Yuki Yoshioka

Intrinsic activation of PI3K/Akt signaling pathway and its neuroprotective effect against retinal injury.

Purpose. The aim of this study was to determine whether the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway can function as a neuroprotective pathway following induced retinal injury. Methods. The activation of Akt was assessed by immunoblot analysis, and the role of PI3K/Akt pathway was evaluated by TUNEL staining and counting the number of retrogradelylabeled retinal ganglion cells (RGCs) in the whole retina at 168 h after injury with or without PI3K specific inhibitor, LY294002. Results. Akt was induced within one hr and reached a maximum 6hrs after optic nerve clamping. The activation was observed in the RGC layer including RGCs, the inner plexiform layer, inner nuclear layer, and in the photoreceptor outer segments. The number of surviving RGCs was decreased significantly 168 hrs after injury. LY294002 partially inhibited the activation of Akt, and significantly decreased the number of surviving RGCs as compared with that of injury alone. Conclusions. These results indicate that the PI3K/Akt signaling pathway is activated intrinsically and has a neuroprotective effect on injured RGCs.

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.

Adult-onset Foveomacular Vitelliform Dystrophy with Retinal Folds

BACKGROUND Adult-onset foveomacular vitelliform dystrophy is characterized by a solitary, oval, slightly elevated, yellowish subretinal lesion of the fovea. We examined a patient with adult-onset foveomacular vitelliform dystrophy with stellate retinal folds by optical coherence tomography and scanning laser ophthalomoscopy. CASE A 58-year-old Japanese woman with a complaint of decreased vision in her right eye was diagnosed as having adult-onset foveomacular vitelliform dystrophy. OBSERVATIONS Ophthalmoscopic examination revealed a yellowish lesion of one-third disc diameter in size at the fovea in the right eye. Fluorescein angiography demonstrated an irregular block of choroidal fluorescence corresponding to the yellowish lesion, which was surrounded by stellate retinal folds. Optical coherence tomography images showed a steep elevation of the retinal pigment epithelium (RPE) as a focally protruded reflective band over an optically clear space. Scanning laser ophthalmoscopy provided morphologic enhancement in the specifically affected layers of the macula. Using an argon green laser, band-shaped bright reflexes were seen in the right fovea. The helium-neon laser revealed a bright patch corresponding to the yellowish lesion over the fovea, which was surrounded by stellate retinal folds. The diode laser revealed a bright patch corresponding to the yellowish lesion. CONCLUSION The stellate retinal folds of this patient were considered to be caused by the steep elevation of the RPE with an extracellular accumulation of the vitelliform deposits.

Clinical Features of Bilateral Acute Idiopathic Maculopathy

PURPOSE To describe the clinical course of bilateral acute idiopathic maculopathy (BAIM), and to analyze its pathophysiology. CASE A 33-year-old Japanese woman presented with a sudden, severe, bilateral visual disturbance following a flu-like illness. She was examined by fluorescein angiography (FA), indocyanine green angiography (IA), scanning laser ophthalmoscopy (SLO), optical coherence tomography (OCT), and multifocal electroretinography (mfERG). OBSERVATIONS A diagnosis of BAIM was made in this patient based on typical ophthalmoscopic features, which included a pathognomonic yellowish-white foveal lesion. FA demonstrated a breakdown of the outer blood-retinal barrier, with the size and location corresponding to the white lesion, and IA disclosed a choroidal circulatory disturbance. SLO demonstrated that the deep retinal and choroidal layers were disorganized, and OCT showed retinal edema. Electrophysiological dysfunction was detected by mfERGs. After steroid therapy, the patients visual acuity recovered to normal. The pooling of fluorescein dye and the OCT-determined retinal edema were resolved. However, the physiological dysfunction detected by mfERGs remained. CONCLUSIONS We conclude that the major abnormality in BAIM is an alteration of the retinal pigment epithelium causing severe edema.

Transgenic rd mice harboring axokine gene by Rpe65 gene promoter does not rescue photoreceptor degeneration.

Neurotrophic factors have reported to rescue photoreceptor degeneration in dystrophic rats (Faktorovich et al., 1990), and variable strains of mice showing hereditary photoreceptor degeneration (LaVail et al., 1998). Axokine is a modified form of human CNTF to enhance its specific activity (Panayotatos et al., 1993) and its signaling pathway is reported in retinal neurons and glia via CNTF receptor (CNTFRa) (Peterson et al., 2000). In this study, we introduced Axokine gene in rd/rd mice, a mice reported to have mutation in s subunit of phosphodiesterase (PDE) gene (Pittler and Baehr, 1991) and examined its effect for retinal degeneration. The Axokine gene was introduced into retinal pigment epithelium (RPE) by Rpr65 promoter, which has acitivity of RPE specific expression