Preventing Engrailed-1 activation in fibroblasts yields wound regeneration without scarring

Abstract

Skin scarring, the end result of adult wound healing, is detrimental to tissue form and function. Engrailed-1 lineage–positive fibroblasts (EPFs) are known to function in scarring, but Engrailed-1 lineage–negative fibroblasts (ENFs) remain poorly characterized. Using cell transplantation and transgenic mouse models, we identified a dermal ENF subpopulation that gives rise to postnatally derived EPFs by activating Engrailed-1 expression during adult wound healing. By studying ENF responses to substrate mechanics, we found that mechanical tension drives Engrailed-1 activation via canonical mechanotransduction signaling. Finally, we showed that blocking mechanotransduction signaling with either verteporfin, an inhibitor of Yes-associated protein (YAP), or fibroblast-specific transgenic YAP knockout prevents Engrailed-1 activation and promotes wound regeneration by ENFs, with recovery of skin appendages, ultrastructure, and mechanical strength. This finding suggests that there are two possible outcomes to postnatal wound healing: a fibrotic response (EPF-mediated) and a regenerative response (ENF-mediated).

Integrated spatial multiomics reveals fibroblast fate during tissue repair

“…Many cell surface and lineage markers have been associated with fibroblasts involved in wound healing, including Pdgfra , Engrailed-1 ( En1 ), and CD26 ( Dpp4 ) ( 22 – 24 ). However, we and others have found expression of such markers to be variable throughout wound tissue ( SI Appendix , Fig.…”

“…S10 E ). To further explore these differences, we employed an automated feature extraction algorithm ( 24 ) to quantify ultrastructure characteristics of wound tissue sections, which demonstrated that FAK i -treated wound specimens were more similar to unwounded skin than to vehicle-control wounds, including for both mature and immature collagen fiber intensities ( SI Appendix , Fig. S10 F ).…”

“…By POD 2, a subset of fibroblasts appears to have differentiated to form an activated-responder subpopulation, while the remaining outer wound fibroblasts comprise the less differentiated mechanofibrotic cells. The latter fibroblasts highly express known fibrosis-associated markers such as Engrailed-1 ( 23 , 24 ), Col1a1 ( 34 ), Tgbf2 ( 35 ), and Jun ( 36 ). At POD 7, mechanofibrotic cells begin to differentiate in response to mechanotransduction cues as they migrate toward the wound center.…”

Furnishing Wound Repair by the Subcutaneous Fascia

“…Using genetic lineage tracing, anatomical fate mapping, and live imaging, we found that fascia-resident fibroblasts orchestrate the mobility of the connective tissue into wounds. Fascial mobility is directed by a single fibroblastic cell lineage termed Engrailed-1 lineage positive fibroblasts (EPFs), which is the profibrotic lineage fibroblasts responsible for skin scarring [47][48][49]. This specialized fibroblast type physically drags the fascia into the wound bed and subsequently into the skin surface in mice (Figure 2a).…”

The Role of Hippo/YAP Signaling in Alveolar Repair and Pulmonary Fibrosis

“…With increasing understanding of the complex roles YAP/TAZ play in lung development, homeostasis, injury repair, and pathologic fibrosis, it has become clear that approaching this pathway in a therapeutic context will not be as simple as global inhibition or activation, in contrast to other organs ( 51 ). While aberrant YAP activation in the epithelium and mesenchyme contribute to failure of repair, initial YAP activation in these cells is likely beneficial for proliferation of progenitor populations and signaling to immune cells ( 12 ).…”