Figure 1.

PDGF-induced proliferation of white matter NG2 cells in forebrain slice cultures of NG2creBAC:ZEG mice. Low-magnification images showing EDU⁺ cells in forebrain slice cultures exposed to no growth factor (A), 50 ng/ml PDGF (B), FGF2 (C), and EGF (D) for 48 h. Quantification of GFP⁺EDU⁺ cells in P8 neocortex (gray matter) and corpus callosum (white matter) after exposure to the different growth factors (E) showing increased proportion of proliferating white matter GFP⁺ cells after exposure to PDGF but not FGF2 or EGF. Dose–response to PDGF demonstrates that gray matter cells do not increase their proliferation even at and above saturating concentrations of PDGF for white matter cells. High-magnification images taken from gray (F, G) and white (H, I) matter regions showing GFP fluorescence and EDU labeling in control (F, H) and PDGF-treated (G, I) slices. MBP and EDU double labeling of cortical slice cultures in control (J) and after exposure to 50 ng/ml PDGF (K) identifies the gray and white matter regions and demonstrates the localization of proliferating EDU⁺ cells to white matter after PDGF exposure. Quantification of GFP⁺EDU⁺ cells in gray and white matter of forebrain slices isolated from P4 and P8 animals (L) demonstrating an age-dependent differential response to PDGF by white matter NG2 cells. Scale bars: A–D, J, K, 100 μm; F–I, 25 μm. *p < 0.001, compared with gray matter (two-way ANOVA, Bonferroni post test). ^#p < 0.05, compared with same region control (two-way ANOVA, Bonferroni post test). ⁺p < 0.001, compared with P8 (two-way ANOVA, Bonferroni post test). Error bars indicate SD.