Abstract
Purpose The global donor cornea shortage has led to the requirement for alternative solutions such as tissue engineered grafts using cultured corneal endothelial cells (CECs). We have created a biosynthetic corneal graft using a methacrylated poly-epsilon-lysine (PeK) hydrogel as a support for a monolayer of CECs. We have previously shown the hydrogel demonstrates good compatibility with CECs and that the hydrogel mechanical properties can be optimised to produce excellent handleability, superior to that of DMEK. The aim of this study was to test the safety of the hydrogel in an in vivo rabbit model.
Methods The PeK was modified by covalent functionalisation with methacrylamide residues to produce hydrogel networks crosslinked with UV light. Lenses were removed from New Zealand White rabbits to deepen the anterior chamber. A descemetorhexis (6mm) was performed and hydrogels approximately 150μm thick and 6mm in diameter were delivered to the anterior chamber using a Viscoject Bio injection device. The graft was secured in place using air tamponade. Rabbits received daily administration of steroid and antibiotic eye drops. Optical coherence tomography (OCT) imaging was performed before graft delivery and weekly post-op until study end at week 16.
Results The hydrogels were easy to handle, had flexibility to be folded without breakage when placed into the clinical delivery device. Once injected into the anterior chamber they unfolded easily with minimal manipulation. The hydrogels were attached at post-op day 1 (4/5 rabbits) as shown by the OCT images. After 1 week the thickness of the cornea increased due to removal of the endothelial layer (1047μm; SD 83μm). After 4 weeks the corneas with attached hydrogels had thinned on average to 742μm (SD +/-54μm) and at 10 weeks were 674μm (SD +/-206μm). The hydrogel thickness did not change significantly in this time (Week 1-132μm +/-SD9μm and Week 10-127μm +/-SD25μm p>0.05).
Conclusions The hydrogel has optimised mechanical properties which confer flexibility and allow the hydrogel to flip open with ease. The hydrogel attaches well to the bare stroma. No adverse reactions were seen in the rabbits. These data suggest the hydrogel is a suitable material to create a corneal endothelial graft and possibly has potential to be used as a substrate to receive CECs injected into the anterior chamber. Efficacy studies are underway using cellular grafts with human CECs.
