The mutations in the genes encoding the subunits of complex I of the mitochondrial electron transport chain are the most common cause of Leber’s hereditary optic neuropathy (LHON), a maternal hereditary disease characterized by retinal ganglion cell (RGC) degeneration. The characteristics of incomplete penetrance indicate that nuclear genetic and environmental factors also determine phenotypic expression of LHON. Therefore, further understanding of the role of mutant mitochondrial nicotinamide adenine dinucleotide dehydrogenase subunit proteins and nuclear genetic factors/environmental effects in the etiology of LHON is needed. In this study, we generated human-induced pluripotent stem cells (hiPSCs) from healthy control, unaffected LHON mutation carrier, and affected LHON patient. hiPSC-derived RGCs were used to study the differences between affected and unaffected carriers of mitochondrial DNA point mutation m.11778G > A in the MT-ND4 gene. We found that both mutated cell lines were characterized by increase in reactive oxygen species production, however, only affected cell line had increased levels of apoptotic cells. We found a significant increase in retrograde mitochondria and a decrease in stationary mitochondria in the affected RGC axons. In addition, the messenger RNA and protein levels of KIF5A in the LHON-affected RGCs were significantly reduced. Antioxidant N-acetyl-L-cysteine could restore the expression of KIF5A and the normal pattern of mitochondrial movement in the affected RGCs. To conclude, we found essential differences in the mutually dependent processes of oxidative stress, mitochondrial transport and apoptosis between two LHON-specific mutation carrier RGC cell lines, asymptomatic carrier and disease-affected, and identified KIF5A as a central modulator of these differences.
Inner nuclear layer(INL) microcysts at central macula are a common finding in patients with epiretinal membrane (ERM) after vitrectomy and membrane peeling. Using en face mode of optical coherence tomography (OCT) angiography, patients with ERM after surgery were retrospectively reviewed to understand the configuration and distribution of microcysts as well as their impact on visual acuity. Forty-six eligible patients were enrolled and their baseline best-corrected visual acuities improved from 20/67 to 20/29 (P < 0.01) after surgery. Twenty-eight (60.9%) patients had microcysts that appeared at a median of 5 months after the surgery and persisted for mean 16 months follow-up. The microcyst appeared as spheroidal shape with length ranged from 20 to 80 μm and widths of 80 μm in average. They tend to group in cluster with a density of 245 microcysts per mm 2 . The frequency of microcyst distribution was 86%, 54%, 32%, 25% and 18% at the nasal, superior, inferior, temporal quadrants and central 1 mm, respectively. Linear regression analysis showed that INL microcysts at central and temporal quadrants were associated with poorer visual acuity (P = 0.02 and P = 0.01, respectively). The presence of INL microcysts in center subfield and involved wider area is a poor prognostic factor for visual outcomes.
Angiotensin-converting enzyme 2 (ACE2) was identified as the main host cell receptor for the entry of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its subsequent infection. In some coronavirus disease 2019 (COVID-19) patients, it has been reported that the nervous tissues and the eyes were also affected. However, evidence supporting that the retina is a target tissue for SARS-CoV-2 infection is still lacking. This present study aimed to investigate whether ACE2 expression plays a role in human retinal neurons during SARS-CoV-2 infection. Human induced pluripotent stem cell (hiPSC)-derived retinal organoids and monolayer cultures derived from dissociated retinal organoids were generated. To validate the potential entry of SARS-CoV-2 infection in the retina, we showed that hiPSC-derived retinal organoids and monolayer cultures endogenously express ACE2 and transmembrane serine protease 2 (TMPRSS2) on the mRNA level. Immunofluorescence staining confirmed the protein expression of ACE2 and TMPRSS2 in retinal organoids and monolayer cultures. Furthermore, using the SARS-CoV-2 pseudovirus spike protein with GFP expression system, we found that retinal organoids and monolayer cultures can potentially be infected by the SARS-CoV-2 pseudovirus. Collectively, our findings highlighted the potential of iPSC-derived retinal organoids as the models for ACE2 receptor-based SARS-CoV-2 infection.
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