Figure 7.

Microglia in the aged hippocampus negatively control neural precursor cell activity. A, The frequency of neurosphere formation, which is a direct reflection of NPC activity, significantly declines with age between 2 and 9 months of age (*p < 0.05; n = 3 per experimental condition). B, Depletion of microglia from the hippocampi of young (2-month-old) sedentary mice did not affect the neurosphere frequency. Note, however, that microglia depletion at more advanced ages significantly increased neurosphere numbers (*p < 0.05; n = 3 per experimental condition). C, Addition of microglia from aged hippocampus to microglia-depleted hippocampal cell cultures of young mice did not significantly impact on the neurosphere frequency compared with control cultures in which hippocampal microglia from 2-month-old mice were added (p > 0.05; n = 6 per experimental condition); MG, microglia; w/o MG, without microglia.