Synovitis, or inflammation of the synovial lining of a joint, threatens a horse’s joint health, as it can progress to osteoarthritis if left unchecked. Orthobiologics such as stem cell therapy show great promise for treating synovitis. A stem cell product containing umbilical cord derived mesenchymal stem cells (MSCs) was recently studied in horses with naturally occurring synovitis, resulting in a significant improvement in lameness scores.*
Off-the-shelf stem cells, also referred to as allogenic stem cells, are prepared products immediately ready for use. In contrast, autologous stem cells, which are those collected from the patient, require culturing to expand the stem cell numbers prior to use. This culture process takes approximately six weeks, thereby delaying treatment.
“Further, the quality and quantity of stem cells in allogenic products may be more ‘uniform’ than autologous products,” explained Catherine Whitehouse, M.S., a Kentucky Equine Research advisor.
To determine if allogenic umbilical cord derived MSCs could effectively treat synovitis, 24 client-owned horses with naturally occurring synovitis were recruited. All horses showed grade 1 to 3 lameness on the AAEP (grade 0 to 5) lameness scale in the fetlock or upper or middle knee (carpal) joint. All horses had joint swelling, heat, or reduced range of motion. None of the horses had been treated with stem cells in the past.
Ten million cryopreserved umbilical cord derived MSCs (1 mL total volume) were injected into the affected joint one time. Half of the horses were treated with regular or “unactivated” stem cells and the remaining horses were treated with “activated” stem cells. This activation, using a proprietary method, reportedly increases immunomodulatory properties. Each horse then underwent a prescribed exercise and rehabilitation program for the duration of the study period.
“Straight-line subjective lameness scores were significantly lower on days 21 and 48 compared to day 1 and day 0 in both treatment groups,” relayed Whitehouse.
More specifically, 75% of the activated and 67% of the nonactivated MSC-treated horses improved by one full lameness grade by six weeks following treatment. No significant difference between activated and nonactivated stem cells was noted.
Further, owner satisfaction determined through surveys conducted at 12 and 18 weeks following treatment was high. Most horses returned to either the previous level of work or higher. Over three-quarters of owners indicated that they were satisfied with treatment at 18 weeks.
“There were no serious adverse events noted in this study,” according to the researchers. However, a transient, self-resolving postinjection “flare” was observed in some horses.
This study shows that treating horses diagnosed with synovitis with 10 million activated or nonactivated allogenic umbilical cord derived MSCs significantly improved lameness of the fetlock or knee attributable to synovitis. This off-the-shelf product may provide a safe and effective treatment option when owners do not want to wait for autologous stem cells to be cultured.
Other joint therapies available for immediate use include platelet-rich plasma, autologous protein solution (APS), and interleukin-1 receptor agonist protein (IRAP).
In addition to orthobiologics or other intra-articular medications, Whitehouse recommends critically evaluating your horse’s nutrition.
“A well-balanced diet supplying essential nutrients creates a great foundation to support health and wellness. For horses experiencing inflammatory-based conditions, including synovitis, it can be helpful to optimize the omega-6 to omega-3 fatty acid ratio in the diet by supplementing with short- and long-chain omega-3 fatty acids,” Whitehouse said.
Additionally, offering oral joint health supplements containing glucosamine, chondroitin sulfate, and hyaluronic acid have anti-inflammatory properties, and this combination of supplements may help slow the progression of OA.
*Seabaugh, K., S. Rao, J.B. Koenig, L. Pezzanite, S. Dow, T.G. Koch, K.A. Russell, S. Mehrpouyan, A.H. Alizadeh, and L.R. Goodrich. 2024. A pilot study to assess the safety and efficacy of umbilical cord blood-derived mesenchymal stromal cells for the treatment of synovitis in horses. Animals (Basel) 14(23):3406.
