Preliminary results from a collaborative study conducted by the Royal Veterinary College (RVC) and the Japan Racing Association (JRA) indicate further support for the use of bone marrow-derived stem cells in the treatment of equine tendon injuries. Findings from the RVC indicate that stem cell therapy for superficial digital flexor tendon (SDFT) injury can significantly reduce the rate of re-injury over a three year period compared to conventionally treated horses.

The JRA collaboration analyses the properties of tendon injuries treated with stem cells.

The most frequently injured tendon in the horse is the SDFT. With conventional treatment the tendon will heal with a fibrous scar, which impairs tendon elasticity. This results in reduced performance and a substantial risk of re-injury.

Early outcome measurements to determine SDFT stiffness have indicated that tendons treated with stem cells show greater elasticity, more normal cellularity, vascularity, and organization on blind-scored assessments than those treated with a placebo.

"We hypothesised that the implantation of bone marrow-derived stromal stem cells in far greater numbers than are present normally within tendon tissue would synthesise a matrix more closely resembling tendon matrix than scar tissue, and hence increase the capacity for the horse to return to performance successfully," explained Roger Smith, MA, VetMB, PhD, DEO, MRCVS, Dipl. ECVS, Professor of Equine Orthopaedics at The Royal Veterinary College.

The most recent outcome data, which studied 168 national hunt horse in the UK, has identified that the re-injury rate, following stem cell therapy for SDFT injury and return to full work, in the three years following treatment is 24%, compared to 56% reported for horses that have undergone more traditional tendon treatment.

The horses included in the follow-up study had suffered moderate to severe SDFT injuries no more than four weeks prior to the proposed stem cell treatment. Bone marrow was aspirated from the sternum under standing sedation. The stem cells were isolated and expanded to in excess of 10 million cells before being re-suspended in growth factor rich bone marrow supernatant and implanted into the injured SDFT under untrasonographic guidance. The horses then entered a 48 week rehabilitation period comprising an ascending exercise regime.

"Although the follow up data does not provide definitive proof, careful evaluation of the most relevant outcome measures provides encouraging aspects to the use to this technology to treat tendon disease," Smith concluded. "It is also extremely encouraging that the initial results from the collaborative study appear to be substantiating the critical tendon elasticity hypothesis."

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