Augmented neovascularization with magnetized endothelial progenitor cells in rats with hind-limb ischemia

Augmenting neovascularization with the use of endothelial progenitor cells (EPCs) is a therapeutic option to rescue critical limb ischemia (CLI). However, the outcomes have been not so satisfactory. The detectable number of injected EPCs at the ischemic site is rather small. If EPCs accumulate more and stay longer there, neovascularization will be augmented. In this study, we tested whether external magnetic forces (EMFs) accumulated magnetized EPCs (Mag-EPCs) at the ischemic site and thereby augmented neovascularization. We cultured peripheral blood-derived mononuclear cells to obtain EPCs and generated Mag-EPCs by a magnetofection method with nanoparticles. Prussian-blue staining revealed magnetic nanoparticles incorporated into the cytoplasms and nuclei of Mag-EPCs. The survival rate of Mag-EPCs at day 9 of culture was 98.7%, indicating no cell toxicity of magnetic nanoparticles. EMFs augmented adhesion capacity of Mag-EPCs not only in the static but also in the flow condition in vitro, compared to without EMFs. The migration capacity of Mag-EPCs with EMFs was 160% more than EPCs or Mag-EPCs without them. After an intravenous injection of Mag-EPCs into the rat with hind-limb ischemia, the recovery of blood flow and capillary density in the ischemic limb were significantly more (p < 0.01) with EMFs than without them. EMFs augmented neovascularization capacity of Mag-EPCs compared to EPCs alone. This method could be a new therapeutic strategy for patients with CLI.

Research highlights
► Neovascularization by endothelial progenitor cells (EPCs) rescues ischemic limbs.
► Poor accumulation of EPCs at the ischemic site may lead to insufficient effects.
► We magnetized EPCs and systemically injected them to rats with ischemic limbs.
► An external magnetic force accumulated the magnetized EPCs at ischemic limbs.
► This method augmented neovascularization without adverse effects for internal organs.