Human Umbilical Cord Mesenchymal Stem Cells Alleviate LPS-Induced Acute Lung Injury in Mice: Association with TLR4/MyD88/NF-κB Pathway Suppression

Objective: In a lipopolysaccharide (LPS)-induced acute lung injury (ALI) mouse model, the present study sought to assess the therapeutic efficacy of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) and characterize their anti-inflammatory mechanistic basis. Methods: Forty mice were randomly divided into four groups: control, LPS model, LPS + DEX (positive control), and LPS + hUC-MSCs. Except for the control group, mice received intratracheal instillation of LPS to establish ALI. One hour after LPS administration, animals in the hUC-MSC group were intravenously infused with hUC-MSCs. The positive control group was given an intraperitoneal injection of DEX for 3 consecutive days, starting at 24 h after modeling. On day 4 after cell transplantation or at 24 h after the completion of DEX injection, lung function indicators were detected. Bronchoalveolar lavage fluid (BALF), serum, and lung tissues were subsequently obtained for evaluation of inflammatory cell infiltration, histopathological injury, lung wet-to-dry (W/D) ratio, and cytokine levels. Additionally, the localization of transplanted hUC-MSCs in lungs was examined, and the mRNA and protein expression levels of TLR4, MyD88, and NF-κB p65 were quantified. Results: LPS exposure markedly impaired pulmonary function and induced robust inflammatory responses, evidenced by elevated levels of pro-inflammatory cytokines, increased inflammatory cell counts in BALF and serum, and extensive histological lung damage. Moreover, hUC-MSC injection improved lung function, decreased inflammatory cytokine production and alleviated pulmonary edema, while inhibiting the TLR4/MyD88/NF-κB pathway at transcriptional and protein levels. Conclusions: Intravenous hUC-MSC administration alleviates LPS-induced ALI in mice, an effect associated with suppression of the TLR4/MyD88/NF-κB cascade. These results indicate that this signaling cascade partially mediates the observed anti-inflammatory effects.