For years, the veterinarians and podiatrists at Rood & Riddle Equine Hospital, in Lexington, Ky., have been testing stem cell therapy's efficacy as an adjunctive treatment for the hoof disease laminitis. Their access to a large stem cell bank combined with a high caseload has created the ideal scenario for studying this cutting-edge treatment.
Most recently, the Rood & Riddle team investigated whether stem cell therapy could help stabilize chronic laminitis cases and during what time period stem cell administration is most effective. Vernon Dryden, DVM, CJF, APF, presented their results at the 2013 International Equine Conference on Laminitis and Diseases of the Foot, held Nov. 1-3 in West Palm Beach, Fla.
Mesenchymal stem cells (MSC) are unique in that they are pluripotent, meaning they can differentiate into multiple types of cells, including those that make up bone and connective tissue. Because previous research has shown that stem cell therapy helps improve the quality of healing in some tendon lesions, veterinarians hope it can also help repair laminar damage (the laminae are the Velcrolike tissues that suspend the coffin bone inside the hoof wall) and stabilize the coffin bone.
In severe chronic laminitis cases, horses experience detachment of the laminar interface resulting in coffin bone displacement and rotation. Over time, affected horses can develop a laminar wedge between the rotated and/or sunken coffin bone and the toe of the hoof wall. This wedge is comprised of poorly organized and irregular laminae that provide little structural integrity to the hoof/coffin bone interface and can be measured using radiographs to determine the “hoof laminar zone” (HLZ). Many veterinarians believe the laminar wedge develops within the first 30 days of laminitis, accompanied by coffin bone displacement.
These types of laminitis cases, said Dryden, are some of the most difficult to treat. Depending on the severity of the disease, multiple traditional modalities (e.g., therapeutic farriery, deep digital flexor tendon transection, hoof casts) might still be unsuccessful in stabilizing the bone and tissues.
"Despite great efforts, many chronic laminitic cases heal with poor-quality laminae or are so unstable that the horse is euthanized," Dryden said.
This is where stem cell therapy might lend a hand in healing.
To test this theory, Dryden and colleagues looked at 30 horses, ages 2-20, admitted to Rood & Riddle between 2010 and 2012 with chronic laminitis that underwent MSC therapy in addition to their routine treatment. Each horse received 20-30 million MSC per affected foot at one-month intervals, averaging three to four treatments. Dryden said he and his colleagues administered allogeneic (harvested from a different horse's body) MSC derived from the hospital's umbilical cord blood bank for the first treatment, followed by autologous (from the horse's own body) bone-marrow-derived MSC for the following treatments. He recommended using autologous MSC, because researchers believe these to be safer, and explained that they had to rely on allogeneic MSC for the first treatment only because it can take weeks for the former to proliferate before being ready for injection.
Dryden and colleagues classified each horse according to disease severity: severe rotation with mild-to-moderate bone disease (6); chronic laminitis with severe bone disease (6); and sinking (18). They deemed the treatment protocol successful if horses were subsequently pasture-sound without heavy medication or maintenance for at least one year. They determined that:
- Of the 30 cases, 21 (70%) were successful;
- Of the 18 sinkers, 15 (83%) were successful;
- The sooner the horse received MSC treatment, the better: The median time to first treatment was 71.5 days. For horses that were first treated sooner than 71.5 days, 87% (13/15) were successful. For horses that were first treated after 71.5 days, 53% (8/15) were successful.
- The younger the horse, the greater the chance of success: The horses' median age was 11. For horses younger than 11, 82% (14/17) were successful. For older horses, 50% (6/12) were successful.
- If a laminar wedge had already formed before MSC treatment, the team saw little reduction in HLZ. For horses that were first treated after 90 days, 17% (2/12) had improved HLZ, while horses that were first treated before 90 days, 69% (11/16) improved.
- Horses with severe bone disease showed no improvement in HLZ.
"Like anything, the earlier the treatment, the better the outcome," Dryden noted.
In conclusion, he said, MSC therapy is showing most usefulness within 30 days of the laminitic insult, before the laminar wedge forms. "The majority of these cases have healed with a decreased distance between the bone and hoof wall.
"But this is by no means a magic bullet," he said. "These horses could not have responded otherwise without traditional treatments."
Dryden said further studies are now under way to evaluate the quality of tissue post-MSC treatment.
The study, "Using stem cells in clinical cases," appeared in the October 2013 issue of the Journal of Equine Veterinary Science.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.
