Mesenchymal stem cell treatment alleviates seawater drowning induced lung injury by inhibiting the TNFα/Snail/EMT pathway.

Background: Seawater drowning (SWD) has been an escalating hazard in recent years. It can not only cause immediate death but can also inflict severe complications, such as acute lung injury (ALI), which greatly increases the mortality rate. Thus, investigating the mechanism of SWD induced lung injury and discovering effective treatments is of great importance. The aim of this study was to minimize the lethality and disability of SWD-ALI.

Methods: Using male C57BL/6 mice, we established a SWD induced ALI (SWD-ALI) model via the oral laryngoscopy endotracheal injection (LEI) of artificial seawater. We then administered mesenchymal stem cells (MSCs) via laryngoscopy endotracheal nebulized inhalation. We tested our hypotheses using pulmonary function tests, micro-computed tomography (Micro-CT), hematoxylin and eosin (HE) staining, Masson staining, immunofluorescence, immunoblotting, flow cytometry, transcriptome sequencing, quantitative real-time polymerase chain reaction (qPCR), and enzyme-linked immunosorbent assay (ELISA).

Results: We successfully established the SWD-ALI model via LEI method of seawater. The results indicated that SWD induced severe ALI by activating the Snail-mediated epithelial-mesenchymal transition (EMT) pathway through the tumor necrosis factor alpha (TNFα) inflammatory response. Further, we administered transoral laryngoscopy endotracheal nebulization to the SWD mice treated with inhaled MSCs. Non-invasive pulmonary function tests revealed that the respiratory symptoms and respiratory function of the mice were significantly alleviated. Additionally, the histological injury and air-blood barrier, and inflammatory response were significantly mitigated, and TNFα-mediated Snail expression was significantly down-regulated. Importantly, we used Masson staining to examine mouse lung tissue after 28 days of drowning and found that the SWD mice suffered from significant long-term pulmonary fibrosis injury, and MSCs treatment significantly attenuated the degree of fibrosis.

Conclusions: Our research revealed that SWD triggered severe ALI, followed by long-term pulmonary fibrosis. However, treatment with nebulized MSCs significantly mitigated the ALI and slowed the progression of fibrosis.