Mechanism of peripheral axonal branch conditioning injury inducing injured central axonal branch of primary sensory neurons repair

Abstract

Objective It has been proved that the repair of injured central branch of primary sensory neurons can be promoting by conditioning injury of the peripheral branch.Present study try to investigate the mechanism of upregulation of cyclic adenosine monophosphate(c AMP) levels via microarray and further interpret this phenomenon. Methods Microarray and bioinformatics were used to investigate the microRNA which is associated with the repair of dorsal column lesion that is promoted by sciatic nerve conditioning injury.To validate the result, real-time quantitative reverse transcriptase-polymerase chain reaction(RT-qPCR), Western blotting, immunohistochemistry, enzyme linked immunosorbent assay (ELISA), antisense oligonucleotide(AMO-139)and rolipram(PDE4 inhibitor)were applied. Results To compare with control group,c AMP levels increased in each check points of sciatic nerve conditioning injury group but has no statistical difference in each check points of simple dorsal column lesion group.The expression level of neurofilament protein(NF-200) in sciatic nerve conditioning injury group (79 473. 86±2 018. 15)was higher than it in simple dorsal column lesion group(89 623. 43±1 984. 69), and the difference was statistically significant.To compare with control group, totally 681 microRNAs'expression were altered in sciatic nerve conditioning injury group and simple dorsal column lesion group. A-mong them, miR-139-5p in sciatic nerve conditioning injury group was upregulated significantly at 4 h, 3 d and 7 d post dorsal column lesion and started to decrease at 14 d post dorsal column lesion.After adding AMO-139 to inhibit miR-139-5p of dorsal root ganglion(DRG) neurons, the relative expression of PDE4A protein was increased, compared with the blank DRG neurons.The axonal length of DRG neurons with rolipram were significantly longer than blank DRG neurons.Whereas the axonal length has no statistical difference between DRG neurons with rolipram and AMP-139 and blank DRG neurons. Conclusion Injured peripheral axonal branch of primary sensory neurons induced the upregulation of miR-139-5p, which can increase c AMP levels through inhibiting the expression of PDE4 and further promote the repair of central axonal branch. Key words: Sciatic nerve conditioning injury; Spinal cord injury; MicroRNA; Phosphodiesterase 4A; Cyclic adenosine monophosphate