Stem cell therapy in humans is not only controversial, but it’s been extremely limited in its scope. Now, stem cell research pioneered to help horses recover from tendon and ligament injuries may help humans recover from injuries to Achilles tendons.

Stem cell therapy in horses has been going on for several years and has shown real promise in helping tissues regenerate, rather than repairing injuries by forming scar tissue. According an article published in the Horse, Linda Black, DVM, PhD, director of Clinical Development, Vet-Stem, Inc. explains that, “Stem cells assist the healing process by decreasing inflammation, providing growth support, and by their ability to develop into other cell types.”

Stem cells are immature cells that are produced by the body that can regenerate into any type of cell the body needs. In horses, stem cells are typically obtained either from fat or bone marrow of adult horses but recent developments enable the collection of stem cells from equine umbilical cords which can be preserved frozen, cultured and differentiated into a host of cell lines including bone, cartilage, fat and those of the nervous system. In stem cell therapy, the stem cells are harvested, cultured and purified. Then the cell sample is injected into the injury site where the cells grow into the type of cell needed to repair the injury.

A company called Vet-Stem in California is using stem cells to treat bowed tendons, injured ligaments and fractures using stem cells derived from the animal’s own fat cells. After a tendon or ligament tear, horses can permanently lose mobility and strength when they heal because they develop scar tissue at the injury site. Scar tissue is fibrous and lacks the elasticity and strength of the original tendon tissue. However, stem cells circumvent this problem because they have the capacity to become a variety of different cell types, so they enable the growth of new tendon tissue instead of scar tissue at the site of the injury.

While the jury is still out, success stories are coming in and vets are excited about being able to offer a more proactive treatment to injuries beyond rest. And human researchers are studying the equine trials with great interest. It’s now reported that human trials, using stem cells to treat Achilles tendon injuries, which are notoriously difficult to treat, will begin in 2111.

According to an article in The Horse, The State of Stem Cell Therapy, Roger Smith, MA, VetMB, DEO, MRCVS, PhD, Dipl. ECVS, professor of equine orthopaedics at the Royal Veterinary College in Herts, U.K., and Lisa Fortier, DVM, PhD, Dipl. ACVS, associate professor of clinical sciences at Cornell University reported on the state of the research at the 2007 American Association of Equine Practitioners Convention. The entire article is worth a read.

Smith reported that lab animal studies have found that treatment of surgically created tendon and ligament lesions with MSCs results in better tissue organization, composition, and mechanics compared to controls. In addition, an equine study in the U.K. using BM-MSCs found that in 82 of 168 treated racehorses that were available for follow-up after one year, there was a 78% success rate (no re-injury) compared to 43% of horses conservatively treated in another study–a 35% improvement in success rate. More specifically, the success rate in National Hunt horses (in training and racing) was 82% of 71 horses, and the success rate in 11 flat racing horses was 50%. Twenty-four sport horses in other disciplines had an 87% success rate, compared to a 57-77% success rate with conservative treatment in another study.

More recent data from Cornell University, published in 2009, is also encouraging: Stem Cell Therapy Effective for Tendonitis in Cornell study

To evaluate the effect of mesenchymal stem cells (the stem cells harvested from bone marrow and capable of transforming to tendon cells) on tendon healing, researchers created tendonitis in the SDFT of both forelimbs. Six days later, stem cells harvested from each horse’s own bone marrow were injected into one of the SDFT lesions. The untreated (control) limb was injected with 1 ml saline.

Researchers performed ultrasound examinations of the tendons at 0, 2, 4, 6, and 8 weeks and mechanical, biochemical, and microscopic evaluation of the tendons 8 weeks after treatment.

“The biochemical composition of the treated and untreated tendons were similar 8 weeks after treatment; however, tendons injected with the stem cells had significantly improved histology scores, indicating a more normal microscopic appearance in treated tendons than untreated tendons,” summarized Nixon.

These results suggest that injecting mesenchymal stem cell directly into the damaged area of the SDFT is beneficial.

Certainly there are a lot of human athletes who are hoping that the results of the equine treatments pan out.