Intratracheal administration of mesenchymal stem cells ameliorates hyperoxia-induced bronchopulmonary dysplasia by inhibiting NLRP3 inflammasome activation: the critical role of Aldh1a2

Abstract

Background Bronchopulmonary dysplasia (BPD) is a chronic lung disease driven by inflammation and oxidative stress. Mesenchymal stem cells (MSCs) have shown protective effects against hyperoxic lung injury. However, few studies have thoroughly examined the significantly differentially expressed genes (DEGs) in the lungs before and after MSC treatment. In this study, we analyzed the significant DEGs in lung tissues during both in vivo and vitro umbilical cord-derived mesenchymal stem cells (UCMSCs)-mediated repair of hyperoxic lung injury and investigated their potential mechanisms of action. Methods Neonatal rats were exposed to hyperoxia and subsequently treated with UCMSCs. Inflammatory responses were quantified via ELISA and RT‒qPCR, while Western blotting (WB) and immunohistochemistry (IHC) were used to examine NLRP3 inflammasome and IL-1β expression. Transcriptomic analysis of UCMSC-mediated lung repair revealed 46 DEGs, which were validated by RT‒qPCR, and WB verified the significant differential expression of ALDH1A2. In RLE-6TN cells, Aldh1a2 expression was reduced during MSC-mediated repair of H2O2-induced oxidative stress injury. Functional evaluations were performed. WB further analyzed NLRP3 inflammasome and IL-1β expression in these processes. A recombinant adenoviral overexpression vector was intratracheally administered to hyperoxia-exposed neonatal rats. Arterial blood gas and RT‒qPCR were performed, and ELISA, WB, and IHC were used to evaluate the impact of Aldh1a2 overexpression on lung inflammation and oxidative stress, focusing on the NLRP3 inflammasome. Results UCMSCs ameliorated hyperoxia-induced alveolar simplification and microvessel loss, reduced inflammation and oxidative stress injury, and inhibited the expression of the NLRP3 inflammasome. RT‒qPCR and WB analyses revealed significant differential expression of Aldh1a2 in UCMSC-treated hyperoxia-induced lung injury. UCMSCs also mitigated H2O2-induced oxidative stress injury in RLE-6TN cells. Inhibition of Aldh1a2 expression exacerbated oxidative stress, upregulated NLRP3 inflammasome and IL-1β expression, and impaired the reparative effects of UCMSCs. Conversely, Aldh1a2 overexpression or UCMSC intervention ameliorated hyperoxia-induced alveolar simplification and microvascular abnormalities, suppressed inflammation, and enhanced lung ventilation and angiogenesis. These findings indicated that Aldh1a2 overexpression inhibits NLRP3 inflammasome activation and IL-1β release. Conclusions Aldh1a2 was significantly differentially expressed in UCMSC-mediated repair of hyperoxic lung injury, and its overexpression ameliorates BPD by inhibiting NLRP3 inflammasome activation, suggesting a novel therapeutic target for BPD.

1. Introduction

Bronchopulmonary dysplasia (BPD) is a chronic lung disease prevalent in premature infants driven by excessive inflammation and oxidative stress. It is a clinically heterogeneous condition primarily linked to oxygen supplementation [1, 2]. BPD is characterized by alveolar simplification, pulmonary fibrosis, and vascular dysplasia [1, 2]. Despite advancements in neonatal intensive care, the incidence of BPD has risen significantly [1]. Current management strategies, including gentle volume-assured ventilation and medication-assisted therapy, have shown limited efficacy and pose developmental risks [3, 4]. Thus, there is an urgent need to develop novel and effective treatments for BPD [5].

Mesenchymal stem cells (MSCs) are multipotent stromal cells with significant potential for organ repair in preclinical models, primarily due to their immunomodulatory and anti-inflammatory properties [6]. Studies have shown that MSCs alleviate acute lung injury by reducing inflammation, modulating inflammatory mediators, inhibiting neutrophil activation, and suppressing macrophage polarization [6, 7]. Additionally, MSCs can regulate neonatal lung development, alveolar epithelial cell apoptosis, the blood‒air barrier, and microvascular reconstruction by modulating vascular endothelial growth factor (VEGF) and the renin‒angiotensin system (RAS) [6]. Emerging evidence suggests that MSCs effectively treat BPD [6–8]. In neonatal rat models of hyperoxic lung injury, MSCs have been shown to suppress lung inflammation, promote microangiogenesis, and improve cardiac and renal function [8]. However, the precise molecular mechanisms underlying MSC-mediated repair remain incompletely understood, and the identification of key differentially expressed genes (DEGs) is crucial for optimizing therapeutic strategies.