Adult stem cells are undifferentiated cells that can be found throughout the body, within various organs systems, maintaining the integrity of different tissues. They are often found among differentiated cells, replenishing these more specialized cells once they have reached the end of their life cycle. While adult stem cells also posses the unique properties of self-renewal and differentiation according to their surrounding niche, they are more limited than their embryonic counterpart in terms of the cellular subsets that can be formed, which is somewhat defined by their origin.
Adult stem cells can be categorized into various subtypes depending on their location including hematopoietic stem cells (HSC,s) found in bone marrow, umbilical cord blood as well as peripheral blood. These cells have the ability to differentiate into different blood cells that form part of the immune system and blood. For decades HSC’s transplants have been used in the treatment of more than 80 blood disorders and are routinely used today. Other adult stem cells also include mammary stem cells, which provide the source of cells for growth of the mammary gland during puberty and gestation, neural stem cells, and testicular cells among others. Of specific interest for the purpose of applying stem cells in medical treatments are mesenchymal stem cells (MSC’s)
Mesenchymal stem cells (MSCs) are multipotent, self-renewing progenitors that are defined by their ability to differentiate into adipocytes (fat), chondrocytes (cartilage), and osteocytes (bone). MSC’s have been discovered in various species and can be isolated from numerous tissue sources including adipose (fat), placental, dental pulp, and umbilical cord. Recent research has also shown that these cells also have the ability to differentiate other mature cell lineages to produce cardiomyocytes (heart muscle tissue), endothelial cells (walls of blood vessels), hepatocytes (Liver cells), and neural cells (nerve tissue). MSC’s also have an immunomodulatory effect, making them particularly useful in research involving autoimmune diseases. This also allows for the allogeneic use (inter-individually) of MSC’s and even xenogeneically (inter-species). Countless research has demonstrated how MSC’s can be utilized in the treatment and management of various degenerative diseases. It has also proven to be a versatile tool for scientist in developing new drugs, understanding the biology of diseases and in predicting the outcome of treatment protocols.