Implantation of bone marrow-derived mesenchymal stem cells demonstrates improved outcome in horses with overstrain injury of the superficial digital flexor tendon.

The study investigates the impact of using mesenchymal stem (progenitor; stromal) cell (MSC) therapy to treat tendon injuries in racehorses. It found no significant adverse effects and suggested a lower reinjury rate, especially in National Hunt racehorses, compared to other treatments.

Objective

• The research aimed to examine the safety and reinjury rate of horses after an intralesional MSC injection. This was achieved through a long-term follow-up on a significant cohort of naturally occurring superficial digital flexor tendinopathy in racehorses. The researchers compared the reinjury rates with data from other published works on different treatments.

Methodology

• The safety of the MSC treatment was assessed on various levels including clinically, ultrasonographically, scintigraphically, and histologically. These tests were conducted on a test group consisting of 141 client-owned and treated racehorses.
• The study followed up these horses for a minimum of 2 years after they returned to full work.
• The data from these horses was compared with 2 other selected groups with similar criteria using alternative treatments.
• The study evaluated various factors including the number of race starts before injury, the discipline of the horse, the age of the horse, the number of MSCs injected, and the interval between the injury and the treatment.

Results

• The findings suggest no adverse effects from the treatment. Histological examination showed no aberrant tissue formation in the treated horses.
• 27.4% of the racehorses followed up (n = 113) sustained reinjury after undergoing MSC treatment. This percentage varied with the type of racing discipline, with National Hunt racehorses having a significantly lower reinjury rate (25.7%) compared to flat racehorses (50%).
• No correlation was found between the outcome and various factors such as age, discipline, number of injected MSCs, or the injury to implantation interval.

Conclusions

• The study concluded the implantation of mesenchymal stem cells was a safe treatment method for tendon injuries in racehorses and could potentially reduce the reinjury rate, especially for National Hunt racehorses.
• The results establish evidence supporting the long-term efficacy of MSC treatment for tendinopathy in racehorses. They also highlight the potential for adaptation and translation of this method to treat human tendon injuries.