Epidermal keratinocytes are vital to normal wound healing by restoring the epidermal barrier and secreting paracrine factors that govern diverse processes including wound angiogenesis. In pathogenic settings, impaired epidermal function results in chronically insufficient (e.g., diabetic ulcers) or over-exuberant healing (e.g., hypertrophic scars). Our long-term goal is to develop therapeutic paradigms through which integrins can be manipulated to modulate pathogenic keratinocyte function. While it is well established that integrins regulate proliferation, migration and growth factor signaling, their rols in orchestrating wound keratinocyte functions remain enigmatic. Moreover, while normal and wound keratinocytes express integrin ?9?1, in vivo, upon explanation integrin ?9?1 is lost, confounding observations made in previous studies, in vitro. Using genetically defined, virally transduced keratinocytes that express integrins ?3?1 and/or ?9?1 in different combinations, we discovered that ?9?1 exerts a cross-suppressive effect on cell functions and gene expression that is governed by ?3?1, including paracrine signals that promote endothelial cell function. Moreover, we have derived genetically defined mice that express ?3?1 and/or ?9?1 in epidermis in different combinations. Strikingly, deletion of ?9?1 from epidermis enhances wound contraction and angiogenesis, two functions that are attributed to paracrine signaling directed by ?3?1. Based on our foundation data, we hypothesize that ?9?1 suppresses ?3?1-dependent paracrine signals from the epidermis that control wound closure and angiogenesis. We further hypothesize that the regulation of ?9?1-mediated suppression of ?3?1, perhaps through ligand-dependent activation of ?9?1 at key stages of wound healing, is critical for proper temporal and spatial orchestration of epidermal functions that promote wound healing. This hypothesis will be tested in three Aims using a combination of genomics, bioinformatics, peptide biochemistry, cell biology, and defined genetic mouse models of wound healing. At the end of this project period, we will have provided the first analyses of keratinocyte ?9?1 functions, determined how ?3?1 and ?9?1 coordinately regulate wound repair, identified molecular mechanisms through which ?9?1 exerts cross-suppressive regulation over ?3?1, and tested the concept that ?9?1-targeting peptides can be used to control certain epidermal wound healing functions. In doing so, we will have developed the basis for novel integrin-targeting therapeutics to modulate keratinocyte functions and wound outcome.
Keratinocyte adhesion receptors are critical to regenerating a functional epidermis after injury. These receptors regulate important keratinocyte functions in part by communicating with each other. The goal of the proposed work is to elucidate their mechanisms of communication and the keratinocyte functions that they impact during wound healing.
