CRYAB_K92 lactylation drives hypertrophy of the ligamentum flavum via an S100A16/RAGE-mediated glycolysis-fibrosis positive feedback loop

Lumbar spinal stenosis (LSS) caused by hypertrophy of the ligamentum flavum (HLF) is a major cause of lower limb dysfunction; however, its underlying pathogenesis remains unclear. Here we show that metabolic reprogramming and epigenetic modifications synergistically drive HLF progression through a glycolysis-lactylation-fibrosis axis. We demonstrate that HLF tissues exhibit enhanced glycolysis, characterized by elevated extracellular acidification rate, increased ATP production, and upregulated glycolytic enzymes, along with lactate accumulation that positively correlates with tissue thickness. Mass spectrometry identifies CRYAB lysine 92 lactylation (CRYAB_K92la) as a significantly upregulated modification in HLF. Lactylation at CRYAB_K92 promotes fibrosis in human ligamentum flavum cells, whereas the lactylation-blocking mutation CRYAB_K92R attenuates lactate-induced fibrosis and proliferation. Mechanistically, CRYAB_K92 enhances S100A16 transcription, stabilizes S100A16 protein by inhibiting its degradation, and strengthens CRYAB-S100A16 binding, collectively upregulating S100A16 expression. Upregulated S100A16 activates the RAGE signaling pathway, further promoting lactate release and ATP production, thereby forming a positive feedback loop that perpetuates glycolysis, lactate generation, and fibrosis. These findings reveal a novel regulatory axis in HLF pathogenesis and identify CRYAB lactylation, S100A16, and the RAGE pathway as potential therapeutic targets for LSS.