Extracellular vesicles derived from clonally expanded immortalized mesenchymal stromal cells reduce neuroinflammation in a pre-clinical model of sepsis-associated encephalopathy

Sepsis is an exacerbated host response against an infection. Sepsis-associated encephalopathies (SAE) are neurological complications which occur during or after sepsis events. Currently, there is no treatment available for SAE-induced neurological damage. Therefore, it is necessary to investigate new therapeutic approaches. Mesenchymal stromal cells (MSCs) have a well-established immunomodulatory capacity. Our group demonstrated MSC administration reduces neuroinflammation and cognitive damage caused by SAE. Moreover, conditioned media from MSCs reduces astrogliosis in vitro, suggesting a paracrine mechanism of action. MSCs release extracellular vesicles (EVs), containing proteins, nucleic acids, and lipids that may confer therapeutic properties to recipient cells. The aim of the present study was to evaluate the effects of intravenous clonally-expanded immortalized MSC-derived EVs on sepsis-induced neuroinflammation. Our model consisted in male adultC57Bl0/6 mice that underwent cecal ligation and puncture (CLP) surgery for sepsis induction versus sham-surgeries. All mice received antibiotics, fluid resuscitation and pain medication. Six hours after surgery, mice were randomized to MSC-EVs versus placebo (platelet-derived EVs) or equal volume saline. Outcomes were measured 72 hours post-CLP. MSC-EV administration resulted in improved survival, reduced expression of inflammatory mediators in the circulation, lungs and hearts,and histological evidence of reduced astrogliosis and microglial activation in the cortex and hippocampus. At 72 hours, we did not detect changes in the local synthesis of pro-inflammatory mediators, assessed by qPCR. In cultured microglial cells (BV2 cells) stimulated with LPS, MSC-EVs resulted in decreased IL-6 and IL-1bgene expression; this effect could be blocked by Dynasore-an inhibitor of clathrin/dynamin-mediated endocytosis. Taken together our results suggest a single dose-therapy with MSC-EVs reduced peripheral inflammation, neuroinflammation, and improved survival from CLP-induced sepsis. In vitro, MSC-EV-mediated reduction in pro-inflammatory gene expression was in part dependent upon MSC-EV uptake, highlighting the potential of EVs as tissue-specific targeted therapies.