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Brian Palmer Hafler, Jaime Grutzendler, Ron A Adelman; Embolus extravasation is a mechanism of microvascular recanalization in human retinal artery occlusions. Invest. Ophthalmol. Vis. Sci. 2014;55(13):241.
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Recently an alternative mechanism of emboli clearance in the cerebral microcirculation involving the engulfment of emboli by the endothelium, followed by their translocation through the vessel wall, leading to recanalization and blood flow reestablishment was identified in mice (C. K. Lam, T. Yoo, B. Hiner, Z. Liu, J. Grutzendler, Embolus extravasation is an alternative mechanism for cerebral microvascular recanalization., Nature 465, 478-82 (2010)). The specific aim of the study was to examine whether the mechanism, which was termed angiophagy, is not limited to the brain but also occurs in the microvasculature of the retina.
To explore the potential presence of angiophagy in humans, we reasoned that, given its accessibility for imaging, the retina would be one of the few places where detection of angiophagy in vivo might be possible. To search for microvascular occlusions, we retrospectively reviewed all fundus photographs and fluorescein angiographies from patients with retinal artery occlusion from the Yale Eye Center from 2002 through 2013. 193 were selected for the study, and nine patients with retinal arterial emboli were identified. Longitudinal retinal photography was used to determine whether the emboli were located within the vessels or in the adjacent perivascular space. Fluorescein angiography was used to identify whether the vessels were occluded or recanalized.
Careful examination of nine cases in which multiple imaging time points had been acquired revealed three patients with emboli that seemed to have moved to the adjacent perivascular spaces, and the corresponding previously occluded microvessels were recanalized. Recanalization of vessels was confirmed by fluorescein angiograms revealing perfusion both proximal and distal to the once occluded area. Additional corroboration of vessel recanalization was the resolution of an adjacent area of ischemia, as evidenced by changes in the typical pattern of abnormal retinal ischemia.
In humans, longitudinal in vivo retina photography and angiography demonstrate that, similar to the observations in mice, vessel recanalization can occur in association with transvascular embolus extrusion. Thus, angiophagy is a ubiquitous mechanism of microvascular recanalization with potentially broad implications in vascular occlusive disorders and could constitute a novel therapeutic target.
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