In a rat study, giving newborn rats human umbilical‑cord stem cells after a bacterial infection helped more of them survive and cleared the bacteria faster. The treatment also raised levels of the natural antimicrobial peptide LL‑37 in the blood, but the work was done in newborn rats with sepsis, not in healthy adults.

Sepsis is the main cause of morbidity and mortality in neonates. Mesenchymal stromal cells (MSCs) are potent immune-modulatory cells. Their effect in neonatal sepsis has never been explored. We hypothesized that human umbilical cord-derived MSCs (hUC-MSCs) improve survival in experimental neonatal sepsis. Sepsis was induced in 3-day-old rats by intravenous injection of Escherichia coli (5 × 10⁵/rat). One hour after infection, rats were treated intravenously with normal saline, hUC-MSCs, or with interferon-γ preconditioned hUC-MSCs (10⁷ cells/kg). Eighteen hours after infection, survival, bacterial counts, lung neutrophil and macrophage influx, phagocytosis and apoptosis of splenocytes plasma, and LL-37 concentration were evaluated. Animals were observed for survival for 72 h after E. coli injection. Treatment with either hUC-MSCs or preconditioned hUC-MSCs significantly increased survival (hUC-MSCs, 81%; preconditioned hUC-MSCs, 89%; saline, 51%; P < 0.05). Both hUC-MSCs and preconditioned hUC-MSCs enhanced bacterial clearance. Lung neutrophil influx was decreased with preconditioned hUC-MSCs. The number of activated macrophages (CD206⁺) in the spleen was increased with hUC-MSCs and preconditioned hUC-MSCs; preconditioned hUC-MSCs increased the phagocytic activity of CD206⁺ macrophages. hUC-MSCs and preconditioned hUC-MSCs decreased splenocyte apoptosis in E. coli infected rats. Finally, LL-37 plasma levels were elevated in neonatal rats treated with hUC-MSCs or preconditioned hUC-MSCs. hUC-MSCs enhance survival and bacterial clearance in experimental neonatal sepsis. hUC-MSCs may be an effective adjunct therapy to reduce neonatal sepsis-related morbidity and mortality.