Pretreatment of eye bank-stored human corneas with alpha-Melanocyte Stimulating Hormone attenuates corneal endothelial morphometric changes induced by acute oxidative stress

Abstract

Purpose : The mechanisms underlying progressive corneal endothelial cell (CEnC) loss in human donor corneas during storage are not completely understood. Herein, we evaluated the cytoprotective effect of alpha-melanocyte stimulating hormone (α-MSH), a trophic neuropeptide present in human aqueous humor, on CEnC survival in the presence of acute oxidative stress in eye bank-stored human corneas.

Methods : An ex vivo study was conducted using paired research-grade human donor corneas (courtesy of Eversight Eye Bank). Randomly selected corneas from each pair (n=7; median donor age of 62 [range 38-66]) were pretreated with either 10^-4M or no α-MSH in Optisol-GS medium for 15 minutes and then subjected to 1.4 mM H₂O₂ in PBS for 15 minutes at 37°C. Corneas were then transferred to Optisol-GS medium and stored at 4°C for 2 weeks. Images were taken at baseline and repeated twice per week using CellChekD+ specular microscope. Endothelial morphometric parameters, including cell density, coefficient of variation (CV), percentage of hexagonality (%HEX), and corneal pachymetry were recorded. CEnC viability was assessed using a fluorescent live–dead viability assay [calcein AM-ethidium homodimer (EthD-1)] at day 14.

Results : Baseline morphometric parameters and pachymetry were comparable between the two groups (p>0.05). Mean CEnC loss was lower in the α-MSH pretreated group (day 5: 4.1±2.0%, day 7: 9.9±4.7%, day 11: 11.9±4.8%, day 14: 14.6±3.9%) compared to the control group (day 5: 6.2±3.2%, day 7: 16.1±7.1%, day 11: 21.2±6.4%, day 14: 22.8±5.8%), although this was not statistically significant (p=0.9, p=0.07, p=0.2, p=0.96, respectively). The values for CV and %HEX fluctuated in both groups with an increase in mean CV and a decrease in mean %HEX in both groups. Pachymetry increased in both groups within 14 days, but to a significantly lower degree in the α-MSH pretreated group (10.8±3.7% vs. 25.1±4.9% [control] at day 7, p=0.001). In addition, fluorescence microscopy images showed a higher percentage of EthD-1 positive dead cells in untreated corneas compared to the α-MSH pretreated group (p=0.0005).

Conclusions : α-MSH pre-treatment of donor corneas attenuates CEnC loss and pachymetry changes during storage in the presence of acute oxidative stress.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.