Mesenchymal Stem Cell-Derived Extracellular Vesicles Mimetics for Enhanced Bone Healing and Regeneration

Introduction: Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) have gained significant attention as promising therapeutic tools in bone-tissue engineering due to their intrinsic bioactivity, regenerative functions, and immunomodulatory and anti-inflammatory properties. However, their clinical translation remains limited by low-yield, high heterogeneity, and lack of standardization. Recently, extracellular vesicle mimetics known as nanoghosts (NGs) have emerged. These nano-sized vesicles are derived from ghost cell plasma membranes, retaining key surface functionalities while enabling more standardized, reproducible production and substantially higher yields than EVs.[2] This study aimed to demonstrate the osteogenic relevance and potential of MSC-derived nanoghosts (MSC-NGs) as novel tools for bone-tissue engineering and nanomedicine.

Method: MSC-NGs were produced by hypotonic lysis of MSCs to generate MSC-ghosts, followed by sonication to form nanoparticles. MSC-NGs were characterized using nanoparticle-tracking analysis, zeta-potential analysis, electron microscopy, and protein assays. MSCs were treated with 5 µg MSC-NGs under osteogenic conditions. Osteogenic differentiation and mineralization were evaluated by alkaline phosphatase (ALP) assay, qPCR, and alizarin red staining. Osteogenic performance was assessed in vivo using a 0.5 mm femoral defect model in C57BL/6J mice (n = 6-8), following McGill Institutional Animal Care and Use Committee approval. µCT imaging monitored bone healing over 21 days, after which bone samples were collected for histological analysis.

Results: MSC-NGs were successfully and reproducibly isolated and exhibited colloidal and vesicular properties comparable to MSC-EVs. Under osteogenic conditions, MSC-NGs enhanced in vitro osteogenic differentiation and mineralization relative to MSC-EVs, with significantly increased osteoblast-lineage gene expression and mineralized nodule formation by day 14. Ongoing in vivo studies are evaluating whether MSC-NG administration at fracture sites accelerates bone healing and defect bridging compared with controls.

Significance: This study provides insight into MSC-NGs as novel therapeutic tools, in the field of bone tissue engineering, with potent biological activities, scalable and clinically relevant production, compared to MSC-EVs.