Stem-cell therapy for tendon injury
After tendon injury, scar tissue often results in reduced performance and/or the potential for re-injury. In theory, adult
stem cells could replace damaged tendon tissue and scar tissue with healthy, viable tissue.
Easter uses stem-cell therapy mainly for flexor tendon injuries and for suspensory ligament injuries. "For flexor tendons,
I find it a rewarding means of returning these horses to a performance level closer to their pre-injury level. Injured tendons
treated with stem cells sonographically resemble normal tendon much earlier than conventionally treated tendons. Getting a
better quality of healed tissue is the goal," Easter says.
He finds the same to be true for suspensory ligament injuries, especially proximal suspensory injuries. "Early on, I had poor
luck with suspensory branch lesions, but I think we were losing our stem cells into the fetlock joint space.
"We started using platelet-rich plasma to glue stem cells in those lesions and then began getting a lot better healing response,"
"As far as what stem cells do for us in tendons and ligaments, I think they make the tears in those structures heal quicker
and in the end more closely resemble the original tissue," he says.
"It's interesting to think about whether the tendons are truly back to normal at the 90-day range, when they look sonographically
normal. Most of us believe the horses probably are not ready to start back into normal exercise, because they haven't had
enough time to gain their tensile strength back, making them subject to re-injury," Easter explains.
"They probably still need at least eight months to get back to the range to where they have enough tensile strength for exercise,
so we may not have shortened the overall time interval that much, but I think the tissue that we have in the end more closely
resembles that of the original horse than what we used to end up with without stem-cell therapy."
Compared to the results he's seen for years with conventional therapies — anti-inflammatories, stall rest, immobilization,
cold therapy, etc. — stem-cell therapy significantly shortens the time for tendon tissue to return to a normal appearance
in sonographs, Easter says.
"We used to tell people that if you have a large tear in a digital flexor tendon, the best you could ever hope for was 80
percent of what the (horse's) original tendon was. I think with stem cells we can get the tissues back closer to original,"
Garcia-Lopez concurs, saying "What we see clinically, especially with the soft-tissue injuries, is an induction of better
regeneration of the tissue that once was occupying (the location) where the lesion is."
"Tendons and ligaments seem to heal in a more normal fashion. Not necessarily a whole lot faster, but ... the fiber pattern
(of healed tendons) is as close to normal as possible — not perfectly normal, but on ultrasound pretty darn close. Some of
the short studies by the group at Cornell show a better type of composition of the lesion area compared to no (stem-cell)
treatment," says Garcia-Lopez.
"With some of those injuries, even with stem cells we have a very hard time getting them to heal on a consistent basis," Garcia-Lopez
With some injuries, the location that is treated with stem cells "plays a huge role on how these horses do. For example, a
suspensory ligament in the front limb responds very differently than a hind limb, because of the amount of tension exerted
by the hind limb. With a front-limb suspensory injury, there is a chance that the horse will recover without doing anything,
as opposed to a hind-limb suspensory injury. Even with stem-cell therapy, it's the same thing. A hind suspensory injury is
more troublesome for event horses or racehorses or high-level sport horses than a front suspensory injury," Garcia-Lopez says.
"Even within the suspensory ligament itself, certain areas react very differently (to treatment). For example, with some
chronic lesions in jumpers or dressage horses affecting the branches of the suspensory as it attaches to the sesamoid bone,
there are a fair amount of setbacks. Colleagues at the university and in private practice also see similar problems in these
types of lesions.
"It's not that we put stem cells in and they do great, or that it's a cure-all for everything, but it does help with some
of these lesions," Garcia-Lopez says.
"Embryonic stem cells have shown promise for cartilage regeneration," says Fortier, but there are some difficulties, so her
group is doing research with equine mesenchymal-derived cells.
Fortier's Cornell laboratory generated a stem-cell concentrate from sternal bone-marrow aspirate and researchers test it in
equine models of articular cartilage loss.
They have treated 10 experimental horses "in which 15-mm full-thickness defects were made on the lateral trochlear ridge of
the femur," and 18 clinical cases, Fortier says. No adverse reactions were seen. The animals are convalescing and follow-up
data is pending.