Development of clustered fenestrae of chorioretinal vessels in pathologic conditions.

The purpose of this study is to reveal the process for the clustered fenestra-formation in endothelial cells. Such a process was investigated in two experimental models by using scanning electron microscopy. One was photocoagulated sites of the choriocapillaris. The other was abnormal vessels seen in urethane-induced retinopathy. In the photocoagulation experiment, no fenestra was seen at the center of the lesion 5 or 7 days after photocoagulation. However, when the observing regions were moved away from the center, clusters of several fenestrae appeared. Further away from the center, larger clusters of fenestrae were observed. Fenestrae were distributed in regular fashion in each cluster regardless of size of the cluster. Similar clusters of fenestrae were found in urethane-induced retinopathy. Fenestration was found in the retinal vessels which were located near the choroid. However, the clusters of fenestrae decreased in number in such retinal vessels located near the vitreous. Based on those observations, the author suggests a hypothesis regarding acquisition of clustered fenestrae in pathologic conditions.