Airway epithelial repair in chronic bronchitis: novel signaling mechanisms

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Project Summary / Abstract This proposal describes a five-year training program for the development of an academic career in the field of cell and developmental biology. The principal investigator is a fully clinically trained pulmonary / critical care medicine physician with 30 months postdoctoral training in airway epithelial cell biology. This program provides a unique opportunity to acquire additional training and techniques during the mentored phase of the award that will allow me to be independent at the end of the first two years of this award. The rest of the aims will then be pursued during the independent phase bringing me closer to my long- term goal of becoming an independent physician scientist. The environment at the University of Miami is uniquely qualified to allow me to explore my hypothesis as the Laboratories for Airway Biology in the Division of Pulmonary, Critical Care and Sleep Medicine have a long record of accomplishment in airway epithelial cell biology. This group has access to high number of human airway epithelial cells through the University of Miami Life Alliance Organ Recovery Group, which allows me to pursue his research. Given the close physical location of the group, with several principal investigators clustered in the same research space, my training during the mentored phase of the award will benefit from many experienced investigators that are close by and collaborate on a routine basis. My career plan combines laboratory experience with formal course work during the mentored phase. This will allow me to pursue my hypothesis with the additional work proposed in the aims during the independent phase. This research is to further examine the relevance of RA effects on Wnt signaling and evaluate possible therapeutic options to improve ciliogenesis and prevent squamous metaplasia. These pathways are poorly studied in the airway, despite their importance for proper epithelial cell repair. The last aim has also a strong potential to develop into a translational project. Chronic inflammatory airway diseases, including smoking-induced chronic bronchitis, lead to damage of the airway epithelium with subsequent impairment of mucociliary clearance, a condition associated with increased morbidity and mortality. On the other hand, the airway epithelium has the capacity to regenerate its regular structure after damage occurred. During repair, an initial phase of cell proliferation is followed by re-differentiation of epithelial cells. This mechanism is regulated by reactivation of developmental signaling mechanism such as Wnt and the pathways stimulated by retinoic acid (RA). My preliminary observations support the hypothesis that RA deprivation and cigarette smoke exposure- induced chronic bronchitis lead to squamous metaplasia (SM) and impaired ciliogenesis via altered expression of Wnt pathway elements and that these outcomes can be improved by activation of PPAR¿ receptors. This hypothesis will be investigated through research constructed to address three major aims. ¿ Aim 1 will determine whether specific Wnt pathway elements are essential for ciliogenesis and prevention of squamous metaplasia and that RA is an indispensable regulator of this process (test of hypothesis in vitro). ¿ Aim 2 will determine whether the expression of Wnt pathway elements is altered in patients with smoking-related chronic bronchitis and whether this alteration leads to SM and impaired ciliogenesis (test of hypothesis with samples of patients). ¿ Aim 3 will determine whether activation of nuclear receptors (e.g., PPAR¿ and vitamin D) prevents the development of SM and improves ciliogenesis by substituting for RA (test of possible therapeutic intervention). This research proposal addresses an important aspect of how airway epithelia are properly repaired and not misdirect their repair mechanism into a squamous metaplasia that could lead to dysplasia and in the worst-case malignancy. This research is especially critical considering the continuing rise in airway diseases, especially related to smoking. The proposed research aims to elucidate critical parameters in airway epithelial cell repair.