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Event: 869

Key Event Title

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

Increase, Respiratory or Squamous Metaplasia

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
Increase, Respiratory or Squamous Metaplasia
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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

Organ 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
Organ term
olfactory 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; 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
Metaplasia increased

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
pH Induced Nasal Tumors KeyEvent Undefined (send email) Open for citation & comment Under Review

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
rat Rattus norvegicus High NCBI
mouse Mus musculus High NCBI
human Homo sapiens Low NCBI

Life Stages

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

Sex Applicability

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

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

Sustained atrophy/degeneration olfactory epithelium under the influence of a cytotoxic agent leads to adaptive tissue remodeling. Cell types unique to olfactory epithelium, e.g. olfactory neurons, sustentacular cells and Bowmans glands, are replaced by cell types comprising respiratory epithelium or squamous epithelium.

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

Respiratory or squamous metaplasia is measured histologically is cross-sections of the nose after H&E staining and/or use of immunohistochemical markers to show the absence of olfactory epithelial cell types and the presence of cell types of the respiratory or squamous epithelium. Olfactory epithelium is normally composed of X cell types. Respiratory epithelium is composed of Y cell types: The squamous epithelium is composed of Z cell types. The absence of structures such as Bowmans glands and olfactory bundles are also markers of the initial step of respiratory metaplasia. Immunohistochemical staining for olfactory marker protein[1] is used to determine the absence of olfactory sensory neurons. Staining for AB/PAS-positive mucosubstances[2] is used to determine the presence mucous cells, which are normally present in respiratory epithelium. The key features of transitional epiethelium metaplasia are the presence of tall columnar cells with cilia on the luminal surface, basal cells, and nonciliated cuboidal to columnar cells[3].

Domain of Applicability

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

This event has been observed in the olfactory epithelium of rats and mice exposed by inhalation to one or more of the listed chemical initiators. Degeneration, necrosis and atrophy are expected in humans based conserved properties of the olfactory epithelium across species.


List of the literature that was cited for this KE description. More help
  1. Islam, Amuzie, Harkema and Pestka (2007). Neurotoxicity and inflammation in the nasal airways of mice exposed to the macrocyclic trichothecene mycotoxin roridin a: kinetics and potentiation by bacterial lipopolysaccharide coexposure. Toxicol Sci. 98: 526-541
  2. Wagner, Van Dyken, Hotchkiss and Harkema (2001). Endotoxin enhancement of ozone-induced mucous cell metaplasia is neutrophil-dependent in rat nasal epithelium. Toxicol Sci. 60: 338-347
  3. Hardisty, Garman, Harkema, Lomax and Morgan (1999). Histopathology of nasal olfactory mucosa from selected inhalation toxicity studies conducted with volatile chemicals. Toxicol Pathol. 27: 618-627