Figure 4.

The ultrastructure of the blood-retinal barrier under electron microscopy during development in mouse.

(A) The blood-retinal barrier ultrastructure in the retinal nerve fiber layer at P3. The barrier is composed of endothelia, basal lamina and astrocytic end-feet. At this time, no tight junctions can be seen between the endothelia. The development of the basal lamina (black arrow) and the astrocytic end-feet (white arrow) is incomplete. (B) The blood-retinal barrier ultrastructure in the retinal inner nuclear layer at P14. The endothelium has many microvilli on the capillary lumen surface (black arrowheads). The basal lamina (black arrow) and astroglial end-feet (white arrow) are relatively more mature than those at P3. (C) The mature blood-retinal barrier ultrastructure in the retinal outer plexiform layer at P30. At this time, the endothelium is smooth, with tight junctions (white arrowheads) between cells, and the basal lamina is complete. (D) shows a higher magnification of the specimen in (C). Typical basal lamina (thin black arrow) and astroglial end-feet (white arrow) are marked. Inside the endothelial cell, there are many organelles, such as endocytic vesicles (bold black arrow). Scale bars: 3,300 nm in A, 1,700 nm in B, 1,000 nm in C, 333 nm in D. P: Postnatal days.