treating tendon injuries in horses

Imagine your horse’s injured tendon as a crushed beehive. With the structure destroyed and flattened, nothing can live between its walls. But as the bees rebuild the matrix of their hive, making strong structures again, their young can thrive in the spaces and grow. And the hive becomes functional once more.

Tendons are sort of like that. Their living cells are surrounded by a structure called matrix. But that matrix can get destroyed during an injury, and if the matrix isn’t rebuilt, the tendon cells will never regain their strength—and the tendon won’t be as functional.

It’s on that basis that a group of French researchers has developed and tested a new “biological” therapy for helping tendons heal. Tendon matrices have a special sugar (a polysaccharide) called heparan sulfate that plays a major role in matrix architecture—bridging and protecting proteins, storing and protecting special molecules, etc.

Unfortunately, when injury occurs, inflammation—and especially the enzymes that are released—degrade heparan sulfates. For the matrix to rebuild, it needs healthy heparan sulfates, says Sandrine Jacquet-Guibon, DVM, of the Centre d’Imagerie et de Recherche sur les Affections Locomotrices Equines (CIRALE) and the French National Veterinary School, in Maisons-Alfort, France.

Jacquet-Guibon and her colleagues, including CIRALE director Jean-Marie Denoix, PhD, tested the efficacy of a therapeutic agent that mimics heparan sulfates. The specific ReGeneraTing Agent (RGTA) they tested, called Equitend, provides an “improved” form of the natural sugar.

“The Equitend RGTA makes it possible to reconstruct the architecture of the spaces surrounding tendon cells as closely as possible to their original state before the lesion occurred,” Jacquet-Guibon said.

The Lameness Study

In their study, Jacquet-Guibon, Denoix, and fellow researchers compared healing in 22 Standardbred racehorses that had confirmed superficial digital flexor tendonitis. Eight of the horses received a single saline injection directly into the lesion, as a placebo. The remaining 14 horses received a single injection of 1 mL of Equitend into their lesions. The horses in both groups averaged 5 years of age and had similar lameness and sensitivity levels. Those in the treatment group had an average of 25 days of tendinopathy (tendon disease), whereas those in the placebo group averaged 12 days.

The scientists performed clinical and ultrasonic evaluations of the horses one, two, and four months post-injection. They ordered the horses to be put back on a standard exercise program adapted to their level of lameness and equivalent shoeing for both groups. They then followed all the horses for the next two years.

Results: Sounder Horses and More Racing Wins

The four-month ultrasounds revealed clearer signs of physical healing (a decrease in the cross-sectional area of the tendon) in the treated group than in the placebo group, Jacquet-Guibon said.

The team also noted that horses in the treatment group were more likely to return to their pre-injury performance level, she said. They raced in and won significantly more races than the horses treated with a placebo. What’s more, they didn’t experience new episodes of tendonitis nearly as often as the placebo horses did.

“I wouldn’t go so far as to call it a ‘miracle’ drug, but our study does clearly show a positive effect of this treatment compared to the placebo for pertinent parameters like recurrence and especially post-injury performance over the long term,” Jacquet-Guibon said. “And this is the first time, to our knowledge, that a treatment has been evaluated this way—comparing treatment versus placebo over long-term performance indicators following spontaneous ligament injury (not induced for research purposes), which gives a good look at the efficacy in a ‘real world’ setting.”

The RGTA agent has the added benefits of being nontoxic and having a long shelf life with easy storage, she said. And unlike stem cell therapy, it doesn’t require cell extractions from the horse or a donor.

The study, “Randomized controlled trial demonstrates the benefit of RGTA based matrix therapy to treat tendinopathies in racing horses,” was published in PLoS One.