Aquaporin 1 expression in control and pathologic retina

Aquaporin 1 (Aqp1) is a transmembrane channel protein, present in various tissues including ocular tissues, carrying water and regulating the cations flow across membranes. Experimental laser photocoagulation in rat retina induces reproducible injuries mimicking some angiogenic features of ocular pathologies such as subretinal neovascularization, gliosis and possible repair mechanisms. Our study was designed to unravel the potential roles of Aqp1 in such processes. We performed immunohistochemical Aqp1 co-immunostainings with a typical marker of Muller cells and astrocytes: the glial acidic fibrillary protein (Gfap) known to be involved in gliosis, with the blood vessel marker called von Willebrand factor (vWf) and with Nestin, a progenitor/stem cell marker in certain contexts. We observed an Aqp1/Gfap co-immunolabeling principally in retinal radial Muller cells. The co-immunoreactivity Aqp1/vWf was partially distributed, mostly in the choroid (Ch) and retina. Aqp1/Nestin co-immunolabeling was not or rarely observed except in some blood vessels principally in the ganglion cell layer (GCL) and Ch. In conclusion, after laser impact in retina, we could not significantly detect the presence of Aqp1 in precursor cells; however we detected it in glial and endothelial cells similarly to what we observed in control retina. Thus, Aqp1 appears to be a protein present in posterior differentiated cells of the eye where it regulates the hydro-ionic flow that is distributed between cells, extracellular matrix and blood vessels.