Mesenchymal Stem Cell Secretome Mitigates Inflammatory Endothelial Dysfunction

BACKGROUND: Endothelial cells (EC) dysfunction and barrier disruption are central drivers of inflammatory lung injury and adverse outcomes, yet targeted therapies remain lacking. We tested the hypothesis that a mesenchymal stem cell (MSC)-derived secretome can directly preserve EC function under inflammatory stress. We evaluated AlloEx (Vitro Biopharma), a Wharton's Jelly MSC-derived secretome enriched in bioactive RNAs, proteins, lipids, and extracellular vesicles with pro-reparative and immunomodulatory activity. METHODS: Human lung microvascular endothelial cells (HLMVEC) were exposed to TNFα (4 h) with AlloEx administered 30 min before or after TNFα stimulation. EC thromboinflammatory gene expression was quantified by qPCR. Barrier integrity was assessed by transendothelial resistance (TEER) and VE-cadherin immunofluorescence. Mitochondrial function was evaluated using MitoSOX, TMRM, and mitochondrial fission imaging. Proteomic profiling was performed using trauma patient plasma as a clinically relevant inflammatory stimulus. RESULTS: AlloEx potently suppressed TNFα-induced EC activation, markedly reducing ICAM1, SELE, IL6, NOS3, ANG2, TEK, VEGFA, and F3 expression. Functionally, AlloEx rescued EC barrier integrity, preserving VE-cadherin localization at endothelial junctions and restoring TEER by 79% with pretreatment and 65% with post-treatment. Mechanistically, AlloEx prevented mitochondrial dysfunction, limiting reactive oxygen species generation, preserving membrane potential, and reducing fission. Proteomic profiling demonstrated that AlloEx induced coordinated remodeling of metabolic, vesicular, and inflammatory signaling pathways while suppressing cellular stress and pro-inflammatory signaling. CONCLUSION: These findings identify MSC-derived secretome therapy as a potent modulator of EC thromboinflammatory activation, barrier integrity, and mitochondrial function. AlloEx represents a promising, clinically translatable strategy to target EC dysfunction in inflammatory lung injury and trauma-associated endotheliopathy.