Title: Extracellular vesicles from mesenchymal stem cells reverse neuroinflammation and cognitive and motor impairment in rats with mild liver damage

Autor: Gergana Mincheva Ganeva

Director: Vicente Felipo y Marta Llansola

Tutor: Carmina Montoliu

Abstract: Cirrhotic patients may develop minimal hepatic encephalopathy (MHE), with mild cognitive impairment, psychomotor slowing and motor incoordination, that reduce their life quality and span. Mild cognitive impairment in patients with no-alcoholic fatty liver disease (NAFLD) has been also recently reported. Human mesenchymal stem cells derived extracellular vesicles (MSC-EVs) have been proposed as therapy for different diseases including liver injury and neurodegenerative diseases, due to their immunomodulatory, anti-inflammatory and regenerative properties. The administration of carbon tetrachloride (CCl4) to rats is a model of progressive liver damage and hepatic encephalopathy (HE). The aim of this study was to assess if MSC-EVs reverse cognitive and motor impairment in rats with mild liver damage induced by CCl4 and MHE, as a model of NAFLD, and to assess the underlying mechanisms. In addition, we assessed if TGF-β, main component of MSC-EVs and with anti-inflammatory properties, has a role in the effects of MSC-EVs.

Mild liver damage was induced by intraperitoneal injection of CCl4 during four weeks. MSC-EVs were isolated from human adipose tissue-derived stem cells and also from these cells after silencing TGF-β expression to assess the role of TGF-β. MSC-EVs were injected intravenously the second and the third weeks of CCl4 treatment. Cognitive and motor functions were assessed. Glutamatergic and GABAergic neurotransmission and neuroinflammation in the cerebellum and the hippocampus were analysed by immunohistochemistry and Western blot. Peripheral inflammation, liver damage and gut microbiota were also analyzed.

MSC-EVs improve spatial learning and memory and working memory in rats with mild liver damage reducing neuroinflammation and normalizing some alterations in glutamatergic and GABAergic neurotransmission in the hippocampus. MSC-EVs improve motor coordination and altered locomotor gait by reducing neuroinflammation and the activation of pathways induced by TNFα that lead to GABAergic neurotransmission alterations. MSC-EVs also reduce peripheral inflammation, liver steatosis and fibrosis, and liver inflammation and counteract some consequences of gut dysbiosis. These effects are different depending on if the EVs proceed from unmodified MSCs or from MSCs with silenced TGF-β, indicating that this modification and the presence of TGF-β, that should also affect the rest of his cargo, is determinant to the effects of MSCs-EVs and the involved mechanisms.

MSC-EVs could be a promising therapy for MHE, and also for other diseases involving similar pathological mechanisms, such as diseases associated with sustained peripheral inflammation and neuroinflammation.