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Event: 1912

Key Event Title

A descriptive phrase which defines a discrete biological change that can be measured. More help

Motile Cilia Number/Length, Decreased

Short name

The KE short name should be a reasonable abbreviation of the KE title and is used in labelling this object throughout the AOP-Wiki. More help

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Biological Context

Structured terms, selected from a drop-down menu, are used to identify the level of biological organization for each KE. More help

Level of Biological Organization
Cellular

Cell term

The location/biological environment in which the event takes place.The biological context describes the location/biological environment in which the event takes place. For molecular/cellular events this would include the cellular context (if known), organ context, and species/life stage/sex for which the event is relevant. For tissue/organ events cellular context is not applicable. For individual/population events, the organ context is not applicable. Further information on Event Components and Biological Context may be viewed on the attached pdf. More help

Cell term
multi-ciliated epithelial cell

Organ term

Organ term
lung epithelium

Key Event Components

The KE, as defined by a set structured ontology terms consisting of a biological process, object, and action with each term originating from one of 14 biological ontologies (Ives, et al., 2017; https://aopwiki.org/info_pages/2/info_linked_pages/7#List). Biological process describes dynamics of the underlying biological system (e.g., receptor signalling).Biological process describes dynamics of the underlying biological system (e.g., receptor signaling). The biological object is the subject of the perturbation (e.g., a specific biological receptor that is activated or inhibited). Action represents the direction of perturbation of this system (generally increased or decreased; e.g., ‘decreased’ in the case of a receptor that is inhibited to indicate a decrease in the signaling by that receptor). Note that when editing Event Components, clicking an existing Event Component from the Suggestions menu will autopopulate these fields, along with their source ID and description. To clear any fields before submitting the event component, use the 'Clear process,' 'Clear object,' or 'Clear action' buttons. If a desired term does not exist, a new term request may be made via Term Requests. Event components may not be edited; to edit an event component, remove the existing event component and create a new one using the terms that you wish to add. Further information on Event Components and Biological Context may be viewed on the attached pdf. More help

Process	Object	Action
	motile cilium	decreased

Key Event Overview

AOPs Including This Key Event

All of the AOPs that are linked to this KE will automatically be listed in this subsection. This table can be particularly useful for derivation of AOP networks including the KE. Clicking on the name of the AOP will bring you to the individual page for that AOP. More help

AOP Name	Role of event in AOP	Point of Contact	Author Status	OECD Status
ox stress-mediated FOXJ1/cilia/CBF/MCC impairment	KeyEvent	Agnes Aggy (send email)	Open for comment. Do not cite

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) that help to define the biological applicability domain of the KE.In many cases, individual species identified in these structured fields will be those for which the strongest evidence used in constructing the AOP was available in relation to this KE. More help

Term	Scientific Term	Evidence	Link
Danio rerio	Danio rerio		NCBI
Homo sapiens	Homo sapiens	High	NCBI
Xenopus laevis	Xenopus laevis		NCBI
Mus musculus	Mus musculus		NCBI

Life Stages

An indication of the the relevant life stage(s) for this KE. More help

Life stage	Evidence
During development and at adulthood	High

Sex Applicability

An indication of the the relevant sex for this KE. More help

Term	Evidence
Mixed	High

Key Event Description

A description of the biological state being observed or measured, the biological compartment in which it is measured, and its general role in the biology should be provided. More help

Motile cilia are microtubule-based organelles that protrude from the cell surface and generate directional flow of fluid with coordinated beating. 50% to 80% of human respiratory epithelium is comprised of ciliated cells covered with multiple motile cilia that move mucus (together with mucus-trapped substances) upward for clearing the airways (Yaghi and Dolovich, 2016). The ciliated airway epithelial cells are typically covered by more than hundred motile cilia (Bustamante-Marin and Ostrowski, 2017). On average, 150 motile cilia were counted per ciliated human epithelial cell in the study by Mao et al. (Mao et al., 2018). In an earlier report, 200 motile cilia per ciliated cell in human trachea is mentioned (Wanner et al., 1996), and, in a more recent study, a range of 100 to 600 ciliary precursors were counted in fully differentiated mouse tracheal epithelial cells correlated with increasing surface area (Nanjundappa et al., 2019). Cilia are 6–7 µm long and 0.2–0.3 µm in diameter (Brooks and Wallingford, 2014; Yaghi and Dolovich, 2016). Ciliated cell density and the motile cilia length and number per cell correlate with ciliary beating frequency which is routinely used as a predictor of the mucociliary clearance efficiency (King, 2006). Morphological changes of airway cilia are expected to impact multiple motile cilia functional integrity. This key event represents the decrease in the numbers or absence of motile cilia or reduction in length of motile cilia.

How It Is Measured or Detected

A description of the type(s) of measurements that can be employed to evaluate the KE and the relative level of scientific confidence in those measurements.These can range from citation of specific validated test guidelines, citation of specific methods published in the peer reviewed literature, or outlines of a general protocol or approach (e.g., a protein may be measured by ELISA). Do not provide detailed protocols. More help

Acetylated tubulin is a common ciliary marker (Kim et al., 2013; Piperno and Fuller, 1985), and apical acetylated tubulin staining with subsequent microscope image scoring is a frequently used method of cilia detection and enumeration (Johnson et al., 2018; Mao et al., 2018; Stubbs et al., 2008). Staining of beta-tubulin IV, a protein enriched in motile cilia, is another common method of cilia detection (Brekman et al., 2014; Milara et al., 2012). Ciliated cells can also be identified by the presence of axonemal structures on the cell surface using scanning electron microscopy (Gomperts et al., 2007). Mature cilia numbers could be deduced from ciliary precursors in immunofluorescence assays: ciliary precursors can be calculated from three-dimensional superresolution structured illumination microscopy (3D-SIM) images using e.g. a spot detection tool (Nikon Elements AR 4 Software) (Nanjundappa et al., 2019).

For cilia length measurement, the ciliated cells/tissue needs to be stained (Diff-Quik: Dade Behring stain, hematoxylin and eosin staining, labelling with antibodies for ciliary markers such as alpha-tubulin), visualized by microscopy and cilia length quantified (using e.g. ImageJ software or MetaMorph Microscopy Automation & Image Analysis Software) (Brekman et al., 2014; Leopold et al., 2009b; Li et al., 2014). Generally, multiple measurements of one sample and multiple sample preparations of cells/tissues are imaged for reliable quantitation.

Domain of Applicability

A description of the scientific basis for the indicated domains of applicability and the WoE calls (if provided). More help

The ultrastructural features of human and other mammalian respiratory epithelial cilia and those from lower animals (e.g. flatworms and mollusks) are remarkably similar (Meunier and Azimzadeh, 2016; Wanner et al., 1996). The master regulators of multiciliated cell differentiation, such as NOTCH, GEMC1, MCIDAS, FOXJ1, RFX2/3 are conserved throughout vertebrates (e.g. mammals, Xenopus, zebrafish) and multiple motile cilia across these organisms are functionally similar in generating fluid flow through coordinated beating (Choksi et al., 2014; Meunier and Azimzadeh, 2016; Wessely and Obara, 2008).

The motile cilia numbers reach adult levels in the mouse airway epithelium at day 21 after birth (Rawlins et al., 2007; Toskala et al., 2005). At birth, there is no discernable cilia-generated airway fluid flow in mice (Francis et al., 2009). Between postnatal days 3 and 7 the flow is established in trachea correlating with the increase in the density of ciliated cells in the tracheal epithelia (Francis et al., 2009). After airway fluid flow establishment, the KE is applicable to all life stages.

References

List of the literature that was cited for this KE description. More help

Brekman, A., Walters, M.S., Tilley, A.E. and Crystal, R.G. (2014). FOXJ1 prevents cilia growth inhibition by cigarette smoke in human airway epithelium in vitro. Am. J. Respir. Cell Mol. Biol. 51, 688-700.

Brooks, E.R. and Wallingford, J.B. (2014). Multiciliated cells. Curr. Biol. 24, R973-982.

Bustamante-Marin, X.M. and Ostrowski, L.E. (2017). Cilia and Mucociliary Clearance. Cold Spring Harb. Persp. Biol. 9, a028241.

Choksi, S.P., Lauter, G., Swoboda, P. and Roy, S. (2014). Switching on cilia: transcriptional networks regulating ciliogenesis. Development 141, 1427-1441.

Francis, R.J., Chatterjee, B., Loges, N.T., Zentgraf, H., Omran, H. and Lo, C.W. (2009). Initiation and maturation of cilia-generated flow in newborn and postnatal mouse airway. Am. J. Physiol. Lung Cell. Mol. Physiol. 296, L1067-1075.

Gomperts, B.N., Kim, L.J., Flaherty, S.A. and Hackett, B.P. (2007). IL-13 Regulates Cilia Loss and foxj1 Expression in Human Airway Epithelium. Am. J. Respir. Cell Mol. Biol. 37, 339-346.

Hessel, J., Heldrich, J., Fuller, J., Staudt, M.R., Radisch, S., Hollmann, C., et al. (2014). Intraflagellar Transport Gene Expression Associated with Short Cilia in Smoking and COPD. PLoS ONE 9, e85453.

Johnson, J.A., Watson, J.K., Nikolic, M.Z. and Rawlins, E.L. (2018). Fank1 and Jazf1 promote multiciliated cell differentiation in the mouse airway epithelium. Biol. Open 7, bio033944.

Kim, G.W., Li, L., Ghorbani, M., You, L. and Yang, X.J. (2013). Mice lacking alpha-tubulin acetyltransferase 1 are viable but display alpha-tubulin acetylation deficiency and dentate gyrus distortion. J. Biol. Chem. 288, 20334-20350.

King, M. (2006). Physiology of mucus clearance. Paediatr. Respir Rev. 7, S212-214.

Lam, H.C., Cloonan, S.M., Bhashyam, A.R., Haspel, J.A., Singh, A., Sathirapongsasuti, J.F., et al. (2013). Histone deacetylase 6–mediated selective autophagy regulates COPD-associated cilia dysfunction. J. Clin. Invest. 123(12), 5212-5230.

Leopold, P.L., O'mahony, M.J., Lian, X.J., Tilley, A.E., Harvey, B.-G. and Crystal, R.G. (2009). Smoking is associated with shortened airway cilia. PloS ONE 4, e8157.

Li, Y.Y., Li, C.W., Chao, S.S., Yu, F.G., Yu, X.M., Liu, J., et al. (2014). Impairment of cilia architecture and ciliogenesis in hyperplastic nasal epithelium from nasal polyps. J. Allergy Clin. Immunol. 134, 1282-1292.

Mao, S., Shah, A.S., Moninger, T.O., Ostedgaard, L.S., Lu, L., Tang, X.X., et al. (2018). Motile cilia of human airway epithelia contain hedgehog signaling components that mediate noncanonical hedgehog signaling. Proc. Natl. Acad. Sci. U. S. A. 115, 1370-1375.

Meunier, A. and Azimzadeh, J. (2016). Multiciliated Cells in Animals. Cold Spring Harb. Perspect. Biol. 8, a028233.

Milara, J., Armengot, M., Bañuls, P., Tenor, H., Beume, R., Artigues, E., et al. (2012). Roflumilast N-oxide, a PDE4 inhibitor, improves cilia motility and ciliated human bronchial epithelial cells compromised by cigarette smoke in vitro. Brit. J. Pharmacol. 166, 2243-2262.

Nanjundappa, R., Kong, D., Shim, K., Stearns, T., Brody, S.L., Loncarek, J., et al. (2019). Regulation of cilia abundance in multiciliated cells. Elife 8, e44039.

Piperno, G. and Fuller, M.T. (1985). Monoclonal antibodies specific for an acetylated form of alpha-tubulin recognize the antigen in cilia and flagella from a variety of organisms. J. Cell Biol. 101, 2085-2094.

Rawlins, E.L., Ostrowski, L.E., Randell, S.H. and Hogan, B.L. (2007). Lung development and repair: contribution of the ciliated lineage. Proc. Natl. Acad. Sci. U. S. A. 104, 410-417.

Simet, S.M., Sisson, J.H., Pavlik, J.A., Devasure, J.M., Boyer, C., Liu, X., et al. (2010). Long-term cigarette smoke exposure in a mouse model of ciliated epithelial cell function. Am. J. Respir. Cell Mol. Biol. 43, 635-640.

Stubbs, J.L., Oishi, I., Izpisua Belmonte, J.C. and Kintner, C. (2008). The forkhead protein Foxj1 specifies node-like cilia in Xenopus and zebrafish embryos. Nat. Genet. 40, 1454-1460.

Tamashiro, E., Xiong, G., Anselmo-Lima, W.T., Kreindler, J.L., Palmer, J.N., and Cohen, N.A. (2009). Cigarette smoke exposure impairs respiratory epithelial ciliogenesis. Am. J. Rhinol. Allergy 23, 117-122.

Toskala, E., Smiley-Jewell, S.M., Wong, V.J., King, D. and Plopper, C.G. (2005). Temporal and spatial distribution of ciliogenesis in the tracheobronchial airways of mice. Am. J. Physiol. Lung Cell. Mol. Physiol. 289, L454-459.

Verra, F., Escudier, E., Lebargy, F., Bernaudin, J.F., De Cremoux, H., and Bignon, J. (1995). Ciliary abnormalities in bronchial epithelium of smokers, ex-smokers, and nonsmokers. Am. J. Respir. Crit. Care Med. 151, 630-634.

Wanner, A., Salathe, M. and O'riordan, T.G. (1996). Mucociliary clearance in the airways. Am. J. Respir. Crit. Care Med. 154, 1868-1902.

Wessely, O. and Obara, T. (2008). Fish and frogs: models for vertebrate cilia signaling. Front. Biosci. 13, 1866-1880.

Yaghi, A. and Dolovich, M.B. (2016). Airway Epithelial Cell Cilia and Obstructive Lung Disease. Cells. 5, 40.