Investigating the role of systemic dehydration in vocal fold wound healing

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Project Abstract The role of hydration in maintaining vocal fold health is still not fully understood. But it is generally believed that increasing hydration can optimize vocal function while decreasing hydration can negatively impact vocal physiology. Dermal literature suggests that systemic dehydration may prolong inflammation and delay re- epithelization of injured skin tissue. This proposal broadly questions whether similar suboptimal outcomes are also observed in vocal fold tissue after systemic dehydration as compared to euhydration (normal hydration state). If these negative outcomes are observed, there may be adverse implications for restoration of vocal function following damage from injury, surgery, or phonotraumatic behaviors. Therefore, we will investigate the vocal fold wound healing processes of acute inflammation, extracellular matrix proliferation, and re- epithelization in dehydrated and euhydrated male rats following vocal injury. Systemic dehydration will be achieved through an ecologically-valid water restriction protocol for 11 days (N = 15). Conversely, euhydrated rats (n=15) will be provided water ad-libitum for 11 days. Vocal injury will be induced in all rats. Vocal fold wound healing outcomes will be measured on the 7th day following vocal injury. Specific Aim 1 will measure the gene and protein expression of inflammatory mediators in dehydrated and euhydrated rats following vocal fold injury. We hypothesize an upregulation of inflammatory mediators (TGF-β1 and IL-6) in dehydrated rats when compared to euhydrated rats. Quantitative-Polymerase Chain Reaction and Western Blotting will be used to measure gene and protein expression levels respectively. Specific aim 2 will characterize the vocal fold epithelia and extracellular matrix in dehydrated and euhydrated rats following vocal fold injury. We hypothesize incomplete stratified squamous epithelial layer, decreased distribution and quantity of collagen and hyaluronan, and inadequate fibroblast proliferation in dehydrated rats as compared to euhydrated controls. Histochemical stains (HE, Alcian Blue and Trichome stains) and staining analysis will be used to observe the morphology and hyaluronan content. Overall, findings demonstrating overexpression of inflammatory mediators, incomplete re-epithelization, and altered concentration of extracellular matrix constituents would suggest increased risk for susceptibility from external irritants, and altered vocal fold biomechanics. The proposed study will provide much needed evidence for the role of hydration in influencing vocal outcomes and shed a light on the effects of systemic dehydration on vocal fold healing following injury.