Phases of epithelial regeneration post-injury strongly support our hypothesis that epithelial cells participate in all phases of epithelial regeneration through autocrine signaling. EGF and TGFb1 showed a similar, time-dependent pattern of staining across early time points post-injury. Both showed diffuse staining throughout the epithelium at day 3 and strongest staining in the superficial layer of the epithelium at day 5. MLN4924 Presence of growth factors in the superficial epithelial layers in the days following injury is consistent with a role for them in guiding proliferation and differentiation of these metabolically active but typically quiescent cells. The possibility that these cells are recruited to proliferate following injury is supported by the absence of terminal differentiation of the cells and staining for the proliferation marker, Ki67 in these cells. The presence of red blood cells in the superficial layer of the epithelium is important in the context of this study as they provide additional sources of growth factors. The sparse, if not absent staining, for the growth factors at later time points suggests that TGFb1 and EGF are not secreted by epithelial cells under homeostatic conditions following restoration of a complete, differentiated epithelium. EGFR activation was observed during the acute phase of wound healing. Concomitant staining for EGFR and the growth factors, EGF and TGFb1, in epithelial cells suggest growth factor-mediated autocrine signaling drives EGFR regulation of wound repair. Presence of activated EGFR in the proliferating, Ki67-positive, epithelium is consistent with the receptor playing a key role in cell growth and wound repair. Our findings are consistent with a correlation between EGFR and Ki67 expression observed in benign and malignant laryngeal lesions. Growth factors were also noted in the lamina propria, particularly during the earliest time points post-injury, day 1 and 3. These observations were expected as both EGF and TGFb1 are secreted by fibroblasts, macrophages, and platelets, all of which are present during the early phases of wound healing. Observation of TGFb1 staining in the ECM of the lamina propria is consistent with secretion of TGFb1 by cells such as fibroblasts, and, we hypothesize, storage of TGFb1 as observed in other ECM. Further, increased TGFb gene expression has been observed during the first week post-injury in rats. To the best of our knowledge, EGF gene and protein expression have not be quantified in a rat model of vocal fold injury. We acknowledge two weaknesses in this study. First, dynamic reciprocity between epithelium and lamina propria likely molds vocal fold healing. Here, we focused exclusively examining on epithelial cell protein expression as a first step to elucidating the role of epithelial cells in mediating wound healing. Understanding the interaction of epithelial cells and fibroblasts, as well as other cells, in the lamina propria awaits controlled, in vitro studies of vocal fold healing. Second, we did not quantify EGF and TGFb1 gene and protein expression in rats post-injury.