Panel A shows immunofluorescence microscopy images of C D 31, V E G F R 2, p V E G F R 2, T I E 2, and p T I E 2 with DAPI in non-C C M and C C M brain vascular tissues with magnified boxed regions; Panel B shows vertical bar graph of V E G F R 2 T y r 951 phosphorylation index comparing Non-C C M and C C M endothelium; Panel C shows vertical bar graph of V E G F R 2 T y r 1175 phosphorylation index comparing Non-C C M and C C M endothelium; Panel D shows vertical bar graph of T I E 2 T y r 992 phosphorylation index comparing Non-C C M and C C M endothelium.
Detection of pTIE2 but not pVEGFR2 in human CCM lesional endothelium. (A) Representative images showing immunostaining for CD31, VEGFR2, pVEGFR2, and TIE2, pTIE2, with DAPI counterstaining in freshly resected human CCM specimens and non-CCM human brain tissue. The boxed regions in the lower-magnification images are shown at higher magnification on the right. Arrows indicate pTIE2-positive endothelial cells lining CCM lesions. Asterisks indicate autofluorescence emitted from lumenal red blood cells. Scale bar: 100 μm. (B–D) Quantification of MFI of (D) pVEGFR2Y951, (E) pVEGFR2Y1175, and (F) pTIE2Y992, normalized to total VEGFR2 and TIE2, respectively, as compared with endothelium in non-CCM brain tissue. N = 4 human samples in each group were analyzed and quantified. Data shown are means ± SEM. **P <0.01 by unpaired two-tailed Welch t test. No statistically significant (n.s.) differences are observed in (B) P = 0.4409 and (C) P = 0.2107.