Mesenchymal stem cells have previously been shown to mediate brain repair after stroke; they secrete 50–100 nm complexes called extracellular vesicles (EVs), which could be responsible for provoking neurovascular repair and functional recovery. EVs have been observed by electron microscopy and NanoSight, and they contain associated proteins such as CD81 and Alix. This purified, homogeneous population of EVs was administered intravenously after subcortical stroke in rats. To evaluate the EVs effects, we studied the biodistribution, proteomics analysis, functional evaluation, lesion size, fiber tract integrity, axonal sprouting and white matter repair markers. We found that a single administration of EVs improved functional recovery, fiber tract integrity, axonal sprouting and white matter repair markers in an experimental animal model of subcortical stroke. EVs were found in the animals’ brain and peripheral organs after euthanasia. White matter integrity was in part restored by EVs administration mediated by molecular repair factors implicated in axonal sprouting, tract connectivity, remyelination and oligodendrogenesis. These findings are associated with improved functional recovery. This novel role for EVs presents a new perspective in the development of biologics for brain repair.

Extracellular vesicles (EVs) have emerged as important mediators of intercellular communication and as possible therapeutic agents in inflammation-mediated demyelinating diseases, including multiple sclerosis (MS). In the present study, we investigated whether intravenously administered EVs derived from mesenchymal stem cells (MSCs) from human adipose tissue might mediate recovery in Theiler’s murine encephalomyelitis virus (TMEV)-induced demyelinating disease, a progressive model of MS. SJL/J mice were subjected to EV treatment once the disease was established. We found that intravenous EV administration improved motor deficits, reduced brain atrophy, increased cell proliferation in the subventricular zone and decreased inflammatory infiltrates in the spinal cord in mice infected with TMEV. EV treatment was also capable of modulating neuroinflammation, given glial fibrillary acidic protein and Iba-1 staining were reduced in the brain, whereas myelin protein expression was increased. Changes in the morphology of microglial cells in the spinal cord suggest that EVs also modulate the activation state of microglia. The clear reduction in plasma cytokine levels, mainly in the Th1 and Th17 phenotypes, in TMEV mice treated with EVs confirms the immunomodulatory ability of intravenous EVs. According to our results, EV administration attenuates motor deficits through immunomodulatory actions, diminishing brain atrophy and promoting remyelination. Further studies are necessary to establish EV delivery as a possible therapy for the neurodegenerative phase of MS.

Exosomes are gaining importance because they show great promise in therapeutic applications for several diseases. Particularly in stroke, exosomes derived from mesenchymal stem cell (MSC) therapy work as paracrine effectors responsible for promoting neurovascular remodeling and functional recovery. Adult male rats were subjected to intracerebral hemorrhage (ICH) by intrastriatal injection of collagenase type IV; 24 h after surgery, MSC-derived exosomes were administered through the tail vein. The rats were euthanized at 7 or 28 days after treatment. Functional evaluation, lesion size, fiber tract integrity, axonal sprouting and white matter repair markers, biodistribution of exosomes and secretome proteomics were analyzed. DiI-labeled exosomes were found in the brains of the ICH-treated group and in the liver, lung and spleen. Animals receiving treatment with exosomes showed significantly better results in terms of functional recovery, lesion size, fiber tract integrity, axonal sprouting and white matter repair markers compared with the control group 28 days after stroke. Proteomics analysis of the exosomes identified more than 2000 proteins that could be implicated in brain repair function. In conclusion, white matter integrity was partly restored by exosome administration mediated by molecular repair factors. Exosomes as a treatment could be a heterogeneous process by nature and presents many factors that can influence brain plasticity in an adaptable and versatile manner.

Rat adipose tissue-derived-mesenchymal stem cells (rAD-MSCs) have proven to be safe in experimental animal models of stroke. However, in order to use human AD-MSCs (hAD-MSCs) as a treatment for stroke patients, a proof of concept is needed. We analyzed whether the xenogeneic hAD-MSCs were as safe and effective as allogeneic rAD-MSCs in permanent Middle Cerebral Artery Occlusion (pMCAO) in rats. Sprague–Dawley rats were randomly divided into three groups, which were intravenously injected with xenogeneic hAD-MSCs (2 × 106), allogeneic rAD-MSCs (2 × 106) or saline (control) at 30 min after pMCAO. Behavior, cell implantation, lesion size and cell death were evaluated. Brain markers such as GFAP (glial fibrillary acid protein), VEGF (vascular endothelial growth factor) and SYP (synaptophysin) and tumor formation were analyzed. Compared to controls, recovery was significantly better at 24 h and continued to be so at 14 d after IV administration of either hAD-MSCs or rAD-MSCs. No reduction in lesion size or migration/implantation of cells in the damaged brain were observed in the treatment groups. Nevertheless, cell death was significantly reduced with respect to the control group in both treatment groups. VEGF and SYP levels were significantly higher, while those of GFAP were lower in the treated groups. At three months, there was no tumor formation. hAD-MSCs and rAD-MSCs were safe and without side effects or tumor formation. Both treatment groups showed equal efficacy in terms of functional recovery and decreased ischemic brain damage (cell death and glial scarring) and resulted in higher angiogenesis and synaptogenesis marker levels.