Severe joint injuries can be career-ending for horses, but veterinarians have been using regenerative medicine routinely—specifically, mesenchymal stem cells (MSCs)—to address these injuries in their practices, determining optimal approaches. At the 2011 Convention of the American Association of Equine Practitioners, held Nov. 18-22, in San Antonio, Texas, David Frisbie, DVM, PhD, Dipl. ACVS, ACVSMR (Medicine and Rehabilitation), of Colorado State University, discussed using stem cells to treat equine joint disease. He addressed not only the effects of MSCs in the equine joint but also the methods of obtaining and processing these cells.

Frisbie stated that although clinical sources of MSCs include both bone marrow and adipose (fat) tissue, bone marrow is the superior source. Allogenic (fetal) stem cells are another source. A clinician can collect a large number of allogenic cells at one time, and these cells do not require any sort of enhancement, he explained. They also have good pluripotential (the ability to become other cell types), but the cost of allogenic cells are high, and little is known about how these cells will differentiate.

Processing methods for MSCs derived from bone marrow or adipose tissue include:

• Direct aspirate using the cells straight from harvestwithout further processing. The main disadvantage of this technique is that the sample tends to yield low MSC numbers.  
• Concentration (by filter or centrifuge) Advantages include a higher MSC concentration, the ability to get platelet rich plasma (PRP), and a relatively low cost. The disadvantage is that total cell numbers are still low.
• Expansion (by cell culture) This technique produces good MSC numbers and is currently considered the state–of-the–art approach. Disadvantages include the higher expense and need for shipment. This technique also requires a two- to three-week turnaround time.

One goal of treating joint disease with MSC therapy is resurfacing the articular cartilage. Typically, clinicians use one of two techniques to administer MSCs into the joint