An In Vitro Bilayer Model of Human Primary Retinal Pigment Epithelial and Choroid Endothelial Cells for Permeability Studies

The blood-retinal barrier (BRB) present in the posterior chamber of the eye plays a major role in maintaining the proper function and integrity of the retina. Retinal pigment epithelium and choriocapillaris form the outer blood retinal barrier (oBRB), and breakdown of this barrier leads to vision-threatening diseases like macular edema, macular degeneration, and diabetic retinopathy. A simplified cell culture model of oBRB will be of great importance in elucidating the molecular mechanism of the disease progression. This chapter describes methods for primary cell isolation from donor eyes to culture human retinal pigment epithelial cells (hRPE) and choroidal endothelial cells (hCEC) and the protocol for construction of a simplified in vitro model of oBRB on fibronectin-coated Transwell inserts. Further, we explained the permeability study using FITC-dextran conjugated tracers for validating the bilayer model. The permeability experiments ensured that the system could easily be manipulated to recapitulate the pathological condition in vitro. Thus, it would be an optimal system for studying the disease mechanisms related to retinal and choroidal pathologies, for screening small molecules, and for performing drug permeability kinetics. Moreover, fundamental understanding of paracellular and transcellular trafficking of cargo in hRPE and hCEC could also be studied using this model.