Figure 12.

Eliminating microglia from the developing cerebral cortex increases the number of neural precursor cells. A, Iba1+ microglia (green) populate an organotypic slice prepared from the E16 cerebral cortex and cultured for 3 d. B, Addition of liposomal clodronate to the culture media for the first 24 h in culture eliminated 97% of microglia from the cerebral cortex. C, A coronal section of a P1 rat brain stained for microglia (green) and nuclei (DAPI, blue). Microglia populate the proliferative zones. D, The number of microglia in the P1 cerebral cortex is reduced by 90% after in utero intraventricular injections of liposomal clodronate at E20. A–D, DAPI (blue). E, F, Liposomal clodronate decreases the number of microglia (green) and significantly increases the number of Pax6+ precursor cells (red) and Tbr2+ precursor cells (G, H). White arrowheads indicate precursor cells targeted or phagocytosed by microglial cells. I, Histogram showing that 3 d after E20 in utero intraventricular injection of liposomal clodronate there is a significant decrease in the number of microglia, and a significant increase in the number of Pax6+ cells and Tbr2+ cells. Double red asterisk: p < 0.01; single red asterisk: p < 0.05. Scale bars: A, 500 μm; C, 200 μm; F, 50 μm.