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Abstract Cellular senescence is a significant contributor to intervertebral disc aging and degeneration. However, the application of senotherapies, such as senomorphics targeting senescence markers and the senescence‐associated secretory phenotype (SASP), remains limited due to challenges in precise delivery. Given that the natural killer group 2D (NKG2D) ligands are increased on the surface of senescent nucleus pulposus (NP) cells, the NKG2D‐overexpressing NP cell membranes (NNPm) are constructed, which is expected to achieve a dual targeting effect toward senescent NP cells based on homologous membrane fusion and the NKG2D‐mediated immunosurveillance mechanism. Then, mesoporous silica nanoparticles carrying a peroxisome proliferator‐activated receptor‐ɣ coactivator 1α (PGC1α)inducer (SP) are coated with NNPm (SP@NNPm) and it is found that SP@NNPm selectively targets senescent NP cells, and the SP cores exhibit pH‐responsive drug release. Moreover, SP@NNPm effectively induces PGC1α‐mediated mitochondrial biogenesis and mitigates senescence‐associated markers induced by oxidative stress and the SASP, thereby alleviating puncture‐induced senescence and disc degeneration. This dual‐targeting nanotherapeutic system represents a novel approach to delivery senomorphics for disc degeneration treatment.

Abstract Exogenous stem cell therapy and endogenous repair has shown great potential in intervertebral disc regeneration. However, limited nutrients and accumulation of lactate largely impair the survival and regenerative capacity of implanted stem cells and endogenous nucleus pulposus cells (NPCs). Herein, an injectable hydrogel microsphere (LMGDNPs) have been developed by immersing lactate oxidase (LOX)‐manganese dioxide (MnO2) nanozyme (LM) into glucose‐enriched decellularized nucleus pulposus hydrogel microspheres (GDNPs) through a microfluidic system. LMGDNPs showed a delayed release profile of LOX and satisfactory enzymatic capacity in consuming lactate. Mesenchymal stem cells (MSCs) plated on LMGDNPs exhibited better cell viability than cells on GelMA and decellularized nucleus pulposus microspheres (DNP) and showed a obviously increased NPCs phenotype. LMGDNPs prevented MSCs and NPCs death and promoted extracellular matrix synthesis by exhausting lactate. It is determined that LMGDNPs promoted NPCs autophagy by activating transforming growth factor β2 overlapping transcript 1 (TGFB2‐OT1), relying on the nanozyme. MSCs‐loaded LMGDNPs largely preserved disc hydration and alleviated matrix degradation in vivo. Summarily, LMGDNPs promoted cell survival and matrix regeneration by providing a nutrient supply, exhausting lactate, and activating autophagy via TGFB2‐OT1 and its downstream pathway and may serve as an ideal delivery system for exogenous stem cell therapy and endogenous repair.

Puerarin (PUR), an 8-C-glucoside of daidzein extracted from Pueraria plants, is closely related to autophagy, reduced reactive oxygen species (ROS) production, and anti-inflammatory effects, but its effects on human nucleus pulposus mesenchymal stem cells (NPMSCs) have not yet been identified. In this study, NPMSCs were cultured in a compression apparatus to simulate the microenvironment of the intervertebral disc under controlled pressure (1.0 MPa), and we found that cell viability was decreased and apoptosis level was gradually increased as compression duration was prolonged. After PUR administration, apoptosis level evaluated by flow cytometry and caspase-3 activity was remitted, and protein levels of Bas as well as cleaved caspase-3 were decreased, while elevated Bcl-2 level was identified. Moreover, ATP production detection, ROS, and JC-1 fluorography as well as quantitative analysis suggested that PUR could attenuate intercellular ROS accumulation and mitochondrial dysfunction. Besides, the rat tail compression model was utilized, which indicated that PUR could restore impaired nucleus pulposus degeneration induced by compression. The PI3K/Akt pathway was identified to be deactivated after compression stimulation by western blot, and PUR could rescue the phosphorylation of Akt, thus reactivating the pathway. The effects of PUR, such as antiapoptosis, cell viability restoration, antioxidation, and mitochondrial maintenance, were all counteracted by application of the PI3K/Akt pathway inhibitor (LY294002). Summarily, PUR could alleviate compression-induced apoptosis and cell death of human NPMSCs in vitro as well as on the rat compression model and maintain intracellular homeostasis by stabilizing mitochondrial membrane potential and attenuating ROS accumulation through activating the PI3K/Akt pathway.