PHB2 mitigates intervertebral disc degeneration by modulating mitophagy to inhibit necroptosis in nucleus pulposus cells.

Intervertebral disc degeneration involves loss of nucleus pulposus (NP) cells driven by inflammatory and mitochondrial stress-related death pathways. Because mitophagy maintains mitochondrial quality, its disruption may influence cell fate during degeneration. Using human tissues, a mouse lumbar instability model, a rat disc puncture model, and human NP cells stimulated with TNF-α, SM-164, and Z-VAD-FMK (TSZ), we examined how mitochondrial quality control shapes necroptotic signaling. Necroptotic cells displayed mitochondrial damage and reduced mitophagy, while mitophagy activation limited necroptosis and preserved extracellular matrix components. We identified the mitochondrial protein PHB2 as a key regulator linking mitophagy to suppression of necroptosis. PHB2 loss impaired mitophagy, disrupted mitochondrial function, and intensified necroptotic death, whereas PHB2 overexpression restored mitophagy, maintained mitochondrial membrane potential, and reduced degeneration. In vivo PHB2 delivery mitigated necroptosis and protected disc structure. These findings highlight a mitochondria-centered mechanism that shapes cell survival during disc degeneration.