Huaiyong Chen

Transitional basal cells at the squamous–columnar junction generate Barrett’s oesophagus

In several organ systems, the transitional zone between different types of epithelium is a hotspot for pre-neoplastic metaplasia and malignancy, but the cells of origin for these metaplastic epithelia and subsequent malignancies remain unknown. In the case of Barrett’s oesophagus, intestinal metaplasia occurs at the gastro-oesophageal junction, where stratified squamous epithelium transitions into simple columnar cells. On the basis of a number of experimental models, several alternative cell types have been proposed as the source of this metaplasia but in all cases the evidence is inconclusive: no model completely mimics Barrett’s oesophagus in terms of the presence of intestinal goblet cells. Here we describe a transitional columnar epithelium with distinct basal progenitor cells (p63+KRT5+KRT7+) at the squamous–columnar junction of the upper gastrointestinal tract in a mouse model. We use multiple models and lineage tracing strategies to show that this squamous–columnar junction basal cell population serves as a source of progenitors for the transitional epithelium. On ectopic expression of CDX2, these transitional basal progenitors differentiate into intestinal-like epithelium (including goblet cells) and thereby reproduce Barrett’s metaplasia. A similar transitional columnar epithelium is present at the transitional zones of other mouse tissues (including the anorectal junction) as well as in the gastro-oesophageal junction in the human gut. Acid reflux-induced oesophagitis and the multilayered epithelium (believed to be a precursor of Barrett’s oesophagus) are both characterized by the expansion of the transitional basal progenitor cells. Our findings reveal a previously unidentified transitional zone in the epithelium of the upper gastrointestinal tract and provide evidence that the p63+KRT5+KRT7+ basal cells in this zone are the cells of origin for multi-layered epithelium and Barrett’s oesophagus.

Increased oxidative stress and disrupted small intestinal tight junctions in cigarette smoke-exposed rats

Chronic obstructive pulmonary disease (COPD) is a major public health problem, and cigarette smoke (CS) is the primary risk factor. The pathology is often observed in the lung, but COPD is also associated with intestinal barrier disruption, although the underlying mechanisms are poorly understood. To address this, a CS‑exposed rat model was evaluated in the present study by analyzing small intestinal gene expression using reverse transcription‑quantitative polymerase chain reaction. CS exposure caused upregulation of the nicotinamide adenine dinucleotide phosphate‑oxidase subunits nox2 and p22phox in the small intestine, while the antioxidative enzyme superoxide dismutase was downregulated. CS exposure also increased bax expression and decreased bcl‑2 expression. This was associated with an elevation of hypoxia‑inducible factor (HIF)‑1α. Claudin‑1 was decreased and claudin‑2 increased, indicating a loosening of small intestinal tight junctions (TJs). These data suggest that during the development of COPD, HIF‑1α expression is altered in the small intestine, which may be associated with the increased oxidative stress and apoptosis, eventually resulting in disruption of the intestinal TJs.

Glucocorticoid dexamethasone regulates the differentiation of mouse conducting airway epithelial progenitor cells

Inhaled glucocorticoid dexamethasone is the most effective treatment of asthma currently available. Epithelial damage and shedding represents a clear manifestation of asthmatic pathologies. However it remains unknown if dexamethasone regulates functions of airway progenitor cells that are responsible for epithelial repair. In present study Secretoglobin1a1 (Scgb1a1) lineage tracing mice were injected intraperitoneally with tamoxifen to induce the expression of green fluorescence protein (GFP) in Scgb1a1-expressing conducting airway progenitor cells. Scgb1a1-expressing progenitor cells were isolated from lungs of Scgb1a1 lineage tracing mice via flow activated cell sorting. In vitro three-dimensional matrigel culture of these progenitor cells revealed that dexamethasone has little effect on the colony forming ability of airway epithelial progenitor cells, but exhibits significant effects on the differentiation of the progenitor cells. Compared to the untreated group, dexamethasone treatment inhibited the expression of forkhead box J1 (FoxJ1) and mucin subtype A & C (Muc5Ac), but promoted the expression of calcium activated chloride channel 3 (Clca3) and cystic fibrosis transmembrane conductance regulator (Cftr). Dexamethasone-induced effects on the expression of FoxJ1, Muc5Ac and Clca3 were abolished or even reversed in the presence of RU486, an antagonist of glucocorticoid receptor, indicating that glucocorticoid receptor plays a role in the regulation of airway epithelial progenitor cells by dexamethasone. These data suggested that, though effective to reduce airway inflammation, dexamethasone treatment alone fails to fully restore the mucociliary clearance function in the treatment of asthma patients.

RORγt Modulates Macrophage Recruitment during a Hydrocarbon Oil-Induced Inflammation

Hydrocarbon oils are often utilized as adjuvants in vaccines. In response to naturally occurring hydrocarbon oils, inflammation is initiated and persists with the continuous recruitment of immune cells such as macrophages and neutrophils. However, the mechanism underlying the chronic inflammation in response to hydrocarbon oils is not fully defined. In this study, we revealed an essential role of retinoid-related orphan receptor gamma t (RORγt) in sustaining the recruitment of macrophages following pristane treatment. RORγt absence resulted in the incompetent formation of mesenteric oil granulomas which may associate to a reduction in the migration of macrophages into the mesentery during pristane-induced inflammation. This is at least partially dependent on the expression of the monocyte chemoattractant protein-1 (MCP-1) in the mesentery and the decrease in the macrophage reservoir in the spleen. However, the absence of RORγt had no impact on the recruitment of neutrophils to the mesentery after pristane treatment. Our data uncovered an important role of RORγt in the recruitment of macrophages during hydrocarbon oil-induced chronic inflammation.

Wnt/Fgf crosstalk is required for the specification of tracheal basal progenitor cells

Basal progenitor cells are critical for the establishment and maintenance of the tracheal epithelium. However, it remains unclear how these progenitor cells are specified during foregut development. Here, we found that ablation of the Wnt chaperon protein Gpr177 (also known as Wntless) in the epithelium causes significant reduction in the numbers of basal progenitor cells accompanied by cartilage loss in Shh-Cre;Gpr177loxp/loxp mutants. Consistent with the association between cartilage and basal cell development, Nkx2.1+p63+ basal cells are co-present with cartilage nodules in Shh-Cre;Ctnnb1DM/loxp mutants which keep partial cell-cell adhesion but not the transcription regulation function of ß-catenin. More importantly, deletion of Ctnnb1 in the mesenchyme leads to the loss of basal cells and cartilage concomitant with the reduced transcript levels of Fgf10 in Dermo1-Cre;Ctnnb1loxp/loxp mutants. Furthermore, deletion of Fgf receptor 2 (Fgfr2) in the epithelium also leads to significantly reduced numbers of basal cells, supporting the importance of the Wnt/Fgf crosstalk in early tracheal development.

Fatty Acid Metabolism is Associated With Disease Severity After H7N9 Infection

Background Human infections with the H7N9 virus could lead to lung damage and even multiple organ failure, which is closely associated with a high mortality rate. However, the metabolic basis of such systemic alterations remains unknown. Methods This study included hospitalized patients (n = 4) with laboratory-confirmed H7N9 infection, healthy controls (n = 9), and two disease control groups comprising patients with pneumonia (n = 9) and patients with pneumonia who received steroid treatment (n = 10). One H7N9-infected patient underwent lung biopsy for histopathological analysis and expression analysis of genes associated with lung homeostasis. H7N9-induced systemic alterations were investigated using metabolomic analysis of sera collected from the four patients by using ultra-performance liquid chromatography-mass spectrometry. Chest digital radiography and laboratory tests were also conducted. Findings Two of the four patients did not survive the clinical treatments with antiviral medication, steroids, and oxygen therapy. Biopsy revealed disrupted expression of genes associated with lung epithelial integrity. Histopathological analysis demonstrated severe lung inflammation after H7N9 infection. Metabolomic analysis indicated that fatty acid metabolism may be inhibited during H7N9 infection. Serum levels of palmitic acid, erucic acid, and phytal may negatively correlate with the extent of lung inflammation after H7N9 infection. The changes in fatty acid levels may not be due to steroid treatment or pneumonia. Interpretation Altered structural and secretory properties of the lung epithelium may be associated with the severity of H7N9-infection-induced lung disease. Moreover, fatty acid metabolism level may predict a fatal outcome after H7N9 virus infection.

Altered Lipid Metabolism in Recovered SARS Patients Twelve Years after Infection

Severe acute respiratory syndrome-coronavirus (SARS-CoV) and SARS-like coronavirus are a potential threat to global health. However, reviews of the long-term effects of clinical treatments in SARS patients are lacking. Here a total of 25 recovered SARS patients were recruited 12 years after infection. Clinical questionnaire responses and examination findings indicated that the patients had experienced various diseases, including lung susceptibility to infections, tumors, cardiovascular disorders, and abnormal glucose metabolism. As compared to healthy controls, metabolomic analyses identified significant differences in the serum metabolomes of SARS survivors. The most significant metabolic disruptions were the comprehensive increase of phosphatidylinositol and lysophospha tidylinositol levels in recovered SARS patients, which coincided with the effect of methylprednisolone administration investigated further in the steroid treated non-SARS patients with severe pneumonia. These results suggested that high-dose pulses of methylprednisolone might cause long-term systemic damage associated with serum metabolic alterations. The present study provided information for an improved understanding of coronavirus-associated pathologies, which might permit further optimization of clinical treatments.

The role of TGFβ‑HGF‑Smad4 axis in regulating the proliferation of mouse airway progenitor cells

The interaction between airway epithelial progenitor cells and their microenvironment is critical for maintaining lung homeostasis. This microenvironment includes fibroblast cells, which support the growth of airway progenitor cells. However, the mechanism of this support is not fully understood. In the present study, the authors observed that inhibition of transforming growth factor (TGF)-β signal with SB431542 promotes the expression of hepatocyte growth factor (HGF) in fibroblast cells. The HGF receptor, c-Met, is expressed on airway progenitor cells; HGF promotes the colony-forming ability of airway progenitor cells. The deletion of Smad4 in airway progenitor cells increases the colony-forming ability, suggesting that Smad4 plays a negative role in the regulating the proliferation of airway progenitor cells. These data demonstrated that the regulation of airway progenitor cells by TGF-β depends on TGF-βR1/2 on stromal cells, rather than on epithelial progenitor cells. These data suggested a role for the TGF-β-TGF-βR1/2-HGF-Smad4 axis in airway epithelial homeostasis and sheds new light on the interaction between airway progenitor cells and their microenvironment.

Altered gene expression of hepatic cytochrome P450 in a rat model of intermittent hypoxia with emphysema

Patients with respiratory overlap syndrome (OS), defined as concomitant chronic obstructive pulmonary disease and obstructive sleep apnea syndrome, may exhibit an increased blood concentration of ingested drugs. This poor elimination of drugs is primarily attributed to downregulated gene expression of the drug‑metabolizing cytochrome P450 enzymes (CYPs) in the liver. However, the underlying mechanisms of the decreased expression of CYPs in OS are poorly understood. In order to address this, a rat model of intermittent hypoxia with emphysema was evaluated in the present study, by analyzing liver gene expression using the reverse transcription‑quantitative polymerase chain reaction. Intermittent hypoxia and cigarette smoke exposure caused upregulation of hepatic inflammatory cytokines, while CYPs were downregulated. This downregulation of CYPs was associated with an increase in nuclear factor (NF)‑κB expression and a decrease in the expression of nuclear receptors pregnane X receptor, constitutive androstane receptor and glucocorticoid receptor, which are the upstream regulatory molecules of CYPs. The results of the present study indicated that, during the development of OS, systematic inflammatory reactions may downregulate hepatic CYP gene expression via the NF‑κB signaling pathway.

Regulation of Leukocyte Recruitment to the Spleen and Peritoneal Cavity during Pristane-Induced Inflammation

Chronic inflammation is associated with an increased number of leukocytes in the spleen, which are then redirected to the site of inflammation. However, it remains unknown how leukocyte recruitment is regulated. Herein, chronic inflammation was induced by intraperitoneal injection of pristane into mice. Leukocytes in the spleen or in the peritoneal cavity were quantified by flow cytometry. We found that the loss of IL-6 decreased macrophage recruitment to the spleen and the peritoneal cavity during pristane-induced inflammation. The loss of TNFα delayed the recruitment of neutrophils and macrophages to the spleen and inhibited the recruitment of neutrophils, macrophages, B cells, and T cells. The recruitment of neutrophils and macrophages into the spleen or peritoneal cavity was largely inhibited in the absence of LTα. The loss of TNFα receptor 1/2 resulted in reduced recruitment of neutrophils, macrophages, and dendritic cells into the spleen, but only neutrophil recruitment was inhibited in the peritoneal cavity. Similarly, a lack of B cells significantly impeded the recruitment of neutrophils, macrophages, and dendritic cells to the spleen. However, only macrophage recruitment was inhibited in the absence of T cells in the spleen. These data provide insight into the development of chronic inflammation induced by noninfectious substances.