ET-33PLACENTA-DERIVED MESENCHYMAL STEM CELLS AND THEIR SECRETED EXOSOMES INHIBIT THE SELF-RENEWAL AND STEMNESS OF GLIOMA STEM CELLS IN VITRO AND IN VIVO

Mesenchymal stromal cells (MSCs) are multipotent stem cells that can be obtained from bone marrow and adipose tissues or from other sources such as placenta and umbilical cord. The latter allow the potential use of universal, allogeneic cell therapy because to reduced antigenicity due to low expression of MHC class II molecules. MSCs can be easily expanded in vitro for therapeutic applications and their safety and therapeutic impact have been demonstrated in various pre-clinical and clinical studies. MSCs have been shown to cross the blood brain barrier and migrate to sites of experimental GBM and can deliver cytotoxic compounds that exert anti-tumor effects. In this study we examined the effects of placenta-derived MSCs and their secreted exosomes on GSCs in vitro and in vivo. Conditioned medium of placenta MSCs or their derived exosomes decreased the self-renewal, stemness markers, Sox2 and Oct4 and the migration of these cells. Similarly, intracranial administration of the MSCs decreased the tumor volume of GSC-derived xenografts and prolonged animal survival. miRNA sequencing analysis of placenta MSC-derived exosomes revealed a set of specific miRNAs that were downregulated in GSCs and that acted as tumor suppressor in these cells. We demonstrated delivery of some of these miRNAs to GSCs following treatments with MSC-derived exosomes. We further demonstrated that MSCs or exosomes that were loaded with exogenous miR-124 delivered high levels of this miRNA into glioma cells as detected by a novel quantitative miRNA reporter. Moreover, administration of placenta MSCs loaded with exogenous miR-124 exerted a strong inhibitory effect on GSC-derived xenograft growth. These results demonstrate that placenta-derived MSCs may have important clinical applications in stem cell-based glioma therapeutics. Moreover, these studies provide a novel approach for the targeted delivery of endogenous and exogenous anti-tumor miRNAs to glioma cells as a miRNA replacement therapy for GBM.