Protective Therapy with Mitochondria Isolated from Mesenchymal Stromal Cells in a Sepsis Model

Abstract

Background & Aim In vivo mitochondrial transfer of mesenchymal stromal cells (MSCs) to immune cells, alveolar and bronchial epithelial cells resulted in metabolic and functional improvements. Thus, we hypothesized that naked mitochondria isolated from MSCs can be internalized by pulmonary structural cells and could be used as systemic therapy in a sepsis model. Methods, Results & Conclusion MSCs-derived mitochondria were incubated with septic murine lung endothelial and epithelial cells. Mitochondrial internalization was assessed by fluorescence microscopy, and its impact on oxidative stress and cellular respiration were evaluated. C57Bl6 mice were divided into control group, sepsis group (CLP, cecal ligation and puncture) and sepsis group with mito-treatment (CLP-mito, intravenous administration of mitochondria derived from 3 × 106 MSCs, 24 hours after CLP). The effects on mortality, pulmonary function and morphometry, liver and kidney histopathological and molecular changes were evaluated after 24 hours of mito-treatment. Mitochondria internalization by septic endothelial and epithelial cells led to reduce oxidative stress which was increased by 250% in endothelial cells and 150% in epithelial cells in CLP mice compared to control. Likewise, by oxygraphy, we analyzed the rate of oxygen consumption (OCR) of these cells. We have seen that, in epithelial cells, only maximal (MR) repolarization was reduced by about 30% after sepsis. In endothelial, both basal (BR) and maximal respiration (MR) were reduced by 50 and 48% respectivelly after sepsis, as well as a significant increase in the proton-leak (PL) rate in relation to the control group (33%). In both cell types, the altered parameters were re-established at control levels after mitocondrial treatment. Mito-treatment induced higher survival rates (60%) and reduced lung elastance (24%). Lung morphometry analysis demonstrated that mito-treatment reversed increases found in septic animals in alveolar collapse (230%), lung neutrophils (90%), lung collagen collagen (300%), elastogenesis (38%). Histological analysis of the liver demonstrates the increase of vacuolization (210%) and inflammatory infiltrate (105%) in septic animals, which were completely normalized after mito-treatment. Treatment also improved sepsis-induced kidney brush border damage (350%) and interstitial edema (205%). This work demonstrates the ability to internalize mitochondria isolated from MSCs by structural cells and the therapeutic potential of mito-treatment in a sepsis model.