The regeneration of axons in the mammalian central nervous system is severely restricted, owing to an age-dependant reduction in intrinsic regenerative capacity, a loss of neurotrophic support, and an inhibitory growth environment. In the dorsal root ganglion (DRG) conditioning lesion model, peripheral axotomy results in transcriptional reprogramming of neurons into a regenerative state, but this reprogramming involves extensive multi-gene changes that are difficult to recapitulate in non-regenerating CNS neurons. MicroRNAs are small non-coding RNAs that individually regulate groups of related genes and are attractive as tool compounds for modulating complex transcriptional changes in cells. Computational modelling was applied to single-cell RNA sequencing datasets from mice subjected to the DRG conditioning lesion paradigm, identifying individual miRNAs that target multiple regeneration associated genes (RAGs). Inhibiting miR-340-5p derepresses RAGs and promotes neurite growth in vitro. A circular RNA sponge designed to sequester miR-340-5p (Circ-340-5p) disinhibits RAGs in the retinal ganglion cells of male and female C57BL/6 mice, whilst simultaneously activating pro-regenerative PI3K signalling and pro-survival BDNF/TRKB signalling. Circ-340-5p enhanced post-axotomy neuronal survival acutely following ONC, but this effect was not sustained at six weeks. Circ-340-5p promoted axon regeneration and the extent of regeneration improved over time. Our findings establish an approach for recapitulating multi-gene transcriptional changes in neurons to promote axon regeneration and neuronal survival following axotomy, and outline a platform for the development of long-acting miRNA-targeting therapeutics.
Keywords: Axon regeneration; Circular RNA; Neuronal survival; Neurotrauma; RNA therapeutic; microRNA.
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