The more researchers understand of the mechanics of therapeutics, the better they may be able to hone treatment. Somatostatin (SST)—a naturally occurring peptide found throughout the central and peripheral nervous systems and other structures—may illuminate one way medications work in the eye. According to a Spanish research team, these SSTs play a role in the regulation of permeability across the retinal pigment epithelium (RPE) and act as an anti-permeability factor in the retina. The investigators believe the application of SSTs can counteract hypoxia and vascular endothelial growth factor (VEGF)-induced breakdown of barrier function.

SST may regulate the outer blood retinal barrier, the researchers found. They speculate that this means it could one day be used to treat conditions characterized by retinal edema.

The team conducted two experiments: first, they exposed cells from human-fetal RPE cultures to VEGF, with or without SST pretreatment; second, they exposed them to hypoxic conditions, again with or without SST pretreatment. The team assessed the paracellular permeability of fetal RPE by measuring the transepithelial electrical resistance (TER) and fluorescein isothiocyanate-sodium (FITC-sodium) flux. They used immunochemistry analysis to assess the expression of occludin and Zonula occludens-1 (ZO-1), both of which are proteins responsible for maintaining tight junctions between cells.

They found that both VEGF and hypoxia increased permeability of the fetal RPE, as measured by TER and tracer flux, according to the report. It also decreased occludin and ZO-1 staining. However, pretreatment of cultures with SST partially counteracted these effects.

Fonollosa A, Valcarcel M, Salado C, et al. Effect of somatostatin on human retinal pigment epithelial cells permeability. Exp Eye Res. 2019;184(7):15-23.