Mechanism study on lactic acid promoting intervertebral disc degeneration by regulating senescence and DNA damage of cartilage endplate stem cells

Intervertebral disc degeneration, a leading cause of low back pain with incompletely elucidated molecular mechanisms, was studied via integrated in vivo/vitro approaches. This study first reveals that lactic acid accelerates intervertebral disc degeneration by inducing cartilage endplate stem cells senescence and DNA damage, thereby activating the P16/P21/P53-centered senescence pathway. In a rat tail vertebra puncture-induced intervertebral disc degeneration model, degenerated discs exhibited increased lactic acid levels, narrowed intervertebral spaces, and disrupted nucleus pulposus structure (P<0.05). In vitro, 0/2/6/10 mM lactic acid dose-dependently suppressed cartilage endplate stem cells viability (10 mM group: 15.7% of the control), elevated intracellular reactive oxygen species (ROS, 2.8-fold relative to the control), induced G0 cell cycle arrest (10 mM group: 85.63%), reduced EdU-positive cells (8.62%), and increased {beta}-galactosidase-positive cells (10 mM group: 33.06%) and {gamma}-H2AX foci (all P<0.01).Molecularly, lactic acid significantly upregulated P16 (2.1-fold), P21 (3.1-fold), P53 (2.4-fold), and {gamma}-H2AX (1.8-fold). In vivo intervertebral disc injection confirmed a positive correlation between lactic acid concentration and intervertebral disc degeneration severity. This study clarifies lactic acids role in intervertebral disc degeneration via the "oxidative stress-cell cycle arrest-cellular senescence" axis, advancing understanding of intervertebral disc degeneration pathogenesis and providing a basis for targeted therapies against lactic acid metabolism.