Periodic Mechanical Stress Induces Extracellular Matrix Expression and Migration of Rat Nucleus Pulposus Cells Through Src-GIT1-ERK1/2 Signaling Pathway

Background/Aims: Periodic mechanical stress has been shown to promote extracellular matrix (ECM) synthesis and cell migration of nucleus pulposus (NP) cells, however, the mechanisms need to be fully elucidated. The present study aimed to investigate the signal transduction pathway in the regulation of NP cells under periodic mechanical stress. Methods: Primary rat NP cells were isolated and seeded on glass slides, and then treated in our self-developed periodic stress field culture system. To further explore the mechanisms, data were analyzed by scratch-healing assay, quantitative reverse transcription polymerase chain reaction (RT-qPCR) analysis, western blotting, and co-immunoprecipitation assay. Results: Under periodic mechanical stress, the mRNA expression of ECM collagen 2A1 (Col2A1) and aggrecan, and migration of NP cells were significantly increased (P < 0.05 for each), associating with increases in the phosphorylation of Src, GIT1, and ERK1/2 (P < 0.05 for each). Pretreatment with the Src inhibitor PP2 reduced periodic mechanical stress-induced ECM synthesis and cell migration of NP cells (P < 0.05 for each), while the phosphorylation of GIT1 and ERK1/2 were inhibited. ECM synthesis, cell migration, and phosphorylation of ERK1/2 were inhibited after pretreatment with the small interfering RNA for GIT1 in NP cells under periodic mechanical stress (P < 0.05 for each), whereas the phosphorylation of Src was not affected. Pretreatment with the ERK1/2 inhibitor PD98059 reduced periodic mechanical stress-induced ECM synthesis and cell migration of NP cells (P < 0.05 for each). Co-immunoprecipitation assay showed that there was a direct interaction between Src and GIT1 and between GIT1 and ERK1/2. Conclusion: In conclusion, periodic mechanical stress induced ECM expression and migration of NP cells via Src-GIT1-ERK1/2 signaling pathway, playing an important role in regulation of NP cells.