Subglottic Stenosis and Laryngotracheal Mucosal Healing

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DESCRIPTION (provided by applicant): The specific clinical problem providing the impetus for this application is scarring in the laryngotracheal mucosa, specifically subglottic stenosis (SGS). With current trends in medicine moving away from invasive surgical interventions towards medical therapies and "minimally invasive" procedures, it is of paramount clinical importance to understand the biological mechanisms that result from mucosal injury and trauma, in order to develop improved treatment strategies, and reduce the risk of morbidity and mortality. Connective tissue wound healing is generally a reparative process that results in the replacement of damaged or lost anatomic structures with fibrotic scar tissue. A striking exception to fibrotic healing of connective tissue has been reported by our group and others to occur in fetal laryngotracheal mucosa. Although not a universal property of fetal tissues, this regenerative or"scarless" healing, occurring in both skin and upper airway mucosa, is intriguing, and supports the theory that the tissue-specific fetal fibroblast plays a significant role in wound healing outcome. Our long-term goal is to elucidate the cellular and molecular processes underlying the formation of SGS by building upon the vast fund of existing knowledge of fibrotic processes in other tissues, primarily the skin and, to a lesser degree, the lower airway. The working hypothesis is that the ultimate degree of mucosal scarring associated with laryngotracheal wound healing is the result of a combination of the degree and nature of the inflammatory response and fibroblast activity. There are three specific aims: 1) Characterize the phenotypes of fetal, postnatal and fibrotic fibroblasts from subglottic mucosa in vitro with respect to responses to a key inflammatory mediator, PGE2; 2) Investigate the correlation of severity of injury and degree of inflammation in SGS; and 3) Experimentally alter the wound environment with mediators that down-regulate inflammation and fibroblast recruitment to measure the effects on wound healing outcome. We will also focus on early events, namely altered expression of cell signaling leading to activation and recruitment of responding cells, because it is well-supported that early signals and responses set the course for subsequent healing, and therefore, critically impact the end results qualitatively and quantitatively. The responses to inflammatory mediators from subglottic fibroblasts of different phenotypes will be examined. Both in vitro and in vivo experimental models will be used. Outcome measure will focus on differences in key responses of subglottic mucosal fibroblasts of different phenotypes, the differential healing of fetal and postnatal subglottic mucosa and the specific contribution of inflammation (or reduction thereof) to the degree of fibrosis. Extensive preliminary data from in vivo and in vitro wound healing models provide support for the underlying premise and promise of this proposal and for the ability of our research team to perform these studies dedicated to advancing our understanding of the cellular processes and molecular mediators that contribute to laryngotracheal wound healing.