Airway basal stem cells are necessary for the maintenance of functional intraepithelial airway macrophages.

Adult stem cells play a crucial role in tissue homeostasis and repair through multiple mechanisms. In addition to being able to replace aged or damaged cells, stem cells provide signals that contribute to the maintenance and function of neighboring cells. In the lung, airway basal stem cells also produce cytokines and chemokines in response to inhaled irritants, allergens, and pathogens, which affect specific immune cell populations and shape the nature of the immune response. However, direct cell-to-cell signaling through contact between airway basal stem cells and immune cells has not been demonstrated. Recently, a unique population of intraepithelial airway macrophages (IAMs) has been identified in the murine trachea. Here, we demonstrate that IAMs require Notch signaling from airway basal stem cells for maintenance of their differentiated state and function. Furthermore, we demonstrate that Notch signaling between airway basal stem cells and IAMs is required for antigen-induced allergic inflammation only in the trachea where the basal stem cells are located whereas allergic responses in distal lung tissues are preserved consistent with a local circuit linking stem cells to proximate immune cells. Finally, we demonstrate that IAM-like cells are present in human conducting airways and that these cells display Notch activation, mirroring their murine counterparts. Since diverse lung stem cells have recently been identified and localized to specific anatomic niches along the proximodistal axis of the respiratory tree, we hypothesize that the direct functional coupling of local stem cell-mediated regeneration and immune responses permits a compartmentalized inflammatory response.

Sanglifehrin A mitigates multiorgan fibrosis by targeting the collagen chaperone cyclophilin B.

Pathological deposition and crosslinking of collagen type I by activated myofibroblasts drives progressive tissue fibrosis. Therapies that inhibit collagen synthesis have potential as antifibrotic agents. We identify the collagen chaperone cyclophilin B as a major cellular target of the natural product sanglifehrin A (SfA) using photoaffinity labeling and chemical proteomics. Mechanistically, SfA inhibits and induces the secretion of cyclophilin B from the endoplasmic reticulum (ER) and prevents TGF-ß1-activated myofibroblasts from synthesizing and secreting collagen type I in vitro, without inducing ER stress or affecting collagen type I mRNA transcription, myofibroblast migration, contractility, or TGF-ß1 signaling. In vivo, SfA induced cyclophilin B secretion in preclinical models of fibrosis, thereby inhibiting collagen synthesis from fibrotic fibroblasts and mitigating the development of lung and skin fibrosis in mice. Ex vivo, SfA induces cyclophilin B secretion and inhibits collagen type I secretion from fibrotic human lung fibroblasts and samples from patients with idiopathic pulmonary fibrosis (IPF). Taken together, we provide chemical, molecular, functional, and translational evidence for demonstrating direct antifibrotic activities of SfA in preclinical and human ex vivo fibrotic models. Our results identify the cellular target of SfA, the collagen chaperone cyclophilin B, as a mechanistic target for the treatment of organ fibrosis.

Promises and Challenges of Cell-Based Therapies to Promote Lung Regeneration in Idiopathic Pulmonary Fibrosis.

The lung epithelium is constantly exposed to harmful agents present in the air that we breathe making it highly susceptible to damage. However, in instances of injury to the lung, it exhibits a remarkable capacity to regenerate injured tissue thanks to the presence of distinct stem and progenitor cell populations along the airway and alveolar epithelium. Mechanisms of repair are affected in chronic lung diseases such as idiopathic pulmonary fibrosis (IPF), a progressive life-threatening disorder characterized by the loss of alveolar structures, wherein excessive deposition of extracellular matrix components cause the distortion of tissue architecture that limits lung function and impairs tissue repair. Here, we review the most recent findings of a study of epithelial cells with progenitor behavior that contribute to tissue repair as well as the mechanisms involved in mouse and human lung regeneration. In addition, we describe therapeutic strategies to promote or induce lung regeneration and the cell-based strategies tested in clinical trials for the treatment of IPF. Finally, we discuss the challenges, concerns and limitations of applying these therapies of cell transplantation in IPF patients. Further research is still required to develop successful strategies focused on cell-based therapies to promote lung regeneration to restore lung architecture and function.

Evaluation of the gut microbiota after metformin intervention in children with obesity: A metagenomic study of a randomized controlled trial.

BACKGROUND: Metformin, a first-line oral antidiabetic agent that has shown promising results in terms of treating childhood and adolescent obesity, might influence the composition of the gut microbiota. We aimed to evaluate whether the gut microbiota of non-diabetic children with obesity changes after a metformin intervention. METHODS: The study was a multicenter and double-blind randomized controlled trial in 160 children with obesity. Children were randomly assigned to receive either metformin (1 g/day) or placebo for 6 months in combination with healthy lifestyle recommendations in both groups. Then, we conducted a metagenomic analysis in a subsample obtained from 33 children (15 metformin, 18 placebo). A linear mixed-effects model (LMM) was used to determine the abundance changes from baseline to six months according to treatment. To analyze the data by clusters, a principal component analysis was performed to understand whether lifestyle habits have a different influence on the microbiota depending on the treatment group. RESULTS: Actinobacteria abundance was higher after placebo treatment compared with metformin. However, the interaction time x treatment just showed a trend to be significant (4.6% to 8.1% after placebo vs. 3.8 % to 2.6 % after metformin treatment, p = 0.055). At genus level, only the abundance of Bacillus was significantly higher after the placebo intervention compared with metformin (2.5% to 5.7% after placebo vs. 1.5 % to 0.8 % after metformin treatment, p = 0.044). Furthermore, different ensembles formed by Firmicutes, Bacteroidetes, and Verrucomicrobia were found according to the interventions under a similar food consumption. CONCLUSION: Further studies with a large sample size controlled by lifestyle patterns are required in obese children and adolescents to clarify whether metformin might trigger gut microbiota alterations. TRIAL REGISTRATION: Registered on the European Clinical Trials Database (EudraCT, ID: 2010-023061-21) on 14 November 2011.

The Gut Microbiota and Its Implication in the Development of Atherosclerosis and Related Cardiovascular Diseases.

The importance of gut microbiota in health and disease is being highlighted by numerous research groups worldwide. Atherosclerosis, the leading cause of heart disease and stroke, is responsible for about 50% of all cardiovascular deaths. Recently, gut dysbiosis has been identified as a remarkable factor to be considered in the pathogenesis of cardiovascular diseases (CVDs). In this review, we briefly discuss how external factors such as dietary and physical activity habits influence host-microbiota and atherogenesis, the potential mechanisms of the influence of gut microbiota in host blood pressure and the alterations in the prevalence of those bacterial genera affecting vascular tone and the development of hypertension. We will also be examining the microbiota as a therapeutic target in the prevention of CVDs and the beneficial mechanisms of probiotic administration related to cardiovascular risks. All these new insights might lead to novel analysis and CVD therapeutics based on the microbiota.