Tissue crosstalk in lung development

Interleukin-11 Is Involved in Hyperoxia-induced Bronchopulmonary Dysplasia in Newborn Mice by Mediating Epithelium-Fibroblast Cross-talk

BACKGROUND

Bronchopulmonary dysplasia (BPD) is a chronic lung disorder predominantly affecting preterm infants. Oxygen therapy, a common treatment for BPD, often leads to hyperoxia-induced pulmonary damage, particularly targeting alveolar epithelial cells (AECs). Crucially, disrupted lung epithelium-fibroblast interactions significantly contribute to BPD's pathogenesis. Previous studies on interleukin-11 (IL-11) in lung diseases have yielded conflicting results. Recent research, however, highlights IL-11 as a key regulator of fibrosis, stromal inflammation, and epithelial dysfunction. Despite this, the specific role of IL-11 in BPD remains underexplored. Our transcriptome analysis of normal and hyperoxia-exposed murine lung tissues revealed an increased expression of IL-11 RNA. This study aimed to investigate IL-11's role in modulating the disrupted interactions between AECs and fibroblasts in BPD.

METHODS

BPD was modeled in vivo by exposing C57BL/6J neonatal mice to hyperoxia. Histopathological changes in lung tissue were evaluated with hematoxylin-eosin staining, while lung fibrosis was assessed using Masson staining and immunohistochemistry (IHC). To investigate IL-11's role in pulmonary injury contributing to BPD, IL-11 levels were reduced through intraperitoneal administration of IL-11RαFc in hyperoxia-exposed mice. Additionally, MLE-12 cells subjected to 95% oxygen were collected and co-cultured with mouse pulmonary fibroblasts (MPFs) to measure α-SMA and Collagen I expression levels. IL-11 levels in the supernatants were quantified using an enzyme-linked immunosorbent assay (ELISA).

RESULTS

Both IHC and Masson staining revealed that inhibiting IL-11 expression alleviated pulmonary fibrosis in neonatal mice induced by hyperoxia, along with reducing the expression of fibrosis markers α-SMA and collagen I in lung tissue. In vitro analysis showed a significant increase in IL-11 levels in the supernatant of MLE-12 cells treated with hyperoxia. Silencing IL-11 expression in MLE-12 cells reduced α-SMA and collagen I concentrations in MPFs co-cultured with the supernatant of hyperoxia-treated MLE-12 cells. Additionally, ERK inhibitors decreased α-SMA and collagen I levels in MPFs co-cultured with the supernatant of hyperoxia-treated MLE-12 cells. Clinical studies found increased IL-11 levels in tracheal aspirates (TA) of infants with BPD.

CONCLUSION

This research reveals that hyperoxia induces IL-11 secretion in lung epithelium. Additionally, IL-11 derived from lung epithelium emerged as a crucial mediator in myofibroblast differentiation via the ERK signaling pathway, highlighting its potential therapeutic value in BPD treatment.

Cell Cross-Talk in Alveolar Microenvironment: From Lung Injury to Fibrosis

Alveoli are complex microenvironments composed of various cell types, including epithelial, fibroblast, endothelial, and immune cells, which work together to maintain a delicate balance in the lung environment, ensuring proper growth, development, and an effective response to lung injuries. However, prolonged inflammation or aging can disrupt normal interactions among these cells, leading to impaired repair processes and a substantial decline in lung function. Therefore, it is essential to understand the key mechanisms underlying the interactions among the major cell types within the alveolar microenvironment. We explored the key mechanisms underlying the interactions among the major cell types within the alveolar microenvironment. These interactions occur through the secretion of signaling factors and play crucial roles in the response to injury, repair mechanisms, and the development of fibrosis in the lungs. Specifically, we focused on the regulation of alveolar type 2 cells by fibroblasts, endothelial cells, and macrophages. In addition, we explored the diverse phenotypes of fibroblasts at different stages of life and in response to lung injury, highlighting their impact on matrix production and immune functions. Furthermore, we summarize the various phenotypes of macrophages in lung injury and fibrosis as well as their intricate interplay with other cell types. This interplay can either contribute to the restoration of immune homeostasis in the alveoli or impede the repair process. Through a comprehensive exploration of these cell interactions, we aim to reveal new insights into the molecular mechanisms that drive lung injury toward fibrosis and identify potential targets for therapeutic intervention.

Innovative explorations: unveiling the potential of organoids for investigating environmental pollutant exposure

As the economy rapidly develops, chemicals are widely produced and used. This has exacerbated the problems associated with environmental pollution, raising the need for efficient toxicological evaluation techniques to investigate the toxic effects and mechanisms of toxicity of environmental pollutants. The progress in the techniques of cell culture in three dimensions has resulted in the creation of models that are more relevant in terms of biology and physiology. This enables researchers to study organ development, toxicology, and drug screening. Adult stem cells (ASCs) and induced pluripotent stem cells (iPSCs) can be obtained from various mammalian tissues, including cancerous and healthy tissues. Such stem cells exhibit a significant level of tissue memory and ability to self-assemble. When cultivated in 3D in vitro environments, the resulting organoids demonstrate a remarkable capacity to recapitulate the cellular composition and function of organs in vivo. Recently, many tumors' tissue-derived organoids have been widely used in research on tumor pathogenesis, drug development, precision medicine, and other fields, including those derived from colon cancer, cholangiocarcinoma, liver cancer, and gastric cancer. However, the application of organoid models for evaluating the toxicity of environmental pollutants is still in its infancy. This review introduces the characteristics of the toxicity responses of organoid models upon exposure to pollutants from the perspectives of organoid characteristics, tissue types, and their applications in toxicology; discusses the feasibility of using organoid models in evaluating the toxicity of pollutants; and provides a reference for future toxicological studies on environmental pollutants based on organoid models.

Preferential FGF18/FGFR activity in pseudoglandular versus canalicular stage human lung fibroblasts

Fibroblast growth factor (FGF) signaling is necessary for proper lung branching morphogenesis, alveolarization, and vascular development. Dysregulation of FGF activity has been implicated in various lung diseases. Recently, we showed that FGF18 promotes human lung branching morphogenesis by regulating mesenchymal progenitor cells. However, the underlying mechanisms remain unclear. Thus, we aimed to determine the role of FGF18 and its receptors (FGFR) in regulating mesenchymal cell proliferation, migration, and differentiation from pseudoglandular to canalicular stage. We performed siRNA assays to identify the specific FGFR(s) associated with FGF18-induced biological processes. We found that FGF18 increased proliferation and migration in human fetal lung fibroblasts (HFLF) from both stages. FGFR2/FGFR4 played a significant role in pseudoglandular stage. HFLF proliferation, while FGFR3/FGFR4 were involved in canalicular stage. FGF18 enhanced HFLF migration through FGFR2 and FGFR4 in pseudoglandular and canalicular stage, respectively. Finally, we provide evidence that FGF18 treatment leads to reduced expression of myofibroblast markers (ACTA2 and COL1A1) and increased expression of lipofibroblast markers (ADRP and PPARγ) in both stages HFLF. However, the specific FGF18/FGFR complex involved in this process varies depending on the stage. Our findings suggest that in context of human lung development, FGF18 tends to associate with distinct FGFRs to initiate specific biological processes on mesenchymal cells.

A Trisomy 21 Lung Cell Atlas

Trisomy 21 (T21), resulting in Down Syndrome (DS), is the most prevalent chromosomal abnormality worldwide. While pulmonary disease is a major cause of morbidity and mortality in DS, the ontogeny of pulmonary complications remains poorly understood. We recently demonstrated that T21 lung anomalies, including airway branching and vascular lymphatic abnormalities, are initiated in utero. Here, we aimed to describe molecular changes at the single cell level in prenatal T21 lungs. Our results demonstrate differences in the proportion of cell populations and detail changes in gene expression at the time of initiation of histopathological abnormalities. Notably, we identify shifts in the distribution of alveolar epithelial progenitors, widespread induction of key extracellular matrix molecules in mesenchymal cells and hyper-activation of IFN signaling in endothelial cells. This single cell atlas of T21 lungs greatly expands our understanding of antecedents to pulmonary complications and should facilitate efforts to mitigate respiratory disease in DS.

FGF18 promotes human lung branching morphogenesis through regulating mesenchymal progenitor cells

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.

Preterm Birth, Developmental Smoke/Nicotine Exposure, and Life-Long Pulmonary Sequelae

This review delineates the main pulmonary issues related to preterm birth, perinatal tobacco/nicotine exposure, and its effects on offspring, focusing on respiratory health and its possible transmission to subsequent generations. We review the extent of the problem of preterm birth, prematurity-related pulmonary effects, and the associated increased risk of asthma later in life. We then review the impact of developmental tobacco/nicotine exposure on offspring asthma and the significance of transgenerational pulmonary effects following perinatal tobacco/nicotine exposure, possibly via its effects on germline epigenetics.

hPSC-derived lung organoids: Potential opportunities and challenges

Three-dimensional hPSC-derived lung organoids resemble the fetal lung stage, making them an excellent model for studying human lung development. However, current hPSC-derived lung organoids remain incomplete as they lack native lung components such as vasculature, neurons and immune cells. This highlights the need to generate more complex hPSC-derived lung organoids that can faithfully mimic native human lungs for studying human lung development, regeneration, disease modeling and drug screen. In this review, we will discuss the current studies related to the generation of hPSC-derived lung organoids, highlighting how hPSC-derived lung organoids can contribute to the understanding of human lung development. We further focus on potential approaches to generate more complex hPSC-derived lung organoids containing native cellular components. Finally, we discuss the present limitations and potential applications of hPSC-derived lung organoids in the future.

Simple Models of Lung Development

Models are essential to further our understanding of lung development and regeneration and to facilitate identification and testing of potential treatments for lung diseases. A wide variety of rodent and human models are available that recapitulate one or more stages of lung development. This chapter describes the existing 'simple' in vitro, in silico and ex vivo models of lung development. We define which stage(s) of development each model recapitulates and highlight their pros and cons.

Niche-mediated repair of airways is directed in an occupant-dependent manner

In injured airways of the adult lung, epithelial progenitors are called upon to repair by nearby mesenchymal cells via signals transmitted through the niche. Currently, it is unclear whether repair is coordinated by the mesenchymal cells that maintain the niche or by the airway epithelial cells that occupy it. Here, we show that the spatiotemporal expression of Fgf10 by the niche is primarily orchestrated by the niche's epithelial occupants-both those that reside prior to, and following, injury. During homeostasis, differentiated airway epithelial cells secrete Sonic hedgehog (Shh) to inhibit Fgf10 expression by Gli1⁺ peribronchial mesenchymal cells in the niche. After injury, remaining epithelial cells produce Wnt7b to induce Fgf10 expression in airway smooth muscle cells in the niche. We find that this reliance on a common activator of airway epithelial stem cells also allows for the recruitment of remote stem cell populations when local populations have been exhausted.

Anatomy and embryology of tracheo-esophageal fistula

Anomalies in tracheo-esophageal development result in a spectrum of congenital malformations ranging from, most commonly, esophageal atresia with or without trachea-esophageal fistula (EA+/-TEF) to esophageal web, duplication, stricture, tracheomalacia and tracheal agenesis. Despite the relative frequency of EA, however, the underlying etiology remains unknown and is likely due to a combination of genetic, epigenetic and environmental factors. In recent years, animal models have dramatically increased our understanding of the molecular and morphological processes involved in normal esophageal development during the key stages of anterior-posterior regionalization, dorsal-ventral patterning and morphogenic separation. Moreover, the use of animal models in conjunction with increasingly advanced techniques such as genomic sequencing, sophisticated live imaging studies and organoid models have more recently cast light on potential mechanisms involved in EA pathogenesis. This article aims to unravel some of the mysteries behind the anatomy and embryology of EA whilst providing insights into future directions for research.

Towards an artificial human lung: modelling organ-like complexity to aid mechanistic understanding

Respiratory diseases account for over 5 million deaths yearly and are a huge burden to healthcare systems worldwide. Murine models have been of paramount importance to decode human lung biology in vivo, but their genetic, anatomical, physiological and immunological differences with humans significantly hamper successful translation of research into clinical practice. Thus, to clearly understand human lung physiology, development, homeostasis and mechanistic dysregulation that may lead to disease, it is essential to develop models that accurately recreate the extraordinary complexity of the human pulmonary architecture and biology. Recent advances in micro-engineering technology and tissue engineering have allowed the development of more sophisticated models intending to bridge the gap between the native lung and its replicates in vitro Alongside advanced culture techniques, remarkable technological growth in downstream analyses has significantly increased the predictive power of human biology-based in vitro models by allowing capture and quantification of complex signals. Refined integrated multi-omics readouts could lead to an acceleration of the translational pipeline from in vitro experimental settings to drug development and clinical testing in the future. This review highlights the range and complexity of state-of-the-art lung models for different areas of the respiratory system, from nasal to large airways, small airways and alveoli, with consideration of various aspects of disease states and their potential applications, including pre-clinical drug testing. We explore how development of optimised physiologically relevant in vitro human lung models could accelerate the identification of novel therapeutics with increased potential to translate successfully from the bench to the patient's bedside.

Congenital lung malformations: Dysregulated lung developmental processes and altered signaling pathways

Congenital lung malformations comprise a diverse group of anomalies including congenital pulmonary airway malformation (CPAM, previously known as congenital cystic adenomatoid malformation or CCAM), bronchopulmonary sequestration (BPS), congenital lobar emphysema (CLE), bronchogenic cysts, and hybrid lesions. Little is known about the signaling pathways that underlie the pathophysiology of these lesions and the processes that may promote their malignant transformation. In the last decade, the use of transgenic/knockout animal models and the implementation of next generation sequencing on surgical lung specimens have increased our knowledge on the pathophysiology of these lesions. Herein, we provide an overview of normal lung development in humans and rodents, and we discuss the current state of knowledge on the pathophysiology and molecular pathways that are altered in each congenital lung malformation.

Phenotypic spectrum of FGF10-related disorders: a systematic review

FGF10, as an FGFR2b-specific ligand, plays a crucial role during cell proliferation, multi-organ development, and tissue injury repair. The developmental importance of FGF10 has been emphasized by the identification of FGF10 abnormalities in human congenital disorders affecting different organs and systems. Single-nucleotide variants in FGF10 or FGF10-involving copy-number variant deletions have been reported in families with lacrimo-auriculo-dento-digital syndrome, aplasia of the lacrimal and salivary glands, or lethal lung developmental disorders. Abnormalities involving FGF10 have also been implicated in cleft lip and palate, myopia, or congenital heart disease. However, the exact developmental role of FGF10 and large phenotypic heterogeneity associated with FGF10 disruption remain incompletely understood. Here, we review human and animal studies and summarize the data on FGF10 mechanism of action, expression, multi-organ function, as well as its variants and their usefulness for clinicians and researchers.

Developmental basis of evolutionary lung loss in plethodontid salamanders

One or more members of four living amphibian clades have independently dispensed with pulmonary respiration and lack lungs, but little is known of the developmental basis of lung loss in any taxon. We use morphological, molecular, and experimental approaches to examine the Plethodontidae, a dominant family of salamanders, all of which are lungless as adults. We confirm an early anecdotal report that plethodontids complete early stages of lung morphogenesis: Transient embryonic lung primordia form but regress by apoptosis before hatching. Initiation of pulmonary development coincides with expression of the lung-specification gene Wnt2b in adjacent mesoderm, and the lung rudiment expresses pulmonary markers Nkx2.1 and Sox9. Lung developmental-genetic pathways are at least partially conserved despite the absence of functional adult lungs for at least 25 and possibly exceeding 60 million years. Adult lung loss appears associated with altered expression of signaling molecules that mediate later stages of tracheal and pulmonary development.

Interleukin-6-dependent epithelial fluidization initiates fibrotic lung remodeling

Chronic disease results from the failure of tissues to maintain homeostasis. In the lung, coordinated repair of the epithelium is essential for preserving homeostasis. In animal models and human lung disease, airway epithelial cells mobilize in response to lung injury, resulting in the formation of airway-like cysts with persistent loss of functional cell types and parenchymal architecture. Using live-cell imaging of human lung epithelial cultures and mouse precision-cut lung slices, we demonstrated that distal airway epithelia are aberrantly fluidized both after injury and in fibrotic lung disease. Through transcriptomic profiling and pharmacologic stimulation of epithelial cultures, we identified interleukin-6 (IL-6) signaling as a driver of tissue fluidization. This signaling cascade occurred independently of canonical Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling but instead was dependent on a downstream SRC family kinase (SFK)-yes-associated protein (YAP) axis. Airway epithelial-fibroblast cocultures revealed that the fibrotic mesenchyme acts as a source of IL-6 family cytokines, which drive airway fluidization. Inhibition of the IL-6-SFK-YAP cascade was sufficient to prevent fluidization in both in vitro and ex vivo models. Last, we demonstrated a reduction in fibrotic lung remodeling in mice through genetic or pharmacologic targeting of IL-6-related signaling. Together, our findings illustrate the critical role of airway epithelial fluidization in coordinating the balance between homeostatic lung repair and fibrotic airspace remodeling.

R-SPONDIN2+ mesenchymal cells form the bud tip progenitor niche during human lung development

The human respiratory epithelium is derived from a progenitor cell in the distal buds of the developing lung. These "bud tip progenitors" are regulated by reciprocal signaling with surrounding mesenchyme; however, mesenchymal heterogeneity and function in the developing human lung are poorly understood. We interrogated single-cell RNA sequencing data from multiple human lung specimens and identified a mesenchymal cell population present during development that is highly enriched for expression of the WNT agonist RSPO2, and we found that the adjacent bud tip progenitors are enriched for the RSPO2 receptor LGR5. Functional experiments using organoid models, explant cultures, and FACS-isolated RSPO2+ mesenchyme show that RSPO2 is a critical niche cue that potentiates WNT signaling in bud tip progenitors to support their maintenance and multipotency.

Hedgehog Signaling Pathway Orchestrates Human Lung Branching Morphogenesis

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 Patient-Derived Cancer Organoids: Promises and Challenges as Platforms for Cancer Discovery

The cancer burden is rapidly increasing in most countries, and thus, new anticancer drugs for effective cancer therapy must be developed. Cancer model systems that recapitulate the biological processes of human cancers are one of the cores of the drug development process. PDCO has emerged as a unique model that preserves the genetic, physiological, and histologic characteristics of original cancer, including inter- and intratumoral heterogeneities. Due to these advantages, the PCDO model is increasingly investigated for anticancer drug screening and efficacy testing, preclinical patient stratification, and precision medicine for selecting the most effective anticancer therapy for patients. Here, we review the prospects and limitations of PDCO compared to the conventional cancer models. With advances in culture success rates, co-culture systems with the tumor microenvironment, organoid-on-a-chip technology, and automation technology, PDCO will become the most promising model to develop anticancer drugs and precision medicine.

In vivo biocompatibility analysis of the recellularized canine tracheal scaffolds with canine epithelial and endothelial progenitor cells

Decellularized extracellular matrix (ECM) has frequently been applied as a biomaterial for tissue engineering purposes. When implanted, their role can be essential for partial trachea replacement in patients that require a viable transplant solution. Acellular canine tracheal scaffolds with preserved ECM structure, flexibility, and proteins were obtained by high pressure vacuum decellularization. Here, we aimed to evaluate the cell adhesion and proliferation of canine tracheal epithelial cells (EpC) and canine yolk sac endothelial progenitor cells (YS) cultivated on canine decellularized tracheal scaffolds and test the in vivo biocompatibility of these recellularized scaffolds implanted in BALB-c nude mice. In order to evaluate the recellularization efficiency, scaffolds were evaluated by scanning electron microscopy (SEM), immunofluorescence, DNA quantification, mycoplasma test, and in vivo biocompatibility. The scaffolds sterility was confirmed, and EpC and YS cells were cultured by 7 and 14 days. We demonstrated by SEM, immunofluorescence, and genomic DNA analyzes cell adhesion to tracheal ECM. Then, recellularized scaffolds were in vivo subcutaneously implanted in mice and after 45 days, the fragments were collected and analyzed by Hematoxylin-Eosin and Gömori Trichrome staining and PCNA, CD4, CD8, and CD68 immunohistochemistry. In vivo results confirmed that the implanted tissue remains preserved and proliferative, and no fibrotic tissue process was observed in animals. Finally, our results showed the recellularization success due the preserved ECM proteins, and that these may be suitable to future preclinical studies applications for partial trachea replacement in tissue engineering.

Human embryonic mesenchymal lung-conditioned medium promotes differentiation to myofibroblast and loss of stemness phenotype in lung adenocarcinoma cell lines

Background

When genes responsible for normal embryonic development are abnormally expressed in adults, it can lead to tumor development. This can suggest that the same mechanism that controls embryonic differentiation can also control tumor differentiation. We hypothesize that the malignant phenotype of lung cancer cells could acquire benign characteristics when in contact with an embryonic lung microenvironment. We cultured two lung cancer cell lines in embryonic lung mesenchyme-conditioned medium and evaluated morphological, functional and molecular changes.

Methods

The human embryonic mesenchymal lung-conditioned medium (hEML-CM) was obtained by culturing lung cells from embryos in the pseudoglandular stage of development. The NSCLC cell lines A549 and H1299 we cultured in the hEML-CM and in a tumor-conditioned medium. Morphological changes were analyzed with optical and transmission electron microscopy. To evaluate the functional effect of conditioned medium in tumor cells, we analyzed cell proliferation, migration, colony formation capacity in 2D and 3D and in vivo tumor growth capacity. The expression of the pluripotency genes OSKM, the adenocarcinoma marker NKX2-1, the lung surfactant proteins SFTP, the myofibroblast marker MYH and DNMT3A/3B was analyzed with qRT-PCR and the presence of the myofibroblast markers vimentin and α-SMA with immunofluorescence. Transcriptomic analysis was performed using Affymetrix arrays.

Results

The A549 and H1299 cells cultured in hEML-CM lost their epithelial morphology, acquired mesodermal characteristics, and decreased proliferation, migration, and colony formation capacity in 2D and 3D, as well as reduced its capacity to growth in vivo. The expression of OSKM, NKX2-1 and SFTP decreased, while that of DNMT3A/3B, vimentin, α-SMA and MYH increased. Distant matrix analysis based on transcriptomic profile showed that conditioned cells were closer to myoblast and human lung fibroblast than to normal epithelial immortalized lung cells. A total of 1631 for A549 and 866 for H1299 differentially expressed genes between control and conditioned cells were identified.

Conclusions

To the best of our knowledge, this is the first study to report that stimuli from the embryonic lung can modulate the malignant phenotype of lung cancer cells, control their growth capacity and activate their differentiation into myofibroblasts. These findings could lead to new strategies for lung cancer management.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02206-z.

Recent research on the mechanism of mesenchymal stem cells in the treatment of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic lung disease due to impaired pulmonary development and is one of the main causes of respiratory failure in preterm infants. Preterm infants with BPD have significantly higher complication and mortality rates than those without BPD. At present, comprehensive management is the main intervention method for BPD, including reasonable respiratory and circulatory support, appropriate enteral nutrition and parenteral nutrition, application of caffeine/glucocorticoids/surfactants, and out-of-hospital management after discharge. The continuous advances in stem cell medicine in recent years provide new ideas for the treatment of BPD. Various pre-clinical trials have confirmed that stem cell therapy can effectively prevent lung injury and promote lung growth and damage repair. This article performs a comprehensive analysis of the mechanism of mesenchymal stem cells in the treatment of BPD, so as to provide a basis for clinical applications.

Scientific Validation and Clinical Application of Lung Cancer Organoids

Lung cancer organoid (LCO) is a novel model of lung cancer that facilitates drug screening. However, the success rate of LCOs varies from 7% to 87%, and the culture medium compositions are markedly different. Airway organoid media can be used for LCO cultures, but this promotes the overgrowth of normal cell organoids especially in LCOs from intrapulmonary lesions. Several modified media are specifically utilized for promoting the cancer cell's growth. For culturing high-purity LCOs, cancer cells from metastatic lesions and malignant effusions are used. Recently, single-cell RNA sequencing has identified previously unknown cell populations in the lungs and lung cancer. This sequencing technology can be used to validate whether the LCO recapitulates the heterogeneity and functional hierarchy of the primary tumor. Several groups have attempted to culture LCOs with mesenchymal cells and immune cells to recapitulate the tumor microenvironment. Disease modeling using LCO provides novel insight into the pathophysiology of lung cancer and enables high-throughput screening for drug discovery and prognosis prediction. An LCO model would help to identify new concepts as a basis for lung cancer targeting by discovering innovative therapeutic targets.

FGF/FGFR signaling: From lung development to respiratory diseases

The fibroblast growth factor/fibroblast growth factor receptor (FGF/FGFR) signaling system regulates a variety of biological processes, including embryogenesis, angiogenesis, wound repair, tissue homeostasis, and cancer. It exerts these regulatory functions by controlling proliferation, differentiation, migration, survival, and metabolism of target cells. The morphological structure of the lung is a complex tree-like network for effective oxygen exchange, and the airway terminates in the middle and distal ends of many alveoli. FGF/FGFR signaling plays an important role in the pathophysiology of lung development and pathogenesis of various human respiratory diseases. Here, we mainly review recent advances in FGF/FGFR signaling during human lung development and respiratory diseases, including lung cancer, acute lung injury (ALI), pulmonary arterial hypertension (PAH), chronic obstructive pulmonary disease (COPD), asthma, and pulmonary fibrosis.

Changes in Nkx2.1, Sox2, Bmp4, and Bmp16 expression underlying the lung-to-gas bladder evolutionary transition in ray-finned fishes

The key to understanding the evolutionary origin and modification of phenotypic traits is revealing the responsible underlying developmental genetic mechanisms. An important organismal trait of ray-finned fishes is the gas bladder, an air-filled organ that, in most fishes, functions for buoyancy control, and is homologous to the lungs of lobe-finned fishes. The critical morphological difference between lungs and gas bladders, which otherwise share many characteristics, is the general direction of budding during development. Lungs bud ventrally and the gas bladder buds dorsally from the anterior foregut. We investigated the genetic underpinnings of this ventral-to-dorsal shift in budding direction by studying the expression patterns of known lung genes (Nkx2.1, Sox2, and Bmp4) during the development of lungs or gas bladder in three fishes: bichir, bowfin, and zebrafish. Nkx2.1 and Sox2 show reciprocal dorsoventral expression patterns during tetrapod lung development and are important regulators of lung budding; their expression during bichir lung development is conserved. Surprisingly, we find during gas bladder development, Nkx2.1 and Sox2 expression are inconsistent with the hypothesis that they regulate the direction of gas bladder budding. Bmp4 is expressed ventrally during lung development in bichir, akin to the pattern during mouse lung development. During gas bladder development, Bmp4 is not expressed. However, Bmp16, a paralogue of Bmp4, is expressed dorsally in the developing gas bladder of bowfin. Bmp16 is present in the known genomes of Actinopteri (ray-finned fishes excluding bichir) but absent from mammalian genomes. We hypothesize that Bmp16 was recruited to regulate gas bladder development in the Actinopteri in place of Bmp4.

The Cellular and Physiological Basis for Lung Repair and Regeneration: Past, Present, and Future

The respiratory system, which includes the trachea, airways, and distal alveoli, is a complex multi-cellular organ that intimately links with the cardiovascular system to accomplish gas exchange. In this review and as members of the NIH/NHLBI-supported Progenitor Cell Translational Consortium, we discuss key aspects of lung repair and regeneration. We focus on the cellular compositions within functional niches, cell-cell signaling in homeostatic health, the responses to injury, and new methods to study lung repair and regeneration. We also provide future directions for an improved understanding of the cell biology of the respiratory system, as well as new therapeutic avenues.

TP63 basal cells are indispensable during endoderm differentiation into proximal airway cells on acellular lung scaffolds

The use of decellularized whole-organ scaffolds for bioengineering of organs is a promising avenue to circumvent the shortage of donor organs for transplantation. However, recellularization of acellular scaffolds from multicellular organs like the lung with a variety of different cell types remains a challenge. Multipotent cells could be an ideal cell source for recellularization. Here we investigated the hierarchical differentiation process of multipotent ES-derived endoderm cells into proximal airway epithelial cells on acellular lung scaffolds. The first cells to emerge on the scaffolds were TP63⁺ cells, followed by TP63⁺/KRT5⁺ basal cells, and finally multi-ciliated and secretory airway epithelial cells. TP63⁺/KRT5⁺ basal cells on the scaffolds simultaneously expressed KRT14, like basal cells involved in airway repair after injury. Removal of TP63 by CRISPR/Cas9 in the ES cells halted basal and airway cell differentiation on the scaffolds. These findings suggest that differentiation of ES-derived endoderm cells into airway cells on decellularized lung scaffolds proceeds via TP63⁺ basal cell progenitors and tracks a regenerative repair pathway. Understanding the process of differentiation is key for choosing the cell source for repopulation of a decellularized organ scaffold. Our data support the use of airway basal cells for repopulating the airway side of an acellular lung scaffold.

Cell-Cell Interaction Mechanisms in Acute Lung Injury

ABSTRACT

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are caused by an exaggerated inflammatory response arising from a wide variety of pulmonary and systemic insults. Lung tissue is composed of a variety of cell populations, including parenchymal and immune cells. Emerging evidence has revealed that multiple cell populations in the lung work in concert to regulate lung inflammation in response to both direct and indirect stimulations. To date, the question of how different types of pulmonary cells communicate with each other and subsequently regulate or modulate inflammatory cascades remains to be fully addressed. In this review, we provide an overview of current advancements in understanding the role of cell-cell interaction in the development of ALI and depict molecular mechanisms by which cell-cell interactions regulate lung inflammation, focusing on inter-cellular activities and signaling pathways that point to possible therapeutic opportunities for ALI/ARDS.

The RNA-binding protein Quaking regulates multiciliated and basal cell abundance in the developing lung

RNA-binding proteins (RBPs) form complexes with RNA, changing how the RNA is processed and thereby regulating gene expression. RBPs are important sources of gene regulation during organogenesis, including the development of lungs. The RBP called Quaking (QK) is critical for embryogenesis, yet it has not been studied in the developing lung. Here, we show that QK is widely expressed during rat lung development and into adulthood. The QK isoforms QK5 and QK7 colocalize to the nuclei of nearly all lung cells. QK6 is present in the nuclei and cytoplasm of mesenchymal cells and is only present in the epithelium during branching morphogenesis. QK knockdown in embryonic lung explants caused a greater number of multiciliated cells to appear in the airways, at the expense of basal cells. The mRNA of multiciliated cell genes and the abundance of FOXJ1/SOX2+ cells increased after knockdown, whereas P63/SOX2+ cells decreased. The cytokine IL-6, a known regulator of multiciliated cell differentiation, had increased mRNA levels after QK knockdown, although protein levels remained unchanged. Further studies are necessary to confirm whether QK acts as a blocker for the IL-6-induced differentiation of basal cells into multiciliated cells, and a conditional QK knockout would likely lead to additional discoveries on QK's role during lung development.

WNT Signalling in Lung Physiology and Pathology

The main physiological function of the lung is gas exchange, mediated at the interface between the alveoli and the pulmonary microcapillary network and facilitated by conducting airway structures that regulate the transport of these gases from and to the alveoli. Exposure to microbial and environmental factors such as allergens, viruses, air pollution, and smoke contributes to the development of chronic lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and lung cancer. Respiratory diseases as a cluster are the commonest cause of chronic disease and of hospitalization in children and are among the three most common causes of morbidity and mortality in the adult population worldwide. Many of these chronic respiratory diseases are associated with inflammation and structural remodelling of the airways and/or alveolar tissues. They can often only be treated symptomatically with no disease-modifying therapies that normalize the pathological tissue destruction driven by inflammation and remodelling. In search for novel therapeutic strategies for these diseases, several lines of evidence revealed the WNT pathway as an emerging target for regenerative strategies in the lung. WNT proteins, their receptors, and signalling effectors have central regulatory roles under (patho)physiological conditions underpinning lung function and (chronic) lung diseases and we summarize these roles and discuss how pharmacological targeting of the WNT pathway may be utilized for the treatment of chronic lung diseases.

Reconstructing the Developmental Trajectories of Multiple Subtypes in Pulmonary Parenchymal Epithelial Cells by Single-Cell RNA-seq

Background

Some lung diseases are cell type-specific. It is essential to study the cellular anatomy of the normal human lung for exploring the cellular origin of lung disease and the cell development trajectory.

Methods

We used the Seurat R package for data quality control. The principal component analysis (PCA) was used for linear dimensionality reduction. UMAP and tSNE were used for dimensionality reduction. Muonocle2 was used to extract lung epithelial cells to analyze the subtypes of epithelial cells further and to study the development of these cell subtypes.

Results

We showed a total of 20154 high quality of cells from human normal lung tissue. They were initially divided into 17 clusters cells and then identified as seven types of cells, namely macrophages, monocytes, CD8 + T cells, epithelial cells, endothelial cells, adipocytes, and NK cells. 4240 epithelial cells were extracted for further analysis and they were divided into seven clusters. The seven cell clusters include alveolar cell, alveolar endothelial progenitor, ciliated cell, secretory cell, ionocyte cell, and a group of cells that are not clear at present. We show the development track of these subtypes of epithelial cells, in which we speculate that alveolar epithelial progenitor (AEP) is a kind of progenitor cells that can develop into alveolar cells, and find six essential genes that determine the cell fate, including AGER, RPL10, RPL9, RPS18, RPS27, and SFTPB.

Conclusion

We provide a transcription map of human lung cells, especially the in-depth study on the development of epithelial cell subtypes, which will help us to study lung cell biology and lung diseases.

Dorsoventral inversion of the air-filled organ (lungs, gas bladder) in vertebrates: RNAsequencing of laser capture microdissected embryonic tissue

How modification of gene expression generates novel traits is key to understanding the evolutionary process. We investigated the genetic basis for the origin of the piscine gas bladder from lungs of ancestral bony vertebrates. Distinguishing these homologous organs is the direction of budding from the foregut during development; lungs bud ventrally and the gas bladder buds dorsally.

Sonic hedgehog signalling as a potential endobronchial biomarker in COPD

BACKGROUND

The hedgehog (HH) pathway has been associated with chronic obstructive pulmonary disease (COPD) in genome-wide association studies and recent studies suggest that HH signalling could be altered in COPD. We therefore used minimally invasive endobronchial procedures to assess activation of the HH pathway including the main transcription factor, Gli2, and the ligand, Sonic HH (Shh).

METHODS

Thirty non-COPD patients and 28 COPD patients were included. Bronchial brushings, bronchoalveolar lavage fluid (BALF) and bronchial biopsies were obtained from fiberoptic bronchoscopy. Characterization of cell populations and subcellular localization were evaluated by immunostaining. ELISA and RNAseq analysis were performed to identify Shh proteins in BAL and transcripts on lung tissues from non-COPD and COPD patients with validation in an external and independent cohort.

RESULTS

Compared to non-COPD patients, COPD patients exhibited a larger proportion of basal cells in bronchial brushings (26 ± 11% vs 13 ± 6%; p < 0.0001). Airway basal cells of COPD subjects presented less intense nuclear staining for Gli2 in bronchial brushings and biopsies (p < 0.05). Bronchial BALF from COPD patients contained lower Shh concentrations than non-COPD BALF (12.5 vs 40.9 pg/mL; p = 0.002); SHH transcripts were also reduced in COPD lungs in the validation cohort (p = 0.0001).

CONCLUSION

This study demonstrates the feasibility of assessing HH pathway activation in respiratory samples collected by bronchoscopy and identifies impaired bronchial epithelial HH signalling in COPD.

Gestational Exposure to Cigarette Smoke Suppresses the Gasotransmitter H2S Biogenesis and the Effects Are Transmitted Transgenerationally

Rationale: Gestational cigarette smoke (CS) impairs lung angiogenesis and alveolarization, promoting transgenerational development of asthma and bronchopulmonary dysplasia (BPD). Hydrogen sulfide (H₂S), a proangiogenic, pro-alveolarization, and anti-asthmatic gasotransmitter is synthesized by cystathionine-γ-lyase (CSE), cystathionine-β-synthase (CBS), and 3-mercaptopyruvate sulfur transferase (3MST). Objective: Determine if gestational CS exposure affected the expression of H₂S synthesizing enzymes in the mouse lung and human placenta. Methods: Mice were exposed throughout gestational period to secondhand CS (SS) at approximating the dose of CS received by a pregnant woman sitting in a smoking bar for 3 h/days during pregnancy. Lungs from 7-days old control and SS-exposed pups and human placenta from mothers who were either non-smokers or smokers during pregnancy were analyzed for expression of the enzymes. Measurements: Mouse lungs and human placentas were examined for the expression of CSE, CBS, and 3MST by immunohistochemical staining, qRT-PCR and/or Western blot (WB) analyses. Results: Compared to controls, mouse lung exposed gestationally to SS had significantly lower levels of CSE, CBS, and 3MST. Moreover, the SS-induced suppression of CSE and CBS in F1 lungs was transmitted to the F2 generation without significant change in the magnitude of the suppression. These changes were associated with impaired epithelial-mesenchymal transition (EMT)-a process required for normal lung angiogenesis and alveolarization. Additionally, the placentas from mothers who smoked during pregnancy, expressed significantly lower levels of CSE, CBS, and 3MST, and the effects were partially moderated by quitting smoking during the first trimester. Conclusions: Lung H₂S synthesizing enzymes are downregulated by gestational CS and the effects are transmitted to F2 progeny. Smoking during pregnancy decreases H₂S synthesizing enzymes is human placentas, which may correlate with the increased risk of asthma/BPD in children.

Understanding Human Lung Development through In Vitro Model Systems

An abundance of information about lung development in animal models exists; however, comparatively little is known about lung development in humans. Recent advances using primary human lung tissue combined with the use of human in vitro model systems, such as human pluripotent stem cell-derived tissue, have led to a growing understanding of the mechanisms governing human lung development. They have illuminated key differences between animal models and humans, underscoring the need for continued advancements in modeling human lung development and utilizing human tissue. This review discusses the use of human tissue and the use of human in vitro model systems that have been leveraged to better understand key regulators of human lung development and that have identified uniquely human features of development. This review also examines the implementation and challenges of human model systems and discusses how they can be applied to address knowledge gaps.

Glucocorticoid regulates mesenchymal cell differentiation required for perinatal lung morphogenesis and function

While antenatal glucocorticoids are widely used to enhance lung function in preterm infants, cellular and molecular mechanisms by which glucocorticoid receptor (GR) signaling influences lung maturation remain poorly understood. Deletion of the glucocorticoid receptor gene (Nr3c1) from fetal pulmonary mesenchymal cells phenocopied defects caused by global Nr3c1 deletion, while lung epithelial- or endothelial-specific Nr3c1 deletion did not impair lung function at birth. We integrated genome-wide gene expression profiling, ATAC-seq, and single cell RNA-seq data in mice in which GR was deleted or activated to identify the cellular and molecular mechanisms by which glucocorticoids control prenatal lung maturation. GR enhanced differentiation of a newly defined proliferative mesenchymal progenitor cell (PMP) into matrix fibroblasts (MFBs), in part by directly activating extracellular matrix-associated target genes, including Fn1, Col16a4, and Eln and by modulating VEGF, JAK-STAT, and WNT signaling. Loss of mesenchymal GR signaling blocked fibroblast progenitor differentiation into mature MFBs, which in turn increased proliferation of SOX9+ alveolar epithelial progenitor cells and inhibited differentiation of mature alveolar type II (AT₂) and AT₁ cells. GR signaling controls genes required for differentiation of a subset of proliferative mesenchymal progenitors into matrix fibroblasts, in turn, regulating signals controlling AT₂/AT₁ progenitor cell proliferation and differentiation and identifying cells and processes by which glucocorticoid signaling regulates fetal lung maturation.

Nascent Lung Organoids Reveal Epithelium- and Bone Morphogenetic Protein-mediated Suppression of Fibroblast Activation

Reciprocal epithelial-mesenchymal interactions are pivotal in lung development, homeostasis, injury, and repair. Organoids have been used to investigate such interactions, but with a major focus on epithelial responses to mesenchyme and less attention to epithelial effects on mesenchyme. In the present study, we used nascent organoids composed of human and mouse lung epithelial and mesenchymal cells to demonstrate that healthy lung epithelium dramatically represses transcriptional, contractile, and matrix synthetic functions of lung fibroblasts. Repression of fibroblast activation requires signaling via the bone morphogenetic protein (BMP) pathway. BMP signaling is diminished after epithelial injury in vitro and in vivo, and exogenous BMP4 restores fibroblast repression in injured organoids. In contrast, inhibition of BMP signaling in healthy organoids is sufficient to derepress fibroblast matrix synthetic function. Our results reveal potent repression of fibroblast activation by healthy lung epithelium and a novel mechanism by which epithelial loss or injury is intrinsically coupled to mesenchymal activation via loss of repressive BMP signaling.

FGF9 and FGF10 activate distinct signaling pathways to direct lung epithelial specification and branching

Fibroblast growth factors (FGFs) 9 and 10 are essential during the pseudoglandular stage of lung development. Mesothelium-produced FGF9 is principally responsible for mesenchymal growth, whereas epithelium-produced FGF9 and mesenchyme-produced FGF10 guide lung epithelial development, and loss of either of these ligands affects epithelial branching. Because FGF9 and FGF10 activate distinct FGF receptors (FGFRs), we hypothesized that they would control distinct developmental processes. Here, we found that FGF9 signaled through epithelial FGFR3 to directly promote distal epithelial fate specification and inhibit epithelial differentiation. By contrast, FGF10 signaled through epithelial FGFR2b to promote epithelial proliferation and differentiation. Furthermore, FGF9-FGFR3 signaling functionally opposed FGF10-FGFR2b signaling, and FGFR3 preferentially used downstream phosphoinositide 3-kinase (PI3K) pathways, whereas FGFR2b relied on downstream mitogen-activated protein kinase (MAPK) pathways. These data demonstrate that, within lung epithelial cells, different FGFRs function independently; they bind receptor-specific ligands and direct distinct developmental functions through the activation of distinct downstream signaling pathways.

Basic and translational science advances in congenital diaphragmatic hernia

Congenital Diaphragmatic Hernia (CDH) is a birth defect that is characterized by lung hypoplasia, pulmonary hypertension and a diaphragmatic defect that allows herniation of abdominal organs into the thoracic cavity. Although widely unknown to the public, it occurs as frequently as cystic fibrosis (1:2500). There is no monogenetic cause, but different animal models revealed various biological processes and epigenetic factors involved in the pathogenesis. However, the pathobiology of CDH is not sufficiently understood and its mortality still ranges between 30 and 50%. Future collaborative initiatives are required to improve our basic knowledge and advance novel strategies to (prenatally) treat the abnormal lung development. This review focusses on the genetic, epigenetic and protein background and the latest advances in basic and translational aspects of CDH research.

Congenital diaphragmatic hernia as a potential target for transamniotic stem cell therapy

PURPOSE

We sought to determine whether TRASCET could impact congenital diaphragmatic hernia (CDH).

METHODS

Twelve pregnant dams received Nitrofen on gestational day 9.5 (E9; term = 22 days) to induce fetal CDH. Fetuses were divided into three groups: untreated (n = 31) and two groups receiving volume-matched intraamniotic injections of either saline (n = 37) or a suspension of 2 × 10⁶ cells/mL of amniotic fluid-derived mesenchymal stem cells (afMSCs; n = 65) on E17. Animals were euthanized at term. Expression of fibroblast growth factor-10 (FGF-10), vascular endothelial growth factor-A (VEGF-A), and surfactant protein-C (SPC) was quantified by qRT-PCR. Statistical analysis was by the Mann-Whitney U test with Bonferroni adjusted criterion (p ≤ 0.01).

RESULTS

Among survivors with CDH (n = 27/133), the TRASCET group showed significant downregulation of FGF-10 and VEGF-A gene expressions compared to the untreated (p < 0.001 for both) and saline groups (p = 0.005 and p = 0.004, respectively). SPC expression was higher in the TRASCET group compared to the untreated group (p = 0.01), but not the saline group (p = 0.043). Lung laterality had minimal impact on these comparisons.

CONCLUSIONS

Transamniotic stem cell therapy affects select processes of lung development in experimental congenital diaphragmatic hernia. Further scrutiny into this novel therapy as a potential component of the prenatal management of this disease is warranted.

LEVEL OF EVIDENCE

N/A (animal and laboratory study).

Mechanical forces induce an asthma gene signature in healthy airway epithelial cells

Bronchospasm compresses the bronchial epithelium, and this compressive stress has been implicated in asthma pathogenesis. However, the molecular mechanisms by which this compressive stress alters pathways relevant to disease are not well understood. Using air-liquid interface cultures of primary human bronchial epithelial cells derived from non-asthmatic donors and asthmatic donors, we applied a compressive stress and then used a network approach to map resulting changes in the molecular interactome. In cells from non-asthmatic donors, compression by itself was sufficient to induce inflammatory, late repair, and fibrotic pathways. Remarkably, this molecular profile of non-asthmatic cells after compression recapitulated the profile of asthmatic cells before compression. Together, these results show that even in the absence of any inflammatory stimulus, mechanical compression alone is sufficient to induce an asthma-like molecular signature.

Endosome-Mediated Epithelial Remodeling Downstream of Hedgehog-Gli Is Required for Tracheoesophageal Separation

The trachea and esophagus arise from the separation of a common foregut tube during early fetal development. Mutations in key signaling pathways such as Hedgehog (HH)/Gli can disrupt tracheoesophageal (TE) morphogenesis and cause life-threatening birth defects (TEDs); however, the underlying cellular mechanisms are unknown. Here, we use mouse and Xenopus to define the HH/Gli-dependent processes orchestrating TE morphogenesis. We show that downstream of Gli the Foxf1+ splanchnic mesenchyme promotes medial constriction of the foregut at the boundary between the presumptive Sox2+ esophageal and Nkx2-1+ tracheal epithelium. We identify a unique boundary epithelium co-expressing Sox2 and Nkx2-1 that fuses to form a transient septum. Septum formation and resolution into distinct trachea and esophagus requires endosome-mediated epithelial remodeling involving the small GTPase Rab11 and localized extracellular matrix degradation. These are disrupted in Gli-deficient embryos. This work provides a new mechanistic framework for TE morphogenesis and informs the cellular basis of human TEDs.

Comprehensive anatomic ontologies for lung development: A comparison of alveolar formation and maturation within mouse and human lung

BACKGROUND

Although the mouse is widely used to model human lung development, function, and disease, our understanding of the molecular mechanisms involved in alveolarization of the peripheral lung is incomplete. Recently, the Molecular Atlas of Lung Development Program (LungMAP) was funded by the National Heart, Lung, and Blood Institute to develop an integrated open access database (known as BREATH) to characterize the molecular and cellular anatomy of the developing lung. To support this effort, we designed detailed anatomic and cellular ontologies describing alveolar formation and maturation in both mouse and human lung.

DESCRIPTION

While the general anatomic organization of the lung is similar for these two species, there are significant variations in the lung's architectural organization, distribution of connective tissue, and cellular composition along the respiratory tract. Anatomic ontologies for both species were constructed as partonomic hierarchies and organized along the lung's proximal-distal axis into respiratory, vascular, neural, and immunologic components. Terms for developmental and adult lung structures, tissues, and cells were included, providing comprehensive ontologies for application at varying levels of resolution. Using established scientific resources, multiple rounds of comparison were performed to identify common, analogous, and unique terms that describe the lungs of these two species. Existing biological and biomedical ontologies were examined and cross-referenced to facilitate integration at a later time, while additional terms were drawn from the scientific literature as needed. This comparative approach eliminated redundancy and inconsistent terminology, enabling us to differentiate true anatomic variations between mouse and human lungs. As a result, approximately 300 terms for fetal and postnatal lung structures, tissues, and cells were identified for each species.

CONCLUSION

These ontologies standardize and expand current terminology for fetal and adult lungs, providing a qualitative framework for data annotation, retrieval, and integration across a wide variety of datasets in the BREATH database. To our knowledge, these are the first ontologies designed to include terminology specific for developmental structures in the lung, as well as to compare common anatomic features and variations between mouse and human lungs. These ontologies provide a unique resource for the LungMAP, as well as for the broader scientific community.

The impact of perinatal nicotine exposure on fetal lung development and subsequent respiratory morbidity

Maternal smoking during pregnancy remains as a significant public health crisis as it did decades ago. Although its prevalence is decreasing in high-income countries, it has worsened globally, along with a concerning emergence of electronic-cigarette usage within the last two decades. Extensive epidemiologic and experimental evidence exists from both human and animal studies, demonstrating the detrimental long-term pulmonary outcomes in the offspring of mothers who smoke during pregnancy. Even secondhand and thirdhand smoke exposure to the developing lung might be as or even more harmful than firsthand smoke exposure. Furthermore, these effects are not limited only to the exposed progeny, but can also be transmitted transgenerationally. There is compelling evidence to support that the majority of the effects of perinatal smoke exposure on the developing lung, including the transgenerational transmission of asthma, is mediated by nicotine. Nicotine exposure induces cell-specific molecular changes in lungs, which offers a unique opportunity to prevent, halt, and/or reverse the resultant damage through targeted molecular interventions. Experimentally, the proposed interventions, such as administration of peroxisome proliferator-activated receptor gamma (PPARγ) agonists can not only block but also potentially reverse the perinatal nicotine exposure-induced respiratory morbidity in the exposed offspring. However, the development of a safe and effective intervention is still many years away. In the meantime, electropuncture at specific acupoints appears to be emerging as a more practical and safe physiologic approach to block the harmful pulmonary consequences of perinatal nicotine exposure.

Noggin depletion in adipocytes promotes obesity in mice

OBJECTIVE

Obesity has increased to pandemic levels and enhanced understanding of adipose regulation is required for new treatment strategies. Although bone morphogenetic proteins (BMPs) influence adipogenesis, the effect of BMP antagonists such as Noggin is largely unknown. The aim of the study was to define the role of Noggin, an extracellular BMP inhibitor, in adipogenesis.

METHODS

We generated adipose-derived progenitor cells and a mouse model with adipocyte-specific Noggin deletion using the AdiponectinCre transgenic mouse, and determined the adipose phenotype of Noggin-deficiency.

RESULTS

Our studies showed that Noggin is expressed in progenitor cells but declines in adipocytes, possibly allowing for lipid accumulation. Correspondingly, adipocyte-specific Noggin deletion in vivo promoted age-related obesity in both genders with no change in food intake. Although the loss of Noggin caused white adipose tissue hypertrophy, and whitening and impaired function in brown adipose tissue in both genders, there were clear gender differences with the females being most affected. The females had suppressed expression of brown adipose markers and thermogenic genes including peroxisome proliferator activated receptor gamma coactivator 1 alpha (PGC1alpha) and uncoupling protein 1 (UCP1) as well as genes associated with adipogenesis and lipid metabolism. The males, on the other hand, had early changes in a few BAT markers and thermogenic genes, but the main changes were in the genes associated with adipogenesis and lipid metabolism. Further characterization revealed that both genders had reductions in VO2, VCO2, and RER, whereas females also had reduced heat production. Noggin was also reduced in diet-induced obesity in inbred mice consistent with the obesity phenotype of the Noggin-deficient mice.

CONCLUSIONS

BMP signaling regulates female and male adipogenesis through different metabolic pathways. Modulation of adipose tissue metabolism by select BMP antagonists may be a strategy for long-term regulation of age-related weight gain and obesity.

Dnmt1 is required for proximal-distal patterning of the lung endoderm and for restraining alveolar type 2 cell fate

Lung endoderm development occurs through a series of finely coordinated transcriptional processes that are regulated by epigenetic mechanisms. However, the role of DNA methylation in regulating lung endoderm development remains poorly understood. We demonstrate that DNA methyltransferase 1 (Dnmt1) is required for early branching morphogenesis of the lungs and for restraining epithelial fate specification. Loss of Dnmt1 leads to an early branching defect, a loss of epithelial polarity and proximal endodermal cell differentiation, and an expansion of the distal endoderm compartment. Dnmt1 deficiency also disrupts epithelial-mesenchymal crosstalk and leads to precocious distal endodermal cell differentiation with premature expression of alveolar type 2 cell restricted genes. These data reveal an important requirement for Dnmt1 mediated DNA methylation in early lung development to promote proper branching morphogenesis, maintain proximal endodermal cell fate, and suppress premature activation of the distal epithelial fate.

Laser-capture microdissection of murine lung for differential cellular RNA analysis

The lung tissue contains a heterogeneous milieu of bronchioles, epithelial, airway smooth muscle (ASM), alveolar, and immune cell types. Healthy bronchiole comprises epithelial cells surrounded by ASM cells and helps in normal respiration. In contrast, airway remodeling, or plasticity, increases surrounding of bronchial epithelium during inflammation, especially in asthmatic condition. Given the profound functional difference between ASM, epithelial, and other cell types in the lung, it is imperative to separate and isolate different cell types of lungs for genomics, proteomics, and molecular analysis, which will improve the diagnostic and therapeutic approach to treat cell-specific lung disorders. Laser capture microdissection (LCM) is the technique generally used for the isolation of specific cell populations under direct visual inspection, which plays a crucial role to evaluate cell-specific effect in clinical and preclinical setup. However, maintenance of tissue RNA quality and integrity in LCM studies are very challenging tasks. It is obvious to believe that the major factor affecting the RNA quality is tissue-fixation method. The prime focus of this study was to address the RNA quality factors within the lung tissue using the different solvent system to fix tissue sample to obtain high-quality RNA. Paraformaldehyde and Carnoy's solutions were used for fixing the lung tissue and compared RNA integrity in LCM captured lung tissue samples. To further confirm the quality of RNA, we measured cellular marker genes in collected lung tissue samples from control and mixed allergen (MA)-induced asthmatic mouse model using qRT-PCR technique. RNA integrity number showed a significantly better quality of RNA in lung tissue samples fixed with Carnoy's solution compared to paraformaldehyde solution. Isolated RNA from MA-induced asthmatic murine lung epithelium, smooth muscle, and granulomatous foci using LCM showed a significant increase in remodeling gene expression compared to control which confirm the quality and integrity of isolated RNA. Overall, the study concludes tissue fixation solvent can alter the quality of RNA in the lung and the outcome of the results.

The Hedgehog target Gli1 is not required for bleomycin-induced lung fibrosis

Sonic Hedgehog (SHH) signaling, a developmental pathway promoting lung mesenchymal expansion and differentiation during embryogenesis, has been increasingly recognized as a profibrotic factor in mature lung, where it might contribute to the pathogenesis of lung fibrosis. Pathway inhibition at the level of the downstream Gli transcription factors Gli1 and Gli2 (by GANT61) ameliorates lung fibrosis in the bleomycin model, whereas inhibition proximally at the level of HH ligand (by anti Hh antibody 5E1) or Smo (by GDC-0449) of the canonical pathway does not, implicating Gli1 and/or Gli2 as a key target. The fact that both the Gli1-labelled cell lineage and Gli1 expressing cells expand during fibrosis formation and contribute significantly to the pool of myofibroblasts in the fibrosis scars suggests a fibrogenic role for Gli1. Therefore to further dissect the roles of Gli1 and Gli2 in lung fibrosis we evaluated Gli1 KO and control mice in the bleomycin model. Monitoring of Gli1^+/+ (n = 12), Gli1^lZ/+ (n = 37) and Gli1^lZ/lZ (n = 18) mice did not reveal differences in weight loss or survival. Lung evaluation at the 21-day endpoint did not show differences in lung fibrosis formation (as judged by morphology and trichrome staining), Ashcroft score, lung collagen content, lung weight, BAL protein content or BAL cell differential count. Our data suggest that Gli1 is not required for bleomycin-induced lung fibrosis.

Retinoic acid signaling in vascular development

Formation of the vasculature is an essential developmental process, delivering oxygen and nutrients to support cellular processes needed for tissue growth and maturation. Retinoic acid (RA) and its downstream signaling pathway is vital for normal pre- and post-natal development, playing key roles in the specification and formation of many organs and tissues. Here, we review the role of RA in blood and lymph vascular development, beginning with embryonic yolk sac vasculogenesis and remodeling and discussing RA's organ-specific roles in angiogenesis and vessel maturation. In particular, we highlight the multi-faceted role of RA signaling in CNS vascular development and acquisition of blood-brain barrier properties.

Effects of Agricultural Organic Dusts on Human Lung-Resident Mesenchymal Stem (Stromal) Cell Function

Agricultural organic dust exposures trigger harmful airway inflammation, and workers experiencing repetitive dust exposures are at increased risk for lung disease. Mesenchymal stem/stromal cells (MSCs) regulate wound repair processes in the lung, and may contribute to either proresolution or -fibrotic lung responses. It is unknown how organic dust exposures alter lung-resident MSC activation and proinflammatory versus prorepair programs in the lung. To address this gap in knowledge, we isolated human lung-resident MSC from lung tissue. Cells were stimulated with aqueous extracts of organic dusts (DE) derived from swine confinement facilities and were assessed for changes in proliferative and migratory capacities, and production of proinflammatory and prorepair mediators. Through these investigations, we found that DE induces significant release of proinflammatory mediators TNF-α, IL-6, IL-8, and matrix metalloproteases, while also inducing the production of prorepair mediators amphiregulin, FGF-10, and resolvin D1. In addition, DE significantly reduced the growth and migratory capacities of lung-resident MSC. Together, these investigations indicate lung-resident MSC activation and wound repair activities are altered by organic dust exposures. These findings warrant future investigations to assess how organic dusts affect lung-resident mesenchymal stem/stromal cell function and impact airway inflammation, injury, and repair during agricultural aerosol exposures.