Distribution of Label-Retaining Cells and their Properties in the Newborn Vocal Fold Mucosa

Objectives. There is growing evidence that the cells in the maculae flavae (MFe) are candidates for tissue stem cells of the vocal fold mucosa and the MFe are a stem cell niche. Distribution of label-retaining cells and their properties in the postnatal vocal fold mucosa were investigated. Methods. Oral administration of bromodeoxyuridine (BrdU) was given to pregnant Sprague-Dawley rats and the label-retaining cells in the postnatal vocal fold mucosa were observed by immunohistochemistry. Immunoreactivity to antibodies directed to Ki-67 was studied to investigate the cell cycle. Results. At day 1 after birth, BrdU positive cells were identified in the MFe (60.1 +/- 1.7%), epithelium (58.7 +/- 10.6%) and lamina propria (52.4 +/- 7.8%) of the vocal fold mucosa. At day 56 after birth, the number of BrdU positive cells in the epithelium (4.8 +/- 2.2%) and lamina propria (32.3 +/- 16.5%) were significantly lower compared to day 1 after birth (P < 0.05). However, the number of BrdU positive cells remaining in the MFe was still high (56.2 +/- 2.5%). The label-retaining cells were distributed throughout the MFe. Few Ki-67 positive cells were identified in the MFe indicating they were resting cells. Conclusions. The results of this study are consistent with the hypothesis that the cells in the postnatal MFe are candidates for tissue stem cells. At birth, these cells are already present in the MFe of the newborn vocal fold and they are likely ready to start the growth and development of the vocal fold mucosa.