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Evaluation of UVA cytotoxicity for human endothelium in an ex vivo crosslinking experimental setting

Session Details

Session Title: Cornea
Session Date/Time: Sunday 22/02/2015 | 08:30-11:00
Paper Time: 08:57
Venue: Hall 2
First Author: : P.Mooren BELGIUM
Co Author(s): :    L. Gobin   N. Bostan   K. Wouters   D. Mathysen   C. Koppen  

Abstract Details

Purpose:

To evaluate endothelial cytotoxicity after exposure of human corneas to UVA (λ = 365 nm; 5.4 J/cm²) in an ex vivo corneal crosslinking experimental setting. Although the applied UVA dosage is identical to the dosage used for crosslinking in patients, the actual dosage at the level of the corneal endothelial cells is much higher in this experimental setting because corneas have been irradiated from the endothelial side, exceeding at least 8 times the cytotoxic thresholds established in rabbit and porcine endothelial cells (0.65 J/cm²).

Setting:

Antwerp University Hospital, Department of Ophthalmology.

Methods:

Seventeen human cornea pairs (left-right; ≥ 2000 endothelial cells/mm²), excluded for transplantation, were cut in two pieces. One piece was treated with 0.025 % riboflavin solution prior to UVA irradiation (5 minutes; 18 mW/cm²), while the other piece was treated only with 0.025 % riboflavin (right) or corneal preservation medium (left) and served as control. Endothelial cell counting was performed by two independent investigators after a short storage period (4-5 days; 31 °C) and staining with Trypan blue and Alizarin red. Normality (Q-Q plot; Shapiro-Wilk test) and equivalence (mixed-effects modelling, 10 % equivalence threshold) of endothelial cell counts were evaluated.

Results:

No statistically significant inter-observer cell counts were observed. The observed endothelial cell density for UVA-irradiated pieces was 2235 ± 202 cells/mm², while 2301 ± 276 cells/mm² were observed for control pieces, with a mean difference between both groups of 66 ± 238 cells/mm², which explains the observation of statistically significant equivalence of endothelial cell density in both groups.

Conclusions:

Despite direct irradiation of human donor endothelium using the dosage used in clinical settings for crosslinking from the epithelial side, no statistically significant differences in endothelial cell counts were observed between irradiated tissues and controls. We conclude from these findings that human corneal endothelial cells are far more resistant to riboflavin enhanced UVA irradiation than previously estimated by animal experiments.

Financial Disclosure:

NONE

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