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Zara is a 10 year old thoroughbred horse who used to compete regularly in show jumping, cross country and eventing. Her owner became concerned that Zara might have damaged a leg tendon as she was lame, had a swollen lower leg and had had previous tendon damage. As tendon damage is common and can end the career of an athletic horse, vet Duncan Ballard was called out.
Duncan examined Zara and confirmed his diagnosis with a portable ultrasound machine: her superficial digital flexor tendon was damaged. Conventional therapy for this injury requires a long period of rest with a slow re-introduction of exercise. Although some horses with this injury will return to the same work level initially, many will re-injure themselves in the future, as damaged tendons do not always regain their original elasticity.
Duncan discussed with Zara's owner the possibility of a new treatment under development at the RVC. The treatment involves collecting stem cells, multiplying them in the laboratory and then injecting them back into the damaged tissue. Research to date suggests the technique will improve the quality of the healed tendon, reduce the scar tissue and result in greater strength and elasticity. This would help Zara attain her pervious athletic performance levels and hopefully reduce the risks of repeated tendon breakdown.
Zara was assessed at the RVC's Equine Hospital by Professor Roger Smith who developed the stem cell technology and techniques. Roger scanned her tendons with an ultrasound machine to produce high definition images of the damaged area. After discussion with Zara's owner the decision was made to carry on with the stem cell treatment. In order to collect the bone marrow in which the stem cells are located, Zara was sedated and then local anaesthetic used where the needle penetrated the skin. The ultrasound machine enabled accurate direction of the needle into the centre of one of Zara's sternum bones from where samples of bone marrow were collected.
The samples were transferred to the laboratory for processing. It is possible to transport the cells, carefully, for up to 48 hours allowing the technique to be made available to horses in any part of the country or even further. A company, VetCell, linked to the College trains vets in the collection and injection techniques, opening up the treatment to a much wider number of horses.
In the laboratory the stem cells are carefully separated from the blood and other fluid and cells in the bone marrow. There are approximately 1000 stem cells in each 1ml of bone marrow and around 12ml of bone marrow is harvested. The twelve thousand stem cells are then treated to encourage them to increase in number. It normally takes 1-2 months to increase the cell numbers sufficiently, as ten million are needed for a single course of treatment. Some samples of bone marrow fail to grow sufficient cells and a second sample has to be taken.
When the cells were ready for transplantation Zara retuned to the Equine Hospital. She was once again sedated and her tendon checked with ultrasound. The ideal position for cell injection was identified and with sterile technique, the cells were injected with some difficulty, as the damaged area had already stated to fill in with scar tissue.
After the injection Zara had a period of rest before beginning a tailored regime of slowly increasing exercise. Tendons needs some activity to encourage the implanted cells to develop but too much strain before it heals can cause further damage. A careful balance has to be struck.
