The Use of Biologic Agents in Performance Horses
Identifying and developing medications and successful treatments for musculoskeletal injuries in performance horses has been a never-ending task in veterinary medicine. In the past, most of our approaches focused on reducing the inflammation associated with the injury. This approach relied heavily on the use of non-steroidal anti-inflammatory drugs (NSAIDs) and corticosteroids. This is considered symptomatic therapy. It allows for increased activity, which stimulates blood flow to the injured tissue and promotes healing. Some of these therapies, such as corticosteroids, diminish the healing response when used at high concentrations.
Presently, several regulatory agencies in equine sports-related disciplines are urging the move towards biologic agents in the management of musculoskeletal injuries. The scientific data to support this contention is not definitive. But, there is the fear that classically utilized chemical pharmaceuticals such as NSAIDs may increase the possibility of catastrophic injury, particularly in our racehorses.
Regenerative medicine relies on the use of biologic agents, which are substances naturally made by the body, for medical treatment. Biologic agents can be harvested, concentrated, and returned to injured tissue to modulate, modify, manipulate, and maximize healing. The idea is a sound one, in that mother nature is very good at healing a great many conditions. The exact molecular mechanism or exact “cause and effect” relationship between the use of these agents and their results remains a bit of a mystery. But there is a general consensus that many of these agents have a positive effect on wound healing. This is a partial list of the substances that are being used and the basic reason for their use.
Conditioned Serum: Irap or ProStride
Interleukin-1 Receptor Antagonist Protein, known as Irap, therapy has been commercially available for several years. It is proving to be an effective treatment for joint origin lameness, and tendon and ligament injuries.
The Irap system makes autologous condition serum (ACS). The conditioned serum has several autologous (self) anti-inflammatory and regenerative cytokines. The use of conditioned serum is using the body’s own regenerative and anti-inflammatory properties to heal musculoskeletal soft tissues, such as tendons, ligaments, and joint capsules.
This technique involves harvesting 50 ml of the horse's own blood using a special syringe containing chromium sulfate beads. After a 24-hour incubation period, the syringe is spun in a centrifuge to separate serum from the blood cells. The serum is extracted and frozen in aliquots for later injection into the same horse at the site(s) of injury or disease. Since the serum is autologous, the risk of an adverse reaction is minute.
ProStride uses a slightly different methodology for concentrating the anti-inflammatory and pro-healing cytokines for stall side use. Blood is harvested, centrifuged in a special container, aspirated, and placed in another container for a secondary centrifuge run. Then it is harvested for the injection. This generally takes 30 minutes, eliminating the 24-hour incubation period. Thus, the conditioned serum can be injected the same day.
PRP- Platelet Rich Plasma
Platelets are part of the circulating blood along with the red blood cells (which carry oxygen) and white blood cells (which fight infections by directly killing the agent of infection or by generating antibodies). Platelets are the most vital component in the first phase of wound healing, which is hemostasis. Hemostasis means forming a clot and calling in other cells to clean the wound and repair damage. These cells are the most potent source of a variety of growth factors required for the remaining phases of wound healing.
To harvest platelets for use on injured tissue, whole blood is taken from the horse. The fraction of blood that contains the highest number of platelets is removed. Commercially available kits allow us to do this stall side. PRP can be ready to inject within 30 minutes after taking the blood sample.
Platelet-rich-plasma (PRP) can be used for the treatment of joints, bursae, and soft tissue injuries. For joints, the procedure is the same as that for injecting any other product, such as corticosteroids. For soft tissue injuries such as tendon or ligament damage, a number of injections may be needed over time, and the PRP is often injected through the skin with ultrasound guidance. The healing response can take several weeks to become evident. However, it is generally thought that the healing process is significantly sped up.
Stem cell therapy has become popular for the treatment of tendon, ligament, and joint diseases in the horse. A stem cell has pluripotency (it can become many types of cells in a cell line) or multipotency (it can become any cell, but with limitations). Cells can be harvested from fat, skin, muscle, blood, or, more commonly, bone marrow. Stem cells can be isolated and cultured (expanded) under laboratory conditions. These cultured cells can be placed in areas of injury, where they can modulate and perhaps integrate into local tissue and aid in repairing injury.
Current technology enables autologous treatment. We take cells from a horse and implant the cultured tissue back into the same horse. The technology has not reached the point where one horse’s stem cells could be used to treat another. Injection of stem cells for a soft tissue injury is done under sedation with ultrasound guidance. This can be performed stall side or at the hospital.
Stem cell therapy offers many advantages. However, the timing, number of cells for the size of the lesion, and the post-injection rehabilitation protocols are still being ironed out with the aid of clinical and benchtop research. Complications are very rare. In most cases, horses can be back into training between one and three months after implantation. The decision to return to training is guided by a follow-up examination.
All these therapies are regularly performed at Pilchuck Hospital, and our surgeons are happy to discuss them with horse owners. We continue to monitor the research as new information becomes available to help determine when and how regenerative medicine can be used most effectively in the treatment of performance horses.