Veterinarians around the world have been researching stem cells’ effectiveness as therapeutic tools for a variety for equine musculoskeletal skeletal conditions with some success. A research team from Texas A&M recently took a closer look at the future of stem cell use in another important part of horses’ bodies: their eyes.

At the 2014 American Association of Equine Practitioners Convention, Ashlee Watts, DVM, PhD, Dipl. ACVS, presented the results of a study in which researchers evaluated allogeneic mesenchymal stem cells’ safety when injected into healthy horses’ subconjunctiva (the area beneath the mucous membrane lining the eyeball and inner eyelid surface). Watts is an assistant professor at the Texas A&M College of Veterinary Medicine & Biomedical Sciences.

Allogeneic stem cells are those harvested from one different horse and injected into another. Mesenchymal stem cells (or MSCs) are present in a variety of equine body tissues and are important to replenish dying cells and regenerate damaged tissue.

"Subconjunctival injection of allogeneic mesenchymal stem cells has the potential to become a new therapeutic in equine ophthalmology," Watts said. "Our objective was to evaluate the safety of allogenetic MSC subconjunctival injection in normal eyes."

The team employed 14 healthy horses and randomly assigned each horse’s eye to receive either 3 million MSCs in the upper-lid subconjuntival area or a control injection consisting of cell medium. She said two masked observers unaware of the treatment group for each eye monitored the horses’ eyes regularly. The team repeated the injections three weeks following the initial injections.

Watts said the team identified no adverse reactions or complications in either the MSC or control treated eyes over the study’s duration. She said MSC-treated eyes exhibited more redness and higher chemosis (conjunctival swelling) scores on Days 1, 22, and 28, but not at other points throughout the study. She also noted that the team observed epiphora (watery eyes) in some horses, but the condition was present prior to the injections. Affected horses’ eyes continued to water throughout the study, and there were no significant differences in the presence of epiphora between the groups.

Watts and colleagues concluded that administering two subconjunctival allogeneic MSC injections appears safe, but further research on the topic is warranted.