The decreased expression of miR-429 in plasma exosomes after spinal cord injury inhibits neuronal apoptosis by mediating the PTEN/PI3K/Akt pathway

BACKGROUND: Neuronal apoptosis after spinal cord injury (SCI) leads to sensorial and motorial dysfunction. Exosomes are vesicles that contain many cellular components, including microRNA, and the role of miR-429 in plasma exosomes in this process after SCI requires further investigation. METHODS: The New York University impactor was used to create a rat model of SCI. We used SH-SY5Y cells to construct a neuronal apoptotic cell model and extracted plasma exosomes from rats in a stimulation. A miR-429 mimic and inhibitor were transfected, and the apoptosis-related indicators of the SH-SY5Y cells were detected by using western blot, cell-counting kit-8 and immunofluorescence. The possible targets of miR-429 were examined to verify the pathway of action. We then used the dual-luciferase reporter assay to verify the binding of miR-429 with downstream molecules and speculate the mechanism of action. RESULTS: We successfully isolated and identified exosomes from plasma. Both the mean of adding exosomes extracted from SCI-patients’ plasma and knockdown of miR-429 in the culture of SH-SY5Y cells promoted their apoptosis. Dual luciferase assays confirmed the interaction of miR-429 and 3'-UTR region of phosphatase and tensin homolog (PTEN), which is the downstream target gene of miR-429, and the knockdown of miR-429 inhibits the phosphoinositide 3-kinase/protein kinase B pathway by upregulating PTEN. CONCLUSIONS: Our study showed that the decreased expression of miR-429 in SCI rat plasma exosomes promotes the apoptosis of nerve cells, which may be achieved by miR-429 interacting with PTEN and then affecting the PI3K/Akt pathway. This can be a possible mechanism of damage caused by SCI.