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Home / Equine Research Bank / Equine Vet J / Immunohistochemical analysis of laryngeal muscle of horses c...
Equine veterinary journal2020; 53(4); 710-717; doi: 10.1111/evj.13362

Immunohistochemical analysis of laryngeal muscle of horses clinically affected with recurrent laryngeal neuropathy.

Abstract: As myosin heavy chain (MyHC) profile of muscle fibres is heavily influenced by neural input, changes in MyHC expression are expected in horses clinically affected with recurrent laryngeal neuropathy (RLN) yet, this has not been thoroughly investigated. Objective: To describe the changes in MyHC and fibre diameter in left cricoarytenoideus dorsalis (L-CAD) muscle of horses with clinical signs of RLN. Methods: Observational cohort study. Methods: Immunohistochemistry was used to assess the MyHC-based fibre-type proportion, size and grouping in the L-CAD of 10 Thoroughbred horses, five clinically affected with RLN and five unaffected controls based on resting endoscopic examination. The Mann-Whitney U test was used to compare the two groups. Results: Compared to controls (of mean age 3.0 ± 1.7 years) which only expressed type I, IIA and IIX MyHC, the L-CAD of affected horses (of mean age 2.8 ± 0.8 years) had obvious fibre-type grouping, and despite apparent compensatory hypertrophy of a small number of fibres, a decrease in overall fibre diameter (median difference -35.2 µm, 95% CI -47.4 to -7.9, P = .02) and diameter of type IIA fibres (median difference -46.8 µm, 95% CI -52.1 to -5.0, P = .03) was observed. Anti-fast MyHC (MY32) cross-immunoreacted with embryonic-MyHC. Whereas MY32-positive fibres were identified as type IIX in controls, in affected horses these fibres were less than 50 µm diameter with internal nuclei and were MYH3-positive for embryonic myosin indicating depletion of type IIX fibres, yet active regeneration and fibre renewal. Conclusions: Small sample size that did not include subclinical cases. Fibre size and appearance rather than staining colour were relied upon to differentiate embryonic from type IIX MyHC. Conclusions: Horses clinically affected with RLN have overall atrophy of fibres, loss of IIX fibres and expression of embryonic myosin indicating regenerative capacity. Despite hypertrophy of some remaining fibres, the overall decline in the bulk of fibres, including those most fatigue-resistant, may be the critical change that results in failure to maintain arytenoid abduction during exercise although direct comparison to subclinical cases is needed to confirm this.
© 2020 EVJ Ltd.
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Publication Date: 2020-10-27 PubMed ID: 33001503DOI: 10.1111/evj.13362Google Scholar: Lookup
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  • Journal Article
  • Observational Study
  • Veterinary

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research investigates changes in the muscle fiber characteristics of horse’s laryngeal muscles affected by recurrent laryngeal neuropathy (RLN), a common disease in horses that affects their capability to breathe properly. The study’s findings reveal overall muscle fiber atrophy, loss of fibre type IIX, and the expression of embryonic myosins – an indication of regenerative potential.

Objective of the Research

  • The research aimed to study changes in the myosin heavy chain (MyHC) – which determines muscle fiber type – as well as fiber diameter, in horses clinically diagnosed with RLN. The researchers focused on the left cricoarytenoideus dorsalis (L-CAD) muscle of the larynx, where the disease usually impacts.

Methods

  • A cohort of ten Thoroughbred horses, half affected by RLN and the other half unaffected, were observed. The horses’ MyHC-based fiber type proportion, size, and grouping in the L-CAD were examined through immunohistochemistry.
  • Data from both groups (affected and non-affected horses) were then compared using the Mann-Whitney U test.

Results

  • The affected horses showed obvious fiber-type grouping in the L-CAD muscle.
  • Even though there was visible compensatory hypertrophy (increase in size) of some muscle fibers, the overall fiber diameter decreased compared to the control group. Additionally, a decrease in the diameter of type IIA fibers was also observed in the affected horses.
  • The control horses expressed type I, IIA, and IIX MyHC, whereas the RLN-affected horses showed evidence of depletion of the type IIX fibers. However, they also exhibited signs of active regeneration and fiber renewal, as evidenced by the presence of embryonic myosin.

Conclusions

  • The RLN condition in horses leads to an overall decline in the size of muscle fibers, including the most fatigue-resistant ones. This may result in the inability to keep the arytenoids (cartilages in the larynx) open during physical exertion, potentially leading to breathing problems.
  • Further studies including subclinical cases are needed to validate these findings.

Cite This Article

APA
Steel CM, Walmsley EA, Anderson GA, Coles CA, Ahern B, White JD. (2020). Immunohistochemical analysis of laryngeal muscle of horses clinically affected with recurrent laryngeal neuropathy. Equine Vet J, 53(4), 710-717. https://doi.org/10.1111/evj.13362

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 53
Issue: 4
Pages: 710-717

Researcher Affiliations

Steel, Catherine M
  • School of Veterinary and Agricultural Sciences, University of Melbourne, Werribee, VIC, Australia.
Walmsley, Elizabeth A
  • School of Veterinary and Agricultural Sciences, University of Melbourne, Werribee, VIC, Australia.
Anderson, Garry A
  • School of Veterinary and Agricultural Sciences, University of Melbourne, Werribee, VIC, Australia.
Coles, Chantal A
  • Murdoch Children's Research Institute, The Royal Children's Hospital, Parkville, VIC, Australia.
Ahern, Benjamin
  • School of Veterinary Science, Equine Specialist Hospital, University of Queensland, Gatton, QLD, Australia.
  • School of Animal and Veterinary Science, The University of Adelaide, Roseworthy, Australia.
White, Jason D
  • Office of the Pro Vice Chancellor Research and Innovation, Charles Sturt University, Wagga Wagga, NSW, Australia.

MeSH Terms

  • Animals
  • Horse Diseases
  • Horses
  • Immunohistochemistry
  • Laryngeal Muscles
  • Muscle Fibers, Skeletal
  • Muscle, Skeletal
  • Myosin Heavy Chains
  • Peripheral Nervous System Diseases / veterinary

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Citations

This article has been cited 3 times.
  1. de Meeûs d'Argenteuil C, Boshuizen B, Vidal Moreno de Vega C, Leybaert L, de Maré L, Goethals K, De Spiegelaere W, Oosterlinck M, Delesalle C. Comparison of Shifts in Skeletal Muscle Plasticity Parameters in Horses in Three Different Muscles, in Answer to 8 Weeks of Harness Training. Front Vet Sci 2021;8:718866.
    doi: 10.3389/fvets.2021.718866pubmed: 34733900google scholar: lookup
  2. Shawaf T. Jugular venous thrombosis as a risk factor for exercise-induced pulmonary hemorrhage in thoroughbred racehorses. Open Vet J 2024 May;14(5):1111-1116.
    doi: 10.5455/OVJ.2024.v14.i5.4pubmed: 38938431google scholar: lookup
  3. Hardwick JL, Ahern BJ, Crawford KL, Allen KJ, Franklin SH. Yearling laryngeal function in Thoroughbreds that underwent a laryngoplasty differs from controls. Equine Vet J 2025 Mar;57(2):431-440.
    doi: 10.1111/evj.14110pubmed: 38847239google scholar: lookup
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