Synthetic circular RNA helps injured optic nerves regrow and protects retinal neurons in mice
A circular RNA that soaks up miR-340-5p switched on regeneration genes in mouse retinal neurons, boosting optic nerve regrowth after injury.
Summary
Adult mammalian central nervous system neurons regenerate poorly, a problem that worsens with age. Researchers used computational modelling of single-cell RNA data from a peripheral nerve conditioning-lesion model to find microRNAs that control many regeneration-associated genes at once. They identified miR-340-5p, and inhibiting it promoted neurite growth in cultured neurons. They then built a synthetic circular RNA sponge (Circ-340-5p) to sequester this microRNA. In mice with optic nerve crush, it activated regeneration genes in retinal ganglion cells, along with PI3K and BDNF/TRKB signalling. Neuron survival improved shortly after injury but not at six weeks, while axon regeneration increased and kept improving over time. The work suggests a route to long-acting, microRNA-targeting therapies for optic nerve and other CNS injuries, though it remains preclinical.
Detailed Summary
Axons in the adult mammalian central nervous system barely regenerate after injury. Contributing factors include an age-related decline in neurons' intrinsic growth capacity, reduced neurotrophic support, and an inhibitory tissue environment. This limits recovery from optic nerve damage and related conditions, such as glaucoma and trauma.
Peripheral neurons behave differently. After a conditioning lesion in the dorsal root ganglion model, they reprogram into a regenerative state through many simultaneous gene changes, which are hard to reproduce in CNS neurons. The researchers reasoned that microRNAs, which each regulate groups of related genes, could mimic this multi-gene shift. They applied computational modelling to single-cell RNA sequencing data from conditioning-lesion mice and found miRNAs targeting multiple regeneration-associated genes. One of them, miR-340-5p, stood out.
Inhibiting miR-340-5p derepressed regeneration-associated genes and promoted neurite growth in vitro. The team then engineered a circular RNA sponge, Circ-340-5p, to sequester it. In retinal ganglion cells of male and female C57BL/6 mice, the sponge disinhibited these genes and activated pro-regenerative PI3K signalling and pro-survival BDNF/TRKB signalling. After optic nerve crush, it improved neuronal survival acutely, but that benefit was gone at six weeks. Axon regeneration, however, was enhanced and increased over time.
The findings support using engineered circular RNAs as a durable platform for reprogramming neurons toward regeneration, and for developing long-acting miRNA-targeting therapeutics.
Caveats: this is a mouse injury study based on the abstract alone. The lack of sustained survival benefit is a notable limit, and functional visual recovery, safety, delivery, and human relevance are not described here.
Key Findings
- Computational analysis of single-cell data identified miR-340-5p as a regulator of multiple regeneration-associated genes.
- Inhibiting miR-340-5p derepressed regeneration genes and promoted neurite outgrowth in cultured neurons.
- Circ-340-5p activated PI3K and BDNF/TRKB signalling in mouse retinal ganglion cells.
- Neuronal survival improved acutely after optic nerve crush but was not sustained at six weeks.
- Axon regeneration was enhanced and continued to improve over time.
Methodology
Single-cell RNA sequencing data from the mouse DRG conditioning lesion model were analysed computationally to find miRNAs targeting regeneration-associated genes. Candidate miR-340-5p was tested in vitro for neurite growth, then targeted in vivo with a circular RNA sponge in male and female C57BL/6 mice after optic nerve crush, assessing signalling, survival, and axon regeneration.
Study Limitations
Only the abstract was available, so quantitative effect sizes, sample sizes, and delivery details are unknown. Survival benefit was not sustained at six weeks, and functional visual outcomes, safety, and applicability to humans or chronic disease such as glaucoma were not reported.
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