MicroRNA-448 inhibits the regeneration of spinal cord injury through PI3K/AKT/Bcl-2 axis.

Objective: This study aims to elucidate the potential role of microRNA-448 in the recovery of spinal cord injury (SCI), and to explore the underlying mechanism.
Materials and Methods: MicroRNA-448 expression was determined by microarray and the established SCI model in mice. The target gene of microRNA-448 was predicted using bioinformatics. The functional binding of the target gene to microRNA-448 was verified by Dual-Luciferase reporter gene assay. The regulatory effects of microRNA-448 and Bcl-2 on apoptosis, motor neuron number and grip strength were evaluated. After injection of microRNA-448 mimics, microRNA-448 inhibitor or Bcl-2 siRNA in mice, expression levels of PI3K/AKT and Caspase3 were detected by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR) and Western blot.
Results: Grip strength of SCI mice significantly decreased compared with mice in the sham group. The microRNA-448 expression gradually increased with the progression of SCI, whereas the Bcl-2 expression decreased. Dual-Luciferase reporter gene assay showed the binding condition between microRNA-448 and Bcl-2. Furthermore, the Bcl-2 expression was negatively regulated by microRNA-448 at both mRNA and protein levels. The injection of microRNA-448 inhibitor into the injured spinal cord of SCI mice significantly upregulated the expressions of p-PI3K, p-AKT and Caspase3, as well as motor neuron regeneration and grip strength. However, the promotive effects of microRNA-448 inhibitor were blocked by Bcl-2 siRNA transfection.
Conclusions: MicroRNA-448 is upregulated after SCI, which may be involved in the regenerative process of spinal motor nerves by regulating PI3K/AKT/Bcl-2 axis.