The protective effect of microRNA-21 in neurons after spinal cord injury

Experimental animal study.

To validate the anti-apoptosis effect of microRNA-21 in neurons after spinal cord injury (SCI) and explore the mechanism.

Xiangya Hospital, Central South University, Changsha, Hunan, People's Republic of China.

In situ hybridization was used to detect the expression of miR-21 in spinal cord neurons (n = 24). In a rat contusion SCI model (n = 48), we upregulated the miR-21 level around the injured area using miR-21 lentiviral vectors and evaluated the therapeutic effect with histology and behavioural scores. In neuronal cells, oxygen-glucose deprivation (OGD) was exerted to imitate SCI, and we explored the biomechanism using molecular biology and a dual-luciferase reporter assay.

miR-21 was expressed in spinal cord neurons and was found to improve neuronal survival and promote functional recovery in rat SCI models. The in vitro results in PC-12 cells revealed that the augmentation of endogenous miR-21 was able to reduce neuronal cell death after OGD. In addition, overexpression of miR-21 was able to reduce cellular apoptosis via decreasing PDCD4 protein levels, and caspase-3 activity was also influenced. Transfection of miR-21 into 293T cells was able to decrease luciferase activity in a reporter assay system, including the 3' untranslated region of PDCD4.

miR-21 may have a protective role in neuronal apoptosis after SCI. PDCD4 may be a functional target gene involved in the miR-21-mediated anti-apoptotic effect through an miR-21/PDCD4/caspase-3 pathway.