Research Article
In vitro angiogenic performance and in vivo brain targeting of magnetized endothelial progenitor cells for neurorepair therapies

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Abstract

Endothelial progenitor cells (EPCs) represent a promising approach for cell-based therapies to induce tissue repair; however, their effective delivery into the brain has remained a challenge. We loaded EPCs with superparamagnetic iron oxide nanoparticles (SPIONs), assessed their angiogenic potential and evaluated their guidance to the brain using an external magnet. SPIONs were stored in the cytoplasm within endosomes/lysosomes as observed by transmission electron microscopy (TEM) and could be visualized as hypointense signals by magnetic resonance imaging (MRI) T2-weighted images. In vitro SPION-loaded EPCs were fully functional, forming vessel-like structures in Matrigel®, and displayed enhanced migration and secretion of growth factors (VEGF and FGF), which was associated with a moderate increase in reactive oxygen species production. Furthermore, in vivo MRI of treated mice showed accumulated hypointense signals consistent with SPION-loaded EPCs engraftment. Thus, we demonstrate that loading EPCs with SPIONs represents a safe and effective strategy for precise cell guidance into specific brain areas.

From the Clinical Editor

This study investigates the potential role of endothelial progenitor cells in neuro-repair strategies of the central nervous system using SPION-loaded EPCs and magnetic guidance to the target organ. The authors demonstrate ex vivo cellular viability and maintained function following SPION load as well as successful guidance of the EPCs to the target site via MR imaging in a murine model.

Graphical Abstract

Endothelial Progenitor cells (EPCs) treatment might become a promising therapy to enhance neurorepair in the injured brain, but its delivery is certainly challenging. We propose that EPCs can be labeled with iron oxide superparamagnetic nanoparticles, enhance certain angiogenic abilities and guide them into specific brain areas by using an external magnetic field.

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Section snippets

Synthesis of the SPIONs in organic solvent and ligand transfer to aqueous dispersions

Synthesis of the SPIONs was adapted from a previous procedure of thermal decomposition of an iron precursor in organic media using oleic acid and oleylamine as surfactants.31 Detailed information can be found in the Supplementary Materials. The final material consisted of a stable colloidal nanoparticle dispersion at pH 7.5. A typical batch was made up of 50-nm SPION aggregates, as determined by dynamic light scattering (DLS), and − 40-mV Z-potential values.

Transmission electron microscopy (TEM)

SPIONs were examined using a JEOL1210

SPION characterization

SPIONs were synthesized through thermal decomposition reactions of iron acetylacetonate [Fe(acac)3] to yield nanoparticles, which were stabilized in hexane. SPIONs were found to display an average diameter of 6 nm and a polydispersity of 20% (Figure 1, A). Moreover, a redox titration procedure was used to determine the presence of Fe+ 3 and Fe+ 2 ions (85% and 15%, respectively), revealing a mixed composition of Fe3O4 and γ-Fe2O3. Following synthesis, the SPIONs were transferred to water using

Discussion

In the present study, we demonstrated that the magnetization of EPCs using an aqueous colloidal suspension of SPIONs is safe. In addition, we showed that magnetized OECs from stroke patients retained their ability to form tubes. Strikingly, these SPION-loaded OECs also displayed enhanced migration and secretion of growth factors, such as VEGF and FGF, which was associated with a moderate increase in ROS production. Finally, after intravenous administration of magnetized EPCs, the cells could be

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    Conflicts of interest: The authors have no conflicts of interest to declare.

    Sources of support: A. Rosell is supported by the Miguel Servet program (CP09/00265) from the Spanish Ministry of Health (Instituto de Salud Carlos III) and A.L. by the Ramon y Cajal program 2010. This work has been funded by Instituto de Salud Carlos III: Grant PI10/00694 co-financed by the European Regional Development Fund (ERDF) and the stroke research network RENEVAS (RD06/0026/0010); the Spanish Ministry of Science and Innovation: EUROSALUD program, MAT2012-35324 and CONSOLIDER-Nanoselect-CSD2007-00041; and the European Commission FP7-People-2011-CIG 303630 project.

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