Abstract
Bone defects and fractures, caused by injury, trauma or tumour resection require hospital treatment and temporary loss of mobility, representing an important burden for societies and health systems worldwide. Autografts are the gold standard for promoting new bone formation, but these may provide insufficient material and lead to donor site morbidity and pain. We previously showed that Fibrinogen (Fg) scaffolds promote bone regeneration in vivo (1), and that modifying them with 10mM of Magnesium (Mg) ions modulates macrophage response in vitro and in vivo (2). Also, we showed that Extracellular Vesicles (EV) secreted by Dendritic Cells (DC) recruit Mesenchymal Stem/Stromal Cells (MSC)(3).
Herein, we aim to functionalize FgMg scaffolds with DC-EV, to promote recruitment and osteogenic differentiation of MSC.
Scaffolds were produced by freeze-drying (2). Ethical permission was sought for all studies. Primary human peripheral blood monocyte-derived DC were cultured, their secreted EV were isolated by differential (ultra)-centrifugation and characterised by transmission electron microscopy and nanoparticle tracking analysis (3). Bone marrow MSC were used to determine the impact of EV-functionalized scaffolds through migration assays and their osteogenic differentiation was assessed by Alizarin Red staining.
Fg and FgMg scaffolds functionalized with EV were characterized. Fg and FgMg scaffolds functionalized with DC-secreted EV were more efficient at recruiting MSC than scaffolds alone. MSC cultured on FgMg scaffolds showed significantly increased calcium deposits, in comparison with those cultured on Fg scaffolds.
Fg scaffold modification by Mg promotes MSC osteogenic differentiation, while their functionalization with DC-secreted EV acts to promote MSC recruitment. This renders the FgMg-EV functionalized scaffolds an attractive material to promote new bone formation.
Acknowledgments: Work funded by Orthoregeneration Network (ON Pilot Grant Spine 2021, EVS4Fusion). MCT supported by ERASMUS+ program.
