Stem Cell Therapy for Horses

Several days ago, my daughter gave me an article she’d clipped from a recent Science News magazine. In “Blind Bet,” writer Laura Beil starts the story by emphasizing the fragility of horses’ legs: “For all their size and brawn, horses move on limbs that are relatively long and slender. That arrangement provides agility and speed to 1000 pounds of body weight, but leaves the animal at risk of injury. At a gallop, a horse places only one hoof on the ground at a time. That means at any given moment, the animal’s great weight depends on a joint about the size of a baseball.” It’s no wonder then that horses injure themselves so much or develop arthritis over time. The usual treatment for an impaired horse is controlled exercise and rest. But now there is a chance that stem cells can manufacture replacement parts, perhaps a new tendon or another part of the joint.

Beil reminds the reader that stem cells have potentiality, that is, they can become many kinds of cells. Veterinarian researchers have mainly concentrated on harvesting stem cells from adult animals. A stem cell is taken from bone marrow or fat and hopefully transformed into the part an afflicted horse needs to resume normal movement. The writer points out that right now, although an injured tendon may heal after light exercise and rest, it becomes entwined with scar tissue; thus the tendon is not as strong as it was originally. Stem cells may grow into tendon tissue without drugs or surgery, or indeed, a high price tag for treatment. Beil adds that the price is “usually only a few thousand dollars.”

The use of stem cells to treat horses is very new. The pioneers are Roger Smith (Royal Veterinary College, England) and veterinarian Robert Harman in America. In 2002, Smith devised a technique for extracting stem cells from a horse’s bone marrow, growing them in the lab for three weeks or so, and injecting them into the animal’s bad leg. The hope was that “chemical cues” would stimulate the cells to develop into tendon cells. Smith formed a company, VetCell Bioscience, and offered his services to horse owners. On the other hand, Harman experimented with using stem cells from the fat tissue on a horse’s rump. His company, Vet-Stem, has been offering the procedure since 2003.

The problem with making these services commercial so fast is that the protocol of clinical trials should always come first before a service or medication is offered to people or animals. But desperate horse owners insist on the stem cell treatments and want nothing to do with blind studies, for example, where their horses might get placebos instead of the real thing. Both Smith and Harman are compiling statistics about their treatments, but more rigorous studies have to be conducted before anything substantive is learned about stem cell therapy for horses.

Many questions about stem cells remain to be answered.  For instance, what is a true stem cell? What is the composition of injected cells? Do the injected cells survive? Do fat and bone, the sources for stem cells in horses, differ in their ability to repair damage? Smith believes that the extensive random trials necessary to answer these and other questions won’t be run until scientists have a similar procedure to use for humans. Until then, horse owners who have seen their horses suffering from many accidents or the degenerative effects of arthritis will insist on trying stem cell therapy for the promise it holds for their animals. For more, see or Science News magazine, January 19, 2008, pages 40-41.

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