Figure 2.

Significant arterial tortuosity and venous dilation are present in retinas of mice exposed to OIR. The retinas of mice exposed to the OIR model and untreated controls were flat mounted and stained with FITC-isolectin B4, a marker for endothelial cells. In OIR-treated mice at P12 (immediately after hyperoxia treatment), the major vessels traversing the central avascular area were straight and without evidence for dilation ([A] left). At P17, the size of the central avascular area was decreased, and vessel sprouts were visible along the dilated central veins. The presence of tufts and vascular tortuosity, as well as the dilation of veins, was clearly evident when compared to what was seen in untreated P17 control mice ([A], middle and right). The quantification of vascular tortuosity (see Materials and Methods for details) showed a significant increase at P17 in mice exposed to OIR compared to untreated controls (B). Measurements of vessel diameter demonstrated that arteries were not dilated in OIR-treated or control mice, whereas veins showed a significant increase in dilation at P17 (C). Ct, controls. The quantification of vaso-obliteration and neovascularization showed a significant increase in the size of the central avascular area (D), as well as in the numbers of endothelial cells that crossed the internal limiting membrane (E), following OIR treatment compared to no treatment. Data represent means ± SEM; *P ≤ 0.05. Images are representative of n = 7 for untreated controls, n = 22 for OIR-treated samples.