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Epithelial Function and Airway Responsiveness
Published in Alastair G. Stewart, AIRWAY WALL REMODELLING in ASTHMA, 2020
Roy G. Goldie, Janet M. H. Preuss
The Clara cell (nonciliated bronchiolar secretory cell) is highly metabolically active and possesses a variety of enzymes including acid and alkaline phosphatases, nonspecific esterase, hydroxylases, transferases, peroxidases, and catalase, in addition to cytochrome P450 monoxygenase.1,182,183 A primary function of the Clara cell is to metabolise xenobiotic cytotoxic agents that enter the respiratory tract via the air or blood. This is achieved via cytochrome P450–mediated metabolism, a pathway which is more active in the Clara cell than in any other pulmonary cell type.3,184–186
Epithelial Cells
Published in Bruce S. Bochner, Adhesion Molecules in Allergic Disease, 2020
At the bronchiolar level, Clara cells constitute the majority of nonciliated epithelial cells. They are columnar in shape and typically project into the airway lumen (1). Their ultrastructure shows abundant rough endoplasmic reticulum, a prominent Golgi apparatus, and electron-dense granules, all indicative of a secretory role (17,18). Clara cell 16-kD protein (CC16kD, previously referred to as Clara cell 10-kD protein), an inhibitor of elastase (19) and phospholipase A2 (20), is believed to be the major product of these cells (21,22). In addition, they may secrete surfactant-associated glycoprotein (23,24). Clara cells also serve as a site of extrahepatic oxidative metabolism of foreign substances through cytochrome P450-dependent mono-oxygenase reactions (25,26).
Ultrastructural Immunocytochemistry
Published in Joan Gil, Models of Lung Disease, 2020
Samuel S. Spicer, Bradley A. Schulte
Evidence for a secretory role for Clara cells has been obtained in the rat lung by ultrastructural immunostaining of these cells with monoclonal antibody to an antigen isolated from pulmonary lavage fluid (Bedetti et al., 1987). This antibody stained secretory granules of Clara cells exclusively in rat lung (Fig. 4). Such staining differentiated Clara cells cytochemically from type II pneumocytes, which in some respects, such as immunostaining and lectin staining for blood group antigen (see Chapter 7), share cytochemical properties with Clara cells.
Simulation of respiratory tract lining fluid for in vitro dissolution study
Published in Expert Opinion on Drug Delivery, 2021
Rakesh Bastola, Paul M. Young, Shyamal C. Das
The RTLF is a thin fluid layer that lies on the surfaces of the nasal airways through to the distal airways including the alveolar region. In the nasal and proximal airways, it consists of two layers namely, the sol layer (periciliary sol) that surrounds cilia and the gel layer (mucus blanket) that lies above the cilia [1]. RTLF present in different regions of the respiratory tract is shown in Figure 1. Submucosal glands and goblet cells present in the epithelium secrete mucus in trachea and bronchi [1]; however, the luminal surface of the non-alveolarized portion of respiratory bronchioles does not contain mucus and basal cells but is lined by ciliated and Clara cells [21]. Clara cells provide surfactant proteins (A, B and D) and other specific proteins including Clara cell secretory protein [21].
Predicting the likelihood of bronchopulmonary dysplasia in premature neonates
Published in Expert Review of Respiratory Medicine, 2019
Patrick A Philpot, Vineet Bhandari
Biomarkers expressed in pulmonary epithelial cells as well as extracellular matrix proteins represent downstream markers of alveolar hypoplasia in preterm infants. Clara cells (now known as club cells), which are epithelial cells that line the respiratory and terminal bronchioles secrete club cell proteins (CCPs). The level of CCPs in cord blood and infant serum has been shown to be decreased in infants who developed BPD [10] but have been shown to be increased at 2 h of life as well as on day of life 14 in infants who developed BPD [11]. Elevated levels of Kerbs von Lungren 6 antigen (KL-6), a marker of lung injury, and the ratio of matrix metalloproteinase (MMP)-9 to tissue inhibitor of metalloproteinase-1 (TIMP-1) have also been reported to be predictors of moderate to severe BPD [12,13]. Although these markers have been associated with the development of BPD, they have yet to be included in predictive models.
Stem cells therapy: a review on approaches that can be used for treatment of respiratory failures in sulfur mustard-injured patients
Published in Immunopharmacology and Immunotoxicology, 2018
Amir Nejad-Moghaddam, Eisa Tahmasbpour, Milad Sohrabiyan, Hosein jafari, Mostafa Ghanei
Pluripotent stem cells are able to be differentiated into a range of cells. Due to differentiation properties of human embryonic stem cells (hESCs) to various organs such as the liver, pancreas, lung, and especially tracheal respiratory epithelial layers, they can be used for clinical treatments [39–41]. Wang et al. [42] demonstrated that hESCs can differentiate into alveolar type II epithelial cells and produce surfactant proteins, which in turn increase survival rate and decrease lung inflammation and fibrosis in mice with lung injuries. Recent in vitro studies have shown that ESCs obtained from mouse and human can produce alveolar epithelial cells, which are able to express surfactant proteins [43,44]. Application and distribution of endotracheal alveolar epithelial cells type II derived from mouse embryonic stem cells (mESCs) result in cell survival in lungs and surfactant expression during the first 24 h [45]. But, whether these cells are properly engrafted in lung damage or act as functionally is still unclear. Caspi et al. [46] showed the potential therapeutic effects of ESCs for cardiovascular diseases, as well as acute and chronic lung disease in rats. In another study, Coraux et al. [47] could differentiate mESCs to Clara cells and functionally airway epithelium with air–liquid interface culture technique.