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An in vitro collagen gel contraction assay to assess the relaxing effect of potential pharmacological alternatives to oxytetracycline on foals’ tendons.
Abstract: Oxytetracycline has been successfully used to treat flexural limb deformities in foals. However, its antimicrobial properties and potential adverse side effects warrant the investigation of alternatives. Inhibition of matrix metalloproteinases (MMPs) or collagen cross-linking have been suggested as possible mechanisms of action. This study assessed the influence of potential alternative substances lacking antimicrobial properties on collagen gel contraction by juvenile equine myofibroblasts in vitro. Myofibroblasts were isolated from forelimb SDFTs and inferior check ligaments from foals euthanised for reasons unrelated to this study, and seeded in collagen gels containing oxytetracycline, MMP-inhibitors incyclinide, ilomastat, aprotinin, and pentoxifylline, β-aminopropionitrile fumarate (BAPN), and control medium. The gels were measured in photographs up to 96 h after release, and differences in contraction were evaluated. Compared to control, BAPN and incyclinide induced significant inhibition (p < 0.05) of collagen gel contraction by myofibroblasts at all time points, and the inhibition was more potent than that observed with oxytetracycline. Consequently, the inhibitory capacity of BAPN and incyclinide on myofibroblast-mediated collagen gel contraction, which demonstrates their effect on tractional structuring of collagen, makes them promising candidates as potential substitutes for oxytetracycline. Further investigations into their side effects, pharmacodynamics, pharmacokinetics, and application methods in juvenile equine patients are needed.
© 2026. The Author(s).
Publication Date: 2026-04-25 PubMed ID: 42034696PubMed Central: PMC13110344DOI: 10.1038/s41598-026-49449-4Google 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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Overview
- This study investigated alternative drugs to oxytetracycline for treating flexural limb deformities in foals by assessing their effects on tendon cell-driven collagen contraction in vitro.
- Two compounds, β-aminopropionitrile fumarate (BAPN) and incyclinide, were found to inhibit collagen gel contraction more effectively than oxytetracycline, highlighting their potential as safer pharmacological alternatives.
Background and Rationale
- Flexural limb deformities are common developmental issues in foals, often treated with oxytetracycline.
- Oxytetracycline, an antibiotic, also relaxes tendons potentially through mechanisms affecting collagen or matrix remodeling.
- Its antimicrobial action raises concerns about resistance and side effects, motivating the search for alternative drugs without antimicrobial properties.
- Two suggested modes of action for tendon relaxation are inhibition of matrix metalloproteinases (MMPs), which degrade extracellular matrix components, or interference with collagen cross-linking, which stabilizes the tendon structure.
Objectives
- To assess the relaxing effects of several candidate drugs—MMP inhibitors and a collagen cross-linking inhibitor—on tendon fibroblasts derived from foals.
- To compare these effects with oxytetracycline in a controlled in vitro collagen gel contraction assay.
Methods
- Myofibroblasts were isolated from superficial digital flexor tendons (SDFTs) and inferior check ligaments of euthanized foals.
- These cells were embedded in 3D collagen gels to mimic tendon extracellular matrix.
- The gels contained one of the following: oxytetracycline, MMP inhibitors (incyclinide, ilomastat, aprotinin, pentoxifylline), β-aminopropionitrile fumarate (BAPN, a collagen cross-linking inhibitor), or control medium without drugs.
- Collagen gel size contraction was measured via photographs at multiple time points up to 96 hours after gel release.
- Statistical analyses compared the degree of gel contraction between treatment groups and control.
Key Findings
- BAPN and incyclinide significantly inhibited collagen gel contraction by myofibroblasts at all time points compared to control (p < 0.05).
- Both compounds demonstrated greater inhibition of contraction than oxytetracycline, indicating stronger relaxation effects.
- Other tested MMP inhibitors (ilomastat, aprotinin, pentoxifylline) did not show significant effects or were less effective.
- This suggests that blocking collagen cross-linking (BAPN) or inhibiting specific MMP activity (incyclinide) may effectively modulate tendon tension.
Interpretation and Implications
- The in vitro collagen gel contraction assay provides a functional model to assess how drugs influence tendon cell-mediated matrix remodeling.
- BAPN and incyclinide are promising candidates to replace oxytetracycline for treating foal tendon deformities without antibiotic effects and potentially fewer side effects.
- The findings support that targeting collagen cross-linking or specific MMP pathways can reduce traction forces generated by myofibroblasts, which contribute to tendon contracture.
Limitations and Future Directions
- The study was conducted in vitro, which may not fully replicate the complex in vivo environment of growing foals.
- Further research is needed to evaluate the safety profiles, dosage optimization, pharmacodynamics, and pharmacokinetics of BAPN and incyclinide in juvenile horses.
- In vivo efficacy studies and investigation of possible adverse effects or long-term outcomes will be essential before clinical application.
- Exploration of administration methods (e.g., systemic vs. local delivery) will also impact therapeutic utility.
Conclusion
- This research identified BAPN and incyclinide as effective inhibitors of myofibroblast-mediated tendon contraction in vitro, surpassing oxytetracycline’s capacity.
- These compounds may serve as safer pharmacological alternatives for managing flexural limb deformities in foals, pending further investigation.
Cite This Article
APA
Cardinaux EM, Oltmanns H, Rohn K, Meißner J, Geburek F.
(2026).
An in vitro collagen gel contraction assay to assess the relaxing effect of potential pharmacological alternatives to oxytetracycline on foals’ tendons.
Sci Rep, 16(1), 13412.
https://doi.org/10.1038/s41598-026-49449-4 Publication
Researcher Affiliations
- Clinic for Horses, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany. emmanuel.mathieu.cardinaux@tiho-hannover.de.
- Department of Pharmacology, Toxicology and Pharmacy, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany.
- Institute of Biometry, Epidemiology, and Information Processing, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany.
- Department of Pharmacology, Toxicology and Pharmacy, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany.
- Clinic for Horses, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany. florian.geburek@tiho-hannover.de.
MeSH Terms
- Animals
- Horses
- Oxytetracycline / pharmacology
- Collagen / metabolism
- Collagen / chemistry
- Tendons / drug effects
- Tendons / metabolism
- Gels
- Myofibroblasts / drug effects
- Myofibroblasts / metabolism
- Myofibroblasts / cytology
- Matrix Metalloproteinase Inhibitors / pharmacology
Conflict of Interest Statement
Declarations. Competing interests: The authors declare no competing interests. Ethics statement: The experiments were approved by the animal welfare officer of the University of Veterinary Medicine Hannover (approval number TVO-2023-V-84).
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