Small extracellular vesicles from 3D PCL/HA scaffold-cultured and EMF-stimulated BMSCs promote lumbar fusion via PTEN/PI3K/AKT pathway

Abstract

Chronic low back pain, typically managed through lumbar fusion, demands innovative approaches to enhance therapeutic outcomes. This study investigated the efficacy of small extracellular vesicles (sEVs) derived from bone marrow mesenchymal stem cells (BMSCs) cultured in three-dimensional (3D) scaffolds concurrently under electromagnetic fields (EMF) stimulation, aiming to enhance osteogenesis and angiogenesis in a rat lumbar fusion model. We utilized a composite of polycaprolactone (PCL) and hydroxyapatite (HA), engineered via 3D printing, to create the scaffolds. sEVs were harvested from BMSCs under three distinct conditions: standard 2D cultures, 3D scaffolds, and 3D scaffolds with EMF stimulation. Specifically, the sEVs from the EMF-stimulated 3D cultures (3D/E-sEVs) were incorporated into these scaffolds before being implanted into rat spines. Therapeutic effectiveness was evaluated in vitro through assays for cell proliferation, migration, and angiogenesis, and in vivo via X-ray imaging, micro-computed tomography (micro-CT), and histological analyses. Results revealed that 3D/E-sEVs markedly enhanced both osteogenesis and angiogenesis. Further mechanistic investigations identified the PTEN/PI3K/AKT signalling pathway as essential in mediating these regenerative effects. Moreover, 3D PCL/HA scaffold loaded with 3D/E-sEVs promote lumbar fusion in a rat model. Conclusively, our findings demonstrated that 3D-printed PCL/HA scaffolds engineered with 3D/E-sEVs significantly promoted bone regeneration and vascular formation, thereby improving lumbar fusion outcomes. This study highlights the profound potential of integrating advanced tissue engineering techniques with cellular therapies to revolutionize the treatment of chronic low back pain and enhance surgical success rates.