Fndc5 modification optimizes the therapeutic effect of rat MSCs on sepsis-induced ALI/ARDS via activating the PI3K/AKT signaling pathway.

BACKGROUND: Acute lung injury/Acute respiratory distress syndrome (ALI/ARDS) is a life-threatening inflammatory lung disorder characterized by high mortality rates and a lack of effective treatment options. Although mesenchymal stem cell (MSC)-based therapies have emerged as a promising approach for ARDS management, optimizing their therapeutic efficacy remains a significant challenge. Recent advances in gene modification techniques have opened new avenues for enhancing MSC functionality. Among these, Fibronectin type III domain-containing protein 5 (Fndc5)/irisin has attracted considerable attention due to its ability to improve endothelial function. This study aims to evaluate the therapeutic potential of Fndc5-modified MSCs in sepsis-induced ALI/ARDS and to elucidate the underlying molecular mechanisms driving their protective effects.

METHODS: To comprehensively evaluate the therapeutic potential of Fndc5-modified MSCs (MSCs-Fndc5) in ARDS, we employed both in vivo and in vitro experimental models. In vivo, a mouse model of sepsis-induced ALI was established through intraperitoneal injection of lipopolysaccharide (LPS), and the protective effects of MSCs-Fndc5 were systematically assessed by analyzing lung histopathology, inflammatory cytokine levels, vascular endothelial integrity, lung wet-to-dry weight ratio, and MSC retention in lung tissue. In parallel, in vitro studies were conducted to investigate the role of MSCs-Fndc5 in mitigating LPS-induced endothelial cell (EC) injury, with a focus on EC proliferation, angiogenesis, barrier permeability, apoptosis, and the regulation of key signaling pathways.

RESULTS: Fndc5 modification significantly increased the retention rate of MSCs in sepsis-induced ALI murine model while augmenting their in vitro proliferation and migration potential. In vivo, treatment with Fndc5-modified MSCs markedly attenuated lung inflammation, as evidenced by reduced levels of pro-inflammatory cytokines, decreased neutrophil infiltration, and improved lung histopathology. Additionally, MSCs-Fndc5 alleviated pulmonary edema, reduced fibrosis, lowered the lung wet-to-dry weight ratio, and preserved vascular endothelial integrity. In vitro, MSCs-Fndc5 significantly enhanced cell proliferation, migration, angiogenesis, endothelial barrier function, apoptosis inhibition, likely via PI3K/AKT pathway activation.

CONCLUSIONS: Fndc5 overexpression in MSCs augments their therapeutic efficacy in sepsis-induced ALI/ARDS, which may be achieved by activating the endothelial PI3K/AKT pathway and improving MSCs retention in vivo. These findings propose MSCs-Fndc5 as a promising therapeutic strategy for sepsis-induced ALI/ARDS by enhancing endothelial repair, curbing inflammation, and modulating pivotal signaling pathways. Further investigation is warranted to explore the clinical applicability of MSCs-Fndc5 therapy for ARDS.