Abstract
Purpose::
Corneas are the most commonly and successfully transplanted tissue. However, if rejection occurs, the probability of a subsequent successful transplantation declines precipitously. Phosphorodiamidate morpholino oligomer anti-sense compounds, AVI 4126 and 5126, are directed at the suppression of c-myc expression. To reduce corneal rejection, we evaluated pretreatment of stored corneas with AVI 4126 or 5126 and also their topical application following corneal transplantation. As most eye banks store corneas in OptisolTM, a proprietary preservation media, it was the storage media of choice.
Methods::
Stability and tolerability of AVI 4126 and 5126 were examined in rat and rabbit models. During in vitro stability tests, aliquots of 500 µg/ml in OptisolTM were stored at 4oC for 30 d and examined for pH, microscopic precipitates and stability by TLC. Human corneas were stored in other aliquots for 8 d and prepared for H&E staining. New Zealand White rabbit corneas, mounted in Ussing chambers, were used determine the corneal transport. Rabbits were treated by IVT with 50 or 500 µg AVI 4126, 5126 or their fluorescent constructs while Sprague Dawley rats were treated topically 3x/day for 8 d with 500µg/ml AVI or OptisolTM alone. All were monitored for ocular toxicity by slit lamp, confocal microscopy and tonometry.
Results::
During the 30 d storage period, no changes in AVI solutions were noted. Corneas, in AVI 4126 or 5126, maintained normal cellular structure and corneal thickness when compared to storage in OptisolTM alone. The Ussing chamber experiments indicated that in 24 hr about 5 µg/ml (or 1%) of the total dose crossed the cornea. Following either IVT or topical application, there were no changes to the normal endothelial, stromal and epithelial cell structure, IOP and corneal thickness nor other ocular pathology. After IVT the fluorescent compounds could be detected in ocular tissues for greater than 24 hours.
Conclusions::
Both AVI 4126 and 5126 are stable for storage in OptisolTM, showed no ocular toxicity, penetrated the cornea to deliver pharmacologically relevant amounts to the interior of the eye, and could be formulated for IVT or topical administration. These results suggest that these oligonucleotides are suitable candidates for antisense testing in a rat corneal rejection model.
Keywords: cornea: storage • transplantation • drug toxicity/drug effects