Regenerative medicine is becoming the go-to treatment for a wide variety of injuries that performance horses encounter. The term regenerative medicine refers to treatment modalities that are derived from the horse’s self and used to heal an injury in less time and result in stronger tissue. It is not meant as the only treatment option available or to be considered as a 100 percent fix. What is does is allow for a faster recovery and a much less likely chance of reoccurrence of that injury.

PRP

PRP stands for platelet rich plasma. The process includes drawing your horse’s blood, centrifuging and processing to obtain a small amount of product that is ready to be used within minutes. Platelets (aka thrombocytes) are small cells that are produced in the bone marrow. Their primary job is to form blood clots during a hemorrhagic event but they also play a major role in inflammation. They rapidly respond and accumulate in areas of inflammation then secrete proteins and growth factors. The proteins secreted regulate maturation, growth and responsiveness of cell populations, and attract immune cells to areas of inflammation. The growth factors are responsible for cellular proliferation, tissue remodeling, cellular differentiation, and angiogenesis (formation of blood vessels).

PRP is typically used for tendon and ligament inflammation, strains and tears although some clinicians are also using it intra-articular (within the joint) for osteoarthritis. PRP is more effective in the acute stages of injury and is often used at the time of diagnosis of the injury before stem cells or combined with shockwave therapy. There are several different companies that manufacture PRP kits, systems and processing machines. Not all PRPs are created equally and have been shown to have different concentrations and purity of product.

IRAP/ACS

IRAP stands for interleukin-1 receptor antagonist protein and is the brand name of ACS (autologous conditioned serum). IRAP involves drawing your horse’s blood into a syringe filled with glass beads that enable concentrating interleukin-1 (IL-1) receptor antagonist protein. The syringe is incubated for 24 hours then centrifuged. The antagonist protein rich serum is then drawn into several syringes and able to be used immediately or frozen to use in the future.

Osteoarthritis causes joint swelling and synovitis that can lead to cartilage damage and inflammation of the joint lining (synovitis) that leads to lameness. This creates a snowball effect of inflammation mediated by cytokines with IL-1 being one of the main contributors that sequentially causes more damage leading to more inflammation. IRAP was designed to stop this cycle. IRAP works by placing a high concentration of protein that binds to IL-1 receptors within a joint; which prevents IL-1 from being able to bind and reduces inflammation.

IRAP is being used intra-articular every eight to 14 days for a series of 3-5 treatments to treat osteoarthritis by stopping damage and inflammation caused by IL-1. The reduction in inflammation within the affected joint usually greatly improves lameness in athletes suffering from arthritis. There are currently two brands available IRAP and IRAP II. Research has proven that IRAP II has significantly more IL-1 receptor antagonist but clinically there is no research if this increase is more beneficial.

Stem cells

Stem cell treatment starts when your veterinarian obtains samples from your horse; either bone marrow or adipose tissue. The bone marrow samples are then sent to a lab where the lab will grow stem cells, which can take about 30 days. The lab then ships out the stem cells (several million) to your veterinarian who will inject them back into your horse’s injury. The lab also has the capabilities to cryopreserve the cells and store them for several years.

Bone marrow-derived mesenchymal stem cells (BM-MSCs) can be collected from the sternum of the tuber coxae (part of the pelvis). Middle aged and older horses have more progenitor cells in the sternum so most clinicians will harvest from this preferred site. However, there is a risk of puncturing the heart. BM-MSCs have the ability to grow and divide many times because they have not become specialized.

They also have the capability to become several types of tissue such as cartilage, tendon, ligament, or bone through a process called differentiation.

Adipose-derived stem cells are fast and easy to harvest but they are less capable to differentiate into musculoskeletal tissue. One benefit is that they are prepared by processing and concentration that takes 48 hours rather than culturing which takes two to four weeks. Nonetheless fat derived stem cells only contain two to four percent stem cells, indicating the BM-MSCs are far superior.

Currently stem cells are being widely used for tendon, ligament and soft tissue injuries. More recently they have begun to be used in cases of laminitis. The possibilities are endless and more research is being published daily with new ways to incorporate this option into a treatment plan.

Bone marrow aspirate concentrate (BMAC)

Bone Marrow Aspirate Concentrate (BMAC) is a concentrated form of bone marrow that provides a smaller number of stem cells. Bone marrow is collected and concentrated in a special centrifuge. The concentrate is then injected into the sight of injury. PRP is almost always used together with the BMAC to add additional growth factors and provide volume for the larger lesions. This is an option when stem cells are needed, but cultured stem cells are cost prohibitive.

Knowing the available treatment options informs owners and trainers of what to expect and allow your veterinarian to educate you about if a dreaded injury does occur. Using your time schedule, budget and type of injury, you and your veterinarian can come up with the best plan for each individual case. Regenerative medicine does not replace the need for stall rest with hand walking followed by a rehabilitation program and slow return to work. Regenerative medicine does keep your athlete doing their job for longer time with a reduced risk of re-injury.

Dr. Roth grew up in North Carolina working with Quarter Horses. She earned a bachelor’s degree from North Carolina State University and DVM from Oklahoma State University. Dr Roth is finishing up an internship with Hassinger Equine Service and will stay on as an associate veterinarian. Questions, comments or suggestions can be e-mailed to Alison.roth@okstate.edu or writing to InStride Edition.