Stem Cell-Derived Exosomes Protect Astrocyte Cultures From in vitro Ischemia and Decrease Injury as Post-stroke Intravenous Therapy.

Xiaoyun Sun,Phillip C Yang,Ji-Hye Jung,Oiva Arvola,Michelle R Santoso,Creed M Stary,Rona G Giffard

doi:10.3389/fncel.2019.00394

Abstract

In the present study, we assessed efficacy of exosomes harvested from human and mouse stem cell cultures in protection of mouse primary astrocyte and neuronal cell cultures following in vitro ischemia, and against ischemic stroke in vivo. Cell media was collected from primary mouse neural stem cell (NSC) cultures or from human induced pluripotent stem cell-derived cardiomyocyte (iCM) cultures. Exosomes were extracted and purified by polyethylene glycol complexing and centrifugation, and exosome size and concentration were determined with a NanoSiteTM particle analyzer. Exosomes were applied to primary mouse cortical astrocyte or neuronal cultures prior to, and/or during, combined oxygen-glucose deprivation (OGD) injury. Cell death was assessed via lactate dehydrogenase (LHD) and propidium iodide staining 24 h after injury. NSC-derived exosomes afforded marked protection to astrocytes following OGD. A more modest (but significant) level of protection was observed with human iCM-derived exosomes applied to astrocytes, and with NSC-derived exosomes applied to primary neuronal cultures. In subsequent experiments, NSC-derived exosomes were injected intravenously into adult male mice 2 h after transient (1 h) middle cerebral artery occlusion (MCAO). Gross motor function was assessed 1 day after reperfusion and infarct volume was assessed 4 days after reperfusion. Mice treated post-stroke with intravenous NSC-derived exosomes exhibited significantly reduced infarct volumes. Together, these results suggest that exosomes isolated from mouse NSCs provide neuroprotection against experimental stroke possibly via preservation of astrocyte function. Intravenous NSC-derived exosome treatment may therefore provide a novel clinical adjuvant for stroke in the immediate post-injury period.

Highlights

Stroke remains the second-leading cause of death worldwide, with ischemic/embolic stroke accounting for ∼87% of total stroke occurrence (Benjamin et al, 2019)
We first assessed in vitro the protective effect of mouse neural stem cell (NSC)- and human cardiac induced pluripotent stem cell-derived cardiomyocyte (iCM)-derived exosomes in primary mouse astrocyte cultures subjected to ischemic injury
We observed that application of human cardiac iCM-derived exosomes was protective in primary mouse astrocytes

Summary

Introduction

Stroke remains the second-leading cause of death worldwide, with ischemic/embolic stroke accounting for ∼87% of total stroke occurrence (Benjamin et al, 2019). Early restoration of cerebral blood flow with thrombolytics remains the only effective intervention to minimize the evolution of injury. The failure to develop novel adjuvant therapies may lie in a historical focus on genes and cell-signaling pathways that are predominant in terminally differentiated cells. Neural progenitor cells persist in the adult brain and recent evidence (Peron and Berninger, 2015) describes latent neurogenic pathways re-activated after ischemic injury that act to preserve and restore neuronal function. In the setting of stroke therapy, the beneficial outcomes of stem cell therapy have been localized to their paracrine effects, and not mediated by cell replacement or transplanted cell differentiation (Chen et al, 2014; Xin et al, 2014). A more immediate focus has been delineating the cellular mechanisms of the stem cell secretome

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Conclusion