Skipping past steroids to enhance joint health in horses

Veterinarians and researchers have made, and continue to make, remarkable progress in understanding osteoarthritis (OA, degenerative joint disease) in horses. We now know, for example, that the horse’s joint is an organ, and OA affects all the associated tissues. This includes the joint’s synovial lining, the articular cartilage lining the bones, the layer beneath the articular cartilage called the subchondral bone, as well as the supporting joint capsules and ligaments. Scientists have also described many of the key players involved in the pathogenesis of equine OA that lead to inflammation and degeneration of the joint tissues, such as interleukin-1β (IL-1β), tumor necrosis factor-α (TNFα), and matrix metalloproteinases (MMPs), among myriad others.

Regenerative therapies, along with oral non-steroidal anti-inflammatory drugs (NSAIDs, e.g., Bute) and intra-articular (IA) corticosteroids, help manage OA pain while keeping horses comfortable and in competition. Interleukin-1 receptor antagonist protein (IRAP), autologous protein solution, stem cell therapy (from either adipose tissue or bone marrow), and platelet-rich plasma now are all widely available for supporting horses diagnosed with OA.

Despite these advances, no treatment has yet halted the progression of equine OA. Researchers, however, continue to explore novel approaches. In the past year multiple groups have tested creative strategies to address this persistent problem in horses, and here we’ll highlight some of the most promising findings.

Next-Level Stem-Cell Therapies

While using stem cells for OA is not new, Ontario Veterinary College researchers looked at using pooled, ready-to-use equine umbilical-cord-derived (eCB) mesenchymal stromal cells (MSCs). In that study, led by Judith Koenig, Dr med vet, DVSc, Dipl. ACVS, ACVSMR, professor of clinical studies, researchers combined pooled eCB-MSCs with hyaluronic acid (HA; Munevar Luque et al., 2024) to evaluate symptom-modifying effects of this treatment in client-owned horses with naturally occurring OA of the carpus (knee) or fetlock.

They cultured and cryopreserved eCB-MSCs collected from healthy Thoroughbred and Standardbred foals. Then they mixed 1 milliliter of cryopreserved eCB-MSCs containing either 10 or 20 million cells with 2 mL HA and injected them into the affected joint of each horse. Control horses received only 3 mL of the HA.

“Evidence suggests that combining cells from several donors may better reduce inflammation than using cells from just one donor,” Koenig says. “Recent studies, including our own, have shown that injecting 10 to 20 million umbilical-cord–derived stem cells into horse joints is safe, with the higher dose even linked to fewer signs of inflammation. Stem cell treatments for joints can be prepared in different solutions, such as HA or saline. Because HA is routinely used to treat OA in horses and other species, we wanted to compare if adding MSCs to HA can improve outcomes compared to HA alone.”

Researchers included horses with lameness localized to a single fetlock or carpus by blocking (diagnostic analgesia) and radiographs (X rays). They assessed baseline joint effusion (swelling) and lameness immediately prior to injection and again 24 to 72 hours and three and six weeks after treatment. Owners completed a satisfaction survey 18 weeks after treatment. In total, the team included nine in each of three groups: 10 million eCB-MSCs + 2 mL HA; 20 million eCB-MSCs + 2 mL HA; and 3 mL HA.

“No significant differences in lameness were observed between treatment groups at either three or six weeks following treatment; however, lameness improved significantly over time within each treatment group,” says Koenig. “Additionally, lameness grade improved by 0.5 grades in the HA group, and by one full grade in both the 10 and 20 million eCB-MSC groups,” she adds