Optimization of the Pig Model for Penetrating Keratoplasty

Abstract

Purpose: : The goal of this study was to report on the advantages and limitations of the pig model for experimental in vivo penetrating keratoplasty (PK), and to optimize this model.

Methods: : Eleven healthy domestic pigs aged from 10 to 20 weeks (range: 6 to 120 kg) were used. Eight animals underwent full thickness PK with either allogeneic (n=3) or autologous (n=5) donor corneal tissue. In three cases, the inflammatory response to partial steps of the surgery was evaluated. Animals were observed daily (slit-lamp, tonometry, and pachymetry) and euthanized on day 7. Postmortem assessment included optical coherence tomography, histology and electron microscopy (SEM and TEM).

Results: : Graft failure was observed in 1 case and was attributed to surgically induced intraocular inflammation. Corneal edema was present at the end of surgery in all cases and decreased after surgery (r=-0.87; p=0.002). Inflammation, which was found to be a key parameter for the success of the graft, was significantly less when the following were used at the time of surgery: full pupil dilatation, dispersive viscoelastic agents, intraocular tissue plasminogen activators, intravenous mannitol, and systemic and topical steroids. Age was also a significant parameter for the success of transplantation. Histopathology of successful grafts showed a nice endothelial monolayer, with no adjacent fibrin membrane, while in the failed graft only a few residual endothelial cells remained, covered with a thick inflammatory membrane. SEM of successful grafts confirmed the presence of the typical hexagonal corneal endothelial pattern and TEM showed a normal endothelial cell ultrastructure.

Conclusions: : Adequate surgical and general anesthesia protocols were successfully developed for experimental in vivo PK in the pig model.

Keywords: cornea: clinical science • cornea: basic science • comparative anatomy