The dentate gyrus (DG) subregion of the mammalian hippocampus mediates critical cognitive processes related to memory and is a site of continuous adult neurogenesis. The mechanisms by which diverse neuronal and non-neuronal cell populations regulate adult neurogenesis and contribute to DG function are an intense, current focus of research. Obtaining an accurate estimate of DG cellular composition is vital for understanding how distinct cell populations contribute to hippocampal function. However, most studies examine only a select few cell types, and the reported numbers vary considerably. Here, we apply consistent stereological methods within a single study to estimate cell density for the major lineages in the dorsal DG of adult mice. Using immunohistochemical phenotypic markers, we quantified cell density for radial glia-like cells, neuronal intermediate progenitors, neuroblasts/immature neurons, mature neurons, stellate astrocytes, oligodendrocytes and their progenitors, microglia, and vascular endothelial cells. The value of a unified dataset was evident when evaluating the relative abundance of different cell types. Ratios of neurons:astrocytes generated using counts of each cell type obtained from separate studies could range from approximately 4.6:1 to 113:1. In contrast, our reported estimate of roughly 12 neurons:1 astrocyte is consistent with the 9:1 ratio from previous work where both cell types were quantified within the same study. This highlights the utility of counts obtained within a single study to make accurate comparisons of relative cell type abundance. We expect the data reported here will facilitate efforts to refine hypotheses about the functional contributions of DG cell populations.

Stereological characterization of the major cell lineages in the mouse dorsal dentate gyrus