Loss of microRNA-124 expression in neurons in the peri-lesion area in mice with spinal cord injury

Micro RNA-124(mi R-124) is abundantly expressed in neurons in the mammalian central nervous system, and plays critical roles in the regulation of gene expression during embryonic neurogenesis and postnatal neural differentiation. However, the expression profile of mi R-124 after spinal cord injury and the underlying regulatory mechanisms are not well understood. In the present study, we examined the expression of mi R-124 in mouse brain and spinal cord after spinal cord injury using in situ hybridization. Furthermore, the expression of mi R-124 was examined with quantitative RT-PCR at 1, 3 and 7 days after spinal cord injury. The mi R-124 expression in neurons at the site of injury was evaluated by in situ hybridization combined with Neu N immunohistochemical staining. The mi R-124 was mainly expressed in neurons throughout the brain and spinal cord. The expression of mi R-124 in neurons significantly decreased within 7 days after spinal cord injury. Some of the neurons in the peri-lesion area were Neu N+/mi R-124-. Moreover, the neurons distal to the peri-lesion site were Neu N+/mi R-124+. These findings indicate that mi R-124 expression in neurons is reduced after spinal cord injury, and may reflect the severity of spinal cord injury.