Lentivirus-Mediated Overexpression of miR-29a Promotes Axonal Regeneration and Functional Recovery in Experimental Spinal Cord Injury via PI3K/Akt/mTOR Pathway

MicroRNAs as a novel class of endogenous small non-coding RNAs, modulate negative gene expression at the post-transcriptional level. Our previous work has demonstrated that miR-29a reduces PTEN expression by directly targeting the 3′-UTRs (untranslated regions) of its mRNA, thus promoting neurite outgrowth. To further confirm the role of miR-29a in the recovery of SCI and its potential mechanisms, a recombinant lentiviral vector was used to promote miR-29a expression in the injured spinal cord. As compared with the LV-eGFP group and normal saline group, a significantly increased level of miR-29a expression and a markedly decreased level of PTEN expression were observed in the LV-miR-29a group. Overexpression of miR-29a increased the phosphorylation of two proteins (Akt and S6) of PI3K–AKT–mTOR signaling pathway and the expression of axonal regeneration associated key marker protein (neurofiament-200). Moreover, quantitative imaging analysis was performed to confirm that LV-miR-29a group expressed axonal regeneration at 4.0 ± 0.2-fold as much as the other two groups. Besides, miR-29a overexpression promoted hindlimb motor functional recovery. Collectively, these results suggested that miR-29a may be an important regulator for axon regeneration, and a potential therapeutic target for SCI recovery.