True stem cells must come from an embryo. Instead, Mund says many researchers opt to use mesenchymal stem cells — a type of stem cell that is found throughout the adult body, particularly in bone marrow and fat. While these cells are more limited in the types of tissue development, they are much easier to collect and could still have an important role in wound healing.
Mund is working with WCVM equine surgeon Dr. Spencer Barber and a team of researchers to better understand how stem cells act during the healing process. Specifically, the researchers are looking at how stem cells influence a horse's inflammatory response, which plays a pivotal role in wound healing.
As Mund explains, researchers believe that stem cells have an anti-inflammatory effect — and abnormal inflammatory processes may lead to abnormal wound healing. That's why it's important for scientists to understand how stem cells may affect healing at different stages since the timing of stem cell administration could influence the healing process.
The long-term goal is to use this understanding of timing to provide a protocol for stem cell use that is fast and accessible to all veterinarians.
"The dream is to have on-the-shelf stem cells," says Mund. "So if you have a horse that just walked through the [clinic] door with a big injury, you could just give them a dose of stem cells and not wait to culture its own [stem cells] from a bone marrow or fat source."
While this scenario may seem a long way off, Mund and Barber are hopeful that their research work can help to make the option of immediate stem cell treatment a reality. But first, they're addressing some important questions in a research study that's supported by the Mark and Pat DuMont Equine Orthopedics Research Fund.
Harvesting a horse's own stem cells and then purifying them takes time which may not be an option for a horse with an acute wound. As an alternative, the WCVM team is using allogenic stem cells (cells collected from other horses) since these cells could be more readily available.
Foreign stem cells could potentially cause horses to have a reaction that would affect their lung function (breathing), but Mund says the study's horses "did just fine" after the research team gave them high doses of allogenic stem cells — the largest known amounts ever administered to horses intravenously.
"We were hyperaware that they could have a reaction, and we monitored the horses very closely," says Mund. "We were very pleased when they didn't have a reaction, considering the cells came from a different individual."
The next step in the project is to determine if the equine stem cells that are given intravenously will migrate and concentrate in a wound.
"We wanted to see if the cells would migrate to the area, and once they are there, do they differentiate into resident cells or do they just secrete growth factors?" says Mund. "Or do they not make it there at all — but still have an influence on healing?"
To test this process, Mund, Barber and other team members made surgical wounds on horses and administered stem cells intravenously 12 hours later. During the healing process, they collected biopsies from the wounds as well as from a non-wounded site on each horse. The researchers then examined the biopsies under a microscope to determine if the stem cells had concentrated in the wounded site.
"So far, it looks as though the cells are preferentially migrating to the wounded site versus the non-wounded site," says Mund.
The research team is still waiting for results to indicate whether these cells that have migrated to the wounded site are actually producing growth factors and other proteins to modulate the inflammatory process and accelerate healing. They will also try to determine if the cells are developing into mature fibroblasts (a cell type that is important for providing structure to tissue) or if they are recruiting more fibroblasts into the area.
Another portion of the study will involve tissue culture, a laboratory technique that's an alternative to using live horses. In the lab, Mund will grow equine skin cells and fibroblasts in a tissue culture plate; she will make a "scratch" in the tissue culture to simulate a wound and then place stem cells on the scratch.
"We want to see if the stem cells accelerate the closure of that scratch or wound that we created and compare that to the same plate that we don't put stem cells on," says Mund.
The field of stem cell research still has so many questions that need answering. By understanding how stem cells may influence wound healing in horses, Mund hopes that the WCVM-based research will work toward providing better wound treatment options for veterinarians.
In addition, Mund's goal is to improve the way that stem cells are used in equine medicine. Most often the cells are injected directly into the site of injury — such as into an arthritic joint or an injured tendon — but there's very little science behind their use.
"We would like to prove or dispel some of the myths surrounding stem cells and their use in equine medicine," says Mund. "If we are not using them correctly, maybe we can look into different ways of using them or start thinking about them differently."
Hayley Kosolofski of Sherwood Park, Alta., is a fourth-year veterinary student at the Western College of Veterinary Medicine (WCVM).