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Event: 2372

Key Event Title

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

Squamous metaplasia, Increase

Short name

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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

Organ term

Organ term
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
Metaplasia	Squamous cell	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

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
mammals	mammals	High	NCBI
Rattus norvegicus	Rattus norvegicus	High	NCBI
Mus musculus	Mus musculus	High	NCBI
Aves	Aves	Moderate	NCBI

Life Stages

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

Life stage	Evidence
Adult	High
Juvenile	Moderate

Sex Applicability

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

Term	Evidence
Unspecific	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

A process in which non-squamous epithelial cells transform into a squamous epithelial phenotype. The metaplastic change can be a normal physiological change, like in the case of nonkeratinizing cervical squamous metaplasia (clevelandclinic) or in response to chronic irritation or injury.

Squamous metaplasia occurs in epithelial tissue. This tissue forms the covering on all internal and external surfaces of the body. It lines the body cavity, hollow organs, and is the major tissue in glands (clevelandclinic).

Squamous metaplasia is a protective adaptation since the stratified squamous cell structure is more resilient to physical and chemical stress than columnar or cuboidal 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

Directly:

Histopathological examination via tissue biopsy followed by fixation, embedding, sectioning, and staining.
Cytological analysis via collecting of exfoliated cells, e.g., smear.

Indirectly:

Immunohistohemistry via tissue staining wiht antibodies specific to epithelial markers.

Domain of Applicability

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

Taxonomic

Squamous metaplasia is well documented humans, rats, and mice, occuring in many epithelial tissues including, but not limited to:

Respiratory tract, cervix, mammary gland, sebaceous gland, and skin (Giroux & Rustgi 2017)
Urothelium (Clouston & Lawrentschuk 2013)
Stomach (Iwamuro et al., 2021)
Uterus (McLachlan et al., 1980)

There is also evidence of squamous metaplasia in birds, typically related to vitamin A deficiency, including:

Ducks (Prabhu et al., 2015)
Chickens (Kim et al., 2022)
Falcons (McKinney et al., 2005)

Evidence of squamous metaplasia in fish, reptiles, and other non-mammal vertebrates is limited.

Lifestage

Squamous metaplasia is most commonly studied as a pathological condition, occuring in response chronic inflammation or other stress conditions. Because of this, it most occurs in adults. Non-pathological squamous metaplasia has been documented during puberty (Hwang et al., 2009).

Sex

Squamous metaplasia occurs does not occur on a sex-specific basis. However, the prevalence, typical sites, and underlying triggers vary between sexes due to the differences in hormones and presence of sex specific structures.

References

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

Clouston, D., & Lawrentschuk, N. (2013). Metaplastic conditions of the bladder. BJU international, 112, 27-31.

Giroux, V., & Rustgi, A. K. (2017). Metaplasia: tissue injury adaptation and a precursor to the dysplasia–cancer sequence. Nature Reviews Cancer, 17(10), 594-604.

https://my.clevelandclinic.org/health/diseases/23307-squamous-metaplasia

Hwang, L. Y., Ma, Y., Benningfield, S. M., Clayton, L., Hanson, E. N., Jay, J., ... & Moscicki, A. B. (2009). Factors that influence the rate of epithelial maturation in the cervix in healthy young women. Journal of Adolescent Health, 44(2), 103-110

Iwamuro, M., Fujii, N., Tanaka, T., Kanzaki, H., Kawano, S., Kawahara, Y., & Okada, H. (2021). Squamous metaplasia of the stomach associated with lymphoma infiltration. Internal Medicine, 60(14), 2229-2234.

Kim, S. H., Song, H. S., Kim, C. H., Kwon, Y. K., Park, C. K., & Kim, H. R. (2022). Histopathological Findings and Metagenomic Analysis of Esophageal Papillary Proliferation Identified in Laying Broiler Breeders. Veterinary Sciences, 9(7), 332.

McKinney, P. A., Wernery, U., Forsman, J., Kinne, J., Arca-Ruibal, B., Wencel, P., ... & Thyagarajan, J. (2025). Squamous Metaplasia Associated With Hypovitaminosis A of the Crop and Salivary Glands in Captive Falcons in the United Arab Emirates. Journal of Avian Medicine and Surgery, 39(1), 12-19.

McLachlan, J. A., Newbold, R. R., & Bullock, B. C. (1980). Long-term effects on the female mouse genital tract associated with prenatal exposure to diethylstilbestrol. Cancer Research, 40(11), 3988-3999.

Prabhu, S. N., Gangwar, N. K., Kumar, R., & Giri, D. K. (2015). Squamous metaplasia of oesophageal mucous glands in a non-descript duck. Indian Journal of Poultry Science, 50(2), 229-230.