O-vanillin Attenuated Toll-like Receptor 2 Induces Senescence in Intervertebral Disc Cells of Patients With Back Pain

Abstract

Backgroud: There are an increased level of senescent cells and Toll Like Receptor-1 -2 -4 and -6 (TLR) expression in degenerating IVDs from back pain patients. However, it is currently not known if the higher expression is related to the senescent cells or if it is a more general increase on all cells. It is also not known if TLR activation in IVD cells will induce cell senescence.Methods: Cells from non-degenerate human IVD were obtained from spine donors and cells from degenerate IVDs came from patients undergoing surgery for low back pain. Gene expression of TLR-1,2,4,6, senescence and senescence-associated secretory phenotype (SASP) markers was evaluated by RT-qPCR in isolated cells. Matrix synthesis was verified with safranin-O staining and Dimethyl-Methylene Blue Assay (DMMB) confirmed proteoglycan content. Protein expression of p16INK4a, SASP factors and TLR-2 was evaluated by immunocytochemistry (ICC) and/or by enzyme-linked immunosorbent assay (ELISA). Results: An increase in senescent cells was found following 48h induction with a TLR-2/6 agonist in cells from both non-degenerate and degenerating human IVDs. Higher levels of SASP factors, TLR-2 gene expression and protein expression was found following 48h induction with TLR-2/6 agonist. Treatment with o-Vanillin reduced the number of senescent cells, and increased matrix synthesis in IVD cells from back pain patients. Treatment with o-Vanillin after induction with TLR-2/6 agonist reduced gene and protein expression of SASP factors and TLR-2. Co-localized staining of p16INK4a and TLR-2 demonstrated that senescent cells have a high TLR-2 expression.Conclusions: Taken together our data demonstrate that activation of TLR-2/6 induce senescence and increase TLR-2 and SASP expression in cells from non-degenerate IVDs of organ donors without degeneration and backpain and in cells from degenerating human IVD of patients with disc degeneration and backpain. The senescent cells showed high TLR-2 expression suggesting a link between TLR activation and cell senescence in human IVD cells. The reduction in senescence, SASP and TLR-2 expression suggest o-Vanillin as a potential disease modifying drug for patients with disc degeneration and backpain.