ASTROCYTES INCREASE BARRIER PROPERTIES AND ZO-1 EXPRESSION IN RETINALVASCULAR ENDOTHELIAL-CELLS

Purpose. Diabetic retinopathy and other diseases associated with retin al edema are characterized by increased microvascular leakage. Astrocy tes have been proposed to maintain endothelial function in the brain, suggesting that glial impairment may underlie the development of retin al edema. The purpose of this study was to test the effects of astrocy tes on barrier properties in retinal microvascular endothelial cells. Methods. Bovine retinal microvascular endothelial cells were exposed t o conditioned media from rat brain astrocytes. Transendothelial electr ical resistance (TER) was determined on 24-mm Transwell (Cambridge, MA ) polycarbonate filters with the End-Ohm device (World Precision Instr uments, Sarasota, FL). ZO-1 protein content was quantified by microtit er enzyme-linked immunosorbent assay. Results. Astrocyte-conditioned m edium (ACM) significantly increased TER (P < 0.0001) and ZO-1 content (P < 0.01). Both serum-containing and serum-free N1B defined ACM incre ased ZO-1 expression, but heating abolished the effect. Serum-free ACM decreased cell proliferation by 16%. Conclusions. Astrocytes release soluble, heat-labile actors that increase barrier properties and tight junction protein content. These results suggest that astrocytes enhan ce blood-retinal barrier properties, at least in part by increasing ti ght junction protein expression. Our findings suggest that glial malfu nction plays an important role in the pathogenesis of vasogenic retina l edema.