Abstract
Purpose :
The retinal pigment epithelium (RPE) is a monolayer of pigmented cells with important functions in the outer blood-retinal barrier and subretinal immune suppression. Failure of RPE functions and chronic inflammation have been both hypothesized to play a role in the pathophysiology of age related macular degeneration (AMD). We have previously shown that acute stimulation of RPE cells by TNFα down-regulates gene expression of OTX2 (Orthodenticle homeobox 2) and that of major visual cycle-related genes . We here investigated the long-term effects of TNFα on RPE morphology and function in vitro.
Methods :
Primary porcine RPE cells were cultivated until confluence, then recombinant TNFα was added daily in the culture medium (at 0.8, 4, 20 or 100ng/ml=C1,C2,C3 and C4) for 10 days. RPE cell morphology and gene expression, barrier, phagocytosis and immunosuppressive functions were assessed.
Results :
Cell morphology and gene expression: 10 day stimulation by TNFα (i) decreased RPE cell numbers (3653.6, 3428, 3227, 2791 and 2020 cells/mm2 respectively for control, C1,C2,C3 and C4, all p<0.01); (ii) increased cell size (+5.3, +12.6, +13.9 and +9.5% for C1,C2,C3 and C4 as compared to control, all p<0.05); (iii) increased the number of multinucleated cells (5.7, 7.7, 9.4, 9.9, 15.9% of multinucleated cells for control, C1,C2,C3 and C4, all p<0.05); (iv) and decreased OTX2 expression (-11.1, -19.7, -52 and -82.9% for C1,C2,C3 and C4 as compared to control, all p<0.05). The number of apoptotic TUNEL+ cells was increased upon TNFα adjunction (112,3 , 158.7 and 189.9% of control for C2,C3 and C4, all p<0.05). Barrier function: 10 day stimulation by TNFα (i) disturbed Zonula Occludens 1 cellular distribution and cytoskeletal architecture (actin F distribution) and (ii) significantly decreased RPE transepithelial resistance in a dose-dependent manner ( -70, -88.5 and -90.8% of control for C2,C3 and C4, p<0.05). Immunossupressive function: 10 day pre-stimulation with -TNFα significantly decreased RPE capacity to induce monocyte death after 24h of co-culture (p<0.05).
Conclusions :
Chronic exposure to TNFα deteriorates major RPE functions that are essential to visual function and might play a key role in the pathophysiology of AMD.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.