While stem cell researchers are making great strides in developing and testing potential treatments, much remains to be learned about how stem cells work in the horse's body and their capacity for improving healing. Over the past several years, some companies have produced various stem cell products for treating a variety of equine conditions, including tendon and ligament injuries, laminitis, and ocular issues, to name a few. There’s no question stem cells carry tremendous promise for the treatment of many diseases and injuries. For example, in human medicine, blood stem cells have saved the lives of thousands of children with leukemia. Many clinical trials involving stem cells are ongoing in human medicine in an effort to fully unlock their potential. While such treatments have been employed widely in equine medicine, the fact is there still is much to learn about stem cells. Their efficacy in improving the quality or period of time in healing remains unproven. Excitement about the potential for new treatments has obscured the fact the science has lagged far behind the hype. In this article, I will try to help equine practitioners understand the current potential and limitations of stem cells, as well as to help them identify misinformation that may be circulated about these treatments. Weighing benefits, risks Stem cell treatments have been shown to be beneficial in a very small number of conditions. In human medicine, hematopoietic stem cell transplantation (e.g. bone marrow) is most commonly used to treat some hemopoietic and immune system disorders, or following some cancer therapies. The effectiveness of some forms for tissue transplantation relies on stem cells. In human medicine, all other stem cell applications are considered experimental. Stem cells may be an attractive option when there are no good existing treatments for certain conditions (e.g. tendon injuries). Given that medicine largely has been unable to provide any improvement in outcomes beyond what is gained through adequate rest and rehabilitation, it’s no wonder some veterinarians may feel there’s nothing to be lost from trying a new, albeit unproven, approach. Unfortunately, to date, there is little but the promise of benefits accompanied by real risks and increased costs. Whereas stem cells have been presented as a solution for a variety of conditions, in fact, different types of stem cells originate from different places in the horse’s body. They have different functions, as well. Regardless, tissue-specific stem cells are unable to generate cell types other than those found in the tissues from where they were obtained. Cells obtained from fat cannot make tendon cells; hematopoietic cells cannot make ligamentous tissue. The idea that a single cell type can be used to treat a variety of unrelated conditions is illusory. Pluripotent stem cells (i.e. embryonic stem cells) carry the potential to form many different cell types; however, they currently aren’t good treatment candidates. Pluripotent stem cells require specific direction from the body to become specific cells—they do not become the cells that treating veterinarians want simply because they are injected into a certain location. Cells can be manipulated in laboratories, but such cells neither have been nor are they available currently to equine practitioners. Autologous stem cells have been used in equine medicine because, in theory, the horse’s immune system would attack foreign cells. However, merely because the cells are autologous does not mean they are also without risk. Consider the following: Autologous cells can become contaminated during processing Manipulation of cells by a clinic theoretically can interfere with their normal function, possibly rendering them ineffective How and where the cells are returned to the horse’s body matter; there is no point injecting stem cells into places where they are not normally present and do not belong Incomplete research The putative benefits of stem cell treatments have been frequently overstated. As a result, in June 2015, the U.S. Food and Drug Administration (FDA) issued a guidance for industry (GFI #218), which discusses the approval requirements for animal cell-based products meeting the legal definition of “drug” and how the agency intends to regulate them. The FDA stated that stem cells show “great promise but proof [is] needed.” While there is no evidence stem cell treatment is necessarily ineffective, current use is at odds with ethical procedures established for the use of such therapies in human medicine. There is rarely any oversight, and most clinical uses are not part of clinical trials. In addition, it is ethically problematic that horse owners are responsible for covering the costs of an unproven treatment where data is not being accumulated. The process of translating promising science into a safe and effective medical treatment is long and involves many steps, including laboratory tests, clinical trials, and replication. While this process is time consuming and laborious, it helps to maximize the possibility of an effective treatment being determined, while also minimizing the possibility of harming horses and wasting client resources. Circumventing this process may bring short-term financial gain, though long-term consequences in terms of loss of trust, should such treatments ultimately be shown to be ineffective. While advances in medicine come slower than anyone would like, scientists researching stem cells are making great strides in understanding diseases and in developing and testing potential treatments. Nevertheless, there remains a great deal to learn about how stem cells work in the horse’s body and their capacity for improving healing. The fact is that safe and effective stem cell treatments for injuries, diseases, and other conditions are still in the future. David W. Ramey, DVM, is a Southern California equine practitioner who specializes in the care and treatment of pleasure horses. Visit his website at doctorramey.com. Columnists' opinions do not necessarily reflect those of Veterinary Practice News. The International Society for Stem Cell Research is an independent, nonprofit organization that promotes and fosters exchange of information and ideas relating to stem cells, encourages stem cell research, and promotes professional and public education in stem cell research and education. Discover developments in current research at isscr.org.
