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9.7 Vocal Fold Stellate Cells in the Human Adult Maculae
Flavae
Interstitial cells with a star-like appearance in the human adult maculae flavae were
discovered in our laboratory in 2001 (Fig. 9.5) (Sato et al. 2001a, 2003b, 2004 ,
2010b; Sato and Nakashima 2005 ). These cells had no nomenclature and were thus
designated “vocal fold stellate cells” in the series of our study. Vocal fold stellate
cells are stellate in shape and possess vitamin A-storing lipid droplets (Sato et al.
2003b). There are a number of morphological differences between vocal fold stel-
late cells and fibroblasts in the human vocal fold mucosa. Along the surface of the
vocal fold stellate cells, a number of vesicles are present and constantly synthesize
extracellular matrices which are essential for the viscoelastic properties of the
human vocal fold mucosa (Sato et al. 2001a).
As a result of this heterogeneity, it is uncertain whether the vocal fold stellate
cells derive from the same embryonic source as fibroblasts in the human vocal fold
mucosa. The vocal fold stellate cells in the maculae flavae form an independent
cell category that are considered a new category of cells in the human vocal fold
mucosa.
9.8 Cell Division of Cells in the Human Maculae Flavae
In vitro culturing of the human maculae flavae yields interesting results. After a few
weeks of primary culture in an MF-start primary culture medium (Toyobo, Osaka,
Japan), two types of cells, fibroblast-like spindle cells (Group A) and cobblestone-
like squamous cells (Group B), grow from the human macula flava fragments
(Fig. 9.6) (Sato et al. 2016a). After removing the two types of cells by cell scraper,
each type of cell is individually subcultured in an MF-medium (Mesenchymal Stem
Cell Growth Medium) (Toyobo, Osaka, Japan) to proliferate the cells.
After a week of first subculture, subcultured Group A cells become stellate in
shape and possess slender cytoplasmic processes (Fig. 9.7a). Small lipid droplets
are present in the cytoplasm. The nuclei are oval in shape and their nucleus- cytoplasm
ratios are low. These cells are morphologically similar to vocal fold stellate cells.
After a week of second subculture, subcultured Group B cells form a colony- forming
unit (Fig. 9.7b), indicating these cells are mesenchymal stem cells or stromal
stem cells in the bone marrow.
Therefore, the colony-forming phenomenon gives rise to the possibility that the
cells in the human maculae flavae are tissue stem cells (Sato et al. 2016a).
As mentioned above, the cell division in the human adult maculae flavae with
mesenchymal stem cell growth medium is reflective of asymmetric self-renewal
(Sato et al. 2016a). Asymmetry in cell division gives rise to the possibility that the
maculae flavae in the human adult vocal fold is a stem cell niche containing tissue
stem cells (Sato et al. 2016a).
K. Sato