BackgroundThe existence of latent low-virulence anaerobic bacteria in degenerated intervertebral discs (IVDs) remains controversial. In this study, the prevalence of low-virulence anaerobic bacteria in degenerated IVDs was examined, and the correlation between bacterial infection and clinical symptoms was analysed.MethodsEighty patients with disc herniation who underwent discectomy were included in this study. Under a stringent protocol to ensure sterile conditions, 80 disc samples were intraoperatively retrieved and subjected to microbiological culture. Meanwhile, tissue samples from the surrounding muscle and ligaments were harvested and cultured as contamination markers. The severity of IVD degeneration and the prevalence of Modic changes (MCs) were assessed according to preoperative MRI analysis.ResultsOf the 80 cultured discs, 54 were sterile, and 26 showed the presence of bacteria: Propionibacterium acnes (21 cases) and coagulase-negative staphylococci (5 cases). MRI revealed that the presence of bacteria was significantly associated with MCs (P<0.001). However, there was no significant association between bacterial infection and the severity of IVD degeneration (P = 0.162).ConclusionsOur findings further validated the presence of low-virulence anaerobic bacteria in degenerated IVDs, and P. acnes was the most frequent bacterium. In addition, the latent infection of bacteria in IVDs was associated with Modic changes. Therefore, low-virulence anaerobic bacteria may play a crucial role in the pathophysiology of MCs and lumbar disc herniation.

Our previous study verified the occurrence of Propionibacterium acnes (P. acnes), a low-virulence anaerobic bacterium, latently residing in degenerated intervertebral discs (IVDs), and the infection had a strong association with IVD degeneration. We explored whether P. acnes induces nucleus pulposus cell (NPC) pyroptosis, a more dangerous cell death process than apoptosis, and accelerates IVD degeneration via the pyroptotic products interleukin- (IL-) 1β and IL-18. After coculturing with P. acnes, human NPCs showed significant upregulation of NOD-like receptor 3 (NLRP3), cleaved IL-1β, cleaved caspase-1, and cleaved gasdermin D in response to the overexpression of IL-1β and IL-18 in a time- and dose-dependent manner. In addition, the gene expression of inflammatory factors and catabolic enzymes significantly increased in normal NPCs when cocultured with pyroptotic NPCs in a transwell system, and the adverse effects were inhibited when NPC pyroptosis was suppressed. Furthermore, inoculation of P. acnes into the IVDs of rats caused significant pyroptosis of NPCs and remarkable IVD degeneration. Finally, coculture of NPCs with P. acnes induced the overexpression of reactive oxygen species (ROS) and NLRP3, while inhibition of both factors reduced NPC pyroptosis. Therefore, P. acnes induces NPC pyroptosis via the ROS-NLRP3 signaling pathway, and the pyroptotic NPCs cause an IVD degeneration cascade. Targeting the P. acnes-induced pyroptosis of NPCs may become an alternative treatment strategy for IVD degeneration in the future.

Osteosarcoma is a malignant tumor with high mortality in children and adolescents. The mechanism of osteosarcoma metastasis is currently unclear. Abnormal expression of long non-coding RNA (lncRNA) plays an important role in tumor metastasis. We used bioinformatics to analyze the differences in gene expression between osteosarcoma in situ and osteosarcoma lung metastases. CCK-8 was used to detect the effect of lncRNA LOC100129620 on the proliferation of osteosarcoma cells. The effect of LOC100129620 on the invasion of osteosarcoma cells was assessed by Transwell assay. The regulatory effect of LOC100129620 on miR-335-3p was examined using RNA pull-down and luciferase reporter gene assays. The effect of LOC100129620 on the polarization of macrophages was detected by quantitative real-time fluorescent PCR. The results show that LOC100129620 can promote the proliferation and migration of osteosarcoma cells. LOC100129620 can promote the proliferation of osteosarcoma in vivo . LOC100129620 can bind to miR-335-3p and regulate its function. MiR-335-3p mediates the regulatory effects of LOC100129620 on CDK6. LOC100129620 promotes the formation of blood vessels and the polarization of macrophages. The LOC100129620/miR-335-3p/CDK6 signaling pathway promotes the metastasis of osteosarcoma by regulating the proliferation of osteosarcoma cells, angiogenesis, and macrophage polarization.

The notorious lung metastatic capability of osteosarcoma aggravates patient mortality and remains the primary challenge to be overcome. We investigated the effect of (-)-epigallocatechin-3-gallate (EGCG) on the metastasis capability of osteosarcoma cells. We performed cytotoxicity assays (MTT) to determine the appropriate concentration of EGCG for experiments. Migration, invasion, wound-healing, and adhesion assays were performed to assess the effect of EGCG on the metastasis of osteosarcoma. Changes in the mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathway were investigated using Western blot analyses. In addition, a MEK inhibitor (U0126) was used in invasion assays to determine the effect of the MEK/ERK signaling pathway. We found that EGCG may markedly inhibit the migration and invasion capacity of osteosarcoma cells, which occurred concurrently with inhibition of the expression of phospho-MEK and phospho-ERK. Inhibitors of MEK inhibited the invasion of osteosarcoma cells, and this effect could be enhanced by EGCG. We also detected the expression of c-Jun N-terminal kinase, p38, and their respective phospho-proteins, but did not find any meaningful changes. Taken together, our results demonstrated that EGCG could inhibit the metastasis capability of osteosarcoma cells by inhibiting MEK/ERK signaling activity and may provide new therapeutic value for osteosarcoma.