Elie Motulsky

Origins and consequences of hyperosmolar stress in retinal pigmented epithelial cells.

The retinal pigmented epithelium (RPE) is composed of retinal pigmented epithelial cells joined by tight junctions and represents the outer blood-retinal barrier (BRB). The inner BRB is made of endothelial cells joined by tight junctions and glial extensions surrounding all the retinal blood vessels. One of the functions of the RPE is to maintain an osmotic transepithelial gradient created by ionic pumps and channels, avoiding paracellular flux. Under such physiological conditions, transcellular water movement follows the osmotic gradient and flows normally from the retina to the choroid through the RPE. Several diseases, such as diabetic retinopathy, are characterized by the BRB breakdown leading to leakage of solutes, proteins, and fluid from the retina and the choroid. The prevailing hypothesis explaining macular edema formation during diabetic retinopathy incriminates the inner BRB breakdown resulting in increased osmotic pressure leading in turn to massive water accumulation that can affect vision. Under these conditions, it has been hypothesized that RPE is likely to be exposed to hyperosmolar stress at its apical side. This review summarizes the origins and consequences of osmotic stress in the RPE. Ongoing and further research advances will clarify the mechanisms, at the molecular level, involved in the response of the RPE to osmotic stress and delineate potential novel therapeutic targets and tools.

Diagnosis of Cytomegalovirus Anterior Uveitis in Two European Referral Centers

ABSTRACT Purpose: To evaluate diagnostic methods and clinical signs of CMV anterior uveitis (AU), a rarely described entity in Europe. Methods: We included patients with clinical characteristics of CMV AU and positive PCR and/or Goldmann-Witmer coefficient (GWc) for CMV. Results: We report 21 patients with unilateral uveitis (100%) and signs of Posner-Schlossman syndrome (PSS) (n = 20, 95.2%), Fuchs uveitis syndrome (FUS) (n = 1, 4.7%), and endotheliitis (n = 4, 19,04%). PCR was positive in 15/21 (71.4%) and GWc in 8/9 patients (88.9%) in aqueous for CMV. GWc was the only positive test in 6/9 patients (66,6%). When PCR alone was performed (without GWc) in the first tap, repeated aqueous taps were needed, twice in five cases and thrice in one case. Conclusion: Combining PCR and GWc were very helpful to confirm the clinical diagnosis of CMV AU. In case of very high clinical suspicion and negative results, repeated tap seems to be recommended.

Modification of aquaporin expression in response to fenretinide-induced transdifferentiation of ARPE-19 cells into neuronal-like cells.

The goal of this study was to investigate the modifications of aquaporin (AQP) expression in ARPE‐19 cells in response to fenretinide‐induced transdifferentiation into neuronal‐like cells

Aquaporin-1 Expression in Proliferative Vitreoretinopathy and in Epiretinal Membranes

Purpose. Aquaporin-1 (AQP1) is involved in cell migration and proliferation; therefore, the purpose of the study was to investigate its expression in proliferative vitreoretinopathy (PVR) and epiretinal membranes (ERM). Methods. 19 membranes from PVR and ERM were collected following eye surgery. AQP1 mRNA and protein expressions were determined by RT-qPCR and immunofluorescence in the membranes from PVR and ERM. Results. AQP1 mRNA and protein were expressed in both PVR and ERM as shown by RT-qPCR and immunofluorescence. AQP1 protein expression was heterogeneous among and between PVR and ERM and colocalized with alpha-smooth muscle actin (αSMA) and with glial fibrillary acidic protein (GFAP). There were a higher percentage of cells coexpressing AQP1 and αSMA than AQP1 and GFAP. GFAP and αSMA did not colocalize. Conclusion. Our data show for the first time AQP1 expression in both PVR and ERM. AQP1 is expressed mostly by the αSMA-positive cells, presumably myofibroblasts, but also by GFAP-positive cells, assumed to be glial cells. These original findings warrant further functional investigations aiming at studying the potential role of AQP1 in cell migration and proliferation occurring during the development of PVR and ERM.