Equine stem cell therapy & Hyperbaric oxygen therapy:

Many times in equine medicine, therapies are used in conjunction with each other to treat injuries.

As Scott Palmer, VMD, Dipl. ABVP (Equine Practice), hospital director and staff surgeon at the New Jersey Equine Clinic in Clarksburg, N.J., explained, hyperbaric oxygen therapy can be a beneficial adjunctive therapy to regenerative therapy, particularly stem cell treatment. Palmer presented on the topic at the 2011 North American Veterinary Regenerative Medicine Conference, held June 2-4 in Lexington, Ky.

What is Hyperbaric Oxygen, and What Does it Do?

When breathing 100% oxygen at increased pressure, the amount of oxygen dissolved in the liquid component of blood (plasma) increases, resulting in delivery of a significantly greater amount of oxygen to all body tissues. At two atmospheres of pressure inside a hyperbaric oxygen chamber, the amount of oxygen dissolved in the bloodstream is approximately 14 times higher than that found in the blood when breathing air at sea level.

Hyperbaric oxygen therapy, used in conjunction with other therapies, enables equine practitioners to more effectively treat a wide variety of serious conditions in horses, particularly those pathologic conditions characterized by soft tissue swelling, bacterial infection, tissue necrosis, or poor blood supply. Hyperbaric oxygen improves the physiologic state of injured or underperfused tissues (those that aren’t receiving enough blood) by providing increased oxygen levels. Additionally, hyperbaric oxygen increases the production of beneficial growth factors and mobilizes and activates stem cells. All of these effects are helpful to repair damaged tissues and heal injuries in horses.

Why Use with Stem Cells?

Palmer explained that there are at least two ways in which hyperbaric oxygen might influence the regenerative process: It has been observed to mobilize stem cells from the bone marrow by a nitric oxide-dependent mechanism, and it also causes an oxidative stress that stimulates stem cell metabolism and cell recruitment.

So what does that mean? In humans and laboratory animals, exposure to hyperbaric oxygen has been shown to double the stem cell population in the peripheral circulation. Palmer noted that similar effect might be achieved in horses, which could play an important role in injury repair and wound healing. 

Stem Cells and Hyperbaric Oxygen in the "Real World"

Palmer discussed one case in which an 8-year-old Thoroughbred gelding was treated with stem cells and hyperbaric oxygen. The horse had been racing poorly and underwent a veterinary examination that revealed bilateral (on both limbs) forelimb lameness related to chronic fetlock injury. Radiographic (X ray) examination revealed multiple large chip fractures in both of his front fetlocks and significant cartilage injury within these joints. Veterinarians performed arthroscopic surgery to remove the bone fragments.

The horse began hyperbaric oxygen therapy the day after surgery, and both joints were injected with a dose of intra-articular stem cells eight days later. He received a total of five hyperbaric oxygen treatments following the stem cell injections.

The horse competed in his first race eight months following surgery, and he raced nine times postinjury, placing first once, second twice, and third once. The degree of bone and cartilage injury in these joints and the chronic nature of the degenerative changes in both fetlocks made his return to racing at any level unlikely.

"The fact that he was able to race at the same level as before surgery and compete in nine races within one year (most race horses race an average of 6.2 starts per year) made his recovery very unusual and suggests that the regenerative therapy and the hyperbaric therapy provided following surgery made a positive difference in his outcome," Palmer added.

Palmer noted that researchers and veterinarians are working to compile a "road map" for hyperbaric oxygen’s effect on stem cells. Thus far, they’ve determined that hyperbaric oxygen therapy generates free radicals in the body that turn on genes that up-regulate (an increased expression of one or more genes) and stabilize growth factor production, which in turn recruits and mobilizes stem cells to help heal damaged tissue and make new blood vessels at the site of injury. Hyperbaric oxygen’s effects can be particularly important in cases of injury to tissues with a poor blood supply, such as tendons and ligaments.

It’s important to remember that both stem cells and hyperbaric oxygen therapy are essentially in their infancy as treatment options for horses. While the anecdotal evidence seems promising, researchers still need to complete controlled studies to evaluate the effects of these treatments against controls. Additionally, the relatively high price tag for these therapies could be prohibitive for some owners. 

All in all, Palmer concluded that hyperbaric oxygen is a useful adjunctive therapy for stem cells. Palmer suggests horse owners consider combining hyperbaric oxygen treatments with regenerative therapy in an attempt to augment the body’s natural response to injury and support the beneficial effects that can be achieved by administration of stem cells.