Human mesenchymal stem cell-derived iron oxide exosomes allow targeted ablation of tumor cells via magnetic hyperthermia.

Magnetic hyperthermia, or the heating of tissues using magnetic materials, is a promising approach for treating cancer. We found that human mesenchymal stem cells (MSCs) isolated from various tissues and MSCs expressing the yeast cytosine deaminase∷uracil phosphoribosyl transferase suicide fusion gene (yCD∷UPRT) can be labeled with Venofer, an iron oxide carbohydrate nanoparticle. Venofer labeling did not affect cell proliferation or the ability to home to tumors. All Venofer-labeled MSCs released exosomes that contained iron oxide. Furthermore, these exosomes were efficiently endocytosed by tumor cells. Exosomes from Venofer-labeled MSCs expressing the yCD∷UPRT gene in the presence of the prodrug 5-fluorocytosine inhibited tumor growth in a dose-dependent fashion. The treated tumor cells were also effectively ablated following induction of hyperthermia using an external alternating magnetic field. Cumulatively, we found that magnetic nanoparticles packaged into MSC exosomes are efficiently endocytosed by tumor cells, facilitating targeted tumor cell ablation via magnetically induced hyperthermia.

Exosomes of human mesenchymal stem/stromal/medicinal signaling cells.

In this review, we intend to explore the potential therapeutic effects of exosomes released from mesenchymal stem/stromal cells (MSCs). MSCs gained credibility as a therapeutic tool due to their potential to differentiate into many cell types like osteoblasts, chondrocytes, adipocytes, muscular, endothelial, cardiovascular, and neurogenic cells. They possess potent wound healing activity due to their immunosuppressive and anti-inflammatory properties. MSCs are tested in large number of clinical trials for treatment of diseases, which do not have adequate therapy at present. MSCs engineered to express suicide genes in preclinical studies have shown promising tumor targeting therapeutic tool for malignancies difficulty treatable at present. It has been increasingly observed in many different kinds of regenerative medicine and in MSCs mediated prodrug gene therapy for cancer that the intravenously administered of MSCs did not necessarily engraft at the site of injury or tumor. The therapeutic effect was exerted mainly through a paracrine action of rich secretome released from the cells. The main biocomponent of secretome are exosomes - naturally occurring membrane nanoparticles of 30-120 nm in diameter that mediate intercellular communication by delivering biomolecules like mRNA, miRNA into recipient cells. These nanosized exosomes derived from MSCs promise to be a new and valuable therapeutic strategy in regenerative medicine and cancer therapy compared with transplanted exogenous MSCs. Advantage of nanosized exosomes compared with administration of exogenous MSCs is multiple. Exosomes are easier to preserve and be transferred, have lower immunogenicity and therefore are safer for therapeutic administration.

Dental pulp mesenchymal stem/stromal cells labeled with iron sucrose release exosomes and cells applied intra-nasally migrate to intracerebral glioblastoma.

We report on a simple iron oxide (Venofer) labeling procedure of dental pulp mesenchymal stem cells (DP-MSCs) and DP-MSCs transduced with yeast cytosinedeaminase::uracilphosphoribosyltransferase (yCD::UPRT-DP-MSCs). Venofer is a drug approved for intravenous application to treat iron deficiency anemia in patients. Venofer labeling did not affect DP-MSCs or yCD::UPRT-DP-MSCs viability and growth kinetics. Electron microscopy of labeled cells showed internalized Venofer nanoparticles in endosomes. MRI relativity measurement of Venofer labeled DP-MSCs in a phantom arrangement revealed that 100 cells per 0.1 ml were still detectable. DP-MSCs or yCD::UPRT-DP-MSCs and the corresponding Venofer labeled cells release exosomes into conditional medium (CM). CM from yCD::UPRT-DP-MSCs in the presence of a prodrug 5-fluorocytosine caused tumor cell death in a dose dependent manner. Iron labeled DP-MSCs or yCD::UPRT-DP-MSCs sustained their tumor tropism in vivo; intra-nasally applied cells migrated and specifically engrafted orthotopic glioblastoma xenografts in rats.