The inhibition of miR-17-5p promotes cortical neuron neurite growth via STAT3/GAP-43 pathway.

Spinal cord injury (SCI) is a devastating disease associated with locomotor function impair. The limited regenerative capability of the neural axon is one of the major factors that hinders the recovery of SCI. To enhance the regenerative ability of neuron is a promising strategy that repairs SCI. We previously proved miR-17-5p could target Signal Transducer and Activator of Transcription 3 (STAT3) in primary sensory neuron. We speculated that miR-17-5p was the miRNA that targets STAT3. The Dual-luciferase reporter assay indicated miR-17-5p could bind the 3'UTR of STAT3 mRNA. The RT-qPCR and Western blot assay showed miR-17-5p could not degenerate the mRNA of STAT3, but inhibit the expression of Signal Transducer and Activator of Transcription 3 (STAT3) via translation inhibition. MiR-17-5p inhibitor promoted the expression of STAT3, phosphorylated-STAT3 (p-STAT3) and Growth Associate Protein-43 (GAP-43), and this promotion was inhibited by STAT3 siRNA. MiR-17-5p mimics and inhibitor inhibited and promoted the neurite growth, respectively. MiR-17-5p inhibitor promoted the axon growth and AG490, the STAT3 phosphorylation inhibitor, inhibited this promotion. MiR-17-5p mimics inhibited the expression of STAT3, p-STAT3 and GAP-43, while the inhibitor promoted their expression. AG490 did not alter the expression of STAT3, while downregulated the expression both p-STAT3 and GAP-43 in miR-17-5p inhibitor&AG490 group. Taken together, these data indicated miR-17-5p could regulated cortical neuron axon growth via STAT3/GAP-43 pathway by targeting STAT3 mRNA 3'UTR. Therefore, miR-17-5p/STAT3/GAP-43 pathway plays a key role in regulating cortical neuron axon growth and could be a novel target to treat SCI.