In the late 1990s, the human biomedical field was teeming with researchers dedicated to the study of embryonic stem cells, which appeared to usher in the age of regenerative medicine. Despite the incredible amount of promise these cells yielded for the future treatment of musculoskeletal and orthopedic injuries, ethical concerns immediately presented themselves, causing researchers to shift their concentration to adult or non-embryonic stem cells.
Although the same ethical concerns were not nearly as noteworthy in equine medicine, veterinarians have turned their attention to the use of stem cells extracted from bone marrow over the course of the last decade as another exciting option in regenerative medicine. To date, the results have been mixed, but in recent years stem cells retrieved from dental pulp have showed incredible promise in regenerative and degenerative medicine.
A study published on the subject from the Ohio State University’s Veterinary Clinical Services in the March 2017 edition of Veterinary Science demonstrates the same ability for regeneration in horses.
“While bone marrow aspirate extracted from the sternum in a horse enjoyed some success, there are concerns about the concentration levels of cells in those samples, as they can vary due to blood contamination and through the method in which they are procured,” said Dr. Alicia Bertone, director of the Comparative Orthopedics Research Laboratories at OSU’s Veterinary Clinical Science and equine surgical chair. “Another issue is, as with humans, bone marrow aspiration can be painful and there can be reactions to the procedure. Research on human dental pulp shows plentiful harvests of cells and offers a much less invasive technique to the patient with consistent results.
“To my knowledge, our study is the only one performed in horses, so while more research is necessary, it did show dental pulp tissue particles offer a potential alternative or addition to non-steroidal anti-inflammatory drugs or steroids for pain, and with regenerative potential unlike either of those products for osteoarthritis, desmitis, or tendonitis.”
Standardbreds, and in fact all high-level performance horses, frequently suffer from musculoskeletal injuries or osteoarthritis (OA). A 2014 article published in BMC Veterinary Research showed the incidence of musculoskeletal injuries in trotters in training over a four-year period indicated a percentage of 92.9% horses in the study sustained at least one musculoskeletal injury during their observation time.
Statistics for the incidence of OA in equines are difficult to retrieve, as just like in human medicine, the disease is not well-defined and is often diagnosed either through the structure that is affected, or the location where pain appears. However, a 2013 article in Bone & Joint Research states, “Spontaneous joint disease is a common clinical problem in the horse. Surveys estimate that up to 60 percent of lameness is related to OA.”
It is apparent both conditions are common reasons for horses to not only remain on the sidelines for extended periods of time, but to be retired from their work. Hence the interest in regenerative medical techniques such as aspiration of stem cells from dental pulp samples which would provide a solution for a major wastage issue in the equine industry.
“The dental pulp is a ball of tissue that is below the gumline in newborn foals,” Bertone said. “It is the most primitive form of stem cell tissue and has the greatest potential for developing into bone, ligaments, blood vessels and more. Studies in human medicine using dental pulp have used tissue generated from the wisdom teeth and the results have been very encouraging.” The dental pulp used in equine treatment is recovered from otherwise healthy foals that perish during dystocia (abnormal or obstructed birth) or more often from equine wolf teeth after they have been extracted.
For her study, Bertone and her colleagues examined 40 client-owned horses with confirmed OA, desmitis (systemic disease of connective tissue), or tendonitis. The study included a variety of breeds and each horse met a specific requirement of lameness, as well as for the conditions mentioned above. The horses were injected with dental pulp stem cells, exercised on a treadmill for two weeks and evaluated for 45 days after the procedure for improvement based on specific parameters. The clients also filled out surveys for their perceptions of a horse’s discomfort or degree of lameness after the horse returned home. As well, half of the research group was evaluated two-and-a-half years after the dental pulp injection.
“The horses that were injected showed a decrease in lameness compared to the control and placebo groups,” Bertone said. “The client assessments also showed improvement, especially in those horses with desmitis and tendonitis. At the evaluation two-and-a-half years later, at least ten of the horses were still in work.
“Interestingly, horses with soft tissue (ST) injury improved in lameness to a greater degree than OA horses. It is reasonable that the dental pulp tissue particles were more effective in ST injury possibly due to similarity of connective tissue phenotype or possibly ST injuries heal better than degenerative cartilage in OA. ST injury horses may also have had less chronic and less permanent injury than OA horses.”
While Bertone obviously envisions tremendous potential in regenerative therapies involving bone marrow aspiration and specifically dental pulp injections, she cautions that a much more extensive body of work must be produced to affirm her initial research.
“Dental pulp injections could be the Holy Grail in regenerative medicine for the treatment of these difficult injuries and possibly many other diseases or conditions,” she said. “However, bear in mind we do not know enough to assign this treatment with that type of label and there is still a large amount of research to be conducted. What we do know is there is promise there, not only with dental pulp, but in many other areas of regenerative medicine. This is an extremely exciting time for this field in horses and in humans, with many more breakthroughs on the horizon in the coming years.”