Localization of label-retaining cells in murine vocal fold epithelium

Purpose: Epithelial homeostasis is critical for vocal fold health, yet little is known about the cells that support epithelial self-renewal. As a known characteristic of stem cells is that they are slowcycling in vivo, the purpose of this prospective controlled study was to identify and quantify slow-cycling cells or putative stem cells in murine vocal fold epithelium. Method: Twelve mice were administered daily intraperitoneal injections of a nucleotide dye, bromodeoxyuridine (BrdU), over 7 consecutive days. Under this pulse-chase paradigm, slow-cycling cells retain the dye (label-retaining cells; LRCs) while more rapidly cycling cells lose dye to dilution during multiple cell divisions. The percentage of label-retaining cells (%LRCs) was calculated following a chase period of 2, 4, and 8 weeks postinjections. Results: The %LRCs decreased significantly from 9.4% at 2 weeks to 3.1% at 8 weeks following injections (p <.05). No statistically significant differences in the quantity of BrdU-positive cells were measured between the anterior, mid-membranous, or cartilaginous regions of the vocal fold (p >.05). Conclusion: These findings are consistent with the presence and first report of a small population of putative stem cells along the length of murine vocal fold epithelium.