MFSD2a, the transporter of the omega‐3 fatty acid DHA, is expressed in the neural retina

Abstract

AbstractPurpose: The omega‐3 fatty acid, DHA, is enriched in the outer disk and synapse membranes, and it exerts an anti‐inflammatory and anti‐apoptotic effect in the neuron cells. Animal models and patients with retinal dystrophies were reported to have reduced levels of DHA in the retina, so different nutraceuticals were designed for these patients. Nevertheless, it is still unknown how DHA is cached and distributed in the retina. MFSD2a was reported as the putative transporter of omega‐3, but its expression was only described in the endothelial cells. In this study, we assessed the expression of MFSD2a in the different cell populations of the neural retina.Methods: The expression of MFSD2a was studied by immunofluorescence in cryostat sections of the retina from healthy human donors. Double immunolabelling with different cell markers was used to study MFSD2a expression in the different retinal cell populations. Cone arrestin was used for the identification of cone photoreceptor cells. Parvalbumin is a cell marker for all horizontal cells. The transcription factors Chx10 and Pax6 were used for the identification of bipolar and amacrine cells, respectively. KDEL, an endoplasmic retention signal peptide, was used for the visualization of ganglion cells. Müller cells and RPE are positive for CRALBP.Results: We found that MFSD2a was expressed in the outer nuclear layer as well as in the inner segments of the photoreceptor cells. Outer segments showed weak or negative immunostaining. Immunoreactivity with anti‐MFSD2a was also detected in the inner nuclear layer. Double immunostaining with parvalbumin and the transcriptional factors Chx10 and Pax6 confirmed that all populations of horizontal, bipolar, and amacrine cells, respectively, expressed the omega‐3 transporter. Also, ganglion cells expressed MFSD2a. In the double immunolabelling with anti‐MFSD2a and anti‐CRALBP, Müller cells showed punctae of immunolabelling in the tips of the external limiting membrane. Although, RPE did not seem to express MFSD2a.Conclusions: MFSD2a is expressed by the neural cells of the retina. Photoreceptor cells, Müller cells, and all populations of bipolar, amacrine, horizontal, and ganglion cells expressed the transporter of the omega‐3 fatty acid, DHA.