MicroRNA-17–92 Cluster in Exosomes Enhance Neuroplasticity and Functional Recovery After Stroke in Rats

Abstract

Background and Purpose Multipotent mesenchymal stromal cell (MSC) harvested exosomes are hypothesized as the major paracrine effectors of MSCs. In vitro, the miR-17-92 cluster promotes oligodendrogenesis, neurogenesis and axonal outgrowth. We therefore investigated whether the miR-17-92 cluster enriched exosomes (Exo-miR-17-92+) harvested from MSCs transfected with a miR-17-92 cluster plasmid enhance neurological recovery compared to control MSC derived exosomes (Exo-Con). Methods Rats subjected to 2 hours of transient middle cerebral artery occlusion (MCAO) were intravenously administered Exo-miR-17-92+, Exo-Con, or liposomes, and were sacrificed 28 days post MCAO. Histochemistry, immunohistochemistry and Golgi-Cox staining were used to assess dendritic, axonal, synaptic and myelin remodeling. Expression of phosphatase and tensin homolog (PTEN) and activation of its downstream proteins, protein kinase B (PKB or Akt), mechanistic target of rapamycin (mTOR), and glycogen synthase kinase 3 beta (GSK-3β) in the peri-infarct region were measured by means of Western blots. Results Compared with the liposome treatment, both exosome treatment groups exhibited significant improvement of functional recovery, but Ex-miR-17-92+ treatment had significantly more robust effects on improvement of neurological function, and enhancements of oligodendrogenesis, neurogenesis and neurite remodeling/neuronal dendrite plasticity in the ischemic boundary zone (IBZ) than the Ex-Con treatment. Moreover, Ex-miR-17-92+ treatment substantially inhibited PTEN, a validated miR-17-92 cluster target gene, and subsequently increased the phosphorylation of PTEN downstream proteins, Akt, mTOR and GSK-3β compared to Ex-Con treatment. Conclusions Our data suggest that treatment of stroke with tailored exosomes enriched with the miR-17-92 cluster increases neural plasticity and functional recovery after stroke, possibly via targeting PTEN to activate the PI3K/Akt/mTOR/GSK-3β signaling pathway.

Concise Review: Extracellular Vesicles Overcoming Limitations of Cell Therapies in Ischemic Stroke

“…In vitro experiments using oxygen‐glucose‐deprivation suggested that the enhanced action of miR‐133b containing EVs may be due to stimulation of secondary EV release from astrocytes . In another study, EVs harvested from MSCs transfected with a miR‐17‐92 cluster plasmid induced better neurological recovery when compared with EVs derived from naïve MSCs . These observations stress the heterogeneity of EV actions depending on the loading of EVs with survival and plasticity promoting molecules.…”

“…To the best of the authors' knowledge, six different studies have examined effects of EVs in ischemic stroke models, most in rats and one in mice . In the first rat study, Chopp and colleagues intravenously applied MSC‐EVs in a model of transient intraluminal middle cerebral artery occlusion.…”

Cell-Based and Exosome Therapy in Diabetic Stroke

“…Over the last few years, exosomes have emerged as a major mediator of cell therapy derived therapeutic benefits, personalized targeted drug delivery vehicles, as well as a biomarker and promising treatment option for several neurological diseases 26, 27, 28, 29. Transplanted stem cells and exosomes stimulate host brain parenchymal cells to generate a plethora of cytokines, growth factors and trophic factors which promote endogenous brain repair mechanisms while suppressing apoptotic signaling and inflammatory responses 27, as summarized in Figure 2.…”

“…Favoring clinical translation, a large quantity of exosomes can be derived from a small quantity of cells; exosomes are stable and can be stored; exosomes can pass the BBB; and exosomes do not elicit immune rejection. Exosomes mediate benefit by transferring genetic instructions, often via microRNA to concurrently stimulate and activate multiple restorative pathways 28, 29. Therefore, by modifying microRNA content, exosomes can be programmed to target specific restorative and protective pathways within recipient and target cells and systemic administration of exosomes may be a means to deliver designer genetic instructions as well as the active components of cell‐based therapy to the central nervous system [27].…”

“…In vitro studies show that microRNA‐17–92 cluster promotes oligodendrogenesis, neurogenesis, and axonal outgrowth 28; and miR‐133b transferred via exosomes to astrocytes and neurons increases neurite outgrowth 43. In addition, treatment of stroke with exosomes derived from miR‐133b‐overexpressed MSCs as well as miR‐17–92 cluster enriched exosomes were found to significantly improve brain plasticity and post stroke functional outcome compared to treatment with MSC derived exosomes 28, 29. Optimizing the microRNA content of MSC derived exosomes to maximize therapeutic potential is of prime interest.…”