Published: 20 Nov 2025 | Last Updated: 20 Nov 2025 09:55:45

A new study from the Royal Veterinary College (RVC) has identified that ageing causes a significant loss of blood vessels in the tendons of horses. This discovery offers vital insight into why older horses and people are more prone to tendon injuries and why these injuries heal more slowly and less effectively. The findings will help vets and trainers identify horses at higher risk of injury and choose the most appropriate treatment and rehabilitation strategies to improve recovery.

Tendon injuries are a leading cause of lameness and reduced performance in horses, with the risk increasing as animals age. Despite this, the biological reasons behind this age-related decline have remained unclear. Understanding how blood flow and tissue structure change with age is essential to supporting the development of more effective treatments and rehabilitation strategies for older horses, as well as offering insight into similar processes in humans.

The RVC research team, led by Dr Nodoka Iwasaki, Postdoctoral Researcher, and Dr Chavaunne Thorpe, Lecturer in Basic Sciences at the RVC’s Department of Comparative Biomedical Sciences, used advanced 3D technologies to capture detailed images of tendon tissue from young (2-5 years old) and older (18-22 years old) horses, enabling them to visualise and quantify the tendon’s vascular network in unprecedented detail. The study specifically examined blood vessels within the superficial digital flexor tendon (SDFT), a structure functionally similar to the human Achilles tendon and one commonly injured in athletic horses. Assessing these images, the researchers that older horses showed a 70% reduction in overall vascular volume, meaning far less blood was present within the tendon’s blood vessels. It also found a 30% decrease in vessel diameter and a 74% reduction in the number of blood vessels overall, compared to younger horses. This means that older tendons receive far less blood flow, making them more vulnerable to damage and slower to heal.

At the same time, the team observed an increase in the formation of smaller blood vessels within aged tendons, suggesting that the tissue attempts to compensate for the loss of larger vessels. However, this new vascular network appeared disorganised, indicating a loss of vascular balance, meaning the normal structure and coordination of blood vessels is disrupted. These changes suggest that the new disorganised vessels may not function effectively, reinforcing the need to monitor tendon health closely as horses age.

Dr Nodoka Iwasaki, Postdoctoral Researcher at the RVC, said:

“This study used advanced 3D imaging to reveal, for the first time, how the blood supply to the horse’s tendon changes with age. We found that older tendons lose many of their larger blood vessels, which are crucial for repair and recovery. This helps explain why older horses are more prone to tendon injuries and why these injuries heal more slowly. We are now exploring ways to prevent this age-related decline, with the aim of improving outcomes for older horses diagnosed with tendon injury”.

Chavaunne Thorpe, Lecturer in Basic Sciences at the RVC’s Department of Comparative Biomedical Sciences, said:

“Using high-resolution 3D imaging techniques, we have shown that the blood supply to the injury prone superficial digital flexor tendon is dramatically altered as horses age, with a loss of larger blood vessels. This may explain why older horses are more at risk of tendon injury, as a lower blood supply means their tendons won't be able to heal as well. We are currently developing methods to prevent this age-related decline, which, if successful, may improve prognosis in older horses diagnosed with tendon injury."

Funded by the Horserace Betting Levy Board and conducted in collaboration with colleagues from the Aristotle University of Thessaloniki in Greece, this research builds on the RVC’s expertise and leadership in equine science, where it undertakes and contributes to world-leading innovation in understanding tendon biology, injury and repair. The RVC continues to lead studies into areas such as stem cell therapies, laminitis, equine Cushing’s disease, lameness and life for racehorses post-retirement.

Notes to Editors

References

Iwasaki, N., J. Llewellyn, J. Brown, et al. 2025. “ Immunolabelling and Micro-Computed Tomography Revealed Age-Related Alterations in 3D Microvasculature of Tendons.” Aging Cell e70293. https://doi.org/10.1111/acel.70293.

The full paper can be accessed at: https://onlinelibrary.wiley.com/doi/10.1111/acel.70293

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About the RVC

• The Royal Veterinary College (RVC) is the UK's largest and longest established independent veterinary school and is a Member Institution of the University of London.  
• It is one of the few veterinary schools in the world that hold accreditations from the RCVS in the UK (with associated recognition from the AVBC for Australasia, the VCI for Ireland and the SAVC for South Africa), the EAEVE in the EU, and AVMA in the USA and Canada. 
• The RVC is ranked as the top veterinary school in the world in the QS World University Rankings by subject, 2025.  
• The RVC offers undergraduate and postgraduate programmes in veterinary medicine, veterinary nursing and biological sciences.  
• The RVC is a research-led institution, with 88% of its research rated as internationally excellent or world class in the Research Excellence Framework 2021. 
• The RVC provides animal owners and the veterinary profession with access to expert veterinary care and advice through its teaching hospitals and first opinion practices in London and Hertfordshire.