How have stem cell therapies advanced?
Within the past year, an increased number of commercial laboratories, universities, and private veterinary practices have become available to process equine tissues to extract and culture stem cells. Recent research has shown that not all “stem cells” are created equal, and it remains somewhat unclear as to the ability of these cells to facilitate the healing of an injury. True stem cells have the ability to differentiate into selected tissue lines (pluripotent) and are harvested from bone marrow, whole blood, and cultured cells from equine embryos. These cells, theoretically, can differentiate into cells that are very similar to the parent injured tissue. Other mesenchymal stem cells are cells harvested from a specific tissue that contain biologic factors that aid in the healing process (multipotent). These cells can be harvested from fat, muscle, blood, and tendon. During the past year, a variety of isolation and culture techniques have made stem cell use more available to veterinarians. Fat collection now is similar to liposuction in order to harvest adequate tissue and reduce the cosmetic scar that was present with the older surgical technique. Some of the more recent processing methods have allowed a shorter turn around time and a more efficient recovery of multipotent cells. In addition, recent research has determined that when collecting bone marrow from either the sternum or pelvis, the greatest numbers of pluripotent cells are in the first 5-10 cubic centimeters of marrow collected. Therefore, less volume is needed if the sample is to be purified or cultured (expanded) in the lab for later use. Cultured (expanded) stem cells, which may take three to four weeks to grow adequately, now can be more pure with a reduced possibility of a reaction once re-injected into a patient. Additionally, stem cell therapy has moved from primarily injection into a specific injury site to use by regional perfusion or systemic intravenous administration. Biologic “pastes” of stem cells also are being used to fill defects following surgery. The jury remains out on the appropriate use of stem cell therapies, but there is a great deal of basic research and clinical use under way that, hopefully, will yield future benefit to the horse.