Progress of iPS cell-based transplantation therapy for retinal diseases.

The discovery of induced Pluripotent Stem) (iPS) cells has instigated innovation in various fields, including ophthalmology. Cell therapy has shown tremendous progress in translational research on retinal diseases, including the first-in-human transplantation of autologous iPS cell-derived retinal pigment epithelium (RPE) cells for patients with age-related macular degeneration (AMD). Cell therapy for retinitis pigmentosa (RP) has also been developed. Retinal organoid and photoreceptor cell transplantation has been shown to incorporate into the degenerated host retina, forming synapses with host neurons and resulting in functional recovery. Based on preclinical data, first-in-human transplantation of iPS cell-derived retinal sheets has been conducted. In this review, we summarize the current progress in iPS cell-based retinal cell transplantation research for retinal diseases, addressing some remaining challenges and future prospects.

Genetically engineered stem cell-derived retinal grafts for improved retinal reconstruction after transplantation.

ESC/iPSC-retinal sheet transplantation, which supplies photoreceptors as well as other retinal cells, has been shown to be able to restore visual function in mice with end-stage retinal degeneration. Here, by introducing a novel type of genetically engineered mouse ESC/iPSC-retinal sheet with reduced numbers of secondary retinal neurons but intact photoreceptor cell layer structure, we reinforced the evidence that ESC/iPSC-retinal sheet transplantation can establish synaptic connections with the host, restore light responsiveness, and reduce aberrant retinal ganglion cell spiking in mice. Furthermore, we show that genetically engineered grafts can substantially improve the outcome of the treatment by improving neural integration. We speculate that this leads to reduced spontaneous activity in the host which in turn contributes to a better visual recovery.

[Toward establishment of regenerative cell therapy for retinitis pigmentosa using iPS cell derived retinal sheet].

Retinitis pigmentosa (RP) is a group of hereditary diseases that involve loss of photoreceptors. There has been no established treatment for RP, and it is now the 2nd leading cause of blindness in Japan. Previous clinical researches using human fetal retina transplantation suggested some functional recovery in vision, but it did not become a standard therapy because of ethical concerns for using fetus tissues. Invention of induced pluripotent stem cells (iPSC) in 2006 and the establishment of retinal organoids induction protocol from ES/iPS cells have paved a way of cell therapy for RP without ethical concerns. Our team has shown that mouse iPSC derived retinas can survive and mature after subretinal transplantation to the end-stage retinal degeneration model mice. Further, human ESC derived retinas survived and matured in retinal degeneration monkey models. Recently, we have established a qualitative and quantitative evaluation tool for photoreceptor synapses, QUANTOS, and showed that photoreceptors in mouse iPSC derived retina can form photoreceptor synapses in a time dependent manner after transplantation. We are now moving toward 1st in human clinical trial using iPSC derived retina for RP.

Quantitative and Qualitative Evaluation of Photoreceptor Synapses in Developing, Degenerating and Regenerating Retinas.

Quantitative and qualitative evaluation of synapses is crucial to understand neural connectivity. This is particularly relevant now, in view of the recent advances in regenerative biology and medicine. There is an urgent need to evaluate synapses to access the extent and functionality of reconstructed neural network. Most of the currently used synapse evaluation methods provide only all-or-none assessments. However, very often synapses appear in a wide spectrum of transient states such as during synaptogenesis or neural degeneration. Robust evaluation of synapse quantity and quality is therefore highly sought after. In this paper we introduce QUANTOS, a new method that can evaluate the number, likelihood, and maturity of photoreceptor ribbon synapses based on graphical properties of immunohistochemistry images. QUANTOS is composed of ImageJ Fiji macros, and R scripts which are both open-source and free software. We used QUANTOS to evaluate synaptogenesis in developing and degenerating retinas, as well as de novo synaptogenesis of mouse iPSC-retinas after transplantation to a retinal degeneration mouse model. Our analysis shows that while mouse iPSC-retinas are largely incapable of forming synapses in vitro, they can form extensive synapses following transplantation. The de novo synapses detected after transplantation seem to be in an intermediate state between mature and immature compared to wildtype retina. Furthermore, using QUANTOS we tested whether environmental light can affect photoreceptor synaptogenesis. We found that the onset of synaptogenesis was earlier under cyclic light (LD) condition when compared to constant dark (DD), resulting in more synapses at earlier developmental stages. The effect of light was also supported by micro electroretinography showing larger responses under LD condition. The number of synapses was also increased after transplantation of mouse iPSC-retinas to rd1 mice under LD condition. Our new probabilistic assessment of synapses may prove to be a valuable tool to gain critical insights into neural-network reconstruction and help develop treatments for neurodegenerative disorders.

Development of a molecular diagnostic test for Retinitis Pigmentosa in the Japanese population.

PURPOSE: Retinitis Pigmentosa (RP) is the most common form of inherited retinal dystrophy caused by different genetic variants. More than 60 causative genes have been identified to date. The establishment of cost-effective molecular diagnostic tests with high sensitivity and specificity can be beneficial for patients and clinicians. Here, we developed a clinical diagnostic test for RP in the Japanese population. STUDY DESIGN: Evaluation of diagnostic technology, Prospective, Clinical and experimental study. METHODS: A panel of 39 genes reported to cause RP in Japanese patients was established. Next generation sequence (NGS) technology was applied for the analyses of 94 probands with RP and RP-related diseases. After interpretation of detected genetic variants, molecular diagnosis based on a study of the genetic variants and a clinical phenotype was made by a multidisciplinary team including clinicians, researchers and genetic counselors. RESULTS: NGS analyses found 14,343 variants from 94 probands. Among them, 189 variants in 83 probands (88.3% of all cases) were selected as pathogenic variants and 64 probands (68.1%) have variants which can cause diseases. After the deliberation of these 64 cases, molecular diagnosis was made in 43 probands (45.7%). The final molecular diagnostic rate with the current system combining supplemental Sanger sequencing was 47.9% (45 of 94 cases). CONCLUSIONS: The RP panel provides the significant advantage of detecting genetic variants with a high molecular diagnostic rate. This type of race-specific high-throughput genotyping allows us to conduct a cost-effective and clinically useful genetic diagnostic test.

Retinal Morphology and Sensitivity Are Primarily Impaired in Eyes with Neuromyelitis Optica Spectrum Disorder (NMOSD).

BACKGROUND: Previous studies of neuromyelitis optica spectrum disorder (NMOSD) using spectral domain optical coherence tomography (SD-OCT) showed that the outer nuclear layer (ONL) in eyes without a history of optic neuritis (ON) was thinner than that of healthy controls. It remains unclear whether the ONL thinning is caused by a direct attack on the retina by an autoantibody or a retrograde degeneration. OBJECTIVE: To determine the mechanisms involved in the retinal damage in eyes with NMOSD without ON. METHODS: SD-OCT was used to determine the thicknesses of the different retinal layers of 21 eyes of 12 NMOSD patients without prior ON and 19 eyes of 10 healthy controls. Eyes with peripapillary retinal nerve fiber layer (RNFL) thinning were excluded to eliminate the confounding effects of retrograde degeneration. Microperimetry was used to determine the central retinal sensitivity. The data of the two groups were compared using generalized estimated equation models to account for inter-eye dependencies. RESULTS: The ganglion cell plus inner plexiform layer and the inner nuclear layer plus outer plexiform layer thicknesses of the NMOSD eyes were not significantly different from that of the control eyes (P = 0.28, P = 0.78). However, the ONL and average macular thickness (AMT) in the NMOSD eyes were significantly thinner than that of the control eyes (P = 0.022, P = 0.036). The retinal sensitivity in the central 10°, 10° to 2°, and 2° sectors were significantly lower in the NMOSD eyes than in the control eyes (P = 0.013, P = 0.022, P = 0.002). CONCLUSIONS: The ONL thinning, AMT thinning, and reduced retinal sensitivity in eyes with NMOSD without significant peripapillary RNFL thinning are most likely due to direct retinal pathology.

Recovery from optic neuritis attack in neuromyelitis optica spectrum disorder and multiple sclerosis.

BACKGROUND: Both neuromyelitis optica spectrum disorder (NMOsd) and multiple sclerosis (MS) patients experience optic neuritis (ON) attacks characterized by rapidly reduced best-correct visual acuity (BCVA) and slow recovery. Prognosis and effects of recurrence on recovery may differ between disorders but remain unclear. OBJECTIVE: To compare ON severity, time and degree of recovery and effects of previous ON between NMOsd and MS patients. METHODS: Retrospective chart review was performed. BCVA measurements acquired before ON, at nadir and during recovery were retrospectively reviewed. Records were obtained on 69 ON attacks in 36 NMOsd patients and 43 attacks in 28 MS patients, including first episodes and recurrences. RESULTS: NMOsd patients exhibited significantly lower BCVA values at all time points after attack (P<0.05), reached nadir earlier (P=0.014) and regained a smaller fraction of baseline BCVA than MS patients (P<0.001). In NMOsd, relapsed ON resulted in worse recovery and tended to reach nadir earlier than first-episode ON (P=0.030 and 0.059, respectively). In MS, relapsed ON also reached nadir earlier (P=0.042); however, there was no difference in recovery. CONCLUSIONS: Recovery from ON was poorer in NMOsd than in MS and was negatively affected by previous ON attacks.

Spontaneous Recovery of Neuromyelitis Optica Spectrum Disorder during Pregnancy.

Neuromyelitis optica spectrum disorder (NMO-SD) is an autoimmune inflammatory disorder associated with the anti-aquaporin-4 (AQP4) antibody. Over 90% of NMO-SD patients have poor prognosis, and pregnancy is a disease-worsening factor. The authors report the findings in a case of NMO-SD that recovered spontaneously during pregnancy. A 28-years-old woman developed optic neuritis (ON) of the right eye in the 14th week of pregnancy. Her best-correlated visual acuity (BCVA) was 0.02 OD, the critical flicker frequency (CFF) was not measurable, and the mean deviation (MD) of the Humphrey perimetry 30-2 was -42 dB. Magnetic resonance imaging (MRI; T2 short-tau inversion recovery [STIR]) showed high-intensity right optic nerve. The patient was diagnosed with NMO-SD by the detection of seropositive anti-AQP4 antibody in her serum. Corticosteroid pulse therapy was considered, but the patient declined any treatment. Two weeks later, her BCVA improved to 1.2 (OD). Nine weeks later, the MD of Humphrey perimetry 30-2 improved to -1.2 dB and the CFF was 39.8 Hz. There have been no signs of recurrence for 6 months. Spontaneously recovered cases of NMO-SD during pregnancy are very rare. Although the factors leading to good outcomes have not been identified, this case suggests that the immunological condition at the early stage of the pregnancy may have different from that at later stages. Further studies are needed to identify the relationship between pregnancy and NMO-SD.