Managing Osteoarthritis in Horses: Stem Cell Vesicles Pack a Punch

Cambridge University researchers recently suggested that stem cell vesicles—small membrane-bound particles spawned by stem cells—may be all that is needed for stem cell therapy, not the entire cell.^* Should this theory hold, many of the drawbacks and adverse effects associated with stem cell therapy could be avoided while still benefiting horses with osteoarthritis and other musculoskeletal injuries.

Osteoarthritis is a common economic and welfare issue affecting horses, especially those engaged in athletic activity. Aggressive research efforts have yet to identify a cure or disease-modifying drugs (i.e., those that can alter the course of disease to restore cartilage). Instead, owners of horses with osteoarthritis are reliant on drugs and biologics that help control clinical signs of disease, such as pain, heat, joint swelling, and lameness.

“Nonsteroidal anti-inflammatory drugs, intra-articular medications, and oral joint supplements such as those containing glucosamine and chondroitin sulfate are popular ways of preventing and controlling the inflammation that leads to articular cartilage degeneration,” explained Kathleen Crandell, Ph.D., a nutritionist for Kentucky Equine Research.

Osteoarthritis is also amenable to stem cell therapy. According to the Cambridge University research team, stem cells secrete vesicles that play vital roles in cell-to-cell communication. Vesicles pinch off from the stem cell and transport genetic material and proteins to target cells, such as chondrocytes, or cartilage cells. Target cells absorb the vesicles complete with the genetic material and proteins contained within them. The vesicles are believed to “recapitulate” or reproduce the therapeutic effects of the injected stem cells.

“There are multiple concerns associated with using stem cells. For example, transient inflammation of the joint frequently develops following intra-articular injection of stem cells. Further, stem cell survival, immune rejection, instability, and loss of function may all affect the success of stem cell therapy for osteoarthritis,” explained Crandell.

Considering these inherent drawbacks to stem cell therapy, Hotham and colleagues suggested that the vesicles alone, rather than the entire stem cell, could effectively manage osteoarthritis.^*

To test this theory, the researchers collected vesicles produced from stem cell cultures in the laboratory. Those vesicles were subsequently labeled with a fluorescent tag so their location could be tracked during subsequent experimentation.

Microscopic analysis revealed that cartilage cells absorbed the tagged vesicles, and those vesicles had anti-inflammatory effects on cartilage cells.

“These findings support the hypothesis that vesicles alone may be sufficient for exerting the beneficial effects of stem cells without the untoward side effects often seen following administration of stem cells themselves,” Crandell concluded.

*Hotham, W.E., C. Thompson, L. Szu-Ting, and F.M.D. Henson. 2021. The anti-inflammatory effects of equine bone marrow stem cell-derived extracellular vesicles on autologous chondrocytes. Veterinary Record Open 8(1):e22.