Tissue Stem Cells and the Stem Cell Niche of the Human Vocal Fold Mucosa

Abstract

1. The latest research shows that the vocal fold stellate cells in the human maculae flavae are involved in the metabolism of extracellular matrices that are essential for the viscoelastic properties of the human vocal fold mucosa. Additionally, vocal fold stellate cells are considered to be important interstitial cells in the growth, development, and aging of the human vocal fold mucosa. 2. Vocal fold stellate cells are considered to be a new category of cells in the human vocal fold. It is uncertain whether the vocal fold stellate cells are derived from the same embryonic source as fibroblasts. 3. There is growing evidence to suggest that the cells including vocal fold stellate cells in the maculae flavae are tissue stem cells of the human vocal fold, and the maculae flavae are a candidate for a stem cell niche. 4. The cells including the vocal fold stellate cells in the human adult maculae flavae possess proteins of all three germ layers. This suggests that the cells are undifferentiated and have the ability of multipotency. 5. The radiosensitivity of the cells in the maculae flavae is high, indicating that the cells are not yet as fully differentiated as fibroblasts. 6. Telomerase resides in the cells in the maculae flavae. They are resting cells (G0-phase). 7. The cell division in the human adult maculae flavae is reflective of asymmetric self-renewal and cultured cells form a colony-forming unit. Therefore, the phenomenon gives rise to the strong possibility that the cells in the human maculae flavae are tissue stem cells. 8. Recent research suggests that the cells in the human maculae flavae arise not from resident interstitial cells of the vocal fold mucosa but from the differentiation of bone marrow cells via peripheral circulation. 9. At birth, the cells have already been supplied from the bone marrow into the maculae flavae in the newborn vocal fold and are ready to start the growth and development of the human vocal fold mucosa as a vibrating tissue. 10. The hyaluronan concentration in the maculae flavae is high and contains cells which possess hyaluronan receptors, indicating that the maculae flavae are hyaluronan-rich matrix, which is required for a stem cell niche. 11. A proper microenvironment in the maculae flavae of the human vocal fold mucosa is necessary to be effective as a stem cell niche maintaining the stemness of the contained tissue stem cells.