Stem Cell-Derived MP/Exosomes

It was shown that administration of exosomes derived from multipotent mesenchymal stromal cells promoted recovery following stroke in a rat model [146]. In a related study, the benefit was attributed to the presence of a micro-RNA (MiR-133b) bound to the exosomes [147]. Others had previously shown the presence of MMP-9 and FGF-2 on mouse MP derived from angioblast stem cells [60]. Most recently, it was reported that MP from endothelial progenitor cells protected against complement-mediated glomerulonephritis [148]. Also recently, traumatic brain injury (TBI) was found to respond very favorably to administration of exosomes derived from mesenchymal stem cells [149]. MP-mediated inflammatory signaling is well summarized by de Rivero et al., in terms of the inflammasome [83].

Conversely, it was shown that MP from ischemic mice induce apoptosis of endothelial cells (EC); this effect was not caused by oxidative stress but instead involved caspase3, since inhibition of caspase reduces cell death [150]. This experimental design could be applied to evaluate harm from MP in neurodegenerative diseases. Those authors define MP as <400 nm in size and demonstrate activation of TNF-a and TRAIL pathways. Hayon et al. provide a broadly informative summary of the role of MP in rehabilitation of ischemic brain [151], with emphasis on factors from platelets and their PMP. Camussi et al. discuss transfer of genetic information via MP/exosomes to result in “epigenetic reprogramming” of cells [152].

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