Claims of the benefits of stem cell therapy in animals are often reminiscent of the magic snake oil potions from the turn of the last century.
Stem cells are touted as the ideal treatment of a large number of ailments, including arthritis, kidney disease and tendon and ligament injuries.
Unfortunately, scientific evidence has not kept pace with the explosion of private companies offering stem cell therapy for animals and the demand for treatment from the public. In veterinary medicine, dogs and horses are by far the most common recipients of stem cell therapy.
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It has been commercially available for animals for almost a decade, but there are few studies evaluating the efficacy or long-term safety of this treatment.
Some tissues, such as skin, have a remarkable ability to regenerate and heal with minimal loss of function, but others, such as cartilage and tendons, have little capacity to regenerate and heal through scar tissue formation, which is weaker and less functional than the original tissue.
Additionally, it can take years for tendons to heal and even then, they are less functional than the original tissue. For this reason, treating arthritis and tendon injuries is difficult and a major incentive for people to try stem cell therapy.
Stem cells are cells that have not yet specialized to form a certain tissue type. However, not all stem cells are created equal. Some have the ability to develop into any cell type in the body, while others are more specialized and can create only certain types of tissues.
Tissues such as fat or bone marrow are harvested from the animal undergoing treatment. From this sample, stems cells are grown in small Petri dishes, which enhance the development of stem cells. Once a large number are cultivated, they can be injected back into the area of injury.
The central concept of stem cell therapy is that these cells will divide and heal the damage in a better way than normal healing mechanisms, which often causes loss of function through scarring.
Stem cells are thought to divide and replace the lost tissue in a way that allows return to function and reduced inflammation, which causes on-going harm in diseases such as arthritis. There is little risk of rejection by the immune system because stem cells are the animal’s own.
A lack of properly designed, blinded clinical trials is a major impediment to investigating whether stem cells are beneficial.
Well-designed studies randomly assign animals to receive either the treatment of interest — in this case, stem cells — or a placebo. The person administering the treatment, the owner of the animal and the person analyzing the data should not know whether an individual animal received the treatment to avoid biasing the results with the so-called “placebo effect.”
This type of clinical trial is difficult to do with companion animals or expensive horses because most people want their animal to receive the treatment, whether or not there is evidence to suggest it is beneficial.
Participants also have to be willing to bring their animal for follow-up appointments and fill out surveys that assess their impression of the treatment.
Arthritis and tendon injuries are the most commonly studied subjects of stem cell therapy because they occur frequently in horses.
Interesting studies involving tendon injuries in racehorses have found that stem cell treated horses were more likely to return to racing and were less likely to suffer re-injury compared to conventionally treated horses with similar injuries. This difference was thought to be due to less scar tissue formation in the stem cell treated horses. The work on arthritis treatment does not seem to show a definitive benefit.
The benefits of stem cells to treat humans are also being actively investigated, with horses and dogs providing a naturally occurring pre-clinical animal model. As with many disease processes, the shorter lifespan in animals provides a unique way to study human diseases.
Moving novel therapies from the research lab to human patients is a long, arduous process designed to protect patient safety.
Similar safeguards are not in place for veterinary applications of treatments such as stem cells, and despite this unknown quality, offer a unique opportunity to study the application of stem cells in naturally occurring disease settings that are much more similar to human injuries that rodent disease models.
Stem cell therapy is not without risks.
Bacteria and fungi can inadvertently be injected into the animal receiving treatment, resulting in serious infections. Carefully cleaning the injection site and including antibiotics in the injection can minimize this risk.
There is pain associated with the injection in some animals, which is suspected to be caused by distention of the joint from the added fluid.
The necessity of heavy sedation in horses and anesthesia in dogs and cats is another potential risk.
And of course, there is the cost associated with an unproven treatment that may not benefit the animal. The price tag isn’t cheap either; expect to pay $1,000 per treatment.
Researchers working on stem cell therapy in horses and dogs have not reached a consensus on the best way to harvest tissues (fat versus bone marrow) or which particular cells are being cultivated. This has led to problems comparing different studies.
