Sustained-release alphitolic acid-loaded hydrogel attenuates intervertebral disc degeneration through regulation of the MIF-SERPINE1-PI3K-Akt/NF-κB axis

Intervertebral disc degeneration (IVDD) is the leading cause of global chronic low back pain, primarily driven by sustained inflammatory microenvironment activation and progressive extracellular matrix (ECM) degradation. Current IVDD therapeutic strategies are limited by unclear core pathogenic mechanisms and rapid in vivo clearance of conventional small-molecule drugs, failing to achieve persistent anti-inflammatory and anti-degenerative effects. Macrophage migration inhibitory factor (MIF) acts as a pivotal pro-inflammatory mediator in musculoskeletal degenerative disorders, yet its exact downstream effector network and targeted therapeutic intervention strategies in IVDD remain poorly defined. To address these limitations, we systematically explored the MIF-centered pathological mechanism and developed an innovative sustained-release hydrogel delivery system for precise IVDD treatment. In this study, quantitative proteomics of clinical degenerative nucleus pulposus (NP) specimens with different Pfirrmann grades was performed to screen key pathogenic molecules. Clinical specimen validation and rat IVDD model experiments confirmed that MIF was highly upregulated in severe degenerative NP tissues. Mechanistically, MIF directly binds to SERPINE1 with high affinity (Kd = 12.8 nM), which further activates the PI3K-Akt/NF-κB pro-inflammatory signaling cascade and ultimately promotes the secretion of TNF-α and IL-1β. Through immobilized MIF affinity chromatography screening from Eucommia ulmoides, alphitolic acid was identified as a high-affinity MIF antagonist with a Kd value of 1.85 μM. To improve the local retention and bioavailability of alphitolic acid, we fabricated an injectable hyaluronic acid-dopamine composite hydrogel (Alp@HDgel) with favorable biocompatibility, stable porous microstructure and mechanical properties, which achieved more than 60% cumulative sustained drug release within 48 hours. In vitro mechanistic assays including Co-IP, SPR and ITC verified the targeted inhibitory effect of alphitolic acid on the MIF-SERPINE1 axis, and in vivo rat puncture-induced IVDD model experiments demonstrated that Alp@HDgel effectively suppressed local inflammatory responses, restored ECM homeostasis, and rescued disc structural deterioration, exhibiting significantly superior therapeutic efficacy compared with free alphitolic acid and blank hydrogel. In conclusion, this study defines the critical MIF-SERPINE1-PI3K-Akt/NF-κB regulatory axis that mediates IVDD inflammatory degeneration. The engineered sustained-release alphitolic acid hydrogel achieves targeted blockade of MIF-driven pathological cascades and effectively reverses IVDD progression, providing a feasible and disease-modifying therapeutic strategy for clinical IVDD treatment.