A research project funded by The Horse Trust has made a surprise discovery about the differences in tendon renewal between low and high strain equine tendons.
The research, which is being carried out by Dr Helen Birch of the Institute of Orthopaedics & Musculoskeletal Science, University College London, aims to understand how tendons are renewed and how this process changes as horses age.
The long-term goal of Dr Birch's research is to improve prevention and treatment of equine tendonitis, reducing suffering in horses. Tendonitis, which particularly affects racing horses, is one of the causes of lameness in horses.
Dr Birch's research, which was given £145,422 funding by The Horse Trust, is a three year programme, which is due to complete in April 2010. The Horse Trust is the largest charitable provider of equine welfare grants and horse research grants in the UK.
Tendons are connective tissues that attach muscle to bone. Dr Birch's research is focused on the tissue surrounding the sparse population of cells in tendon, known as the matrix, and the rate at which this tissue renews in horses. The mechanical properties of the tendon depend on the matrix, so understanding this tissue is key to understanding tendon injury.
Dr Birch compared matrix turnover in the superficial digital flexor tendon (SDFT) and the common digital extensor tendon (CDET). The SDFT is a high-strain, spring-like tendon that is prone to injury1, while the CDET is low-strain, positional tendon that is less prone to injury2.
Dr Birch originally hypothesised that the SDFT would have a higher turnover of matrix to repair the damage caused by the higher strain experienced by the tendon.
However, she has been surprised to discover that it is the opposite way round - the high-strain SDFT has less ability to renew the matrix. Dr Birch does not yet know why this is, but hypothesises that SDFTs are protected from being turned over too much as this weakens the tendon.
Earlier research carried out by Dr Birch found that the tendon matrix in older horses show an accumulation of age-related products. She hypothesised that old cells will also synthesise less of the protein collagen which is responsible for providing the tendon with high strength, but early findings have found that cells in old tendons are still capable of producing new collagen.
Her research will now focus on investigating how the matrix is turned over and looking at the differences in the enzymatic process between CDET and SDFT and tendons of different ages. She hopes that a better understanding of the enzymatic process will enable researchers to understand why tendons degenerate and how to diagnose and prevent tendon injuries.
Her research into equine tendons should also impact understanding of human tendons. For example, SDFT is similar to the Achilles tendon in humans.
Dr Birch's research interests are in tendon biology and the mechanisms leading to tendon degeneration and subsequent rupture. Her work has been published in a variety of peer-review publications including Journal of Orthopaedic Research, Journal of Biomechanics, Spine Journal, The Journal of Physiology.
More information on Dr Birch's work can be found here: http://www.ucl.ac.uk/orthopaedics/centres/helenbirch.htm
1 The SDFT is located at the back of the distal part of the equine limb, running from the carpus to the fetlock.
2 The CDET is located at the front of the distal part of the equine limb, running from the carpus to the fetlock.
