400 - Human Mesenchymal Stem Cell Derived Extracellular Vesicles Attenuate Sepsis-Induced Acute Lung Injury via Immune Modulation

Publication Number: 2389.400

Maria Triantafyllou, Children's National Health System, Washington, DC, United States; Nora Wolff, Children's National Research Institute, Washington, DC, United States; Garrett G. Denney, Children's National Health System, Washington, DC, DC, United States; Dylan Crawford, Seattle Children's, Seattle, WA, United States; Georgios Sanidas, Children National Hospital, Washington, DC, United States; Gabriele Simonti, Children's National Health System, Washington, DC, United States; Vittorio Gallo, Seattle Childrens Hospital, Seattle, WA, United States; Panagiotis Kratimenos, Children's National Health System, Washington, DC, United States; Ioannis Koutroulis, Children's National Health System, Washington, DC, United States

Background: Sepsis is a leading cause of morbidity and mortality in critically ill children, often progressing to multi-organ failure. The lung is typically the first organ affected, with acute lung injury (ALI) driven by uncontrolled immune activation and endothelial disruption. Despite advances in pediatric critical care, there are no targeted therapies that directly address the immune and vascular dysfunction underlying sepsis-associated ALI. Mesenchymal stem cells have shown therapeutic promise in studies of ALI, but the mechanisms responsible for their protective effects remain poorly defined.

Objective: To determine whether human mesenchymal stem cell–derived extracellular vesicles (MSC-EVs) mitigate sepsis-induced ALI in a murine model of polymicrobial sepsis.

Design/Methods: Male C57BL/6 mice were subjected to cecal slurry-induced polymicrobial sepsis and controls received equivalent volume of PBS. Clinical status was assessed every two hours post-injection using a validated scoring system incorporating respiratory parameters. Six hours post-intraperitoneal injection, mice received an intravenous tail vein injection of either MSC-EVs or EV-depleted media. This resulted in four experimental groups: control, control MSC-EVs, sepsis and sepsis MSC-EVs. Mice were euthanized 24 hours post-sepsis induction. Lung tissue was harvested from all animals (n=4 per group) for subsequent histopathological, flow cytometric, and transcriptomic analyses (Fig1A).

Results: MSC-EVs reduced overall illness severity and improved respiratory performance (Fig1B-C). On the tissue level there was a clear attenuation of injury (diminished perivascular cuffing and fewer microthrombi Fig1D-E). Flow cytometry demonstrated a shift towards immune-surveillance phenotype, marked by increased interstitial CD11b⁺CX3CR1⁺ macrophages and a rise in surveillant CD4⁺T cells, alongside a reduction in cytotoxic CD8⁺T cells (Fig2). Molecular profiling revealed down-regulation of pro-inflammatory signaling and up-regulation of immunoregulatory and vascular-repair programs, with accompanying enhancements in metabolic/energy-homeostasis pathways.

Conclusion(s): MSC-EVs mitigate sepsis-associated ALI by modulating the immune response and promoting tissue repair. EVs likely exert these beneficial effects by delivering bioactive molecules, such as miRNAs to recipient cells. This targeted delivery results in reduced inflammation, a more balanced immune response, and enhanced tissue regeneration.

Figure 1: MSC-EVs are effective in ameliorating respiratory performance and mitigating lung injury during sepsis.
PAS figure 1 Triantafyllou.pdf(A) Experimental overview (B) Overall clinical performance at harvest (C) Respiratory clinical performance at harvest (D) Representative hematoxylin & eosin-stained mouse lung tissue showing perivascular cuffs and microthrombi (E) Morphological assessment score of H&E-stained mouse lung tissue.

Figure 2: Redistribution of immune cell populations and endothelial preservation after MSC-EVs in the lung of septic mice.
PAS Figure 2 Triantafyllou.pdf(A) CD11b+ (B) CD11b^veryhiCX3CR1+ (C) CD4+ (D) CD4+CD62L+ (E) CD8+ (F) CD8+CD44^hi (G) CD8+CD62L+ (H) CD31^hi