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

Abstract

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.

1. Introduction

Acute Respiratory Distress Syndrome (ARDS) is a critical condition characterized by rapid, widespread lung inflammation, leading to severe respiratory failure [1], whereas acute lung injury (ALI) was previously used to describe a milder form of this condition prior to the 2012 Berlin definition reclassification [2]. ARDS, a heterogeneous syndrome with various underlying pathologies, is most commonly a complication of pneumonia or sepsis [3]. This syndrome poses a significant challenge to healthcare systems due to its high mortality rates and the limited therapeutic options beyond supportive care [4]. Despite significant advancements in supportive care, effective therapeutic options for ARDS remain scarce, highlighting the urgent need for innovative treatments [5]. Mesenchymal stromal cells (MSCs) have emerged as a promising therapeutic option for ARDS, owing to their immunomodulatory, anti-inflammatory, and tissue regenerative properties [6–9].

MSC therapy has shown potential in preclinical models and early-phase clinical trials for ARDS, but challenges such as inconsistent outcomes and suboptimal efficacy limit its widespread application [10, 11]. This variability is believed to stem from the complex interplay of factors, including the severity of lung injury, the timing of MSC administration, and the patient’s immunological state [12]. Certain published studies indicate that the documented survival rates of transplanted cells are exceedingly minimal, thereby rendering the entire endeavor of cellular therapy ineffective [13]. Therefore, enhancing the in vivo survival of MSCs represents a pivotal challenge in advancing cellular therapy. Recent studies suggest that enhancing the therapeutic capabilities of MSCs through genetic modification may improve their effectiveness.