Role of fibroblast Dipeptidyl peptidase 4 (DPP4/CD26) in dermal wound healing, scarring and regeneration
Final Report Abstract
We were able to dissect the expression of DPP4 in murine skin during HF cycle and in non-regenerative areas vs. regenerative areas of mouse wounds. We could show that contrary to was previously described, DPP4 in expressed not only by fibroblast but by endothelial cells, keratinocytes and immune cells, although up-regulation of DPP4 during HF resting phase is restricted to stromal cells. In human cicatritial alopecia there is also increased DPP4 expression in lesional scalp, which mirrors the situation of large murine wounds. Own data and reanalysis of scRNAseq libraries from previous studies show similar distribution of Dpp4 expression in nin-regenerative wound settings and HF telogen. Topical DPP4 inhibition (DPP4i) with FDA/EMA-approved Sitagliptin (Sit) on models of HF- activation/regeneration was shown to decrease pro-fibrotic signaling in the skin, induce a differentiation trajectory of HF-cells, and activate Wnt-targets related to HF-activation/growth but not those supporting fibrosis. Functionally, DPP4i of depilated murine backs in telogen results in accelerated anagenprogress, while treatment of wounds with Sit resulted in reduced expression of fibrosis markers, increased induction of anagen around wounds, and HF-regeneration in the wound center. These effects were associated with higher expression of Wnt-target Lef1, known to be required for HF- anagen/regeneration. Taken together, our study demonstrates a role for DPP4 in HF biology and shows how DPP4i, currently used as oral medication to treat diabetes, could be repurposed into a topical treatment agent to potentially reverse HF-loss in alopecia and after injury. We expected to have DPP4 expression only on fibroblast, nevertheless our studies show expression by many cell types in murine skin including interfollicular and follicular keratinocytes and immune cells. Since the expression increased during telogen (HF rest) compared to anagen (HF growth) we further analyzed expression of different cell populations at these two phases and could see upregulation only on stromal cell populations during telogen (fibroblasts, dermal papilla, endothelial cells). We also saw a topographical distribution of DPP4 expression in large murine wounds, having the highest expression in wound periphery, where fibrosis takes place, whereas the regenerative wound centers had very low expression of DPP4. This prompted us to study whether DPP4 is also differentially expressed in lesional and non-lesional skin from patients affected by cicatricial vs. non cicatricial alopecia. We could see more DPP4 in cicatricial alopecia, especially in lesional skin. We planned to specifically study the role of DPP4 on fibroblast by using a double knockout mouse line (Dpp4fl/fl;Col1a2-CreERT). We could see an effect of this knockout after wound healing in terms of more HF regeneration, nevertheless DPP4 expression (measured with flow cytometry and immunofluorescence) on cutaneous cells was reduced only modestly to a maximum of 50% compared to controls. This occurred despite strong Cre expression after tamoxifen administration and efficient knockout of the floxed allele. We are currently developing a new line using other promoters for cell specific expression of Cre in fibroblast as wells as a lentiviral delivery of floxed shRNA against Dpp4 to confirm our findings.
Publications
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Phagocytosis of Wnt inhibitor SFRP4 by late wound macrophages drives chronic Wnt activity for fibrotic skin healing. Science Advances, 6(12).
Gay, Denise; Ghinatti, Giulia; Guerrero-Juarez, Christian F.; Ferrer, Rubén A.; Ferri, Federica; Lim, Chae Ho; Murakami, Shohei; Gault, Nathalie; Barroca, Vilma; Rombeau, Isabelle; Mauffrey, Philippe; Irbah, Lamya; Treffeisen, Elsa; Franz, Sandra; Boissonnas, Alexandre; Combadière, Christophe; Ito, Mayumi; Plikus, Maksim V. & Romeo, Paul-Henri
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Cell Population Dynamics in Wound-Induced Hair Follicle Neogenesis Model. Life, 12(7), 1058.
Helm, Maria; Loui, Juliane; Simon, Jan C. & Ferrer, Ruben A.
