Purpose: Corticosteroids are a major risk factor for central serous chorioretinopathy (CSC), a posterior eye disease with a poorly understood pathophysiology. Choroidal vascular hyperpermeability is as a sign of impaired barrier function in patients with CSC. Here, we evaluated the barrier function of choroidal endothelial cells (CECs) in vitro in response to cortisol and the role of ZBTB16 gene, a strongly cortisol responsive gene in CECs.

Methods: Human CECs were isolated and purified from the bulbi of 2 independent non-CSC donors. The cells were treated with increasing concentrations of cortisol or vehicle and in the presence or absence of the glucocorticoid receptor antagonist mifepristone for 24 hours. We also performed an siRNA-mediated knockdown experiment for the ZBTB16 gene. The functional response of CECs was measured in real-time with a CellZscope® system with trans-endothelial electrical resistance (TEER) and capacitance (C_cl), as parameters of barrier function. Transcellular and paracellular endothelial permeability was measured at the end of the treatment using fluorescently labelled tracer molecules (70 kDa and 766 Da).

Results: CECs formed a low permeable barrier as indicated by a low TEER value. Cortisol dose-dependently increased the TER and simultaneously decreased the C_cl values in a GR-depedent manner. Subsequently, cortisol significantly reduced the permeability of fluorescent tracers. CECs with knockdown ZBTB16 showed a higher TEER with cortisol treatment than the control, suggesting that ZBTB16 restrained the effect of cortisol-induced GR.

Conclusions: The response of CECs to cortisol leads to increased barrier integrity and decreased endothelial permeability, which mimics the response in other vascular beds. Therefore, the current model may be suitable to study the pathophysiology of CSC, where we hypothesize that this effect is absent or attenuated. To better understand the pathophysiology of CSC, we will extend our research using CSC patient-derived endothelial cells.