These are scanning electron microscopic images of the retina from the side of vitreous body. Image 2 and 3 are the higher magnification views of image 1. While (I) in image 1 is the cell just below inner limiting membrane, (G) is a ganglion cell and (V) is a blood vessel (capillary) in retina. Pericytes (P) in image 3 with processes (arrowhead) associate the endothelial tube in retina. The blood vessels in retina are quite different from those of choriocapillaris described here before.
These are SEM images of the capillaries in the mice skin (dermis of the back skin). These are regarded as normal capillaries. Pericytes (arrows in the upper and lower images) associate the endothelial tubes. The pericytes have cell bodies (arrows) and slender processes (arrowhead of the lower image). The connective tissue composed of collagen fibers was dissolved in advance and the blood vessels remained. The slender string like structures are elastic fibers remained after the treatment for removal of connective tissue.
These are the images of Bruch's membrane (No 1, B) and choriocapillaris (C). No. 1 is a view from RPE (retinal pigmented epithelium). No. 2 is a Bruch membrane composed of collagen fibers. No. 3 is a higher magnification view of the choriocapillaris in No. 1. No. 4 is a high magnification view of choriocapillaris. Endothelial cells of choriocapillaris have fenestrations.
Mice choriocapillaris has variation in morphology. In the upper image, choriocapillaris is a sheet of the endothelial cells (within the square line), while in the other areaschoriocapillaris shows mono-layered vascular network. In the middle image, the upper site is a sheet of the endothelial cells. The lower image is the high magnification view of the area surrounded with rectangle in the middle image. pericytes (arrows) fit the endothelial cells which have nuclear swellings. These findings show that remodeling of the choriocapillaris occurs in adult eye and it is by intussusception. Pericytes may remove from choriocapillaris in parallel with remodeling from sheets of endothelial cells to capillary network by VEGF from pigmented epithelial cells.
Pericyte processes and endothelial cells at outer (scleral) side of choriocapillaris. (P) is a pericyte process and (F) is a fenestrated endothelial cells. Lower image is a higher magnification view. Fenestration sparsely distributed around the pericyte process. Endothelial cells without pericytes have rich fenestration. Pericytes seem to restrict fenestration by VEGF. Indeed, endothelial cells have fenestration at inner (retinal) side of choriocapillaris, which is influenced by VEGF secretion from retinal pigmented epithelial cells (RPE).
This is a outer (scleral) side of the choriocapillaris that shows the pericyte associating the endothelial cells. The pericyte has long and slender processes indicated with white bars in the right high magnification image. The processes are branching. The pericyte observed here is similar to that of capillary in the ordinary vessels.
These are images of retina, Bruch's membrane and choroid including choriocapillaris. Choriocapillaris is broken but visible from lateral or scleral side. Choriocapillaris is fenestrated at the medial (retinal) side without pericyte coverage, but covered with pericytes at the lateral side. Next, I will show the details of choriocapillaris at lateral (scleral side).
We can see the endothelial junctions of the choriocapillaris. Knob or flap like overlapping is visible at the junction away from the fenestration.
These are high magnification views of choriocapillaris. In the upper images, red blood cells remained in the vessels. In the lower images, we can see the borders and fenestration of endothelial cells. Area of fenestration is 0.5 or 1 µm away from the border. The knobs or leave shaped borders of the endothelial cells overlap with each other.
Choriocapillaris just below Bruch's membrane of mice eye. Choriocapillaris is a mesh of the blood vessels, which feeds retina. Upper images are the low or moderate magnification SEM views of the choriocapillaris seen from the retinal side. The lower image is a high magnification view of the surface of choriocapillaris. Small holes or fenestrations are at the surfaces of the endothelial cells of choriocapillaris, which are similar to This is a normal choriocapillaris, but I can show the pathological change of the choriocapillaris in detail three dimensionally.
These are retinal vessels (upper and lower left), and choriocapillaris (left) of mice eyes. Left view is the choriocapillaris viewed from Bruch membrane, which is dissolved and disappeared by KOH treatment. Right views are a retinal venule (up) and arteriol (down). Choriocapillaris does not have smooth muscle cells or pericytes at retinal side in contrast that retinal vessels have them.
