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MicroRNA signatures of equine asthma phenotypes in serum and bronchoalveolar lavage fluid.
Abstract: Equine asthma (EA) is a highly prevalent, chronic, inflammatory disease of the lower airways ranging from mild-to-moderate to severe clinical presentations. Diagnosis currently relies on bronchoalveolar lavage fluid (BALF) cytology, an invasive method associated with interobserver variability, which highlights the need for more reproducible approaches. MicroRNAs (miRNAs) are small noncoding RNAs involved in gene regulation. They are stable and readily detectable in body fluids and have shown promising results as biomarkers in human asthma. The aim of this pilot study was to characterize miRNA expression profiles in BALF and serum from horses with distinct EA phenotypes to evaluate their biomarker potential and explore their putative involvement in disease pathogenesis. Results: A total of 43 horses were included and classified as either EA (n = 32) or controls (n = 11), based on clinical examination and BALF cytology. The EA horses were further divided into three phenotypes based on BALF inflammatory cell composition: neutrophilic asthma (n = 10), mastocytic asthma (n = 15), and mixed asthma (n = 7). RNA was isolated from both serum and BALF samples and analyzed by quantitative real-time PCR (qPCR) targeting 103 miRNAs linked to asthma and pulmonary inflammation in humans. Differential miRNA expression was analyzed across EA phenotypes. The most significantly differentially expressed miRNAs were used for hypothesis-generation by in silico target prediction and pathway enrichment exploratory analyses. Horses with mixed EA had significantly lower levels of eca-miR-125a-3p and eca-miR-125b-5p in BALF compared to controls. Additionally, eca-miR-146a-5p expression was significantly increased in BALF from horses with neutrophilic EA compared to mastocytic EA. For serum, none of the miRNAs showed significant differential expression within the EA phenotypes. Target and pathway enrichment analyses for eca-miR-146a-5p identified immune-relevant pathways supporting its possible involvement in inflammatory processes associated with asthma. Conclusions: This study identified three promising candidates, eca-miR-125a-3p, eca-miR-125b-5p, and eca-miR-146a-5p, as potential biomarkers in BALF associated with different EA phenotypes. These miRNAs are interesting candidates for further validation in an independent cohort before they can be used in diagnostics.
© 2026. The Author(s).
Publication Date: 2026-08-03 PubMed ID: 42881456PubMed Central: 7438831DOI: 10.1186/s12917-026-05761-9Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
Summary
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MicroRNA expression patterns in fluid samples from horses reveal potential biomarkers that distinguish different types of equine asthma, enhancing understanding of disease mechanisms and aiding diagnosis.
Background and Objective
- Equine asthma (EA) is a common chronic inflammatory disease affecting the lower airways of horses, with symptoms ranging from mild to severe.
- Current diagnostic methods rely on bronchoalveolar lavage fluid (BALF) cytology, which is invasive and subject to variability between observers.
- MicroRNAs (miRNAs) are small, stable noncoding RNA molecules detectable in body fluids and have potential as non-invasive biomarkers.
- The study aimed to profile miRNA expression in both BALF and serum of horses with different EA phenotypes to evaluate their potential as biomarkers and to understand their role in disease pathogenesis.
Study Design and Methods
- Total of 43 horses participated: 32 diagnosed with EA and 11 control horses without EA.
- EA horses were further categorized into three inflammatory phenotypes based on cell types found in BALF:
- Neutrophilic asthma (n=10)
- Mastocytic asthma (n=15)
- Mixed asthma (n=7)
- Samples of serum and BALF were collected from all horses.
- RNA was isolated from these samples and analyzed using quantitative real-time PCR (qPCR) focusing on 103 miRNAs previously linked to human asthma and lung inflammation.
- Differential expression analyses were performed to compare miRNA levels across EA phenotypes and controls.
- Significantly different miRNAs were further analyzed using in silico methods to predict target genes and enriched biological pathways.
Key Findings
- In BALF samples:
- Horses with mixed EA showed significantly decreased levels of eca-miR-125a-3p and eca-miR-125b-5p compared to controls.
- eca-miR-146a-5p was significantly upregulated in neutrophilic EA horses compared to those with mastocytic EA.
- In serum samples:
- No significant differences in miRNA expression were observed across EA phenotypes or controls.
- Pathway analysis of eca-miR-146a-5p targets suggested involvement in immune-related signaling pathways, supporting a role in inflammatory processes linked to asthma.
Conclusions and Implications
- Three miRNAs (eca-miR-125a-3p, eca-miR-125b-5p, and eca-miR-146a-5p) in BALF have potential as biomarkers distinguishing equine asthma phenotypes.
- Their expression patterns may reflect underlying inflammatory mechanisms unique to each EA subtype.
- Serum miRNAs were not useful biomarkers within this study, suggesting BALF may be a more relevant fluid for miRNA-based diagnostics in EA.
- These miRNAs should be validated in larger independent cohorts before clinical application.
- Future research might focus on understanding how these miRNAs contribute to asthma pathogenesis and evaluating whether they can be targeted therapeutically or used to monitor disease progression.
Cite This Article
APA
Røgild ER, Mármol-Sánchez E, Toft K, Hansen S, Cirera S.
(2026).
MicroRNA signatures of equine asthma phenotypes in serum and bronchoalveolar lavage fluid.
BMC Vet Res, 22(1), 610.
https://doi.org/10.1186/s12917-026-05761-9 Publication
Researcher Affiliations
- Department of Veterinary and Animal Sciences, University of Copenhagen, Copenhagen, Denmark.
- Center for Evolutionary Hologenomics, The Globe Institute, University of Copenhagen, Copenhagen, Denmark. emilio.marmol.sanchez@gmail.com.
- Department of Veterinary Clinical Sciences, University of Copenhagen, Copenhagen, Denmark.
- Department of Veterinary Clinical Sciences, University of Copenhagen, Copenhagen, Denmark. sannih@sund.ku.dk.
- Department of Veterinary and Animal Sciences, University of Copenhagen, Copenhagen, Denmark. scs@sund.ku.dk.
MeSH Terms
- Animals
- Horses
- Asthma / veterinary
- Asthma / blood
- Asthma / genetics
- Asthma / metabolism
- Horse Diseases / blood
- Horse Diseases / genetics
- Horse Diseases / metabolism
- Bronchoalveolar Lavage Fluid / chemistry
- Bronchoalveolar Lavage Fluid / cytology
- MicroRNAs / blood
- MicroRNAs / metabolism
- MicroRNAs / genetics
- Female
- Male
- Biomarkers / blood
- Pilot Projects
- Phenotype
Conflict of Interest Statement
Declarations. Ethics approval and consent to participate: This study was approved by the ethics committee of the Department of Veterinary Clinical Sciences, University of Copenhagen (2020-013) with informed client consent. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests.
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