Oligopotent stem cells are a class of stem cells that can develop into a few closely related cell types. Found within various tissues, they act as a localized source for replacing cells lost through normal turnover or injury. Their specialization commits them to a particular cellular lineage, such as the cells that make up the blood or specific cells within the nervous system.
The Stem Cell Potency Hierarchy
Stem cell potential, known as potency, describes a cell’s ability to differentiate into other cell types. This ability ranges from nearly unlimited to highly restricted.
At the top of the hierarchy are totipotent stem cells. A fertilized egg is the primary example, as it can develop into a complete organism, including embryonic tissues and extraembryonic structures like the placenta.
Below totipotency are pluripotent stem cells. Found in the early embryo, they can form virtually any tissue or organ in the body. However, they cannot create supportive structures like the placenta and therefore cannot develop into a full organism. Embryonic stem cells are a well-known type of pluripotent cell.
Further down the hierarchy are multipotent stem cells, which are more limited than pluripotent cells. Found in various adult tissues, these cells can differentiate into a specific range of cell types to maintain and repair the tissues in which they reside. For example, mesenchymal stem cells are multipotent and can become bone, cartilage, muscle, and fat cells.
Oligopotent stem cells are a subsequent step in specialization and are more restricted than multipotent cells. They differentiate into only a few closely related cell types within a specific lineage.
At the end of the hierarchy are unipotent stem cells. These have the most limited potential and can only differentiate into a single cell type, such as a muscle stem cell that produces only muscle cells.
Examples of Oligopotent Stem Cells in the Body
The human body contains several types of oligopotent stem cells. A well-documented example is in the hematopoietic system of the bone marrow, which produces all blood cells from multipotent hematopoietic stem cells (HSCs). These HSCs give rise to more specialized, oligopotent progenitor cells.
These progenitors are divided into two main lines. The first is the common lymphoid progenitor, which differentiates into various immune cells. These include B-cells that produce antibodies, T-cells involved in cell-mediated immunity, and Natural Killer (NK) cells that respond to infected cells.
The second line is the common myeloid progenitor, which generates all other blood cells. This diverse group includes erythrocytes (red blood cells) that transport oxygen, megakaryocytes that produce platelets for blood clotting, and various immune cells like granulocytes. The existence of these two distinct progenitors allows the body to independently manage the production of its lymphoid cells and its oxygen-carrying myeloid cells.
Beyond the blood system, neural stem cells in the adult brain also exhibit oligopotent characteristics. Found in regions like the subventricular zone, their potential is restricted to a limited range of neural cells. For instance, some differentiate into glial cells like astrocytes and oligodendrocytes, which support and protect neurons.
Natural Role in Tissue Maintenance and Repair
The primary function of oligopotent stem cells is to sustain and repair the tissues where they reside. Since many of the body’s tissues undergo constant turnover, these cells are responsible for replenishing old or damaged cells. This process ensures that tissues like blood and skin remain healthy and functional.
These stem cells exist in a quiescent, or dormant, state until activated by specific biochemical signals. Such signals can be triggered by tissue injury, inflammation, or the programmed death of older cells. Once activated, the oligopotent cells begin to divide.
Upon activation, one of the resulting cells remains an oligopotent stem cell, preserving the original stem cell pool for future needs. The other cell embarks on a path of differentiation, maturing into one of the few specific cell types it is programmed to become. This process ensures that the population of functional cells is replenished without depleting the reserve of stem cells.
Use in Research and Regenerative Medicine
The predictable nature of oligopotent stem cells is useful in research and medicine. Their limited differentiation potential makes them easier to control in a lab compared to pluripotent cells. This predictability also makes them a safer option for therapies, as there is a lower risk of unintended cell types forming after transplantation.
In regenerative medicine, researchers are exploring the use of oligopotent cell transplants to restore specific cell populations that have been depleted by disease or injury. For example, therapies could involve transplanting specific hematopoietic progenitors to rebuild the blood and immune systems in patients who have undergone chemotherapy. This targeted approach ensures that only the needed cell types are generated.
These cells also serve as a platform for disease modeling. Scientists can isolate oligopotent cells from patients with a genetic disorder affecting a specific lineage. By growing these cells in a lab, researchers can observe how a disease develops at a cellular level and test the effectiveness of potential drugs.