Stem Cell Transplantation in the treatment of tendon injuries

Unfortunately tendon and ligament injuries are all too common in horses, particularly those used for national hunt and point-to-point racing.  The tendon most commonly injured is the superficial digital flexor tendon (SDFT), although the suspensory ligament and inferior check ligament can also be damaged.  Horses that have suffered a SDFT injury are often referred to as having ‘done a leg’.  Although there are exceptions to the rule the majority of racehorses that sustain a SDFT injury require 9-12 months rehabilitation, many do not return to racing and are sold on for less strenuous careers.  In a few cases the extent of the tendon damage is such that some horses are put down on humane grounds.  During the last 20 years numerous treatments have claimed to be the answer to a successful outcome; these include carbon fibre implants, intra-tendonous injects, BAPTEN, superior check ligament desmotomy, tendon splitting, firing of the skin over the tendons, Adequan, blistering and many more.  As suggested by the sheer number of treatments none have significantly altered the quality and speed of tendon healing.  One main reason why tendon healing is so relatively poor is because there are relatively few tenocytes (tendon cells) within the tendon.  Healing also relies on new blood vessels and associated ‘healing’ cells arriving from the surrounding tissue of the damaged tendon, rather than from within the tendon itself.

The use of stem cells potentially addresses some of these problems of poor tendon healing. Stem cell implantation provides a large numbers of young cells directly into the area of damage. After implantation the stem cells metamorphose into tenocytes. The type of stem cells needed to transform into new tendon or ligament cells are ‘mesenchymal’ stem cells that are found in great numbers in bone marrow.  Whilst the treatment is still in the early stages, in theory it should be the most effective treatment to date. It has to be stressed that the stem cells are autologous (from the same animal) and have no connection with embryonic stem cell research.  In the United States they are using stem cells derived from fat tissue.  There are still arguments as to which is the best source.

Numerous racehorses since 2000 have had the procedure done.  The stem cells are extracted from bone marrow taken from the horse’s own sternum. Over the following two to three weeks pioneering company VetCell then multiplied the cells up in the laboratory, before they were implanted back into the area of damaged tendon.  The whole procedure requires the use of detailed ultrasound, firstly to diagnose the area of damage within the tendon, then to locate the site to extract the bone marrow and finally to inject the cells (usually 10-30 million) back into the damaged tendon tissue.  Injected into tendons the stem cells transform into tendon cells that help repair the damage. 

In time stem cell implantation may become a routine procedure if the results for these early cases and others prove a success.  It will however take a few years to really know how successful the procedure is going to be. 


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The advice given in any of our web pages cannot be used as the basis for a diagnosis or choice of treatment.

Clyde Vet Group advises that you should always consult a veterinary surgeon about any queries with animals under your care.