Carcinoma and benign vocal fold disorders, EGFR LY2109761 clinical trial expression in vocal fold epithelium following injury has not been examined. As a necessary first step to uncovering the role of EGFR in various phases of mucosal remodeling, here we examined the density and location of EGFR in injured vocal fold epithelium during the acute phase of wound healing. We anticipated observing EGFR activation during the proliferative and inflammatory phases of mucosal healing. Based on findings in other airway epithelia, epithelial regeneration following vocal fold injury likely follows three overlapping steps: cell adhesion and migration, proliferation and stratification, and differentiation. While these steps have not been explicitly identified in vocal fold epithelial regeneration, their occurrence can be inferred from literature. Cell adhesion and migration, as evidenced by an emerging but incomplete layer of epithelium, will occur three days post-injury. Epithelial cell proliferation and stratification will occur five days post-injury. We hypothesized that these migratory and proliferative stages of repair will be marked by heightened levels of expression of ki67, a maker of proliferation, K14, a marker of proliferative epithelial cell, EGF, TGFb1 and EGFR. A confluent, multilayered epithelium will be present within 14 days postinjury. Cell proliferation will be expected to continue to be elevated until 14 days post-injury. We anticipatedthat this stage will be marked by elevated Ki67 and K14 expression. Based on observations of cell differentiation in airway epithelia, we anticipate that a fully differentiated, complete epithelium will be restored within 35 days following injury. At day 35, Ki67 will be expected to return to uninjured levels, consistent with return of a complete, stable epithelium. Further, observation of K14 staining in the basal layer only, will be consistent with non-injured, differentiated stratified epithelium. Although the studies cited above provide a likely timeline of the critical stages of epithelial regeneration, there remain important gaps in our knowledge of the re-epithelialization process. First, we needed to establish a timeline for regeneration of an epithelium. Second, we needed to demonstrate the presence of growth factors in the epithelium likely to play an important role in each stage of epithelial regeneration. Consequently, we elected to examine wound healing in a rat model at five time points post-injury. These time points were chosen to determine the sequence and timing of each stage of epithelial healing. Third, we needed to confirm that epithelial cells, not a different cell type, secreted observed growth factors. To that end, we examined EGF and TGFb1 expression in primary epithelial cells. Given the low number of epithelial cells in a rat vocal fold and the difficulty in isolating rat epithelial cells from the underlying lamina propria because of its small size, quantification of gene and protein expression by epithelial cells was not feasible. Therefore, we used primary pig cells to confirm EGF and TGFb1 gene expression in vocal fold epithelial cells.