Zhili Yang

Cellular dysfunction induced by senescent nucleus pulposus (NP) cells is a key factor in the pathogenesis of intervertebral disc degeneration (IDD). Stathmin 1 (STMN1) has been proposed as a telomere-associated senescence marker implicated in senescence in many age-related diseases. Nevertheless, its role in NP cell senescence remains unclear. This study revealed that STMN1 was significantly upregulated in human degenerative and naturally aged rat NP tissue specimens. In vitro models demonstrated that STMN1 expression levels were elevated in replicative and TNF-α-induced NP senescence models. Lentiviral knockdown of STMN1 inhibited NP cell senescence, while overexpression promoted NP cell senescence, along with extracellular matrix (ECM) degradation. An in-depth mechanism indicated that insulin-like growth factor-binding protein 5 (IGFBP5), a downstream pro-senescence gene of STMN1, can induce NP cellular senescence and ECM degradation following its upregulation by STMN1. Furthermore, STMN1 knockdown reduced IGFBP5 expression and mitigated IDD development in a rat model of caudal discs puncture-induced IDD. Combined with the abovementioned results, we demonstrated for the first time that the STMN1–IGFBP5 axis can induce NP cell senescence and ECM degradation, thereby accelerating IDD development. This provides a robust foundation for the development of molecular-targeted therapies for IDD.

Intervertebral disc degeneration (IDD) is a major cause of lower back pain. The pathophysiological development of IDD is closely related to the stimulation of various stressors, including proinflammatory cytokines, abnormal mechanical stress, oxidative stress, metabolic abnormalities, and DNA damage, among others. These factors prevent normal intervertebral disc (IVD) development, reduce the number of IVD cells, and induce senescence and apoptosis. Stress-activated protein kinases (SAPKs), particularly, c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38 MAPK), control cell signaling in response to cellular stress. Previous studies have shown that these proteins are highly expressed in degenerated IVD tissues and are involved in complex biological signal-regulated processes. Therefore, we summarize the research reports on IDD related to JNK and p38 MAPK. Their structure, function, and signal regulation mechanisms are comprehensively and systematically described and potential therapeutic targets are proposed. This work could provide a reference for future research and help improve molecular therapeutic strategies for IDD.

Lower back pain, a leading cause of disability worldwide, is associated with intervertebral disc degeneration (IDD) in approximately 40% of cases. Although nucleus pulposus (NP) cell senescence is a major contributor to IDD, the underlying mechanisms remain unclear. We collected NP samples from IDD patients who had undergone spinal surgery. Healthy and senescent NP tissues (n = 3) were screened using the Pfirrmann grading system combined with immunohistochemistry, as well as hematoxylin and eosin, Safranin O, Alcian blue, and Masson staining. Differentially expressed proteins (DEPs) were identified using quantitative TMT-based proteomics technology. Bioinformatics analyses included gene ontology (GO) annotation, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, and protein–protein interaction (PPI) analyses. In addition, immunofluorescence was used to verify protein expression. In total, 301 DEPs were identified in senescent NP tissues, including 92 upregulated and 209 downregulated proteins. In GO, DEPs were primarily associated with NF-kappaB transcription factor, extracellular regions, cellular protein metabolic processes, and post-translational protein modification. The enriched KEGG pathways included TGF-β, Wnt, RAP1, interleukin-17, extracellular matrix-receptor adhesion, and PI3K/Akt signaling pathways. PPI analysis demonstrated interactions between multiple proteins. Finally, immunofluorescence verified the expressions of MMP3, LUM, TIMP1, and CDC42 in senescent NP cells. Our study provides valuable insights into the mechanisms underlying senescent NP tissues in IDD patients. DEPs provide a basis for further investigation of the effects of senescent factors on IDD.