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Clemens Alt, Judith Runnels, Grace Teo, Charles Lin; Assessment of Vascular Integrity and Leukocyte Endothelial Interaction in the Murine Retina After Ionizing Radiation by in vivo retinal imaging. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4876.
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Whole-body irradiation is commonly administered to patients in preparation for bone marrow transplantation. As ionizing radiation can cause injury outside the hematopoietic compartment, we investigate dynamic cellular responses and the integrity of the blood retinal barrier after lethal whole body irradiation by longitudinal, non-invasive in vivo imaging of the murine retina.
We developed a scanning laser ophthalmoscope (SLO) for mouse retinal imaging that allows detection of three different colors simultaneously. Previously, we tracked resident GFP-expressing microglial cells (CX3CR1+/-) and bone marrow derived cells (BMDCs) from a universal DsRed donor for four months after lethal irradiation (10 Gy gamma) and observed 1) progressive loss of the native microglia and 2) concomitant but delayed engraftment of bone marrow derived cells. Since the presence of an intact blood-retina barrier obstructs free trafficking of cells, we hypothesized that inflammation may accompany the observed microglial turnover. Here, we assess inflammation by quantifying leukocyte endothelial interaction (LEI) and fluorescein angiography (FLA) over three months after irradiation and bone marrow transplant. LEI was determined by enumerating the number of rolling cells in time lapse imaging and FLA leakage was quantified as the decrease in contrast between vasculature and surrounding parenchyma. LEI and fluorescein leakage were compared to the baseline values taken prior to the irradiation.
Increased vascular leakage and leukocyte endothelial interaction were detected after lethal irradiation. Leukocyte endothelial interaction and fluorescein leakage peaked after the first week, but continued throughout the observation period of three months. In many cases, LEI and fluorescein leakage occurred near the optic nerve head. Initial engraftment of BMDCs was also observed near the optic nerve head.
Our results suggest that exposure to gamma radiation compromises the integrity of the blood-retina barrier. The correlation of LEI and fluorescein leakage with the location of initial engraftment suggests that inflammation may be involved in the microglial turnover observed after lethal irradiation.
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