Abstract: BACKGROUND: There is a central sensitization mechanism for lumbar disc herniation-specific pain sensitization, and it is unclear whether cyclic RNAs in the paraventricular nucleus brain region are involved in lumbar disc herniation-specific pain sensitization.
OBJECTIVE: To investigate the mechanism by which cyclic RNA circ05188 in the paraventricular nucleus of rats with lumbar disc herniation regulates the participation of microRNAs in pain sensitization.
METHODS: Fifty-two Sprague-Dawley rats were randomly divided into a sham operation group, a lumbar disc herniation group, a knockdown control group and a circ05188 knockdown group, with 13 rats in each group. Except for the sham operation group, the lumbar disc herniation model was established in the other three groups. On the 7th day after modeling, the hypothalamic paraventricular nucleus of the knockdown control group and circ05188 knockdown group were injected with siRNA-NC and siRNA-circ05188, respectively, at 1 day intervals, for a total of three injections. On the 7th day after modeling, high-throughput sequencing technology was used to detect the expression of differential circRNAs in the hypothalamic paraventricular nucleus of rats in the sham operation group and the lumbar disc herniation group, and RT-qPCR was used to detect the expression of circ05188 and miR-199a-5p in the hypothalamic paraventricular nucleus. On the 3rd, 7th, 14th, 21st, and 28th days after modeling, we detected the mechanical and thermal mechanical paw withdrawal thresholds of the rat’s hindfoot in the modeled side of rats in the sham operation group and the lumbar disc herniation group. On the 3rd day after siRNA injection, immunofluorescence staining was used to detect the expression of c-Fos in the hypothalamic paraventricular nucleus of rats in the knockdown control group and circ05188 knockdown group; RT-qPCR was used to detect the expression of circ05188 and miR-199a-5p in the hypothalamic paraventricular nucleus of rats in the knockdown control group and circ05188 knockdown group; on the 5th day after siRNA injection, mechanical and thermal mechanical paw withdrawal thresholds of the rat’s hindfoot were detected in the knockdown control group and circ05188 knockdown group. Bioinformatics analysis and dual luciferase reporter elucidated the underlying molecular mechanism of circ05188 in pain sensitization after lumbar disc herniation. 
RESULTS AND CONCLUSION: High-throughput sequencing results showed that circRNAs were differentially expressed in the paraventricular nucleus brain region of rats with lumbar disc herniation. The expression of circ05188 was higher in the lumbar disc herniation group than in the sham operation group (P < 0.05), the expression of miR-199a-5p was lower than in the sham operation group (P < 0.05), and the mechanical and thermal mechanical paw withdrawal thresholds of the hindfoot were lower than those of the sham operation group at 3, 7, 14, and 21 days after modeling. RT-qPCR results showed that compared with the knockdown control group, the expression of c-Fos and circ05188 was lower in the circ05188 knockdown group (P < 0.05), while the expression of miR-199a-5p was higher (P < 0.05). The mechanical and thermal mechanical paw withdrawal thresholds of the rat’s hindfoot in the circ05188 knockdown group were higher than those in the knockdown control group at 1, 2, and 3 days after injection. Bioinformatics analysis and dual luciferase reporter assay results showed that miR-199a-5p had a binding site with circ05188 and circ05188/miR-199a-5p competitive endogenous RNA axis. To conclude, lumbar disc herniation induces an increase in circ05188 expression in the paraventricular nucleus of the hypothalamus, which produces central sensitization through the inhibition of miR-199a-5p and ultimately triggers neuropathic pain.

中国组织工程研究杂志出版内容重点：组织构建；骨细胞；软骨细胞；细胞培养；成纤维细胞；血管内皮细胞；骨质疏松；组织工程

Key words: lumbar disc herniation, paraventricular nucleus, cyclic RNA, microRNA, neuropathic pain, engineered tissue construction