Inflammation and Cartilage Turnover in Horses
By Meredith K. Kahn, M.S., Sales & Marketing Manager
Part of Jaguar’s staff contribution series
Horses of varying age can suffer from osteoarthritis. In fact, osteoarthritis is the primary cause of lameness for athletic horses, commonly leading to early retirement. While commonly seen in older horses, the disease likely begins early during skeletal development with the overloading of joints during early training and exercise. In young horses, adaptation of bone and soft tissue occurs during growth and training, potentially leading to the overproduction of inflammatory mediators and the consequent breakdown of articular cartilage. A metabolic shift toward synthesis takes place in young equines, which serves to mend damaged cartilage. It is speculated that cartilage turnover in response to arthritic inflammation is slower in skeletally mature horses, however this process is not well understood. Nevertheless, previous research that has been compared across studies indicates that inflammation and cartilage metabolism vary depending on the age of the horse in question.
Current treatments for osteoarthritis in horses focus solely on pain management and can have negative side effects. As such, research has been focusing more on early preventative methods. A recently published study in the Journal of Animal Science entitled, “Age-related effects on markers of inflammation and cartilage metabolism in response to an intra-articular lipopolysaccharide challenge in horses”, is the first study to investigate inflammation and turnover of cartilage in horses across three different age groups. This pivotal study is the first of many that may help identify an age range in which addition of preventative nutritional strategies or change in exercise protocol may be the most beneficial for the working horse. In an age where all-natural, nutritional therapies are rapidly growing in popularity among horse owners and trainers, there could not be a better time for release of this research.
Eighteen quarter horses from the Texas A&M University herd were utilized for a 28-day experiment in the recently published study. Horses were grouped into one of three categories based on their age: yearlings, two- and three-year-olds, and skeletally mature five- to eight-year-olds. A temporary inflammation that mimics inflammation as seen under arthritic conditions was induced in all horses. Vitals were monitored over 24 hours and additional joint measurements were taken at specific timepoints throughout the study. Synovial fluid samples were taken before inflammation was induced and at numerous timepoints after induction. The samples were analyzed in the laboratory using commercial ELISA kits for a marker of inflammation (PGE2), one for cartilage breakdown (C2C) and another that indicates cartilage synthesis (CPII). As expected, differences were noted between age groups.
As indicated by previous research, older horses tended to have greater inflammation than young horses. In response, more mature horses had increased cartilage breakdown and, consequently, greater amounts of cartilage re-synthesis. Ratios of synthesis to breakdown were also analyzed and results demonstrated that older horses had higher anabolic to catabolic ratio values than young horses. Nevertheless, ratio values for mature horses peaked later than peak values for young horses, indicating a slower turnover rate. Therefore, while this study suggests that mature horses may have an increased ability to re-synthesize cartilage in response to inflammation when compared to younger horses, the process takes longer and may be accompanied by increased damage to the newly synthesized molecules. Compromised cartilage may be an important factor dictating the integrity of the joint and its ability to function. Furthermore, while the slow turnover rate in mature horses did not pose a significant threat to horses under experimental conditions, it is possible that without adequate rest, the older equine athlete returning to work may not have time to sufficiently complete the cartilage repair process.
Further studies are needed to clarify the effects of age on inflammation and cartilage metabolism in horses, specifically exercising horses, exposed to chronic inflammation. Nevertheless, this study provides a solid platform to investigate osteoarthritis in horses of varying age. Also, with the development of nutritional therapies as preventatives, future research will likely focus on effectiveness of these types of therapies. Osteoarthritis is estimated to contribute to a significant portion of lameness for equine athletes and, as indicated by this study and previous research, this not only applies to the mature horse. As members of the equine community we can help prevent premature retirement by making use of nutritional therapies early on for use as potential preventatives or adjusting exercise protocol when needed.