Characterization and Treatment of the Scarred Vocal Fold

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DESCRIPTION (provided by applicant): Vocal fold (VF) mucosal injury resulting in scar formation and its associated dysphonia is a debilitating and challenging clinical problem, for which there is no consistently effective treatment. One of the most poorly understood but potentially transformative areas of investigation in VF scar biology is the role of the vitamin A- storing VF stellate cell. Localized to the anterior and posterior macula flavae, this cell populatin is a local repository of essential vitamin A and has been hypothesized to play a primary role in development, maintenance, injury response and scar formation within the VF lamina propria. Stellate cells in other organs (e.g., liver, pancreas, and lung) are known fundamental regulators of fibrosis. In these organs, inflammatory stimuli promote stellate cell activation, leading to los of cytoplasmic vitamin A, increased extracellular matrix (ECM) synthesis, differentiation to a contractile (myofibroblast) phenotype, and scar formation. Emerging research, some of which was conducted during our most recent funding cycle, suggests that VF stellate cells undergo a similar activation process and may have a comparable role in VF mucosal injury and scar formation. Our long- term goal is to definitively characterize the role of the VF stellate cell in F wound healing and scar formation, as well as the therapeutic potential of retinoic acid (bioactive vitamin A) to reverse VF stellate cell activation and attenuate scar formation. The proposed project has three Specific Aims. In Aim 1, we will conduct animal experiments and use tissue/serum harvested from human cadavers to identify the mechanism(s) of vitamin A transport to VF stellate cells, provide an estimate of population variation in VF stellate cell vitamin A storage, and establish the degree of correspondence between vitamin A stores in VF mucosa, liver and serum. In Aim 2, we will use computational modeling and in vitro cell culture techniques to study the effects of biomechanical, biochemical/cytokine, ECM and cellular environmental factors on the VF stellate cell phenotype, under injury and non-injury conditions. In Aim 3, we will examine the ability of retinoic acid (bioactive vitamin A) to rescue VF stellate cells from an activated/fibrotic phenotype, in vitro and in vivo. On completion, this therapeutically- driven project will provide clear definition of the phenotypic differences between VF stellate cells, VF fibroblasts and stellate cells in other organs, reveal the best approach to deliver systemic vitamin A (and other therapeutic molecules conjugated to vitamin A) to VF stellate cells in both animals and humans, and quantify the ability of retinoic acid to attenuate scar formation by restoring VF stellate cells to their quiescent state. Retinoic acid is approved for clinical use by the United States Food and Drug Administration, holds demonstrated efficacy as an antifibrotic agent in other organ systems, and is therefore well-positioned for future translation to patients with VF mucosal injury and scar.