A new study from the Royal Veterinary College (RVC) has revealed that ageing causes a significant loss of blood vessels in the tendons of horses, a finding that could explain why older horses are more prone to tendon injuries and why these injuries heal more slowly.
Using advanced 3D imaging, researchers found that older horses showed a 70% reduction in overall vascular volume, a 30% decrease in vessel diameter, and a 74% reduction in the number of blood vessels compared to younger horses. This dramatic loss of blood supply means older tendons receive far less oxygen and nutrients, making them more vulnerable to damage and slower to repair.
The research, led by Dr Nodoka Iwasaki and Dr Chavaunne Thorpe from the RVC’s Department of Comparative Biomedical Sciences, focused on the superficial digital flexor tendon (SDFT) – a structure similar to the human Achilles tendon and one commonly injured in athletic horses. The team’s detailed 3D analysis provided an unprecedented view of the tendon’s vascular network, offering fresh insight into how ageing affects tendon health.
Interestingly, the study also found signs that ageing tendons attempt to compensate for the loss of larger vessels by forming new, smaller blood vessels. However, these appeared disorganised and less functional, indicating that the tissue’s ability to repair itself effectively is compromised.
Dr Iwasaki explained: “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.”
Dr Thorpe added, “Using high-resolution 3D imaging techniques, we have shown that the blood supply to the injury-prone SDFT is dramatically altered as horses age. 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 developing methods to prevent this decline and improve prognosis in older horses.”
The study, funded by the Horserace Betting Levy Board and conducted in collaboration with the Aristotle University of Thessaloniki in Greece, highlights the importance of age-related tendon research. It builds on the RVC’s world-leading work into tendon biology, injury, and repair – including research into stem cell therapies, laminitis, equine Cushing’s disease, lameness, and post-retirement care for racehorses.
Read the full paper
👉 Iwasaki, N., Llewellyn, J., Brown, J., et al. (2025). “Immunolabelling and Micro-Computed Tomography Revealed Age-Related Alterations in 3D Microvasculature of Tendons.” Aging Cell e70293.
Read the study here
