痤疮丙酸杆菌诱导髓核细胞焦亡在椎间盘退变中的作用及其机制研究

近来研究表明椎间盘退变与低毒性细菌感染有关，其中最常见的为痤疮丙酸杆菌（P.acnes）。我们新近在退变的椎间盘组织中培养出P.acnes且发现感染标本中髓核细胞坏死率增高。P.acnes感染髓核细胞后焦亡相关蛋白Caspase-1和GSDMD表达增强，炎症因子分泌增多，抑制NLRP3表达后焦亡蛋白表达减弱且炎症因子分泌减少。综上，我们推测P.acnes可能通过NLRP3/Caspase-1/GSDMD通路诱导髓核细胞焦亡导致椎间盘退变。本项目拟首先明确隐性感染在国人椎间盘退变性疾病中的发生率以及与患者预后相关性；通过形态学检测、分子标记等方法明确P.acnes可以导致髓核细胞焦亡；最后围绕NLRP3/Caspase-1通路研究P.acnes诱导髓核细胞焦亡的机制。本项目首次研究P.acnes通过诱导髓核细胞焦亡参与椎间盘退变，揭示感染导致椎间盘退变的新机制，为临床治疗提供新思路。

In recent years, multiple studies have reported low-virulent bacteria which is mainly Propionibacterium acnes (P. acnes) in disc material suggesting that such infection may contribute to disc degeneration. However, until now, there is still no pathophysiologic mechanism to explain why and how bacteria induces disc degeneration. In our previous study, we also found the presence of low-grade infection in patients undergoing surgery for disc degeneration by microbiological culturing and found that infection may play a role in the pathophysiology of Modic Changes (MCs). More recently, we found that bacteria could induce the nucleus pulposus cells death. Moreover, low-grade bacteria could significantly induce expression of caspase-1, GSDMD, IL-1β and IL-18 by nucleus pulposus cells via NLRP3. We hypothesized that low toxic bacteria may induce intervertebral disc degeneration by inducing nucleus pulposus cell pyroptosis. In this study, we will further explore the roles of low-virulence bacteria in nucleus pulposus cells pyroptosis during disc degeneration and the underlying mechanisms. We will test and verify the pyroptosis of nucleus pulposus cells caused by bacteria via morphological detection, tunel staining and western blot analysis in vivo and vitro for the first time. Then we will explore the underlying mechanism of pyroptosis that whether it is correlated with NLRP3/Caspase-1/GSDMD pathway or not by siRNA. At last, we will explore the correlation between the low toxicity infection and the prognosis of patients. Overall, it is the first time to elucidate that low toxic bacteria may induce pyroptosis of nucleus pulposus cells in degenerative discs, which will provide a new way for clinical treatment of intervertebral disc degeneration.