Fibroblast growth factor (FGF) signaling is known to play an important role in lung organogenesis. However, we recently demonstrated that FGF10 fails to induce branching in human fetal lungs as is observed in mouse. Our previous human fetal lung RNA sequencing data exhibited increased FGF18 during the pseudoglandular stage of development, suggestive of its importance in human lung branching morphogenesis. Whereas it has been previously reported that FGF18 is critical during alveologenesis, few studies have described its implication in lung branching, specifically in human. Therefore, we aimed to determine the role of FGF18 in human lung branching morphogenesis. Human fetal lung explants within the pseudoglandular stage of development were treated with recombinant human FGF18 in air-liquid interface culture. Explants were analyzed grossly to assess differences in branching pattern, as well as at the cellular and molecular levels. FGF18 treatment promoted branching in explant cultures and demonstrated increased epithelial proliferation as well as maintenance of the double positive SOX2/SOX9 distal bud progenitor cells, confirming its role in human lung branching morphogenesis. In addition, FGF18 treated explants displayed increased expression of SOX9, FN1, and COL2A1 within the mesenchyme, all factors that are important to chondrocyte differentiation. In humans, cartilaginous airways extend deep into the lung up to the 12th generation of branching whereas in mouse these are restricted to the trachea and main bronchi. Therefore, our data suggest that FGF18 promotes human lung branching morphogenesis through regulating mesenchymal progenitor cells.

Chronic obstructive pulmonary disease (COPD) is a frequent respiratory disease. However, its pathophysiology remains partially elucidated. Epithelial remodeling including alteration of the cilium is a major hallmark of COPD, but specific assessments of the cilium have been rarely investigated as a diagnostic tool in COPD. Here we explore the dysregulation of the ciliary function (ciliary beat frequency (CBF)) and differentiation (multiciliated cells formation in air-liquid interface cultures) of bronchial epithelial cells from COPD (n = 17) and non-COPD patients (n = 15). CBF was decreased by 30% in COPD (11.15 +/− 3.37 Hz vs. 7.89 +/− 3.39 Hz, p = 0.037). Ciliary differentiation was altered during airway epithelial cell differentiation from COPD patients. While the number of multiciliated cells decreased (p < 0.005), the number of primary ciliated cells increased (p < 0.05) and primary cilia were shorter (p < 0.05). Altogether, we demonstrate that COPD can be considered as a ciliopathy through both primary non-motile cilia modifications (related to airway epithelial cell repair and remodeling) and motile cilia function impairment (associated with decrease sputum clearance and clinical respiratory symptoms). These observations encourage considering cilia-associated features in the complex COPD physiopathology and highlight the potential of cilia-derived biomarkers for diagnosis.

The Hedgehog (HH) signaling pathway plays an essential role in mouse lung development. We hypothesize that the HH pathway is necessary for branching during human lung development and is impaired in pulmonary hypoplasia. Single-cell, bulk RNA-sequencing data, and human fetal lung tissues were analyzed to determine the spatiotemporal localization of HH pathway actors. Distal human lung segments were cultured in an air-liquid interface and treated with an SHH inhibitor (5E1) to determine the effect of HH inhibition on human lung branching, epithelial-mesenchymal markers, and associated signaling pathways in vitro. Our results showed an early and regulated expression of HH pathway components during human lung development. Inhibiting HH signaling caused a reduction in branching during development and dysregulated epithelial (SOX2, SOX9) and mesenchymal (ACTA2) progenitor markers. FGF and Wnt pathways were also disrupted upon HH inhibition. Finally, we demonstrated that HH signaling elements were downregulated in lung tissues of patients with a congenital diaphragmatic hernia (CDH). In this study, we show for the first time that HH signaling inhibition alters important genes and proteins required for proper branching of the human developing lung. Understanding the role of the HH pathway on human lung development could lead to the identification of novel therapeutic targets for childhood pulmonary diseases.

The gene cluster region, CHRNA3/CHRNA5/CHRNB4, encoding for nicotinic acetylcholine receptor (nAChR) subunits, contains several genetic variants linked to nicotine addiction and brain disorders. The CHRNA5 single-nucleotide polymorphism (SNP) rs16969968 is strongly associated with nicotine dependence and lung diseases. Using immunostaining studies on tissue sections and air-liquid interface airway epithelial cell cultures, in situ hybridisation, transcriptomic and cytokines detection, we analysed rs16969968 contribution to respiratory airway epithelial remodelling and modulation of inflammation. We provide cellular and molecular analyses which support the genetic association of this polymorphism with impaired ciliogenesis and the altered production of inflammatory mediators. This suggests its role in lung disease development.

Urban pollution is known to have major adverse effects on lung health. To assess the effect of pollution on alveolar regeneration, we exposed adult mice to a simulated high-pollution urban atmosphere, using an innovative CESAM simulation chamber (Multiphase Atmospheric Experimental Simulation Chamber, https://cesam.cnrs.fr/ ). We demonstrated that urban atmosphere alters alveolar mesenchymal stem cell niche properties by inducing a lipofibroblast to myofibroblast shift and induces alveolar epithelial dysfunction.