Nobuhiko Ohno | Search PubMed

PubMed2026

Long-term functional synaptic integration of genome-edited retinal organoids in a primate model of macular degeneration.

Retinal organoids represent a promising regenerative strategy for restoring vision in retinal degenerative diseases, but the capacity of host cone bipolar cells in the primate macula to rewire with transplanted photoreceptors has not been established. In this study, we transplanted genome-edited ISL1-/- human retinal organoids lacking ON-bipolar cells into an acute laser-induced macular photoreceptor ablation non-human primate model. Using immunohistochemistry, ultrastructural imaging, and focal macular electroretinography, we demonstrate that host rod and cone bipolar cells actively extend dendrites toward grafted photoreceptors and form synaptic contacts, with evidence of functional signal transmission in a subset of transplanted eyes. Longitudinal, per-eye analyses revealed that host ON-bipolar responses improved in two of four eyes with ISL1-/- graft by up to 21.6% and remained stable for up to 2 years post transplantation. Moreover, OFF-pathway connectivity showed potential progressive maturation, with delayed increase in d-wave after 13 months in one of those eyes. These findings provide the first demonstration of long-term anatomical host-graft synaptic integration in the primate macula, establishing that central cone bipolar circuits retain the capacity for durable rewiring with human stem-cell-derived grafts. Our results highlight ISL1-/- retinal organoids as a promising approach for central vision restoration in macular degeneration.

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PubMed2026

Synaptic Mitochondrial Oxidative Stress Contributes to Individual Variability in Age-Related Cognitive Inflexibility in Mice.

Aging is associated with impairments in cognitive flexibility, a key executive function supported by the medial prefrontal cortex (mPFC), yet the biological mechanisms underlying individual variability in age-related decline remain poorly understood. Here we investigated behavioral, ultrastructural, and proteomic correlates of cognitive inflexibility in mice across aging. Using a touchscreen-based attentional set-shifting task, we observed substantial individual variability in cognitive inflexibility among aged C57BL/6J mice. Volume electron microscopy of the mPFC revealed age-related reductions in synaptic density, but these structural changes did not correlate with cognitive performance. Instead, the proportion of synapses containing presynaptic mitochondria was inversely associated with cognitive flexibility in aged mice. To identify molecular correlates, we performed proteomic profiling of mPFC whole tissue and synaptosome fractions. Proteins associated with individual variability in cognitive inflexibility were largely distinct from those associated with chronological aging. Notably, synaptosomal proteins negatively correlated with cognitive performance were strongly enriched for mitochondrial pathways, including oxidative phosphorylation, mitochondrial translation, and the tricarboxylic acid cycle. Consistent with these findings, the mitochondria-targeted antioxidant MitoQ improved attentional set-shifting performance in aged mice without affecting initial learning. Proteomic analyses revealed that MitoQ reduced the abundance of synaptosomal mitochondrial proteins, particularly those involved in mitochondrial apoptotic signaling. Together, these results suggest that synaptic mitochondrial oxidative stress in the mPFC contributes to individual vulnerability to cognitive inflexibility. Targeting synaptic mitochondrial oxidative stress may therefore represent a promising strategy to preserve executive function during aging.

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