Exhaustion of Airway Basal Progenitor Cells in Early and Established Chronic Obstructive Pulmonary Disease

Intermittent exposure to whole cigarette smoke alters the differentiation of primary small airway epithelial cells in the air-liquid interface culture

Cigarette smoke (CS) is the leading risk factor to develop COPD. Therefore, the pathologic effects of whole CS on the differentiation of primary small airway epithelial cells (SAEC) were investigated, using cells from three healthy donors and three COPD patients, cultured under ALI (air-liquid interface) conditions. The analysis of the epithelial physiology demonstrated that CS impaired barrier formation and reduced cilia beat activity. Although, COPD-derived ALI cultures preserved some features known from COPD patients, CS-induced effects were similarly pronounced in ALI cultures from patients compared to healthy controls. RNA sequencing analyses revealed the deregulation of marker genes for basal and secretory cells upon CS exposure. The comparison between gene signatures obtained from the in vitro model (CS vs. air) with a published data set from human epithelial brushes (smoker vs. non-smoker) revealed a high degree of similarity between deregulated genes and pathways induced by CS. Taken together, whole cigarette smoke alters the differentiation of small airway basal cells in vitro. The established model showed a good translatability to the situation in vivo. Thus, the model can help to identify and test novel therapeutic approaches to restore the impaired epithelial repair mechanisms in COPD, which is still a high medical need.

Organoid models in lung regeneration and cancer

Improper regeneration is associated with lung diseases including lung cancer. Lung cancer is one of the leading causes of death worldwide, with nearly 2 million new cases diagnosed each year. The diagnosis is often too late for successful therapeutic intervention. Lung cancer shows substantial phenotypic and genetic heterogeneity between individuals, making it difficult to model in animals. Organoids, derived from regional stem/progenitor cells in lung epithelia, have attracted extensive interest in both research studies and the clinic, because of their great potential for use in cancer treatment. Various lung cancer organoids have been established to recapitulate the tissue architecture of primary lung tumors and maintain the genomic alterations of the original tumors during long-term expansion in vitro. In this review, we summarize the current data on lung epithelial regeneration by regional endogenous stem/progenitor cells, describe the development of organoid technology, and present its applications in lung cancer research. Furthermore, recent challenges and future directions to improve organoid technologies for lung cancer treatment are discussed.

Aberrant Epithelial Cell Proliferation in Peripheral Airways in Bronchiectasis

Dilation of bronchi and bronchioles caused by destruction and excessive epithelial remodeling is a characteristic feature of bronchiectasis. It is not known how epithelial progenitor cells contribute to these pathologic conditions in peripheral airways (bronchioles) in bronchiectasis. We aimed to explore the expression levels of signature airway progenitor cells in the dilated bronchioles in patients with bronchiectasis. We obtained the surgically resected peripheral lung tissues from 43 patients with bronchiectasis and 33 control subjects. Immunostaining was performed to determine the expression patterns of thyroid transcription factor-1 (TTF-1, for labeling progenitor cells in distal airways), P63 (basal cells), club cell 10 kDa protein (CC10, club cells), and surfactant protein C (SPC, alveolar type II epithelial cells) in epithelium or sub-epithelium. Here, we reported significantly lower percentage of TTF-1⁺ cells and CC10⁺ cells, and higher percentage of P63⁺ cells within the epithelium of dilated bronchioles compared with control bronchioles. In airway sub-epithelium of the dilated bronchioles, epithelial hyperplasia with disarrangement of TTF-1⁺ cells yielded cuboidal (100%) and columnar (93.0%) type among bronchiectasis patients. Most progenitor cell markers co-localized with TTF-1. The median (the 1st, 3rd quartile) percentage of P63⁺TTF-1⁺, CC10⁺TTF-1⁺, and SPC⁺TTF-1⁺ cells was 16.0% (8.9, 24.0%), 14.5% (7.1, 20.8%), and 52% (40.3, 64.4%), respectively. For cuboidal epithelial hyperplasia, 91.0% (86.5, 94.0%) of areas co-stained with SPC and TTF-1. Columnar epithelial hyperplasia was characterized by TTF-1 co-staining with P63⁺TTF-1⁺ and CC10⁺TTF-1⁺ cells. Taken together, aberrant proliferation of airway progenitor cells in both epithelium and sub-epithelium are implicated in bronchiectasis.

CD90+CD146+ identifies a pulmonary mesenchymal cell subtype with both immune modulatory and perivascular-like function in postnatal human lung

Our understanding of mesenchymal cell subsets and their function in human lung affected by aging and in certain disease settings remains poorly described. We use a combination of flow cytometry, prospective cell-sorting strategies, confocal imaging, and modeling of microvessel formation using advanced microfluidic chip technology to characterize mesenchymal cell subtypes in human postnatal and adult lung. Tissue was obtained from patients undergoing elective surgery for congenital pulmonary airway malformations (CPAM) and other airway abnormalities including chronic obstructive pulmonary disease (COPD). In microscopically normal postnatal human lung, there was a fivefold higher mesenchymal compared with epithelial (EpCAM⁺) fraction, which diminished with age. The mesenchymal fraction composed of CD90⁺ and CD90⁺CD73⁺ cells was enriched in CXCL12 and platelet-derived growth factor receptor-α (PDGFRα) and located in close proximity to EpCAM⁺ cells in the alveolar region. Surprisingly, alveolar organoids generated from EpCAM⁺ cells supported by CD90⁺ subset were immature and displayed dysplastic features. In congenital lung lesions, cystic air spaces and dysplastic alveolar regions were marked with an underlying thick interstitium composed of CD90⁺ and CD90⁺PDGFRα⁺ cells. In postnatal lung, a subset of CD90⁺ cells coexpresses the pericyte marker CD146 and supports self-assembly of perfusable microvessels. CD90⁺CD146⁺ cells from COPD patients fail to support microvessel formation due to fibrinolysis. Targeting the plasmin-plasminogen system during microvessel self-assembly prevented fibrin gel degradation, but microvessels were narrower and excessive contraction blocked perfusion. These data provide important new information regarding the immunophenotypic identity of key mesenchymal lineages and their change in a diverse setting of congenital lung lesions and COPD.

Lung epithelium damage in COPD - An unstoppable pathological event?

Chronic obstructive pulmonary disease (COPD) is a common term for alveolar septal wall destruction resulting in emphysema, and chronic bronchitis accompanied by conductive airway remodelling. In general, this disease is characterized by a disbalance of proteolytic/anti-proteolytic activity, augmented inflammatory response, increased oxidative/nitrosative stress, rise in number of apoptotic cells and decreased proliferation. As the first responder to the various environmental stimuli, epithelium occupies an important position in different lung pathologies, including COPD. Epithelium sequentially transitions from the upper airways in the direction of the gas exchange surface in the alveoli, and every cell type possesses a distinct role in the maintenance of the homeostasis. Basically, a thick ciliated structure of the airway epithelium has a major function in mucus secretion, whereas, alveolar epithelium which forms a thin barrier covered by surfactant has a function in gas exchange. Following this line, we will try to reveal whether or not the chronic bronchitis and emphysema, being two pathological phenotypes in COPD, could originate in two different types of epithelium. In addition, this review focuses on the role of lung epithelium in COPD pathology, and summarises underlying mechanisms and potential therapeutics.

Altered generation of ciliated cells in chronic obstructive pulmonary disease

In COPD, epithelial changes are prominent features in the airways, such as goblet cell hyperplasia and squamous metaplasia. In contrast, it remains unclear whether ciliated cells are reduced and which pathways dysregulate epithelial differentiation. We hypothesized that bronchial epithelial cell lineage specification is dysregulated in COPD because of an aberrant reprogramming through transforming growth factor (TGF)-β1. Surgical lung tissue from 81 COPD and 61 control (smokers and non-smokers) patients was assessed for bronchial epithelial cell phenotyping by immunohistochemistry, both in situ and in vitro in reconstituted air-liquid interface (ALI) cultures. The role of TGF-β1 was studied in vitro. COPD epithelium in large airways, when compared to controls, showed decreased β-tubulin IV + ciliated cells (4.4%, 2.5–8.8% versus 8.5%, 6.3–11.8% of surface staining, median and IQR, p = 0.0009) and increased MUC5AC + goblet cells (34.8%, 24.4–41.9% versus 10.3%, 5.1–17.6%, p < 0.0001). Both features were recapitulated in the ALI-cultured epithelium from COPD patients. Exogenous TGF-β1 reduced mucociliary differentiation while neutralizing TGF-β1 during ALI increased both specialized cell types. The COPD airway epithelium displays altered differentiation for ciliated cells, which recapitulates in vitro, at least in part through TGF-β1.

Pathogenesis of chronic obstructive pulmonary disease (COPD) induced by cigarette smoke

Chronic obstructive pulmonary disease (COPD) is a common respiratory disease that is characterized by functional and structural alterations primarily caused by long-term inhalation of harmful particles. Cigarette smoke (CS) induces airway inflammation in COPD, which is known to persist even after smoking cessation. This review discusses the basic pathogenesis of COPD, with particular focus on an endogenous protective mechanism against oxidative stress via Nrf2, altered immune response of the airway inflammatory cells, exaggerated cellular senescence of the lung structural cells, and cell death with expanded inflammation. Recently, CS-induced mitochondria autophagy is reported to initiate programmed necrosis (necroptosis). Necroptosis is a new concept of cell death which is driven by a defined molecular pathway along with exaggerated inflammation. This new cell death mechanism is of importance due to its ability to produce more inflammatory substances during the process of epithelial death, contributing to persistent airway inflammation that cannot be explained by apoptosis-derived cell death. Autophagy is an auto-cell component degradation system executed by lysosomes that controls protein and organelle degradation for successful homeostasis. As well as in the process of necroptosis, autophagy is also observed during cellular senescence. Aging of the lungs results in the acquisition of senescence-associated secretory phenotypes (SASP) that are known to secrete inflammatory cytokines, chemokines, growth factors, and matrix metalloproteinases resulting in chronic low-grade inflammation. In future research, we intend to highlight the genetic and epigenetic approaches that can facilitate the understanding of disease susceptibility. The goal of precision medicine is to establish more accurate diagnosis and treatment methods based on the patient-specific pathogenic characteristics. This review provides insights into CS-induced COPD pathogenesis, which contributes to a very complex disease. Investigating the mechanism of developing COPD, along with the availability of the particular inhibitors, will lead to new therapeutic approaches in COPD treatment.

Rhinovirus-Induced SIRT-1 via TLR2 Regulates Subsequent Type I and Type III IFN Responses in Airway Epithelial Cells

IFN responses to viral infection are necessary to establish intrinsic antiviral state, but if unchecked can lead to heightened inflammation. Recently, we showed that TLR2 activation contributes to limitation of rhinovirus (RV)-induced IFN response in the airway epithelial cells. We also demonstrated that compared with normal airway epithelial cells, those from patients with chronic obstructive pulmonary disease (COPD) show higher IFN responses to RV, but the underlying mechanisms are not known. Initially, RV-induced IFN responses depend on dsRNA receptor activation and then are amplified via IFN-stimulated activation of JAK/STAT signaling. In this study, we show that in normal cells, TLR2 limits RV-induced IFN responses by attenuating STAT1 and STAT2 phosphorylation and this was associated with TLR2-dependent SIRT-1 expression. Further, inhibition of SIRT-1 enhanced RV-induced IFN responses, and this was accompanied by increased STAT1/STAT2 phosphorylation, indicating that TLR2 may limit RV-induced IFN responses via SIRT-1. COPD airway epithelial cells showed attenuated IL-8 responses to TLR2 agonist despite expressing TLR2 similar to normal, indicating dysregulation in TLR2 signaling pathway. Unlike normal, COPD cells failed to show RV-induced TLR2-dependent SIRT-1 expression. Pretreatment with quercetin, which increases SIRT-1 expression, normalized RV-induced IFN levels in COPD airway epithelial cells. Inhibition of SIRT-1 in quercetin-pretreated COPD cells abolished the normalizing effects of quercetin on RV-induced IFN expression in these cells, confirming that quercetin exerts its effect via SIRT-1. In summary, we show that TLR2 is required for limiting RV-induced IFNs, and this pathway is dysregulated in COPD airway epithelial cells, leading to exaggerated IFN production.

Alveolar Differentiation Potency of Human Distal Airway Stem Cells Is Associated with Pulmonary Pathological Conditions

Background

This study is aimed at characterizing the human distal airway stem cells (DASCs) and assessing their therapeutic potential in patients with chronic, degenerative lung diseases. These findings will provide a comprehensive understanding for further clinical applications utilizing autologous airway stem cells as therapeutic intervention in respiratory diseases.

Methods

DASCs were isolated from healthy subjects or patients diagnosed with bronchiectasis, chronic obstructive pulmonary diseases (COPD), or interstitial lung disease (ILD). Differentiation capacity, a key property of the stem cells, was studied using a novel monolayer differentiation system. The differentiated cells were evaluated for alveolar and bronchial cell marker expression, and the quantified expression level of differentiated cells was further examined for their relationship with age and pulmonary function of the subjects.

Results and Conclusions

Differentiation of DASCs and tracheal stem cells (TSCs) yielded an alveolus-like structure and a tube-shaped structure, respectively, with distinct marker gene expression. Additionally, single-cell-derived clones showed diverse differentiation fates, even if the clones arise from identical or different individuals. More importantly, the alveolar differentiation potency was higher in DASCs derived from patients than from healthy people. The differentiation efficiency of DASCs also correlates with age in patients with bronchiectasis and ILD.

Exaggerated BMP4 signalling alters human airway basal progenitor cell differentiation to cigarette smoking-related phenotypes

Airway remodelling in chronic obstructive pulmonary disease (COPD) originates, in part, from smoking-induced changes in airway basal stem/progenitor cells (BCs). Based on the knowledge that bone morphogenetic protein 4 (BMP4) influences epithelial progenitor function in the developing and adult mouse lung, we hypothesised that BMP4 signalling may regulate the biology of adult human airway BCs relevant to COPD.BMP4 signalling components in human airway epithelium were analysed at the mRNA and protein levels, and the differentiation of BCs was assessed using the BC expansion and air-liquid interface models in the absence/presence of BMP4, BMP receptor inhibitor and/or small interfering RNAs against BMP receptors and downstream signalling.The data demonstrate that in cigarette smokers, BMP4 is upregulated in ciliated and intermediate undifferentiated cells, and expression of the BMP4 receptor BMPR1A is enriched in BCs. BMP4 induced BCs to acquire a smoking-related abnormal phenotype in vitro mediated by BMPR1A/Smad signalling, characterised by decreased capacity to differentiate into normal mucociliary epithelium, while generating squamous metaplasia.Exaggerated BMP4 signalling promotes cigarette smoking-relevant airway epithelial remodelling by inducing abnormal phenotypes in human airway BCs. Targeting of BMP4 signalling in airway BCs may represent a novel target to prevent/treat COPD-associated airway disease.

Regenerative pharmacology for COPD: breathing new life into old lungs

Chronic obstructive pulmonary disease (COPD) is a major global health concern with few effective treatments. Widespread destruction of alveolar tissue contributes to impaired gas exchange in severe COPD, and recent radiological evidence suggests that destruction of small airways is a major contributor to increased peripheral airway resistance in disease. This important finding might in part explain the failure of conventional anti-inflammatory treatments to restore lung function even in patients with mild disease. There is a clear need for alternative pharmacological strategies for patients with COPD/emphysema. Proposed regenerative strategies such as cell therapy and tissue engineering are hampered by poor availability of exogenous stem cells, discouraging trial results, and risks and cost associated with surgery. An alternative therapeutic approach is augmentation of lung regeneration and/or repair by biologically active factors, which have potential to be employed on a large scale. In favour of this strategy, the healthy adult lung is known to possess a remarkable endogenous regenerative capacity. Numerous preclinical studies have shown induction of regeneration in animal models of COPD/emphysema. Here, we argue that given the widespread and irreversible nature of COPD, serious consideration of regenerative pharmacology is necessary. However, for this approach to be feasible, a better understanding of the cell-specific molecular control of regeneration, the regenerative potential of the human lung and regenerative competencies of patients with COPD are required.

The Kinome of Human Alveolar Type II and Basal Cells, and Its Reprogramming in Lung Cancer

The discovery of mutant tyrosine kinases as oncogenic drivers of lung adenocarcinomas has changed the basic understanding of lung cancer development and therapy. Yet, expressed kinases (kinome) in lung cancer progenitor cells, as well as whether kinase expression and the overall kinome changes or is reprogrammed upon transformation, is incompletely understood. We hypothesized that the kinome differs between lung cancer progenitor cells, alveolar type II cells (ATII), and basal cells (BC) and that their respective kinomes undergo distinct lineage-specific reprogramming to adenocarcinomas and squamous cell carcinomas upon transformation. We performed RNA sequencing on freshly isolated human ATII, BC, and lung cancer cell lines to define the kinome in nontransformed cells and transformed cells. Our studies identified a unique kinome for ATII and BC and changes in their kinome upon transformation to their respective carcinomas.

Genetic landscape of chronic obstructive pulmonary disease identifies heterogeneous cell-type and phenotype associations

Chronic obstructive pulmonary disease (COPD) is the leading cause of respiratory mortality worldwide. Genetic risk loci provide new insights into disease pathogenesis. We performed a genome-wide association study in 35,735 cases and 222,076 controls from the UK Biobank and additional studies from the International COPD Genetics Consortium. We identified 82 loci associated with P < 5 × 10-8; 47 of these were previously described in association with either COPD or population-based measures of lung function. Of the remaining 35 new loci, 13 were associated with lung function in 79,055 individuals from the SpiroMeta consortium. Using gene expression and regulation data, we identified functional enrichment of COPD risk loci in lung tissue, smooth muscle, and several lung cell types. We found 14 COPD loci shared with either asthma or pulmonary fibrosis. COPD genetic risk loci clustered into groups based on associations with quantitative imaging features and comorbidities. Our analyses provide further support for the genetic susceptibility and heterogeneity of COPD.

Accelerated lung aging and chronic obstructive pulmonary disease

INTRODUCTION

The prevalence of chronic obstructive pulmonary disease (COPD) increases exponentially with aging. Its pathogenesis, however, is not well known and aside from smoking cessation, there are no disease-modifying treatments for this disease. Areas covered: COPD is associated with accelerating aging and aging-related diseases. In this review, we will discuss the hallmarks of aging including genomic instability, telomere attrition, epigenetic alteration, loss of proteostasis, mitochondrial dysfunction, deregulated nutrient sensing, cellular senescence, stem cell exhaustion, and altered intercellular communication, which may be involved in COPD pathogenesis. Expert commentary: COPD and the aging process share similar molecular and cellular changes. Aging-related molecular pathways may represent novel therapeutic targets and biomarkers for COPD.

Heterogeneity of Pulmonary Stem Cells

Epithelial stem cells reside within multiple regions of the lung where they renew various region-specific cells. In addition, there are multiple routes of regeneration after injury through built-in heterogeneity within stem cell populations and through a capacity for cellular plasticity among differentiated cells. These processes are important facets of respiratory tissue resiliency and organism survival. However, this regenerative capacity is not limitless, and repetitive or chronic injuries, environmental stresses, or underlying factors of disease may ultimately lead to or contribute to tissue remodeling and end-stage lung disease. This chapter will review stem cell heterogeneity among pulmonary epithelia in the lower respiratory system, discuss recent findings that may challenge long-held scientific paradigms, and identify several clinically relevant research opportunities for regenerative medicine.

Cognitive Impairment in Chronic Obstructive Pulmonary Disease (COPD): Possible Utility of Marine Bioactive Compounds

Chronic obstructive pulmonary disease (COPD) is characterized by long-term airflow limitation. Early-onset COPD in non-smoker subjects is ≥60 years and in the elderly is often associated with different comorbidities. Cognitive impairment is one of the most common feature in patients with COPD, and is associated with COPD severity and comorbidities. Cognitive impairment in COPD enhances the assistance requirement in different aspects of daily living, treatment adherence, and effectual self-management.This review describes various bioactive compounds of natural marine sources that modulate different targets shared by both COPD and cognitive impairment and hypothesizes a possible link between these two syndromes.