Inner Blood-Retinal Barrier Regulation in Retinopathies

The neural retina is protected from the blood circulation by the presence of a highly selective inner blood-retinal barrier (iBRB). The presence of sophisticated tight junctions (TJs) between the endothelial cells (ECs) of the iBRB helps mediate the very low passive permeability of the tissue, permitting entry of nutrients into the retina but excluding harmful toxic material and inflammatory cells. The most highly enriched TJ protein is claudin-5, which is critical in mediating the passive paracellular diffusion barrier properties of the iBRB. In numerous retinal degeneration pathologies, TJ disruption is observed, and a more refined understanding of this disruption could be used for therapeutic benefit.