Are Exosomes the Future of Suspensory Injury Healing?

Suspensory ligament injuries. 

The dreaded ‘s’ word in the equine veterinary industry. 

“I call it the ‘s’ word just because I’ve made quite a few girls and, I think, a few men cry, using this word,” said Dr. Beau Whitaker or Brazos Valley Equine Hospital.

And for good reason. 

Suspensory injuries affect 30% of performance horses, making it the most common injury, and routinely take six to 12 months to heal with treatment. The prognosis for horses with scar tissue around the ligament, or periligamentous fibrosis, is even less favorable—less than 50% will return to full athletic function. 

Regenaflex-RT is giving renewed hope to horses with soft tissue injuries. 

The latest in regenerative treatment options, Regenaflex-RT is a next-generation therapy that uses exosomes and a spectrum of biologically active factors to support tissue regeneration and reduce scarring. But it’s still early days for this therapy and much still needs to be learned.  

In a recent webinar, presented by Hilltop Bio, Dr. Whitaker discussed the prevalence of suspensory injuries in performance horses, advancements in regenerative medicine, and the results of a study he’s currently conducting on Regenaflex-RT. 

Why does the suspensory get injured?

The suspensory ligament is made up of the proximal suspensory, or the origin, the body, and the branches. The sesamoid ligaments are also part of the suspensory apparatus, attaching to the sesamoid bones and at different points on the pastern. Together, the suspensory apparatus functions to help stabilize the fetlock and prevent hyperextension of the limb.

There are several reasons for suspensory injuries and they may occur at different parts in the suspensory apparatus. 

One is genetic collagen disorders, the most common of which is degenerative suspensory ligament desmitis (DSLD). “Horses with collagen disorders do take longer to heal or develop these little micro injuries that build up over time,” explained Dr. Whitaker.

Breeding for “elastic” movement—think dressage horses with heightened elevation and Paso Finos with exaggerated limb motion—may make horses more susceptible to injury, he continued.

“I think sometimes these horses get selected that are really elastic because they move beautifully,” said Dr. Whitaker.

“But, nothing comes without a cost. When you have increased elasticity and increased flexibility, you also have decreased stability. These horses I think sometimes are more prone to getting injured just because they are more elastic moving and there’s less stability around these joints.”

Progressive overload injuries—for example, a horse compensating for arthritis in its right knee by bearing more load in the left leg—are another common cause. Acute overload injuries are still another. “This is your typical horse runs across the pasture, steps in a hole or goes over a fence and you get a big tear or a hole in the ligament.”

How common are suspensory injuries? 

In a word: very.

Two large studies conducted by world-renowned equine orthopedics expert, Sue Dyson, DVM, and University in Zurich found that suspensory injuries affect roughly 30% of performance horses.

“Dr. Dyson did a retrospective study, meaning they looked back to past cases and compiled the data. They found that suspensory injuries for the most common injury, for general purpose horses, for elite show jumping horses, elite dressage horses, and also for non-elite dressage horses,” said Dr. Whitaker.

“In her study, 28% of the injuries to elite dressage horses and 29.5% in the elite non dressage horses were due to suspensory ligament.”

The University in Zurich study found an even higher incidence in dressage horses in its 17-year retrospective study looking at over 1500 horses. 

“They found that suspensory injuries accounted for 31% of injuries and the frequency of those injuries was 41% dressage horses, 28.6% in show jumpers and 28% and pleasure horses.”

The gist: based on these two studies, injuries to the suspensory ligament represent a statistically high for one structure in the body. 

Discipline also plays in a role in which limb is commonly affected. Another study by Dr. Dyson on suspensory branches found that 76% of eventers had forelimb injuries, while 87% of dressage horses had hindlimb injuries. In that same study, horses that had periligamentous fibrosis—that is, thickening around the branches caused by scar tissue—were less likely to have favorable outcomes.

“Periligamentous fibrosis was found in 78% of those horses in the hindlimb and in 35% in the forelimbs. Of those horses, 43% return to full athletic function of the previous level for at least one year, so less than 50%.” 

Regenerative medicines

We know that suspensory issues are both common and complicated to treat. Legacy treatments like PRP, IRAP, ProStride and stem cells are frequently used in conjunction with shockwave or other modalities to help heal these injuries.

More recently, exosomes have become a potent area of interest for suspensory healing. A growing body of scientific evidence suggests that it’s not just stem cells that fix soft tissue injuries, but rather the exosomes within those stem cells that have the proteins, growth factors and cytokines as well as the cell-signaling power of the horse’s body.

What are exosomes? 

Exosomes are messenger particles that release naturally from a cell. 

“What happens is a bunch of vesicles form inside the cell and create a little capsule with a bunch of proteins in it. It goes and infuses with the cell membrane, and releases all those little vesicles outside of the cell,” explained Dr. Whitaker.

“Now inside those vesicles are proteins, peptides, lipids, and nucleic acids. There’s six plus different types of RNA, which as you probably know, are the little genetic messengers in the body and then there are 11 metabolites as well.

“Those cells are released out of the body with a target cell in mind. So it’s being sent directly to a cell to perform a specific function.”

What does it do? 

The tissue regeneration is a very complex process. “I certainly don’t understand all of it,” continued Dr. Whitaker. “But it’s highly coordinated and there’s so many proteins and cells and genes involved that it can be mind boggling sometimes.” 

Exosomes are known to play the leading role in this process.

“They’re like the carrier pigeon and the messenger in one. So they’re being sent out to go tell a cell to do something and they have the package inside with genetic material that gets released into that cell and tells that cell what to do. Think of it like a repair toolbox. If a cell needs to do something to help heal an area, these exosomes go there to help tell it what to do.”

The Regenaflex study

A year and half ago, Dr. Whitaker began a study tracking horses he had treated with Regenaflex-RT. All horses in his study were treated with 2ml of Renenaflex-RT and with shockwave therapy on the first day of injection and twice more, two weeks apart. 

“Of the ten horses we’ve examined, 80% were sound at three months, so that’s a pretty large number being sound that quickly, and 80% also had no pain on flexion in three months,” he shared.

“All those horses showed significant improvement on ultrasound at three months as well. We had 60% that had a normal appearance at five months.” 

What’s more, 70% of the horses were in full work within a year. Two were not in full work because they had injured a different structure in the body once reintroduced to work.

One Arabian horse with a large hole in its suspensory ligament saw the lesion almost completely filled in two and a half months. Similar results were seen on a jumping pony with fibrosis. The lesion filled and fibrosis was almost completely gone in the same time frame. One year later, both are in full work. 

“I’m not going to claim that every horse responds this well, but these were two cases where I was like, ‘Wow, I can’t believe that’s almost too good to be true.”

Can the promise meet the hype? 

“We’re going to find out,” said Dr. Whitaker. 

“There’s quite a few studies at universities where they’re looking more into what exosomes are and what they do. I think there’s some potential to customize exosomes for specifically what you’re treating or specifically for that horse.”

His own study is continuing as well.  

“Hopefully, we’re going to continue getting similar really great results. Really excited about what the future holds for this, for these products, for Regenaflex-RT and also for just exosomes, in general.”

To learn more about Regenaflex-RT visit hilltopbio.com.