Arg-Gly-Asp Peptide-Functionalized Superparamagnetic γ-Fe2O3 Nanoparticles Enhance Osteoblast Migration In Vitro

Making osteoblast migration manageably target to injury sites has been the key challenging in cell therapy for bone and cartilage regeneration. Superparamagnetic materials, the magnetic guide for cell migration, have been applied to increase cell retention. However, additional targeting modifications are still needed to accelerate the low uptake efficiency and moving speed. Arg-Gly-Asp peptide (RGD)-functionalized magnetic nanoparticles showed cutting-edge competence in cell differentiation control and targeted drug delivery. However, more evidence was required to corroborate its role in osteoblast migration in bone repair. In the present study, RGD-modified γ-Fe2O3 nanoparticles (RGD-Fe2O3 NPs) were prefabricated with the grafting ratio of 33.3–37.4%. The RGD-Fe2O3 NPs unveiled excellent water dispersibility with uniform size distribution at 5–6 nm and negligibly low cytotoxicity. As a result, MC3T3-E1 osteoblasts treated with RGD-Fe2O3 NPs boosted its migration speed in a magnetic field compared with those incubated with unmodified Fe2O3 NPs. Furthermore, osteoblasts treated with RGD-Fe2O3 NPs exhibited more Fe uptake. The results exposed the fact that RGD-mediated specific cellular uptake presented higher efficiency than the non-RGD-mediated one, resulting from a stronger superparamagnetic force between the labeled cells and the magnetic field. These findings indicate that the RGD-functionalized Fe2O3 NPs can promote osteoblast migration in the magnetic field, providing a promising strategy in magnet-guided cell therapy for bone and cartilage regeneration.

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Comment on: Food for Bone: Evidence for a Role for Delta-Tocotrienol in the Physiological Control of Osteoblast Migration. Int. J. Mol. Sci. 2020, 21, 4661

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Food for Bone: Evidence for a Role for Delta-Tocotrienol in the Physiological Control of Osteoblast Migration

Bone remodeling and repair require osteogenic cells to reach the sites that need to be rebuilt, indicating that stimulation of osteoblast migration could be a promising osteoanabolic strategy. We showed that purified δ-tocotrienol (δ-TT, 10 μg/mL), isolated from commercial palm oil (Elaeis guineensis) fraction, stimulates the migration of both MC3T3-E1 osteoblast-like cells and primary human bone marrow mesenchymal stem cells (BMSC) as detected by wound healing assay or Boyden chamber assay respectively. The ability of δ-TT to promote MC3T3-E1 cells migration is dependent on Akt phosphorylation detected by Western blotting and involves Wnt/β-catenin signalling pathway activation. In fact, δ-TT increased β-catenin transcriptional activity, measured using a Nano luciferase assay and pretreatment with procaine (2 µM), an inhibitor of the Wnt/β-catenin signalling pathway, reducing the wound healing activity of δ-TT on MC3T3-E1 cells. Moreover, δ-TT treatment increased the expression of β-catenin specific target genes, such as Osteocalcin and Bone Morphogenetic Protein-2, involved in osteoblast differentiation and migration, and increased alkaline phosphatase and collagen content, osteoblast differentiation markers. The ability of δ-TT to enhance the recruitment of BMSC, and to promote MC3T3-E1 differentiation and migratory behavior, indicates that δ-TT could be considered a promising natural anabolic compound.