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Cartilage2026; 19476035261484024; doi: 10.1177/19476035261484024

The Effect of Training Exercise on Cartilage Zonal Composition and Structure at Two Differently Loaded Sites in the Juvenile Equine Metacarpophalangeal Joint.

Abstract: BackgroundThe aim of this study was to investigate the depth related spatial distribution of biochemical and structural components in articular cartilage at different topographical sites experiencing different loading within the juvenile equine metacarpophalangeal joint in two groups of foals subjected to different exercise conditions.MethodsSixteen Warmblood foals were included in the study and were randomly assigned into 1 of 2 exercise groups (box rest and box rest plus training) during the first 5 months of life and subsequently euthanized. Osteochondral plugs were harvested from two sites which have previously been shown to experience different load levels and sectioned into 100 μm thick slices. Cartilage slices were analysed for glycosaminoglycan, DNA, and total collagen content, as well as content of hydroxylysine residues (HYL) in collagen and the collagen cross-link Hydroxylysylpyridinoline (HP). Collagen fibril architecture (Orientation Angle and Parallelism Index) was determined using quantitative polarized light microscopy.ResultsThe constantly loaded site 2 exhibited higher glycosaminoglycan (GAG) and HP content with HYL higher in the superficial and middle layers of the trained group, while the intermittently peak loaded site 1 showed greater collagen accumulation in deeper layers but lower cross-link density. Structural analyses (Oa and PI) confirmed that collagen fibril orientation and alignment adapt regionally, with training enhancing fibril organization in superficial zones.ConclusionThis study illustrates that mechanical loading is a key driver of functional adaptation, resulting in distinct zonal and topographical differences in the biochemical and structural composition of equine cartilage at 5 months.
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Publication Date: 2026-10-11 PubMed ID: 42859922PubMed Central: PMC13655274DOI: 10.1177/19476035261484024Google Scholar: Lookup
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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.

Overview

  • This study examined how early exercise influences the biochemical composition and structural organization of cartilage in different loading regions of the juvenile horse’s finger joint.
  • It compared cartilage properties in foals subjected to rest versus training to understand how mechanical loading drives cartilage adaptation.

Background and Purpose

  • The metacarpophalangeal joint in horses is subject to varying mechanical loads depending on the location within the joint.
  • Articular cartilage in this joint is layered (zonal) and can respond differently to mechanical stresses.
  • The study aimed to investigate how exercise-induced loading affects the depth-related distribution of biochemical and structural components of cartilage, focusing on two sites with different load profiles in foals.
  • Understanding these adaptations can provide insights into cartilage development and potentially inform training regimens or therapies to prevent joint disease.

Methods

  • Subjects: Sixteen Warmblood foals, randomly divided into two groups:
    • Box rest (minimal exercise)
    • Box rest plus training (exercise group)
  • Duration: First 5 months of life, after which foals were euthanized for analysis.
  • Sample Collection: Osteochondral plugs harvested from two topographical sites:
    • Site 1: Intermittently peak loaded area
    • Site 2: Constantly loaded area
  • Tissue Processing: Cartilage sliced into 100 μm thick layers to analyze depth-wise (zonal) differences.
  • Parameters Measured:
    • Glycosaminoglycan (GAG) content: Important for cartilage resilience and hydration.
    • DNA content: Indicates cellularity.
    • Total collagen content: Provides structural framework.
    • Hydroxylysine residues (HYL) in collagen: Related to collagen maturity and stability.
    • Hydroxylysylpyridinoline (HP) cross-links: Reflect collagen cross-linking and strength.
    • Collagen fibril architecture assessed by quantitative polarized light microscopy, measuring:
      • Orientation Angle (Oa): Reflects the direction of collagen fibrils.
      • Parallelism Index (PI): Indicates how well aligned the collagen fibers are.

Results

  • Site-Specific Differences:
    • Site 2 (constantly loaded) exhibited:
      • Higher GAG content, implying greater capacity for load resistance and water retention.
      • Increased HP cross-link density, indicating more mature and stable collagen network.
      • Higher HYL levels in superficial and middle cartilage layers for the trained group, suggesting enhanced collagen modification with exercise.
    • Site 1 (intermittently peak loaded) showed:
      • Greater collagen accumulation particularly in the deeper layers.
      • Lower density of collagen cross-links compared to site 2, implying less mature collagen network.
  • Effect of Training:
    • Training improved collagen fibril organization, especially in the superficial zones, as indicated by more aligned fibrils (higher Parallelism Index) and more consistent orientation angles.
    • Mechanical loading via exercise promoted region-specific biochemical and structural changes within the cartilage layers.

Conclusion

  • Mechanical loading from exercise during early development is a key factor in functional adaptation of juvenile equine cartilage.
  • This adaptation leads to distinct biochemical and structural properties depending on location within the joint and depth within the cartilage layers.
  • The findings underscore the importance of exercise-induced mechanical cues for healthy cartilage maturation, which could have implications for training management and prevention of joint disorders in horses.

Cite This Article

APA
Duggan MJS, Labberté MC, van Weeren R, Stoop R, Hyttinen MM, Rieppo J, de Groot J, Brama PAJ. (2026). The Effect of Training Exercise on Cartilage Zonal Composition and Structure at Two Differently Loaded Sites in the Juvenile Equine Metacarpophalangeal Joint. Cartilage, 19476035261484024. https://doi.org/10.1177/19476035261484024

Publication

Cartilage
ISSN: 1947-6043
NlmUniqueID: 101518378
Country: United States
Language: English
Pages: 19476035261484024
PII: 19476035261484024

Researcher Affiliations

Duggan, Michael J S
  • Translational Research Unit, School of Veterinary Medicine, College of Health & Agricultural Sciences, University College Dublin, Ireland.
  • UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Ireland.
Labberté, Margot C
  • Translational Research Unit, School of Veterinary Medicine, College of Health & Agricultural Sciences, University College Dublin, Ireland.
van Weeren, René
  • Department of Clinical Sciences, Faculty of Veterinary Medicine, Utrecht University, Netherlands.
Stoop, Reinout
  • Department of Biomedical Research, The Netherlands Organization for Applied Scientific Research (TNO), Leiden, The Netherlands.
Hyttinen, Mika M
  • Institute of Biomedicine, Department of Anatomy, University of Eastern Finland, Kuopio, Finland.
Rieppo, Jarno
  • Institute of Biomedicine, Department of Anatomy, University of Eastern Finland, Kuopio, Finland.
de Groot, Jeroen
  • Ncardia Services B.V, Leiden, Netherlands.
Brama, Pieter A J
  • Translational Research Unit, School of Veterinary Medicine, College of Health & Agricultural Sciences, University College Dublin, Ireland.

Conflict of Interest Statement

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

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