Spheroid-Derived BMSC Exosomes Enhance Proliferation and Matrix Remodeling of Nucleus Pulposus Cell Clusters in Degenerative Disc Repair.

Current intervertebral disc degeneration (IDD) treatments mainly relieve symptoms but fail to enable biological repair. This study develops a clinical combination therapy involving autologous nucleus pulposus (NP) tissue fragments mixed with bone marrow aspirate (BMA)-enriched gelatin sponge, sealed with fibrin glue, and reimplanted into the NP cavity, followed by posterior dynamic stabilization. This restored disc hydration and structure, as confirmed by MRI. Histological analysis of IDD samples reveals NP cell clusters (NPCCs) expressing CD105⁺, CD90⁺, and PCNA⁺, with strong proliferative capacity in vitro. Given the paracrine effects of BMA-derived mesenchymal stem cells (BMSCs), their exosome-mediated functions are explored to elucidate regenerative mechanisms. Spheroid-cultured BMSCs produce exosomes (Sph-Exos) with higher yield and richer cargo than 2D-derived exosomes, significantly enhancing NP cell function. Mechanistically, Sph-Exos enrich in miR-148a-3p and miR-152-3p, synergistically regulate the NF-κB/FOXO3 pathway to suppress inflammation and matrix degradation, thereby promoting ECM remodeling. Based on this, an injectable tissue-engineered NP construct is developed by embedding NPCCs and Sph-Exos within GelMA hydrogel. Under hydrostatic pressure in vitro and after in vivo implantation, this construct improves cell viability, proliferation, and ECM deposition. This study elucidates the mechanism behind clinical efficacy and proposes a novel, translatable in situ regenerative strategy for IDD.