αB crystallin peptide fused to elastin-like polypeptide provides long-term neuroprotection in a mouse model of AMD

Abstract

Purpose : Administration of NaIO₃ to mice causes marked retinal pigment epithelium (RPE) damage and retinal degeneration on day 7. A single intravitreal injection of αB crystallin peptide fused to elastin-like polypeptide (crySI) significantly inhibited retinal degeneration compared to a free 20-mer αB crystallin mini-peptide (mini cry) (Sreekumar et al. ARVO 2017). Herein, we report the long-term protective effect of crySI in the NaIO₃ mouse model as well as protection of human polarized RPE monolayers.

Methods : Ten male 129S6/SvEvTac mice (4-8 weeks old) were used per group.

See scheme at end of abstract.

Intra-ocular disposition of crySI and mini cry were compared by color fundus images after intravitreal injection of fluorescein-labeled substrates. Polarized human RPE monolayers were cotreated in apical and basal cellular compartments with NaIO₃ and either mini cry, SI or crySI for 24h. Transepithelial resistance (TER) of RPE monolayers was measured and cells were labeled for ZO1.

Results : Eyes challenged with NaIO₃ had large areas of retinal degeneration (>50%) compared to controls. In contrast, challenged mice pre-treated from 7 to 14 days with a single intra-vitreal injection of crySI had significantly lower retinal degeneration (<25%) compared to mice treated with the mini cry. H&E staining revealed major tissue disruption in all control NaIO₃ challenged mice; however, only crySI consistently protected against this disruption. The retention of crySI was prolonged (6 weeks) in the vitreous when compared to mini cry that was cleared within two days, which confirms that ELP-mediated assembly of crySI increases exposure to the retina. In vitro studies in polarized RPE monolayers showed that 2.5 mM NaIO₃ significantly reduced TER and caused disruptions in tight junction protein ZO-1; furthermore, crySI (10 µM) maintained TER similar to controls confirming a protective role for crySI.

Conclusions : Intra-vitreal injection of crySI attenuates NaIO₃ induced retinal degeneration in mice by rescuing RPE and preventing disruption of other retinal layers. crySI has potential as a treatment for AMD since the ELP fusion results in long-term (at least 6 weeks) retention thereby offering extended retinal protection.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.