071 TGF‐ß‐Mediated Paracrine Regulation of Keratinocyte Wound Closure

Abstract

The importance of stromal‐epithelial interactions in wound healing is well established. These interactions likely involve autocrine and paracrine action of multiple growth factors, including members of the TGF‐ß family. TGF‐ß1, ß2 and ß3 isoforms signal by sequentially binding to the TGF‐ß type II and type I receptors, respectively. We address the role of TGF‐ß signaling in dermal fibroblasts using a conditional fibroblastic TGF‐ß type II receptor knockout mouse model (termed FßKO). We found that the loss of TGF‐ß signaling in the dermal fibroblasts results in accelerated excision‐wound closure compared with similar wounds in wild type mice. The mechanism of the altered rate of re‐epitheliaization in the FßKO mice was examined with regard to keratiocyte motility and proliferation. The migration of keratinocytes through collagen I coated 8 μm pore filters in the presence or absence of fibroblast‐conditioned media was tested. These experiments showed increased keratinocyte migration when incubated with FßKO dermal fibroblast conditioned media compared to media conditioned in wild type fibroblasts. Immuno‐histochemical staining of paraffin embedded intact skin indicated both wild type and FßKO mice had similar low levels of keratinocyte proliferation, based on Ki67 staining. In healing wounds, only the distal wound edges of wild type mice were proliferative. In contrast, the FßKO mice exhibited elevated proliferation across the length of the wound, including the leading edge of epithelial closure. Together our results suggest TGF‐ß signaling by the dermal fibroblasts suppresses re‐epithelialization of excision wounds by regulating keratinocyte motility and proliferation through paracrine mechanisms. Funding: DOD BC99184 and NIH CA85492.