Topical Phosphorodiamidate Morpholino Oligomer Antisense Compounds Effectivly Delay Cornea Rejection in a Transplant Rat Model

Abstract

Purpose: : Corneas are the most common and successfully transplanted tissue. However, if rejection occurs, the probability of a subsequent successful transplantation declines precipitously. Phosphorodiamidate morpholino oligomer (PMO) antisense compounds, AVI-4126 and AVI-5126, suppress c-myc expression. Stability and tolerability of AVI-4126 and AVI-5126 were previously examined in rat and rabbit models. To evaluate their ability to inhibit corneal rejection, we compared incubation of corneas stored in Optisol^TM + AVI-4126 or AVI-5126 with or without post transplant topical treatment with AVI-4126 or AVI-5126.

Methods: : In vivo sterile cornea transplants were performing by transplanting donor corneas from ACI rats to right eye of Lewis rats using 3mm trephine and 10-0 nylon suture. In a masked, randomized fashion, corneas from ACI rats were preserved in either 0.5 or 1mg/ml AVI-4126 or AVI-5126 in Optisol^TM or in Optisol^TM alone for 24 hr before transplantion. All rats were treated post-operatively with topical Tobradex^TM TID until rejection occurred. Some Lewis rats received TID post transplant topical treatment with 0.5 or 1mg/ml AVI-5126 or with the vehicle, 0.9% NaCl, as a control. There was daily toxicity monitioring using a modified McDonald-Shadduck System: Slit Lamp Scale for Ocular Irritation. Rejection criteria were an opacity score > 2 or a total score > 4.5.

Results: : Transplanted rats with graft corneas stored in either 0.5 or 1mg/ml AVI-5126 with post transplant TID 1mg/ml AVI-5126 showed significant improvement in survival times compared to Optisol^TM and TID 0.9% NaCl controls. Cornea storage in 1mg/ml AVI-5126 + post transplant treatment increased survival time from 5.6+-0.79 days to 7.0 + 1.21 days (mean+ standard deviation, n=9, p<0.05), while storage in 0.5 mg/ml AVI-5126 + post transplant treatment increased survival time to 7.0+1.7 days (n=3, p<0.05).

Conclusions: : This rat model of in vivo corneal transplantation shows significant delay in graft rejection by storing donor corneas followed by topically treating graft recipients with new, highly stable antisense drugs. This improvement occurs without the local or systemic immunosuppression seen in rejection models treated with local or systemic cyclosporine. In addition, these anti-sense agents can be successfully applied topically without irritation or local toxicity.

Keywords: cornea: basic science • transplantation • cornea: storage