Generation of a 3D Outer Blood-Retinal Barrier with Advanced Choriocapillaris and Its Application in Diabetic Retinopathy in a Microphysiological System

The outer blood-retinal barrier (oBRB) providesan optimalenvironment for the function of the photoreceptor by regulating theexchange of molecules between subretinal space and the choriocapillaris,and its dysfunction could impair the photoreceptor's functionand vision. The existing in vitro models have limitations in reproducingthe barrier function or physiological characteristics of oBRB andchoriocapillaris. Here, we engineered a microphysiological system-basedoBRB-choriocapillaris model that simultaneously incorporates the desiredphysiological characteristics and is simple to fabricate. First, wegenerated microvascular networks to mimic choriocapillaris and investigatedthe role of fibroblasts in vasculogenesis. By adding retinal pigmentepithelial cells to one side of blood vessels formed with endothelialcells and fibroblasts and optimizing their culture medium conditions,we established an oBRB-choriocapillaris model. To verify the physiologicalsimilarity of our oBRB-choriocapillaris model, we identified the polarizationand expression of the tight junction of the retinal pigment epithelium,Bruch's membrane, and the fenestral diaphragm of choriocapillaris.Finally, we tried to recapitulate the diabetes mellitus environmentin our model with hyperglycemia and diabetes-related cytokines. Thisinduced a decrease in tight junction integrity, loss of barrier function,and shrinkage of blood vessels, similar to the in vivo pathologicalchanges observed in the oBRB and choriocapillaris. The oBRB-choriocapillarismodel developed using a microphysiological system is expected to offera valuable in vitro platform for retinal and choroidal vascular diseasesin preclinical applications.