Abstract: The dentate gyrus subregion of the mammalian hippocampus is an adult neural stem cell niche and site of lifelong neurogenesis. Hypotheses regarding the role of adult-born neuron synaptic integration in hippocampal circuit function are framed by robust estimations of adult-born versus pre/perinatally-born neuron number. In contrast, the non-neurogenic functions of adult neural stem cells and their immediate progeny, such as secretion of bioactive growth factors and expression of extracellular matrix-modifying proteins, lack similar framing due to few estimates of their number versus other prominent secretory cells. Here, we apply immunohistochemical methods to estimate cell density of neural stem/progenitor cells versus other major classes of glial and endothelial cell types that are potentially secretory in the dentate gyrus of adult mice. Of the cell types quantified, we found that GFAP+SOX2+ stellate astrocytes were the most numerous, followed by CD31+ endothelia, GFAP–SOX2+ intermediate progenitors, Olig2+ oligodendrocytes, Iba1+ microglia, and GFAP+SOX2+ radial glia-like neural stem cells. We did not observe any significant sex differences in density of any cell population. Notably, neural stem/progenitor cells were present at a similar density as several cell types known to have potent functional roles via their secretome. These findings may be useful for refining hypotheses regarding the contributions of these cell types to regulating hippocampal function and their potential therapeutic uses. All experimental protocols were approved by the Ohio State University Institutional Animal Care and Use Committee (protocol# 2016A00000068) on July 14, 2016.

Key words: adult neurogenesis, dentate gyrus, endothelia, glia, hippocampus, neural stem cell, secretome, stereology