The image depicts a scientific study on the activation of T I E 2 in the lesional endothelium of cavernous malformations (C C M s) in the adult mouse brain. Panel A shows a schematic of the experimental setup where K r i t 1 f l slash f l; i P i k 3 c a H 1047 R mice undergo A A V-C r e injection to induce focal K r i t 1 deletion and P i k 3 c a H 104 7 R overexpression. Panel B presents representative images of H and E staining, highlighting a popcorn lesion appearance with enlarged vasculature and peri-lesional hemosiderin. Panel C includes immunostaining images for 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 counterstaining, showing detailed views of the lesional endothelium. Panels D to F quantify the mean fluorescence intensity (M F I) of p V E G F R 2 Y 951, p V E G F R 2 Y 1175, and p T I E 2 Y 992 normalized to total V E G F R 2 and T I E 2, respectively, compared to the contralateral brain. Panel G and H show immunostaining for t d Tomato, 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 counterstaining in brains harvested on P O D 7, with higher magnification views of boxed regions. Panels I to K quantify the M F I of p V E G F R 2 Y 951, p V E G F R 2 Y 1175, and p T I E 2 Y 992 normalized to total V E G F R 2 and T I E 2 in t d Tomato-negative regions. Arrows indicate p V E G F R 2- or p T I E 2-positive endothelial cells at the C C M lesions, and asterisks indicate autofluorescence from lumenal red blood cells. Scale bar is 100 micrometers. Data shown are means plus or minus standard error of the mean (S E M). Statistical significance is indicated with asterisks, and non-significant differences are noted.
TIE2, but not VEGFR2, is activated at the CCM lesional endothelium in adult mouse brain. (A) Schematic representation of the adult inducible CCM model incorporating both loss of CCM function and gain of PI3K function. Krit1fl/fl; iPik3caH1047R mice between age 8–10 wk underwent craniotomy and received AAV-Cre injections to induce focal Cre-mediated Krit1 deletion and Pik3caH1047R overexpression in the cerebral cortex below a cranial window. (B) Representative images of H&E staining revealing a classic popcorn lesion appearance (left) with enlarged vasculature (“caverns”) and peri-lesional hemosiderin indicative of hemorrhage in older lesions (right). (C) Representative images showing immunostaining for CD31, VEGFR2, pVEGFR2, TIE2, and pTIE2, with DAPI counterstaining in a mouse CCM harvested on POD 155. The boxed regions, a–c, are shown at higher magnification in a’–a’’’ to c’–c’’’, respectively. (D–F) Quantification of MFI of (D) pVEGFR2Y951, (E) pVEGFR2Y1175, and (F) pTIE2Y992 normalized to total (D and E) VEGFR2 and (F) TIE2, respectively, compared with vasculature in the contralateral, uninjected side of the brain. A total of 10 regions in each group were measured and quantified. (G and H) Representative images showing immunostaining for tdTomato, VEGFR2, pVEGFR2, TIE2, and pTIE2, with DAPI counterstaining in brains harvested on POD 7. The boxed regions, a–f, are shown at higher magnification in a’–a’’’ to f’–f’’’, respectively. (I–K) Quantification of MFI of (I) pVEGFR2Y951, (J) pVEGFR2Y1175, and (K) pTIE2Y992 normalized to total (I and J) VEGFR2 and (K) TIE2, respectively, as compared with the tdTomato-negative regions. A total of three mice in each group were measured and quantified. Arrows indicate pVEGFR2- or pTIE2-positive endothelial cells at the CCM lesions. Asterisks indicate autofluorescence emitted from lumenal red blood cells. Scale bar: 100 μm. Data shown are means ± SEM. **P <0.01 and ****P <0.0001 by two-tailed Mann–Whitney U test (D–F) and unpaired two-tailed Welch t test (I–K). No statistically significant (n.s.) differences are observed in (D) P = 0.1839, (E) P = 0.1051, (I) P = 0.1652, and (J) P = 0.8967.