Introduction: Extracellular vesicles such as exosomes has opened a new field of research. Exosomes are able to transfer DNAs, mRNAs, microRNAs, non-coding RNAs, proteins, trophic factors and lipids associated with brain plasticity enhancement after stroke.
Aim: To investigate white matter repair after exosomes administration in two experimental models of subcortical stroke: ischemic and hemorrhage.
Material/Methods: Subcortical ischemic stroke was induced by Endothelin-1 and Collagenase IV was used to induce subcortical hemorrhagic stroke into striatum. Intravenous exosomes or saline only were administrated at 24h after cerebral infarct as treatment. Exosomes were isolated from culture of adipose mesenchymal stem cell and they were characterized by Nanoshight, Electronic microscope, Western blot and Immunofluorescence. Proteins contained into exosomes were analyzed by Orbitrab. We analyzed functional recovery by Rotarod, beam walking and Rogers tests. Lesion volume and tract connectivity were studied by magnetic resonance image. Anterograde and retrograde tracers were used to analyze axonal sprouting. Myelin formation was analyzed by cryomielin.
Results: Proteomics analysis of exosomes identified more than 1400 proteins, many of them involved in intercellular communication. DiI labeled-Exosomes were detected in brain and peripheral organs (liver, lung and spleen). After 28 days, treated groups showed smaller functional deficit compared to control groups in both hemorrhagic and ischemic models. Moreover, treated group showed an increase in tract connectivity at 7 and 28 days compared to control groups. Also, animals which received exosomes showed an increase axonal sprouting and myelin formation at 28 days after stroke in both hemorrhagic and ischemic stroke. The treated groups also showed higher levels of white matter-associated markers in the injured area than the control groups.
Conclusion: White matter integrity in different subcortical strokes is in part restored by exosomes treatment, probably mediated by repair molecular factors implicated in axonal sprouting, remyelination and oligodendrogenesis. These findings are associated with improved functional recovery in both kinds of strokes.