Initially, differentiation was thought to be the primary function of mesenchymal stem cells. While mesenchymal stem cells (MSCs) do possess the ability to differentiate into multiple tissue types, it is now known that MSCs rely on multiple mechanisms of action to aid the healing process.
Anti-Inflammatory and Immunomodulation
Perhaps one of the most important mechanisms of MSCs is the ability to down-regulate inflammation. Studies have demonstrated that MSCs limit inflammatory responses and promote anti-inflammatory pathways. Another tool that stem cells utilize is immunomodulation, or the ability to modify the immune response. Several in-vitro studies have demonstrated the immunomodulatory effects of MSCs. While studies are ongoing, the initial results support that MSCs have the ability to modulate the immune system.
Trophic Support
Multiple studies demonstrate that MSCs secrete bioactive levels of cytokines (cell-signaling proteins) and growth factors that support angiogenesis (the development of new blood vessels), tissue remodeling, differentiation, and antiapoptotic events. Simply put, trophic support is a fancy way to say stem cells secrete material that supports cellular growth, differentiation, and survival, all of which are necessary components of quality healing.
Differentiation
While we mentioned differentiation earlier, it is important to note all of the different types of tissues that MSCs can differentiate into. MSCs have demonstrated the ability to differentiate into multiple cell types including fat, bone, cartilage, muscle, heart, endothelial, liver, nerve, epithelial, and blood cells. This mechanism is important to help heal various injuries and diseases.
Homing
Homing (chemotaxis) is an event by which a cell migrates from one area of the body to a distant site where it may be needed for a given physiological event such as an injury. Homing is an important function of MSCs, especially when stem cells are administered intravenously like in the recent COVID-19 clinical trial. Stem cells given intravenously have been shown to migrate from the site of injection to a distant site where they may be needed.
To summarize, MSCs rely on multiple mechanisms for success. Adipose derived mesenchymal stem cell therapy delivers a functionally diverse cell population able to communicate with other cells in their local environment. MSC therapy should be viewed as a complex, yet balanced, approach to a therapeutic goal. Unlike traditional medicine, in which one drug targets one receptor, regenerative medicine can be applied in a wide variety of traumatic and developmental diseases.