Amphiregulin secreted by cartilage endplate stem cells inhibits intervertebral disk degeneration and TNF-α production via PI3K/AKT and ERK1/2 signaling pathways

Background Intervertebral disk degeneration (IDD) is a common orthopedic disorder, and nucleus pulposus cells (NPCs) serve to stabilize the intervertebral disk. Objective This study was implemented to explore the protective effect of endplate stem cells (EPSCs) on IDD. NPCs and EPSCs were isolated from rats and tert -Butyl peroxide (TBHP) was used to treat NPCs and simulate IDD. EPSC-derived conditioned medium (CM) was collected and mixed with a culture medium at different proportions, which was then used to treat NPCs. SOD assay was employed to examine the oxidative stress level in the NPCs. To assess apoptosis and caspase-3 activity, flow cytometry and western blots for cleaved PARP1 and BAX were carried out. The mRNA expression levels of different genes were detected by quantitative real-time polymerase chain reaction. Furthermore, the concentrations of amphiregulin (Areg) and inflammatory factors were measured with ELISA kits and cell signaling pathways were evaluated using western blotting. Results Following TBHP treatment, caspase-3 activity in the NPCs increased. However, exposing TBHP-induced NPCs to the EPSC-derived CM reduced oxidative stress, caspase-3 activity, cell apoptosis, fibrotic response, and cytokine production. Additionally, the EPSC-derived CM contained a higher concentration of Areg compared to that in the NPCs. Furthermore, Areg decreased oxidative stress, cell apoptosis, fibrosis, and inflammation via both PI3K/AKT and ERK1/2 signaling pathways. Conclusion ECSCs reduce NPC apoptosis, oxidative stress, production of inflammatory factors, and fibrotic response via the release of Areg. Moreover, Areg can exert these protective effects on NPCs via PI3K/AKT and ERK1/2 signaling pathways.