Neovascular endothelial cell apoptosis in αB-crystallin knockout^−/−mice in OIR. In panels A-D, DAPI nuclear staining (A; blue), TUNEL staining (B,D; red), and isolectin-B4 endothelial cell staining (C-D; green) in OIR in αB^−/− mice at P17. Several TUNEL⁺ apoptotic cells are detected in neovascular tufts (A-B; arrows), some of which colocalize with isolectin-B4–positive endothelial cells (C,D) on the retinal surface. Bar indicates 50 μm. In panel E, the number of apoptotic cells is significantly greater in αB crystallin^−/− mice than that in wild-type mice (P < .01). In panels F through I, DAPI nuclear staining (F), and expression of cleaved caspase-3 (G,I; red), and isolectin-B4 endothelial cells (H-I; green) in αB crystallin^−/− mice at P17. Immunoreactivity for cleaved caspase-3 is observed in neovacular endothelial cells (F-I; arrow). Bar indicates 50 μm. Original magnification, ×200. In panels J through U, expression of VEGFR2 (J-M; red), NG2 (N-Q; red), and CD105 (R-U; red) and colocalization with DAPI (blue) and isolectin-B4 (green) in wild-type (J,K,N,O,R,S) and αB crystallin^−/− (L,M,P,Q,T,U) retinas in OIR model at P17. Bar indicates 50 μm. Original magnification, ×100. Images obtained with a confocal microscope (Zeiss) with a 40×/1.3 oil immersion NA (C,D,H,I) with SpotII digital camera and fluorescence microscope (Leica) with a 40×/0.75 NA (F,G,J-O).