1779.9 Transition Area Between the Human Adult Maculae
Flavae and Surrouding Tissue
The transition area between the maculae flavae and their surrounding tissue is
interesting.
The posterior macula flava is attached to the vocal process of the arytenoid carti-
lage posteriorly (Figs. 9.1 and 9.2). Elastic cartilage located at the tip of the vocal
process facilitates movement of the vocal process during adduction and abduction
(Sato et al. 1990 ). The transition of cells and extracellular matrices between the
posterior macula flava and the elastic cartilage portion of the vocal process is grad-
ual, and the border between them is not clearly delineated. The cells in the posterior
macula flava appear to differentiate into chondrocytes in the tip of the vocal process
(Sato et al. 2012b).
The cells in the human maculae flavae express CD44 (mesenchymal stem cell
marker). Most of the fibroblasts in the tissue surrounding the maculae flavae do not
express CD44. However, CD44-positive fibroblasts are observed at the periphery of
the maculae flavae. The cells in the macula flava appear to differentiate into fibro-
blasts in the surrounding tissue (Sato et al. 2012b).
These findings raise the possibility that the cells in the maculae flavae generate
functionally differentiated cells, such as chondrocytes and fibroblasts in the human
vocal fold mucosa (Sato et al. 2012b). Additional investigations are needed to
determine whether the cells in the maculae flavae have the capacity to self-renew
and generate functionally differentiated cells (multipotency) that replenish lost cells
throughout an organism’s lifetime.
9.10 Hierarchy of Tissue Stem Cells in the Human
Maculae Flavae
Here, the question arises whether the vocal fold stellate cells are tissue stem cells or
progenitor cells (transit-amplifying cells).
Both colony-forming subcultured cells (cobblestone-like squamous cells) and
non-colony-forming subcultured cells (fibroblast-like spindle cells) (Fig. 9.6)
express cytoplasmic cytokeratin, vimentin, GFAP and desmin (Kurita et al. 2015 ).
Consequently, both colony-forming cells (cobblestone-like squamous cells) and
non-colony-forming cells (fibroblast-like spindle cells) express ectoderm and meso-
derm germ layers. This suggests that they are undifferentiated cells and have the
ability of multipotency (Kurita et al. 2015 ).
The vocal fold stellate cells are possibly transit-amplifying cells, that is, progeni-
tor cells (Sato et al. 2016a). However, at the present state of our investigation, it is
difficult to clarify the stem cell system and hierarchy of stem cells in the human
maculae flavae and determine whether the vocal fold stellate cells are tissue stem
cells or progenitor cells.
9 The Macula Flava of the Human Vocal Fold as a Stem Cell Microenvironment