慢性神经病理性疼痛小鼠空间记忆损伤及其海马转录组学特征

Spatial memory impairment and its transcriptomic profile in the hippocampus of chronic neuropathic pain mice

目的探究慢性神经病理性疼痛小鼠是否出现空间记忆障碍并研究其海马转录组学变化。方法24只雄性C57BL/6小鼠按随机数字表法分为两组:假手术组(Sham组)、坐骨神经慢性缩窄性损伤(chronic constrictive injury of sciatic nerve,CCI)组(CCI组),每组12只。分别于术前、术后7 d、术后28 d采用Von Frey纤维丝实验检测小鼠机械刺激缩足阈值(paw withdrawal mechanical threshold,PWMT);在术后7、28 d通过旷场实验检测小鼠运动能力和焦虑状况,通过空间位置识别实验检测小鼠空间记忆;于术后28 d取新鲜海马组织进行转录组学测序检测两组小鼠基因表达差异并分析测序结果,采用实时荧光定量聚合酶链反应(real time fluorescent quantitative polymerase chain reaction,RT-qPCR)验证纤调蛋白(fibromodulin,FMOD)、骨形态发生蛋白7(bone morphogenetic protein 7,Bmp7)、前列腺素D2合成酶(prostaglandin D2 synthase,PTGDS)、醛脱氢酶1家族成员A2(aldehyde dehydrogenase 1 family member A2,Aldh1a2)四组基因表达情况。结果与Sham组比较,CCI组小鼠造模侧后足PWMT在术后7 d(t=6.01,P<0.001)、术后28 d(t=4.49,P<0.001)明显降低。术后7、28 d两组小鼠运动能力和焦虑状况差异无统计学意义(运动距离:术后7 d t=0.25,P=0.962,术后28 d t=0.32,P=0.939。旷场中心区域活动时间:术后7 d t=1.16,P=0.439,术后28 d t=0.34,P=0.931)。术后7 d两组小鼠空间记忆差异无统计学意义(t=2.00,P=0.101),而在术后28 d CCI组小鼠空间记忆较Sham组明显降低(t=2.93,P=0.011)。转录组学测序发现两组小鼠海马存在大量差异表达基因(differentially expressed genes,DEGs)。RT-qPCR检测发现:与Sham组小鼠海马组织比较,CCI组小鼠海马组织中FMOD(t=8.07,P<0.001)、Bmp7(t=4.81,P=0.003)、PTGDS(t=4.07,P=0.007)、Aldh1a2(t=7.93,P<0.001)基因表达均降低。结论慢性神经病理性疼痛小鼠可出现空间记忆障碍,且小鼠海马组织转录组学发生显著变化。

Objective To investigate whether spatial memory impairment occurred in mice with chronic neuropathic pain and to investigate transcriptome changes in their hippocampus.Methods A total of 24 male C57BL/6 mice were divided into two groups according to the random number table method(n=12):a Sham group and a chronic constrictive injury of sciatic nerve(CCI)group.The paw withdrawal mechanical threshold(PWMT)of each mouse was measured by Von Frey filament test before operation,and 7 days and 28 days after operation.The open-field test was used to detect motor ability and anxiety of the mice 7 days and 28 days after operation.The spatial memory of the mice was detected by the spatial position recognition test.Fresh hippocampal tissue was collected 28 days after operation for transcriptome sequencing to detect gene expression differences between the two groups.Real-time fluorescent quantitative polymerase chain reaction(RT-qPCR)was used to verify the gene expression of fibromodulin(FMOD),bone morphogenetic protein 7(Bmp7),prostaglandin D2 synthase(PTGDS),and aldehyde dehydrogenase 1 family member A2(Aldh1a2).Results Compared with the Sham group,mice in the CCI group presented significantly decreased PWMT on the hind foot of the injured side 7 days(t=6.01,P<0.001)and 28 days(t=4.49,P<0.001)after operation.There were no significant differences in movement and anxiety between the two groups 7 and 28 days after surgery(movement distance:7 days after surgery,t=0.25,P=0.962,and 28 days after surgery,t=0.32,P=0.939;time in center of the open field:7 days after surgery,t=1.16,P=0.439,28 days after surgery,t=0.34,P=0.931).There was no statistical difference in spatial memory between the two groups 7 days after surgery(t=2.00,P=0.101),while the spatial memory of the CCI group was significantly lower than that of the Sham group 28 days after surgery(t=2.93,P=0.011).Transcriptome sequencing results indicated the presence of a large number of differentially expressed genes(DEGs)in the hippocampus of the two groups.RT-qPCR showed that compared with that in the Sham group,the gene expression of FMOD(t=8.07,P<0.001),Bmp7(t=4.81,P=0.003),PTGDS(t=4.07,P=0.007)and Aldh1a2(t=7.93,P<0.001)in the hippocampus of mice in the CCI group decreased.Conclusions Mice with chronic neuropathic pain may show spatial memory impairment,and the transcriptome of hippocampal tissue significantly changes.