Tissue Engineered Cornea Stromal Matrix Replacements

Abstract

Abstract: : Purpose: To evaluate safety and efficacy of corneal stromal replacements composed of hybrid biological and synthetic components, in a Yucatan mini-pig model, chosen for its similarities to human corneas. Methods: Collagen-synthetic terpolymer (Coll-TERP) hydrogel stromal replacements were fabricated to the shape and dimensions of human/pig corneas. According to ARVO guidelines, lamellar keratoplasty (LKP) was performed on one cornea of each animal. A 5 mm button of the pig’s cornea was removed, and transplanted polymer was cut out, with the diameter of the transplanted polymer 0.50 mm larger to allow adequate wound apposition between the graft and the recipient keratectomy bed. The polymer was sutured into the host keratectomy bed with 8 interrupted 10-0 nylon sutures. Postoperative medication consisted of dexamethasone qid and gentamycin qid for 21 days. The animals were followed up to 8 weeks post-surgery. Results: Implants demonstrated successful regeneration of host tissues and in particular, functional nerve regeneration in pig models. Epithelial migration from the host over the implant was observed. By 4 days, fluorescein was excluded. At 3 weeks post-operative, the regenerated epithelium was fully stratified, and in-growth of nerves and stromal cells were observed by in vivo confocal microscopy. Histopathological examination of corneas with implants at 3 and 6 weeks showed a very seamless host-graft interface. At 6 weeks post-operative, the implant was fully populated by stromal cells and the sub-epithelial nerve plexus was re-established. However, the density of in-growing cells will require better control. Esthesiometry showed that by 3 weeks post-operative, much of the nerve touch sensitivity was re-gained and by 6 weeks post-operative, they were at original pre-op levels. Also, the toughness of the matrix can be improved. Conclusions: Bio-synthetic polymers are promising materials as stromal matrix replacements. However, a lot more testing and refinement is still necessary.

Keywords: cornea: basic science • transplantation • extracellular matrix