beta-Galactosidase transgene expression in transplanted rabbit retinal pigment epithelial cells in vivo

Subretinal transplantation of retinal pigment epithelium overexpressing fibulin-5 inhibits laser-induced choroidal neovascularization in rats

Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly. Choroidal neovascularization (CNV) is the abnormal angiogenesis that causes severe visual loss in AMD. Fibulin-5 (Fbln5), which functions as an angiogenesis inhibitor, plays an important role in the pathogenesis of AMD. Here, we investigated whether subretinal transplantation of Fbln5-overexpressing retinal pigment epithelial (RPE) cells can inhibit CNV in vivo. Adult Long-Evans rats were used in this study. CNV was induced by laser photocoagulation. One week after laser-induced CNV, RPE cells expressing pZlen-Fbln5-IRES-GFP or the control pZlen-IRES-GFP vectors were transplanted into the subretinal space of the right and left eyes, respectively. CNV was evaluated using fundus photography, fundus fluorescein angiography (FFA), and hematoxylin and eosin staining. We found that CNV occurred at 1 week after photocoagulation, reaching peak activity at 3 weeks and remaining at a high level at 4-5 weeks after photocoagulation. Transplanted RPE cells survived for at least 4 weeks and migrated toward the retina. Subretinal transplantation of Fbln5-overexpressing RPE cells resulted in a significant reduction in the total area of leakage and the number of leakage spots compared with transplantation of RPE cells expressing only green fluorescent protein. Our findings suggest that subretinal transplantation of Fbln5-overexpressing RPE cells inhibits laser-induced CNV in rats and thus represents a promising therapy for the treatment of AMD.

RPE transplantation and its role in retinal disease

Retinal pigment epithelial (RPE) transplantation aims to restore the subretinal anatomy and re-establish the critical interaction between the RPE and the photoreceptor, which is fundamental to sight. The field has developed over the past 20 years with advances coming from a large body of animal work and more recently a considerable number of human trials. Enormous progress has been made with the potential for at least partial restoration of visual function in both animal and human clinical work. Diseases that have been treated with RPE transplantation demonstrating partial reversal of vision loss include primary RPE dystrophies such as the merTK dystrophy in the Royal College of Surgeons (RCS) rat and in humans, photoreceptor dystrophies as well as complex retinal diseases such as atrophic and neovascular age-related macular degeneration (AMD). Unfortunately, in the human trials the visual recovery has been limited at best and full visual recovery has not been demonstrated. Autologous full-thickness transplants have been used most commonly and effectively in human disease but the search for a cell source to replace autologous RPE such as embryonic stem cells, marrow-derived stem cells, umbilical cord-derived cells as well as immortalised cell lines continues. The combination of cell transplantation with other modalities of treatment such as gene transfer remains an exciting future prospect. RPE transplantation has already been shown to be capable of restoring the subretinal anatomy and improving photoreceptor function in a variety of retinal diseases. In the near future, refinements of current techniques are likely to allow RPE transplantation to enter the mainstream of retinal therapy at a time when the treatment of previously blinding retinal diseases is finally becoming a reality.

Gene therapy for genetic and acquired retinal diseases

We present an overview of the current status of basic science and translational research being applied to gene therapy for eye disease, focusing on diseases of the retina. We discuss the viral and nonviral methods being used to transfer genes to the retina and retinal pigment epithelium, and the advantages and disadvantages of each approach. We review the various genetic and somatic treatment strategies that are being used for genetically determined and acquired diseases of the retina, including gene replacement, gene silencing by ribozymes and antisense oligonucleotides, suicide gene therapy, antiapoptosis, and growth factor therapies. The rationales for the specific therapeutic approaches to each disease are discussed. Schematics of gene transfer methods and therapeutic approaches are presented together with a glossary of gene transfer terminology.

The expression of the plasmid DNA encoding TGF-beta 1 in endothelium after injection into the anterior chamber

The method of gene transfer into corneal endothelium was investigated to provide a foundation for the study of TGF-beta 1 gene transfer to inhibit corneal graft rejection. Two days after direct injection of pMAM TGF-beta 1 mediated by liposome into the anterior chamber of rabbits, one half of corneas were made into paraffin slides and the endothelial layer was carefully torn from the other half to make a single layer slide of endothelia. By means of immunohistochemical technique, the plasmid pMAM TGF-beta 1 expression product TGF-beta 1 in the endothelia was detected. Specific TGF-beta 1 expression was positive in the endothelia on both the paraffin slide and the single layer slide. The results showed that by direct injection into the anterior chamber, foreign plasmid DNA could be transferred into the endothelia and its expression was obtained. This may provide a foundation for further study on TGF-beta 1 participating in local induction of corneal immune tolerance.

Experimental study of plasmid TGF-beta 1 DNA gene transfer with lipofectamine into rabbit corneal epithelial cells in vitro

To investigate whether the TGF-beta 1 plasmid DNA carried by lipofectamine could be introduced into cultured rabbit corneal epithelial cells, specific expression of the plasmid pMAM TGF-beta 1 in the cultured corneal epithelial cells was studied. Two days after 12 h of transfection of pMAMT-GF-beta 1 mediated by lipofectamine into the cultured corneal epithelial cells, the TGF-beta 1 protein expression specific for pMAMTGF-beta 1 in the cells was detected by means of immunohistochemical staining and the positive rate was 23.37%. The results suggested that foreign plasmid DNA could be effectively delivered into cultured rabbit corneal epithelial cells by means of lipofectamine, and this will provide a promising method of studying TGF-beta 1 on the mechanism of physiology and pathology concerned with corneal epithelial cells.

Gene delivery and expression in human retinal pigment epithelial cells: effects of synthetic carriers, serum, extracellular matrix and viral promoters

Non-viral gene therapy is a potential treatment to many incurable retinal diseases. To fulfill this promise, plasmid DNA must be delivered to the retinal target cells. We evaluated the efficacy of synthetic DNA complexing compounds in transfecting primary human retinal pigment epithelial (RPE) cells in vitro. Fetal human RPE cells were cultured with or without extracellular matrix (ECM), produced using calf corneal endothelial cells. Plasmids encoding nuclear localizing beta galactosidase or luciferase (pRSVLuc, pCLuc4, pSV2Luc) were complexed in water at various +/- charge ratios using cationic lipids (Lipofectin, DOTAP, DOGS), polyethylene imines (25 and 750 kDa), and with degraded 6th generation starburst polyamidoamine dendrimers. Luciferase was quantified using a luminometric assay and beta galactosidase with X-gal staining. Toxicities of transfections were evaluated with the MTT-assay. Using beta galactosidase as the reporter gene naked DNA did not transfect RPE cells at measurable levels whereas 1-5% of the cells expressed histochemically detectable amounts of the gene after transfection with cationic lipid DNA complexes. In RPE cells, Rous sarcoma virus and cytomegalovirus (CMV) were more efficient promoters than SV40 in driving luciferase expression, and CMV was chosen for further experiments. At optimal complex charge ratios, expression levels of luciferase were > 10(9) light units/mg protein after transfection using dendrimers and PEI25, while transfection mediated with the other carriers resulted in luciferase expression levels of 10(7)-10(9) light units/mg protein or less. In general, dendrimers and large molecular weight PEI were less toxic than cationic lipids or PEI25 to RPE cells. Serum and ECM decreased gene expression to the RPE cells with all carriers. Despite low percentage of transfected cells the transgene expression per RPE cell is high, important feature in the retinal tissue with small dimensions, in particular in the case of secreted gene products. Degraded dendrimers and high molecular weight PEI exhibited the best combination of high activity and low toxicity in RPE cell transfection.