Characterization of the canine rostral ventricular‐subventricular zone: Morphological, immunohistochemical, ultrastructural, and neurosphere assay studies
The components of these niches have been widely studied by ultrastructure in rodents (Bernier, Vinet, Cossette, & Parent, 2000; Rezza, Sennett, & Rendl, 2014; Weickert et al., 2000). The organization of the V‐SVZ niche is based on four major cell types: ependymal cells (E1 and E2 cells), V‐SVZ astrocytes (B1 and B2 cells), transient amplifying progenitor cells (type C cells), and neuroblasts (type A cells) (Doetsch, Garcı'a‐Verdugo, & Alvarez‐Buylla, 1997; Mirzadeh, Merkle, Soriano‐Navarro, Garcia‐Verdugo, & Alvarez‐Buylla, 2008). B1 are reminiscent embryonic neuroepithelial cells with astrocytic appearance and in contact with the ventricular lumen through the intercellular space between the ependymocytes. These cells proliferate at a slow rate and are considered to be adult resident NSCs. Type B2 cells form a subependymal band and support the migratory neuroblasts that move toward the olfactory bulb. Type C cells are rapidly proliferating transient amplifying cells that arise from B1 cells and produce neuroblasts or type A cells.
In domestic animals, cellular components of the V‐SVZ have been described in oxen (Rodriguez‐Perez, Perez‐Martin, Jimenez, & Fernandez‐Llebrez, 2003), sheep (Low, Faull, Bennet, Gunn, & Curtis, 2013), pigs (Costine et al., 2015), and rabbits (Bonfanti, Aimar, & Ponti, 2006; Bonfanti & Ponti, 2008; Luzzati et al., 2003). Cellular composition and cytoarchitecture of the V‐SVZ have also been studied in humans (Nogueira et al., 2014; Quiñones‐Hinojosa et al., 2006; Sanai, Tramontin, Quinones‐Hinojosa, & Barbaro, 2004) and nonhuman primates (Gil‐Perotin, Duran‐Moreno, Belzunegui, Luquin, & Verdugo, 2009; Sawamoto et al., 2011). Important differences between mammalian species have been described. Thus, in the adult human brain the V‐SVZ is composed of an ependymal cell monolayer, a hypocellular gap and a ribbon of astrocytic cells layers (Quiñones‐Hinojosa et al., 2006; Sanai et al., 2004). Moreover a small amount of proliferating neuroblasts have been identified both in fetal and adult individuals (Wang et al., 2011).