIHN) can frequently result in a regenerative repair response. Here we show in single cell RNA-seq comparisons of semi-regenerative and fibrotic WIHN wounds, increased expression of phagocytic/lysosomal genes in macrophages associated with predominance of fibrotic myofibroblasts in fibrotic wounds. Investigation revealed that macrophages in the late wound drive fibrosis by phagocytizing dermal Wnt inhibitor SFRP4 to establish persistent Wnt activity. In accordance, phagocytosis abrogation resulted in transient Wnt activity and a more regenerative healing. Phagocytosis of SFRP4 was integrin-mediated and dependent on the interaction of SFRP4 with the EDA splice variant of fibronectin. In the human skin condition Hidradenitis suppurativa, phagocytosis of SFRP4 by macrophages correlated with fibrotic wound repair. These results reveal that macrophages can modulate a key signaling pathway via phagocytosis to alter the skin wound healing fate.
Project description:Adult mammalian skin wound healing is typically accompanied by fibrotic scar that impairs normal skin function and regeneration of skin appendages. Interestingly, however, in adult mice, large severe skin injuries exhibit de novo formation of HFs following severe skin injuries (a phenomenon termed wound-induced HF neogenesis, WIHN). Understanding the competent cell types and molecular mechanisms that enable regenerative wound healing will be critical for developing treatments that restore skin function after injury. We described the existence of an adult bipotent hair follicle dermal stem cell (hfDSC) that functions to regenerate the connective tissue sheath and to populate the DP with new cells (Rahmani et al., 2014). Based on this, we hypothesized that the mesenchymal cells comprised within the neogenic HFs might originate from hfDSCs. To test this, we employed αSMACreERT2:ROSAYFP and Hic1CreERT2:TDTmt mice to examine the contribution of hfDSCs or hfDSCs and reticular/hypodermal progenitors, respectively, to the formation of neodermis and regeneration of de novo HFs. Mice received full-thickness excision wounds (>1 cm2) and then harvested at 18-140 days post-wounding (dpw). αSMA+ve and Hic1-lineage cells were activated upon wounding, migrated into the wound, and contributed to both DP and DS in almost all de novo-formed HFs. Surprisingly, hfDSCs contributed only a minority of cells (20%) to nascent DP cells, whereas Hic1-lineage cells generated >90% of the neogenic DP cells. In both cases, cells integrating into neogenic HF mesenchyme appeared to restore the hfDSC pool, since they repopulated the neogenic mesenchyme over successive regenerative hair cycles. Finally, using an ex vivo HF formation assay, we found that prospectively isolated extrafollicular Hic-lineage cells could participate in HF formation when exposed to a permissive environment. Our data reveal that despite their origin in the reticular/hypodermis, Hic1-lineage dermal progenitors are able to adopt a regenerative response during wound healing if provided with a permissive local environment.
Project description:After skin injury fibroblasts migrate into the wound and transform into contractile extracellular matrix-producing myofibroblasts to promote skin repair. Persistent activation of myofibroblasts can cause excessive fibrotic reactions, but the underlying mechanisms are not fully understood. We used SMA-GFP transgenic mice to study myofibroblast recruitment and activation in skin wounds. Myofibroblasts were initially recruited to wounds three days post injury reached a maximum after seven days and subsequently declined. Expression profiling showed that 1749 genes were differentially expressed in sorted myofibroblasts from wounds seven days post injury. GO-Term analysis associated most of these genes with the extracellular region and cell periphery including upregulated genes encoding for ECM proteins, integrins and focal adhesion proteins and a specific set of growth factors, cytokines and chemokines promoting the healing response. In contrast, cell adhesion molecules involved in cell-cell interaction were downregulated. Novel genes not yet known to be expressed in myofibroblast were found. Hence, this first characterization of a myofibroblast specific expression network at the peak of granulation tissue formation in situ provides important insights into myofibroblast activation in skin wounds and identifies novel target genes to control excessive ECM deposition during fibrotic reactions.
Project description:Standardized skin wounds were established surgically on mice and allowed to heal during a 15-day period. Expression of genes related to heparan sulfate biosynthesis was studied in wound bed and edges during the healing process. Total RNA was isolated from wound edge (regenerating skin) and wound bed at 2, 6 and 15 days post wounding, as well as from intact control skin. Three animals were used for each time point.
Project description:Chronic cutaneous wounds remain a persistent unmet medical need that decrease expectancy and quality of life. Here, we report that topical application of PY-60, a small molecule activator of the transcriptional coactivator YAP, promotes regenerative repair of cutaneous wounds in pig and human models. Pharmacological YAP activation enacts a reversible pro-proliferative transcriptional program in keratinocytes and dermal cells that results in accelerated re-epithelization and regranulation of the wound bed. These results demonstrate that transient topical administration of a YAP activating agent may represent a generalizable therapeutic approach to treating chronic wounds.