Extracorporeal shockwave therapy (ESWT) is used to promote
healing of injured tendons and
This can cause problems if pain is masked before healing is
complete. Overworked minor injuries could lead to major ones or even pose the
risk of catastrophic life-threatening breakdown.
Competition authorities have introduced restrictions
on horses participating after treatment. For example, the British Horseracing
Authority banned the use of ESWT on the day
of the race or on any of the preceding five days.
However, it’s one thing to restrict the use of ESWT; quite
another to enforce a ban, as the therapy leaves no trace. That is, until now.
A team led by Mary Robinson, director of the University of
Pennsylvania’s Equine Pharmacology Research Laboratory, and lab member Jinwen
Chen has found that the practice does in fact leave a trail. In a paper in
Equine Veterinary Journal, they report finding potential biomarkers of ESWT
that, with further testing, could one day be used to enforce the ESWT ban.
"Because it's not a drug--it's applied to the surface
of the skin--it's just not an easy thing to detect," says Robinson.
"After a lot of trial and error, our study was able to measure changes in
levels of five inflammatory factors, some of which we could detect up to three
weeks after the shockwave therapy."
The search for these biomarkers dates back roughly a decade.
"It was Dr. Lawrence Soma, my predecessor, who said the
lab was going to have to look at blood-based or urine-based biomarkers to try
to detect shockwave therapy," Robinson notes.
To find the fingerprints that ESWT might leave behind, the
researchers tested the therapy on 11 horses kept as a study herd at the University’s
New Bolton Center. The researchers collected blood samples from the group of
horses, composed of Thoroughbreds and Standardbreds, at several times both
before and after each received a single dose of ESWT to a leg.
Over the years, the lab investigated various potential
biomarkers - molecules that would indicate a horse received ESWT. They targeted
10 pro-inflammatory and anti-inflammatory signaling molecules, called
cytokines, which they can measure from the blood using a sensitive test called
ELISA, short for enzyme-linked immunosorbent assay.
"We looked a week before giving the shockwave therapy
to see if there were any changes in the baseline period, due to changes in time
of day or anything else, and didn't see anything we could define as
significant," Robinson says. "And in the post-shockwave period we
went out to three weeks."
No changes were detected in five of the cytokines they examined.
But the other five-- TNF‐α, IL‐1β, IL‐1RA, IL‐6 and TLR2 – were significantly
affected by EWST.
Of those, TNF‐α levels were significantly increased through
the whole of the three-week post-therapy study period.
More study is necessary, Robinson emphasizes, before these
biomarkers could be used to assess inappropriate use of ESWT in racehorses. For
one, the researchers would like to see if measuring these same molecules in
horses that are actively training and racing or that have an acute injury might
change their results.
For that, she and her colleagues are actively pursuing
follow-up studies to look at these biomarkers and other indicators using a
biobank of samples from client-owned animals, including injured and active
racehorses, treated at New Bolton Center.
The end goal is to keep the sport safe.
"Shockwave therapy is great as long as people rest the
horse after using it," she says. "We are concerned that it's being
abused in the racehorse industry and that it could potentially result in
breakdowns. That's exactly what we're trying to avoid."
For more details, see:
Inflammatory
mediators are potential biomarkers for extracorporeal shockwave therapy in
horses
J.‐W. Chen, D.
Stefanovski, J. Haughan, Z. Jiang, R. Boston, L. R. Soma, M. A. Robinson
Equine Vet J
(2019)
