The Horse

FEB 2019

The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.

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TheHorse.com | The Horse February 2019 45 One of the key findings was that veterinarians primarily used time-tested rehabilitation modalities to manage injured sport horses. The most commonly reported techniques were: ■ Controlled hand-walking (used by 97.3% of survey respondents); ■ Therapeutic shoeing (96.1%); ■ Icing (95.2%); and ■ Compression bandaging (89.25%); In that same survey researchers found that platelet-rich plasma and IRAP were also quite popular rehabilitation mo- dalities, with 86.5% and 81.4% of survey respondents reporting having used these techniques, respectively. Nonetheless, stem cell therapy ranked much lower, with only 62.7% and 36.6% of survey respondents reporting having used mes- enchymal and adipose-derived stem cells, respectively (Wilson et al. 2018). Indications for Stem Cell Therapy That survey also showed that tendon and ligament injuries were by far the most common reasons for incorporating stem cell therapy. Other far distant indi- cations for stem cell therapy included: ■ Managing neck or back pain/injuries; ■ Following arthroscopic surgeries and fracture repairs; ■ Generalized "poor performance"; and ■ Maintaining the horse's current level of performance. Kyla Ortved, DVM, PhD, an assistant professor of large animal surgery at the University of Pennsylvania's New Bolton Center, in Kennett Square, confirms that tendon and ligament injuries are very common among sport horses. These are typically "overstrain" injuries, where the stress on those structures exceeds tissue strength. "Certain injuries are more common in specific disciplines, and many of these are certainly amenable to stem cell therapy," she says. "Common examples of these include superficial digital flexor tendinitis in racehorses, or proximal suspensory desmitis in dressage horses." Other less common indications for stem cells, with far less, if any, research sup- porting their safety and efficacy, include: ■ Podotrochlosis (navicular disease); ■ Laminitis; ■ Osteoarthritis/joint disease; ■ Following arthroscopy for chip fracture removal or osteochondritis dissecans/ osteochondrosis debridement; and ■ Roaring (recurrent laryngeal neuropathy). A Closer Look at Stem Cells and How They Work There are four main types of stem cells; we've outlined them in the chart on page 46. The ones we are primarily inter- ested in are the mesenchymal stem cells (MSCs). These are a subclass of multipo- tent stem cells—meaning they can create different cell types—that veterinarians can easily obtain from multiple sources throughout the bodies of fetal/neonatal, young, or adult horses. While it might seem like the goal of stem cells is to "become" new tendon or ligament cells (or whatever type of cell is needed to repair a certain injured tissue), researchers have disproven this myth. "Stem cells actually function by con- trolling the cells and inflammatory mol- ecules at the site of injury," says Ortved. So, instead of transforming into a tendon cell, or tenocyte, MSCs injected directly into a tendon injury release chemical mediators that recruit resident stem cells to the injured area. It is those stem cells that differentiate into teno- cytes. In essence, MSCs don't play the instruments but direct the orchestra. "Injected stem cells also release anti- inflammatory compounds and media- tors that promote the formation of new blood vessels, growth factors to help the new tendon tissue grow," says Fortier. "Those mediators are thought to be at least partly responsible for the heal- ing effects of biologics through their characteristic ability to promote heal- ing. Examples of these bioactive growth factors include transforming growth factor β-1 (TGFβ-1), TGFβ-3, indoleamine 2,3- dioxygenase, prostaglandin E2 alpha, and platelet-derived growth factor." "The combination of these activities di- rected by injected stem cells promotes the natural regeneration of injured tissues," adds Ortved. "This means the healed tis- sue more closely resembles native tissue, rather than weak scar tissue that forms during 'natural' healing. Helping mini- mize the development of scar tissue will decrease the chances of future reinjury." Taking Rehab Step by Step Regardless of which combination of rehabilitation techniques you and your veterinarian ultimately select to manage injuries, generally your goal is to facili- tate return to performance. This requires working closely with your horse's rehab team to know which modality to use at what point during the recovery process. "To garner the most benefit from rehabilitation, the first step is to pinpoint the underlying injury," says Fortier. "Only once a firm diagnosis has been achieved can a rehabilitation plan be mapped out." When to use which rehabilitation technique depends on the exact nature of the injury, whether the goal at that point is pain reduction, restoring range of motion, contributing to tissue healing, and/or strengthening healing tissues. Even the veterinarian's experience with biologics greatly impacts how each horse is treated. As excited as you might be about the prospect of having stem cell technology at your fingertips, know that it's not a magic bullet. Researchers recently reviewed the plights associated with obtaining, processing, transporting, and administer- ing stem cells to horses so you can get Tendon and ligament injuries are the most common reasons for stem cell therapy in sport horses. ISTOCK.COM

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