Intrascleral transplantation of a collagen sheet with cultured brain-derived neurotrophic factor expressing cells partially rescues the retina from damage due to acute high intraocular pressure.

We constructed brain-derived neurotrophic factor (BDNF) expressing rat retinal pigment epithelial (RPE) cells by stable transfection of BDNF cDNA, and the RPE cells were cultured on a cross-linked collagen sheet (Coll-RPE-BDNF). BDNF expression of the Coll-RPE-BDNF was confirmed by western blot, and the Coll-RPE-BDNF was transplanted into the rabbit sclera. In vivo BDNF expression was confirmed by His expression that was linked to the expressing BDNF. The effect of the released BDNF was examined in a rabbit acute high intraocular pressure system by electroretinogram and histological examination. Statistically significant preservation of ERG b wave amplitude was observed in the rabbits treated by Coll-RPE-BDNF when compared to that of no treatment. Statistically significant preservation of the thickness of the inner nuclear layer at the transplanted area was observed in the rabbits treated by Coll-RPE-BDNF compared to that of no treatment. Intra-scleral Coll-RPE-BDNF transplantation may partially rescue retinal cells from acute high intraocular pressure.

Evaluation of retinal degeneration in P27KIP1 null mouse.

PURPOSE: p27kip1 is well-known as a cell cycle inhibitor and also plays an important role for cell differentiation. We hypothesized that if we caused retinal degeneration in a p27(-/-) mouse, then the appropriate method of restoration may be different from that of wild mice and therefore suggest a therapeutic methodology for retinal regeneration. METHODS: Histological and electrophysiological (ERG) examination was performed on p27(-/-) mice retina. We injected N-methy-N-nitrosourea (MNU) to induce retinal degeneration. BrdU was used to identify the dividing cells in the retina. RESULTS: Thicker retina were observed in the p27(-/-) mice when compared to those of the p27(-/+) mice or wild type mice. Almost all retinal layers were thick and optic nerves were also enlarged. A statistically significant decrease of a and b waves amplitudes of ERG was observed in p27(-/-) mice when compared to those of the other mice. BrdU and nestin positive cells were present at the outer nuclear layer with no difference between p27(-/-) and wild type mice after MNU injection. CONCLUSION: p27(-/-) mice showed thicker retina and less retinal function than those of other mice. The MNU-induced retinal degeneration in p27(-/-) mice closely resembled the reaction of the other mice with no retinal regeneration observed in our experimental condition.

TrkB-T1 receptors on Muller cells play critical role in brain-derived neurotrophic factor-mediated photoreceptor protection against phototoxicity.

PURPOSE: To determine how brain-derived neurotrophic factor (BDNF) protects photoreceptors against phototoxicity. METHODS: Iris pigment epithelial cells (IPE) that were transduced with different concentrations of adeno-associated virus (AAV) mediated BDNF (AAV-BDNF-IPE) were transplanted into the subretinal space of rats. We also injected small interfering RNAs (siRNAs) for TrkB, a BDNF receptor. The rats were exposed to continuous light to induce phototoxicity. We examined the expression of TrkB in the retina by Western blot and immunohistochemistry. RESULTS: Significant photoreceptor protection was detected when more than 1 x 10(7) capsids/ml AAV-BDNF was transplanted. An intravitreal injection of siRNAs showed that the photoreceptor protection by AAV-BDNF-IPE was reduced by injecting the siRNA of TrkB-T1, one of the TrkB isoforms. TrkB-T1 was slightly upregulated by Western blot, and one of the cells that upregulated TrkB-T1 was Muller cells by immunohistochemistry. CONCLUSION: We conclude that Muller cells are one of the cells responsible for the expression of TrkBs, and TrkB-T1 may play a role in the protection of photoreceptors against phototoxicity.

Iris pigment epithelial cell transplantation for degenerative retinal diseases.

The transplantation of different types of cells into the eye to treat retinal diseases has advanced in the past 20 years. One of the types of cells used for transplantation is the iris pigment epithelial (IPE) cell, because autologous IPE cells are easily obtained and their properties are similar to those of retinal pigment epithelial (RPE) cells and retinal cells. IPE cells are transplanted as; freshly isolated or cultured cells to replace defective or diseased RPE cells, genetically modified IPE cells for delivering target molecules to the retina or RPE, and retinal progenitor cells. IPE cells have also been transplanted for non-retinal disorders. The survival of the transplanted cells in the host is an important factor for the success of transplantation. Autologous IPE cells have been found in the transplanted subretinal space and were able to phagocytose rod outer segments even 6 months after transplantation. Allogeneic and xenogenic cells will not remain in the region longer than autologous cells. Allogenic cells transplanted into the subretinal space are rejected in humans. Thus, we have transplanted cultured autologous IPE cells in 56 patients with age-related macular degeneration. The long-term results (more than 2 years with a maximum of 8 years) showed that the visual acuity (VA) was significantly improved over the pre-transplantation VA, although a slight decrease of VA was observed 2 weeks after the transplantation. One patient showed a vasculitis-like lesion. IPE cells that were transduced with neurotrophic factors by plasmid or viral vectors have also been transplanted in animals. We have transduced several neurotrophic factor genes into IPE cells with a plasmid vector, adeno-associated virus, or adenovirus. Transplantation of these transduced IPE cells into the subretinal space rescued photoreceptor cells from several types of photoreceptor toxicities. In addition, transduction of a gene into the IPE cells suppressed the systemic dissemination of the viral genome. The neuroprotective effects of the IPE cells were different for the different types of neurotrophic factor, and some of the neurotrophic factors may enhance systemic immune reaction after transplantation. IPE cells have also been used as retinal progenital cells because they originate from the same cell lines that give rise to the neural retina and RPE cells. The transduction of the photoreceptor-related homeobox gene was reported to induce photoreceptor phenotypes in IPE cells. Furthermore, transplantations of IPE cells have been performed to treat central nervous system disorders. In this review, we summarize recent progress on IPE transplantation.