Comparison of immunogenicity and porcine-to-rhesus lamellar corneal xenografts survival between fresh preserved and dehydrated porcine corneas.

BACKGROUND

To compare the immunogenicity of fresh preserved and dehydrated lamellar porcine corneas in porcine-to-mouse heterotopic transplantation and to investigate the survival of preserved porcine corneas as xenografts in porcine-to-rhesus lamellar corneal transplantation.

METHODS

Dehydrated and fresh preserved, endothelium deprived, porcine corneas were cut into fragments and grafted beneath the kidney capsule of BALB/c mice. Porcine-specific delayed type hypersensitivity (DTH) and antibody (IgM, IgG) immune responses of the recipient mice were assessed. In addition, fresh preserved and dehydrated porcine corneas were used in porcine-to-rhesus lamellar corneal xenotransplantation. The rhesus recipients were divided into three groups. Dehydrated corneas were applied to Group 1 and 3, and fresh preserved corneas were applied to Group 2. Only Group 3 received subconjunctival injections with triamcinolone acetonide for 1 month. All xenografts were evaluated by slit-lamp microscopy for 6 months. Two recipients in each group were examined by in vivo confocal microscopy and then killed for corneal histopathological staining 3 months after surgery.

RESULTS

Neither fresh preserved nor dehydrated corneal fragments evoked any measurable change in mice recipient humoral immune status, but both could induce porcine-specific DTH at 1, 2, and 4 week after being grafted. However, the intensity of the DTH responses evoked by dehydrated corneas was lower than that evoked by fresh preserved corneas. In porcine-to-rhesus lamellar keratoplasty, with the exception one graft in Group 2 that developed characteristics of rejection, all the xenografts remained transparent or translucent up to 6 month after surgery. Histopathological examination of Group 1 showed that the infratemporal xenografts were much thicker and displayed some inflammatory cell infiltration in the peripheral portion of the graft and bed interface. However, in Group 3, which was treated with triamcinolone acetonide, there was an easily identified scar at the lamellar interface with no inflammatory cells present. In the rejected graft in Group 2, infiltrating cells included a few eosinophils and massive lymphocytes. Confocal microscopy examination showed that activated keratocytes localized in the anterior stroma and highly reflective tissue at the interface of the graft and bed.

CONCLUSIONS

Porcine corneas might be an ideal source for clinical lamellar corneal xenotransplantation. In cases of tectonic lamellar transplantation, the possibility to use dehydrated pig material may become an option in the future.