Galectin-1 involvement in neovascular retinopathies

Abstract

Purpose : Vascular Endothelial Growth Factor (VEGF) inhibitors have been established as the mainstay of current treatment of neovascular retinopathies (NVRx), however, it remains an unmet medical need. Galectin-1 (Gal1) has been implicated in pathologies associated with neovascularization (NV) through VEGF independent pathways and by its interaction with N-acetyllactosamine (NAcLc) structures in N- and O- glycans on glycosylated receptors. Here, we hypothesize that Gal1 is participating in experimental and clinical NVRx and independently of anti-VEGF therapy.

Methods : Oxygen-Induced Retinopathy (OIR) mouse model was carried out. Briefly, C57BL/6 mice (OIR, N=33) were exposed to 75% O2 from P7 to P12, after which they were brought to room air for additional five (P17) or nine days (P26). Age-match mice maintained in room air (RA, N=15) were used as controls. Some OIR mice were intraocular injected at P12 with 1,25 µg of anti-VEGF (N=9) or vehicle (N=9). At P12, P17 and P26 mice were sacrificed. Some eyes were fixed to obtain cryosections for immunofluorescences and retinas were isolated to analyze Gal1 expression by Western blots and qRT-PCR. Moreover, aqueous humor of patients with NVRx (N=16) or from control patients (N=6) was used to measure Gal1 levels by ELISA assays. GraphPad Prism program was employed for statistical analysis.

Results : Gal1 protein and mRNA levels were increased in P17 and P26 OIR retinas respect to RA controls (p<0,05). Immunofluorescence assays showed that it was located in the layers closest to the vitreous humor and its expression was most prominent in areas with NV. Moreover, Gal1 colocalization with Glial Fibrillary Acidic Protein (GFAP) and Glutamine Synthase (GS) suggested that it was present in astrocytes and activated Müller cells. In addition, it was within neovessels (OIR) but not in normal retinal vessels (RA) at P17. Byotinilated lectin staining demonstrated that OIR conditions modify the ‘‘glycosylation signature’’ of the normal retina showing a glycosylation pattern permissive to Gal1 binding at P17 OIR. Furthermore, anti-VEGF therapy was not able to reduce the OIR Gal1 induction (p<0,05). Finally, Gal1 levels were also elevated in aqueous humor of patients with NVRx (p<0,05).

Conclusions : We conclude that Gal1 is participating in the pathogenesis of OIR and it is independently of the anti-VEGF therapy. In light of our results, we also suggest that it is involved in the clinical NVRx.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.