MiR-325-3p promotes locomotor function recovery in rats with spinal cord injury via inhibiting the expression of neutrophil elastase.

Objective This study aims to investigate the potential function of miR-325-3p in vascular integrity and inflammatory response following spinal cord injury (SCI). Materials and methods The protein levels of ANG-1, ANG-2, and caspase-3 in HUVECs incubated with 0, 100, 200, 400, and 800 ng/ml NE for 24 h were determined. The regulatory effect of overexpressed miR-325-3p on the protein levels of ANG-1 and ANG-2 was determined by Western blot. The SCI model in SD rats was established by spinal injury at T10. Subsequently, the relative levels of miR-325-3p, ANG-1, and ANG-2 were determined in SCI rats and controls. Furthermore, SCI rats were administrated with miR-325-3p mimics or negative control and the relative levels of miR-325-3p, ANG-1, and ANG-2 were examined as well. At day 14, the protein levels of iNOS and GFAP in SCI rats and those overexpressing miR-325-3p were detected. BBB (Basso, Beattie, and Bresnahan) locomotor rating scale was applied for evaluating the locomotor function recovery at day 1, 3, 7, 14, 21, and 28 following SCI. Results NE treatment in HUVECs downregulated ANG-1 and upregulated ANG-2 and caspase-3 in a dose-dependent manner. The overexpression of miR-325-3p upregulated NE-induced decreased the level of ANG-1 and downregulated NE-induced increased level of ANG-2. After the establishment of the SCI model in rats, the miR-325-3p level gradually decreased in SCI rats relative to controls in a time-dependent manner. ANG-1 level in SCI rats decreased to the lowest on the first day following SCI, and gradually increased at day 3, 5, and 7. ANG-2 level was firstly upregulated and achieved the peak on day 3, and then decreased at day 5 and 7. Moreover, SCI rats overexpressing miR-325-3p showed a higher level of ANG-1 and lower level of ANG-2 than those of SCI rats. Overexpression of miR-325-3p downregulated the protein levels of iNOS and GFAP in SCI rats. BBB scale showed elevated locomotor function recovery in SCI rats overexpressing miR-325-3p compared with SCI rats. Conclusions MiR-325-3p protects the integrity of the vascular wall, reduces infiltration of inflammation, and improves locomotor function recovery at post-SCI.