Leukemia inhibitory factor promotes extracellular matrix synthesis in degenerative nucleus pulposus cells via MAPK-ERK1/2 signaling pathway

Extracellular matrix (ECM) anabolism and catabolism imbalance is key feature of chondrocyte and intervertebral disc nucleus pulposus (NP) cell degeneration. The role of LIF as a multifunctional cytokine in the ECM metabolism of chondrocytes is controversial, but no relevant research in the ECM metabolism of NP cells. This study aimed to explore the biofunction and related mechanisms of LIF in the degenerative NP cells. We obtained an increase in the expression of LIF in the human degenerated NP specimens. The addition of recombinant human Leukemia Inhibitory Factor (rhLIF) to the degenerated NP cells cultured in vitro was found to stimulate the synthesis of ECM, and rhLIF could activate the ERK1/2 signaling pathway. However, coculture with PD98059, a signal inhibitor of ERK1/2, blocked the effect of rhLIF on the synthesis of ECM. To furtherly clarify the role of LIF, we carried out animal experiments and found that rhLIF treatment could successfully delay the degree of degeneration of the intervertebral disc in a rabbit model; but with the addition of PD98059, the function of rhLIF for degeneration protection disappeared. In summary, this study demonstrates that LIF plays a role in promoting ECM synthesis in the degenerated NP cells as a protective role in intervertebral disc degeneration (IDD), which is related to the activation of ERK1/2 signaling pathway.