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.

PEITC promotes neurite growth in primary sensory neurons via the miR-17-5p/STAT3/GAP-43 axis.

The present study explored a key miRNA that plays a vital role in sciatic nerve conditioning injury promoting repair of injured dorsal column, and validated its function. Microarray analysis revealed miR-17-5p expression decreased sharply at 3, 7 and 14 days in the sciatic nerve conditioning injury group compared with the simple dorsal column lesion group. After miR-17-5p inhibition in DRG neurons, GAP-43 expression was upregulated and neurite growth was increased. STAT3 together with p-STAT3 showed opposite trends with miR-17-5p. MiR-17-5p inhibition extended neurite and upregulated STAT3, p-STAT3 and GAP-43. To further determine a substitution therapy for sciatic nerve conditioning injury, beta-phenethyl isothiocyanate (PEITC), which downregulates miR-17-5p, was assessed. The results showed that treatment with 10 µM PEITC resulted in longest neurite length. Further experiments demonstrated PEITC induced neurite growth by inhibiting miR-17-5p and further upregulating STAT3, p-STAT3 and GAP-43. The somatosensory evoked potential test confirmed similar treatment effects for PEITC, Ad-miRNA-17-5p inhibitor, and sciatic nerve conditioning injury on the dorsal column lesion. In conclusion, the miR-17-5p/STAT3/GAP-43 axis is an indispensable component of sciatic nerve conditioning injury promoting repair of injured dorsal column. PEITC could promote repair of injured dorsal column via the miR-17-5p/STAT3/GAP-43 axis, and could mimic the treatment effect of sciatic nerve conditioning injury.

MiR-20a Plays a Key Regulatory Role in the Repair of Spinal Cord Dorsal Column Lesion via PDZ-RhoGEF/RhoA/GAP43 Axis in Rat.

Spinal cord injury (SCI) causes sensory dysfunctions such as paresthesia, dysesthesia, and chronic neuropathic pain. MiR-20a facilitates the axonal outgrowth of the cortical neurons. However, the role of miR-20a in the axonal outgrowth of primary sensory neurons and spinal cord dorsal column lesion (SDCL) is yet unknown. Therefore, the role of miR-20a post-SDCL was investigated in rat. The NF-200 immunofluorescence staining was applied to observe whether axonal outgrowth of dorsal root ganglion (DRG) neurons could be altered by miR-20a or PDZ-RhoGEF modulation in vitro. The expression of miR-20a was quantized with RT-PCR. Western blotting analyzed the expression of PDZ-RhoGEF/RhoA/GAP43 axis after miR-20a or PDZ-RhoGEF was modulated. The spinal cord sensory conduction function was assessed by somatosensory-evoked potentials and tape removal test. The results demonstrated that the expression of miR-20a decreased in a time-dependent manner post-SDCL. The regulation of miR-20a modulated the axonal growth and the expression of PDZ-RhoGEF/RhoA/GAP43 axis in vitro. The in vivo regulation of miR-20a altered the expression of miR-20a-PDZ-RhoGEF/RhoA/GAP43 axis and promoted the recovery of ascending sensory function post-SDCL. The results indicated that miR-20a/PDZ-RhoGEF/RhoA/GAP43 axis is associated with the pathophysiological process of SDCL. Thus, targeting the miR-20a/PDZ-RhoGEF /RhoA/GAP43 axis served as a novel strategy in promoting the sensory function recovery post-SCI.

miR-142-3p is a Potential Therapeutic Target for Sensory Function Recovery of Spinal Cord Injury.

Spinal cord injury (SCI), which is a leading cause of disability in modern society, commonly results from trauma. It has been reported that application of sciatic nerve conditioning injury plays a positive role in repairing the injury of the ascending spinal sensory pathway in laboratory animals. Because of the complexity of SCI and related ethics challenges, sciatic nerve conditioning injury cannot be applied in clinical therapy. Accordingly, it is extremely important to study its mechanism and develop replacement therapy. Based on empirical study and clinical trials, this article suggests that miR-142-3p is the key therapeutic target for repairing sensory function, based on the following evidence. Firstly, studies have reported that endogenous cAMP is the upstream regulator of 3 signal pathways that are partially involved in the mechanisms of sciatic nerve conditioning injury, promoting neurite growth. The regulated miR-142-3p can induce cAMP elevation via adenylyl cyclase 9 (AC9), which is abundant in dorsal root ganglia (DRG). Secondly, compared with gene expression regulation in the injured spinal cord, inhibition of microRNA (miRNA) in DRG is less likely to cause trauma and infection. Thirdly, evidence of miRNAs as biomarkers and therapeutic targets in many diseases has been reported. In this article we suggest, for the first time, imitating sciatic nerve conditioning injury, thereby enhancing central regeneration of primary sensory neurons via interfering with the congenerous upstream regulator AC9 of the 3 above-mentioned signal pathways. We hope to provide a new clinical treatment strategy for the recovery of sensory function in SCI patients.