A Biocompatibility Study of the Implantation of Plant Photosystem I Reaction Centers in Normal and S334ter–3 Rats

Abstract

Abstract: : Purpose: Photosystem I (PSI) reaction centers derived from plant photosynthetic organelles have been proposed as a method for providing phototransduction capability to non–light responsive retinal cells.This study evaluated the biocompatibility of the intraocular delivery of Photosystem I (PSI) Reaction Centers purified from Spinach in both normal and S334ter–3 retinal degenerate rats. Methods:Pure PSI proteoliposomes (30ug/ml) or liposomes (25ug/ml) were injected within the vitreous or subretinal space of both normal and late stage S334ter–3 retinal degeneration rats. Animals were evaluated at baseline as well as weekly for four weeks after implantation with fundus exam, color fundus photos and Fluorescein Angiography (FA). After sacrifice eyes were fixed in 4% paraformaldehyde, then bisected for both paraffin section and H+E staining, or frozen section and immuno–staining. Frozen sections were assayed immunohistochemically with the primary antibodies Glial Fibrillary Acidic Protein (GFAP), and Mouse anti–rat CD11b (OX–42.) Immunohistochemical data were evaluated with confocal microscopy. Results: Fundus exam and color photos did not reveal any evidence of vitritis or endophthalmitis. One degenerate rat with liposomes implanted in the vitreous developed a thin epiretinal membrane. Mildly engorged vessels were observed in two animals implanted with PSI proteoliposomes both within the vitreous and sub–retinal space. FA showed areas of hyperfluoresence near retinal vessels in rats with PSI–proteoliposomes subretinal injection. H+E staining demonstrated mild perivascular inflammatory cell infiltration in some implanted eyes. Immunohistochemistry analysis demonstrated GFAP upregulation in implanted normal rats when compared with nonimplanted rats. A few OX–42 positive cells were found in S334ter–3 rats only without any significant change related to treatments. Conclusions: Clinically and histologically only a mild inflammatory response was observed in both normal and S334ter–3 rats treated with PSI proteoliposomes and liposomes. Plant derived PSI proteoliposomes appear to be compatible with mammalian retinal tissue following intraocular implantation.

Keywords: retina • drug toxicity/drug effects • immunohistochemistry