Stem cell therapy has been utilized in horses to help heal tendon, ligament, and joint injuries for more than 20 years. Mesenchymal stromal cells (MSCs) are isolated from fetuses, foals or adult horses, and are not the same as embryonic stem cells from embryos. MSC stem cells can be isolated from almost any tissue but are most commonly from bone marrow, fat tissue or the umbilical cord of newborn foals.
A laboratory culture is required to isolate and expand the cells. MSCs are characterized by their ability to become other types of cells in the laboratory and ability to modify the function of cells from the immune system such as lymphocytes. Cells from bone marrow and fat tissue are also used after a brief laboratory processing step where all the cells are concentrated from the sample without a culture step to select and expand MSCs. These processes are known as bone marrow concentrate or stromal vascular fraction, depending on whether the starting material is bone marrow aspirate or fat tissue. Sometimes these cell preparations are referred to as stem cell treatments although very few of these cells would be MSCs.
Autologous versus allogeneic use of cells is another distinction. Autologous cells are from the patient itself. Allogeneic cells are from one horse that are placed in other horses. The advantage of using autologous cells are that they are not rejected by the patient’s immune system, and there are less regulatory concerns with their use. Disadvantage of using autologous MSCs is that it takes 2-3 weeks to isolate and expand the cells prior to use This involves a two-step process requiring the horse to return for treatment after diagnosis and initial sample collection.
This may hamper optimal treatment time since the cells are not readily available. Allogeneic use of cells has the advantage of having cells readily available, with time to select, and potentially enhance cell functions prior to use.