Optimizing Subretinal Bleb Formation in a Porcine Model for Retinal Gene Therapy

Abstract

Purpose : The aim of this study is to elucidate bleb formation after subretinal injection in porcine models used for the evaluation of gene therapy. Porcine models are a promising avenue for preclinical evaluation of novel gene therapies, while subretinal injection is the current standard for gene therapy application. A crucial component of a successful subretinal injection is targeted placement of the subretinal fluid (usually referred to as “bleb”). To achieve the desired bleb placement (e.g. the area centralis), it is essential to evaluate the forces which guide bleb formation.

Methods : Subretinal injection after 23-gauge pars plana vitrectomy was performed in 41 eyes of 21 animals (sus scrofa). In 27 eyes (65.9%), the retinotomy site was placed superior to the area centralis, while in 14 eyes (34.1%) it was placed inferior to it. After subretinal injection the resulting blebs were classified regarding retinotomy placement (superior vs. inferior of the area centralis) and propagation behavior relative to the area centralis (towards it, away from it, or no tendency in either direction).

Results : Across all injections, 18 blebs (43.9%) displayed a tendency to propagate away from the area centralis, while 11 blebs (26.8%) displayed a tendency to propagate towards the area centralis. 12 blebs (29.3%) developed in a balanced manner without a tendency in either direction. In addition, placement of the retinotomy site immediately superior to the area centralis was associated with a significantly reduced rate of blebs propagating away from the area centralis, compared to retinotomies placed immediately inferior of it (33.3% vs. 71.4%, p=0.0022).

Conclusions : This study is one of the first to elucidate bleb propagation dynamics in the porcine model. Overall, there was a tendency of blebs to develop away from the cone-rich area centralis. Yet, subretinal bleb formation could still be guided via retinotomy site placement, with a placement superior to the area centralis increasing the likelihood of visual streak detachment. This may reflect the marked asymmetry between superior/inferior large vessel configuration in the porcine model, and/or slightly increased adhesion forces in the area centralis. This study will aid the planning of surgeries for targeted subretinal delivery in pig models.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.