Abstract Rationale Pneumonia remains a major global health concern, associated with high rates of morbidity and mortality and having its treatment mainly restricted to antibiotics. Multilineage-differentiating Stress-Enduring (MUSE) cells are a unique subpopulation of mesenchymal stem cells (MSCs) exhibiting immunomodulatory and regenerative properties that may enhance host defense mechanisms, mitigate inflammation, and promote lung tissue repair. Beyond the known antimicrobial properties of MSCs, their ability to modulate the immune response and support tissue regeneration suggests a potential role in preventing pneumonia complications such as residual inflammation, which is a key factor in poor prognosis. This study aims to identify the therapeutic and immunomodulatory effects of MUSE cells as a novel approach for pulmonary infection. Methods MUSE cells were isolated from human lipoaspirate derived MSCs by Magnetic Activated Cell Sorting (MACS) and their marker expression was confirmed in the total population by flow cytometry. Cells were cultured in serum-free media for 24h to collect conditioned media (CM), and their therapeutic potential tested in a human pulmonary epithelial cell line (A549) injury model through cell viability (AlamarBlue), wound-healing, inflammatory response assays, and quantification of secreted cytokines by ELISA. To assess antimicrobial properties of MUSE, CM was added to a known number of colony forming units of Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae and Streptococcus pneumoniae and the proliferation determined by spectrophotometry. Results Unstimulated MUSE cells display enhanced properties over conventional MSC populations. Results show very similar therapeutic properties to cytokine pre-activated MSCs, both in inhibiting bacterial growth and in the assays performed to evaluate lung tissue level effects using pulmonary epithelial cells. There was an improvement in inflammation markers (NF-κB, IL-8, IL-6, and TNF-α), inhibition of bacterial growth, and cellular metabolism when compared to the injury control group. Conclusion The results demonstrate that MUSE cells in their naive state are capable of mitigating important indices of injury and inflammation in the context of pulmonary infection, proving to be promising candidates for a more comprehensive investigation into their utilization in pneumonia caused by antimicrobial-resistant bacteria. This abstract is funded by: European Defense Fund
Santos et al. (2026) studied this question.