Breaching the retinal barrier
Trinity College Dublin researchers have developed a way to use RNAi to reversibly enhance the permeability of the blood retina barrier.1 The technique improved systemic delivery of two small molecules to the mouse retina, and the researchers are now adapting the approach for use in humans.
Much like the brain, the retina has evolved cellular barriers to exclude potentially harmful blood-borne agents while allowing passage of nutrients to ensure proper functioning. The retina has two such barriers: the inner blood retina barrier (BRB), which consists of retinal endothelial cells, and the outer BRB, which consists of a single layer of retinal pigment epithelial cells.
In both retinal barriers, protein complexes called tight junctions exist between individual cells to block passive diffusion of small molecules. Tight