Subretinal Implant of Polycarbonate Membrane in Pig Model, Tomographic and Histological Results at Eleven Weeks

Abstract

Abstract: : Purpose: ARMD is the main cause of severe visual loss in elderly people, choroidal neovascularization involves degenerative process of photoreceptors, retinal pigment epithelium (RPE) and Bruch's membrane. In some cases it is possible to restore visual function if photoreceptors are re–located over healthy RPE. For RPE regeneration a basement membrane is necessary that replace Bruch's membrane. Our group previously reported feasibility to culture iris pigment epithelium cells over a synthetic membrane and to implant it into the subretinal space in a non–vascularized retina model. Our purpose is to test the biocompatibility of polycarbonate membrane implanted in the subretinal space of a vascularized retina model. Methods: Porous membranes of polycarbonate (thickness 10 µm, surface area 2 mm²), were implanted in the subretinal space of 2 pigs, a three port vitrectomy was performed, a small serous detachment was created in the macular area, and membrane was injected using a modified Grieshaber Cannulated Extrusion Needle. Air/fluid interchange was completed, and silicone oil was used as tamponade. After eleven weeks in vivo pigs were sacrificed, OCT and histological analysis was performed. Results: Polycarbonate membrane showed good macroscopical aspect, without any sign of rejection.Tomographic aspect for membrane showed a tiny hiperreflective signal under retina without shadow over posterior structures, retinal layers over the membrane had the same tomographic structure than adjacent retina, also pigment epithelium layer looked like a normal hiperreflective signal. Histological results showed outer retinal cell loss and mild fibrosis over a broad area of retina, we think related to surgical trauma. Away from retinotomy, around the membrane no additional fibrosis or inflamatory reaction appeared in histology. Conclusions: Polycarbonate membrane seems to be well tolerated when is implanted in subretinal space of vascularized model after eleven weeks, but it is necessary to improve surgical technique in order to limit retinal damage.

Keywords: choroid: neovascularization • retinal pigment epithelium • Bruch's membrane