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The lungs are exposed to a hostile environment from both sites: the airways and the vasculature. However, an efficient gas exchange of oxygen (O2) and CO2 is only possible through a very thin alveolo‐capillary membrane. Therefore, maintaining cell barrier integrity is essential for respiratory health and function. On the vascular site, endothelial cells form a natural barrier, while in the airways epithelial cells are most important for protection of the lung tissues. Moreover, fibroblasts, by transforming to myofibroblasts, are essential for wound closure after mechanical and chemical microinjuries in the respiratory tract. Along this line, loss of cell resistance in vascular endothelial and lung epithelial cells enhances invasion of pathogens (e.g., SARS‐CoV‐2) and results in pulmonary edema formation, while increasing barrier function of pulmonary (myo)fibroblasts blocks gas exchange in patients with pulmonary fibrosis. Therefore, electrical cell‐substrate impedance sensing‐based quantification of changes in cell barrier function in lung endothelial and epithelial cells as well as fibroblasts after application of harmful triggers (e.g., hypoxia, receptor agonists, and toxicants) is a convenient and state‐of‐the‐art technique. After isolation of primary cells from mouse models and human tissues, changes in cell resistance can be detected in real time. By using lung cells from gene‐deficient mouse models, microRNAs or the small‐interfering RNA technology essential proteins for cell adhesion, for example, ion channels of the transient receptor potential family are identified in comparison to wild‐type control cells. In the future, these proteins may be useful as drug targets for novel therapeutic options in patients with lung edema or pulmonary fibrosis. [ABSTRACT FROM AUTHOR]

TRPA1 (transient receptor potential ankyrin 1) is a nonselective Ca2+-permeable cation channel, which was originally cloned from human lung fibroblasts (HLFs). TRPA1-mediated Ca2+ entry is evoked by exposure to several chemicals, including allyl isothiocyanate (AITC), and a protective effect of TRPA1 activation in the development of cardiac fibrosis has been proposed. Yet the function of TRPA1 in TGF-β1 (transforming growth factor-β1)-driven fibroblast-to-myofibroblast differentiation and the development of pulmonary fibrosis remains elusive. TRPA1 expression and function were analyzed in cultured primary HLFs, and mRNA concentrations were significantly reduced after adding TGF-β1. Expression of genes encoding fibrosis markers (e.g., ACTA2, SERPINE1 [plasminogen activator inhibitor 1], FN1 [fibronectin], COL1A1 [type I collagen]) was increased after siRNA-mediated downregulation of TRPA1 mRNA in HLFs. Moreover, AITC-induced Ca2+ entry in HLFs was decreased after TGF-β1 treatment and by application of TRPA1 siRNAs, while AITC treatment alone did not reduce cell viability or enhance apoptosis. Most interestingly, AITC-induced TRPA1 activation augmented ERK1/2 (extracellular signal-regulated kinase 1/2) and SMAD2 linker phosphorylation, which might inhibit TGF-β-receptor signaling. Our results suggest an inhibitory function of TRPA1 channels in TGF-β1-driven fibroblast-to-myofibroblast differentiation. Therefore, activation of TRPA1 channels might be protective during the development of pulmonary fibrosis in patients. [ABSTRACT FROM AUTHOR]

Background: Tissue organoids derived from primary cells have high potential for studying organ development and diseases in numerous organs. They recreate the morphological structure and mimic the functions of given organ while being compact in size, easy to produce, and suitable for use in various experimental setups. Results: In this study we established the number of cells that form mouse kidney rudiments at E11.5, and generated renal organoids of various sizes from the mouse primary cells of the metanephric mesenchyme (MM). We investigated the ability of renal organoids to undergo nephrogenesis upon Wnt/ β‐catenin pathway—mediated tubule induction with a GSK‐3 inhibitor (BIO) or by initiation through the ureteric bud (UB). We found that 5000 cells of MM cells are necessary to successfully form renal organoids with well‐structured nephrons as judged by fluorescent microscopy, transmission electron microscopy (TEM), and quantitative Polymerase Chain Reaction (qPCR). These mouse organoids also recapitulated renal secretion function in the proximal tubules. Conclusions: We show that a significant decrease of cells used to generate renal mouse organoids in a dissociation/re‐aggregation assay, does not interfere with development, and goes toward 3Rs. This enables generation of more experimental samples with one mouse litter, limiting the number of animals used for studies. Key Findings: Generation of functional renal mouse organoids requires to reach a minimal cell number.The type of cells generating renal organoids is also important.Reduction of cells required for generation of organoids reduce the number of animals used and goes well with 3R's. [ABSTRACT FROM AUTHOR]

Members of the transient receptor potential (TRP) superfamily are broadly expressed in our body and contribute to multiple cellular functions. Most interestingly, the fourth member of the vanilloid family of TRP channels (TRPV4) serves different partially antagonistic functions in the respiratory system. This review highlights the role of TRPV4 channels in lung fibroblasts, the lung endothelium, as well as the alveolar and bronchial epithelium, during physiological and pathophysiological mechanisms. Data available from animal models and human tissues confirm the importance of this ion channel in cellular signal transduction complexes with Ca2+ ions as a second messenger. Moreover, TRPV4 is an excellent therapeutic target with numerous specific compounds regulating its activity in diseases, like asthma, lung fibrosis, edema, and infections. [ABSTRACT FROM AUTHOR]