The effect of lyophilization on graft acceptance in experimental xenotransplantation using porcine cornea.

The immunogenicity of lyophilized porcine cornea is unknown. The purpose of this study was to examine the possibility of using lyophilized porcine cornea as a substrate for ocular surface reconstruction. A porcine cornea stromal button was freeze-dried and vacuum-packed. Lyophilized and fresh porcine corneas were examined histologically, and then implanted into intrastromal pockets in live rat corneas. Cytokine concentrations in plasma and protein extracts from the corneal buttons of rats were measured using the fluorokine multianalyte profiling assay, and histologic examination was performed. Immunoreactivity to the alpha-gal epitope was not found in lyophilized porcine corneas, whereas it was found in several keratocytes in fresh porcine corneas. The median survival time of rat corneas receiving lyophilized porcine transplants was 28.0 days, significantly longer than the 14.0-day survival of rat corneas that received fresh porcine transplants (P < 0.05). CD45RO(+) and CD68(+) cells were observed in rejected corneas, and interleukin-2 and interferon-gamma were elevated in rat plasma and corneal tissue. The lyophilized porcine corneal stroma, which is devoid of alpha-gal epitope, is less antigenic, and may be a useful biomaterial for ocular surface reconstruction and corneal collagen supplementation.