For years now, veterinarians and horsemen have dreamed of a day when a simple blood test could give them an early clue about whether a racehorse was about to experience a serious injury, before that horse showed any signs of lameness or abnormal imaging. That day is still a ways off, but early results from a project at the University of Kentucky's Gluck Equine Research Center suggest it's closer to reality.
Research has long indicated the majority of fatal injuries in racehorses (at least 85 percent, according to several studies from the University of California-Davis) happen in areas that had preexisting damage. Veterinarians are also aware, however, that such damage may not show up as perceptible lameness, making it difficult to detect and more challenging for veterinarians to take a horse with a brewing problem out of a race.
Gluck researchers Drs. Allen Page and David Horohov received funding approval from the Kentucky Equine Drug Research Council (EDRC) last week for the second phase of a study they believe could have a promising outcome for early injury prediction. Page was on hand during the meeting to update council members on early results from the study's first phase.
Previous research has focused on biomarkers as a potential source of injury prediction. Biomarkers are proteins, which may be produced in different levels in response to a variety of changes in the body, including inflammation. Page said so far, studies trying to find a correlation between biomarkers and fatal injury in racehorses have had mixed results, due in part to biomarkers' tendency not to be discovered until an injury has already happened.
“We try to avoid a lot of that confusion by looking upstream, at the intermediate step between the DNA and the protein,” said Page.
Rather than DNA or proteins, Page and Horohov have chosen instead to concentrate on messenger RNA (mRNA), which is responsible for carrying instructions from genes leading to the production of proteins. The number of these instructions, or gene copies, change if the body is increasing or decreasing inflammation somewhere.
Page and Horohov have worked with several racing jurisdictions to collect blood samples from horses suffering fatal injuries and paired control samples from uninjured horses in the same race. They now have more than 800 samples and have analyzed about half of them. The control blood samples are collected during pre-race TCO2 testing and post-race samples are taken in the test barn.
While the first phase of the study is expected to be completed this summer, early results show two out of 23 genes being measured are consistently higher in the injured horses. Page said he hopes to present the full study at the American Association of Equine Practitioners convention later this year and believes at least one manuscript will come from the results that will be publishable in a peer-reviewed journal.
“My view of where you are now is we're a lot farther down the road than we once were,” said Dr. Johnny Mac Smith, EDRC member and veterinary consultant to the Grayson-Jockey Club Research Foundation, during the council meeting. “Although it may be a road with a few more curves than you anticipate, I think it's a worthwhile effort to pursue this. Who's to say, if your work was finished and we had a screening test, we might still have Mongolian Groom.”
Horses are believed to have more than 20,000 genes responsible for directing the creation of proteins. By utilizing RNA-sequencing, an emerging research technology, the study's newly-funded second phase will use the same blood samples from the injured and uninjured horses to examine differences between tens of thousands of genes. To assist with this phase of the study, fellow Gluck researchers Drs. James MacLeod, Ted Kalbfleisch, and Emma Adam have been enlisted for their extensive experience with RNA-sequencing and subsequent data analysis.
Page said that while many people think of genes as being constant, they can be turned on or off by various factors like injury. Page is hopeful there will be additional genes that are increased in fatally-injured horses, as this may help to further identify a horse with a higher risk.
Page was quick to credit the assistance of the EDRC, which has now given approximately $300,000 to the two phases of the project. EDRC committee members acknowledged during the meeting that funding research is always risky since there's no way to know in advance what the results will be, or if those conclusions will be able to practically assist veterinarians in the field. EDRC committee members agreed Page and Horohov's initial results look like they could provide that kind of useful guidance.
“As both a veterinarian and scientist, I hate hearing about horses breaking down,” said Page. “I'm always considering what we could be doing better and I think this is a good step. It has the potential to go hand in hand with the recent increased focus and interest in imaging since this is a fairly cheap potential screening tool that could be used to help direct horses towards advanced imaging.
“I think anybody who's involved in the industry realizes we're at a pretty significant crossroads. We all need to be doing whatever we can to provide not only opinions but solutions. Based on the first year and a half's worth of data, we're definitely excited about the potential that this research holds.”
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