What are examples of unipotent and multipotent stem cells?
More broadly, stem cells have the ability to do two key things. They can make more of themselves through a process called self-renewal. Also, they have the ability to differentiate into other cell types. This latter property is called potency.
Taken together this means by definition that a true stem cell has both the ability to self-renew and has potency.
What are unipotent stem cells?
The idea of unipotent stem cells is a bit controversial.
While unipotent cells can self-renew they only have the ability to differentiate into one other cell type. Many cell biologists define such cells as progenitor cells instead. For instance, there are B-cell progenitors that can multiple themselves (self-renew) and ultimately make mature B cells. I was taught that these are B-cell progenitors, not unipotent stem cells. Signaling can also activate B cells to mature into plasma cells that secrete antibodies.
If you accept the idea of unipotent stem cells as stem cells, then what are some other types?
Maybe the best example of unipotent stem cells are certain skin stem cells and blood progenitors. Again, these could just as easily be simply called progenitors.
There are ways that unipotent cells could be very useful clinically. For example, blood progenitors have clinical utility. In a sense CAR-T cells or cells used to make CAR-T cells could be technically considered unipotent. Skin progenitors are also going to be very useful for patients I think.
What are multipotent stem cells?
As their name suggests, multipotent stem cells have broader potency. We can define multipotent stem cells as having self-renewal and potency of the kind where they can make multiple types of daughter cells. Not just one type.
The best example of multipotent stem cells may be earlier hematopoietic stem cells that can make several distinct progeny like multiple white blood cells. There are also specific multipotent cells in the brain. True mesenchymal stem cells, which must be purified from mixed populations of MSCs that contain non-stem cells, can also be multipotent.
In contrast to unipotent and multipotent stem cells, pluripotent stem cells can form every type of cell in the entire body. Their only limit is that they cannot make extraembryonic tissues like placenta. Pluripotent stem cells include iPS cells and embryonic stem cells.
Multipotent cells are likely to have more reparative function for more complex tissues as opposed to unipotent cells. There has been hope that iPS cells may have robust ability to replace or repair complex tissues too. So far, the speediest translational and clinical work using iPS cells or ES cells has been focused on differentiating them into homogenous populations of just one cell type though.
Oh, Admin:
Consider no longer parroting the cliche that “pluripotent stem cells can form every type of cell in the entire body.” It has been known for some time now that both human embryonic stem cells and human induced pluripotent stem cells DO NOT make every type of cell in the postnatal human body, which is the body that everyone is talking about treating. So far, their limitation is that they primarily differentiate into body cells with the functional properties of embryonic and fetal cells, and not many of the cells of mature tissues, which is needed for therapies for adults and children.
Unlike in the case of mouse embryonic stem cells, for which embryo-derived chimeric mice confirm their ability to “produce every cell in the body” of mice, similar experiments have not been performed with people. And hopefully they never will be!
So, we are left with only in vitro differentiation for human pluripotent stem cells; and so far, studies with them do not support this common erroneous cliche asserted from experiments with mice.
James @Asymmetrex®
Hello, Admin:
There are some very well described postnatal unipotent tissue stem cells. The spermatogonial stem cells of the testes make only sperm. The lens stem cells of the lens make only crystalline-producing cells. The limbal stem cells of the cornea make only corneal epithelium cells.
Committed progenitor cells, like B-cells, are not “tissue stem cells” by the strict definition that they lack asymmetric self-renewal, which is the ability to divide with some progeny cells retaining the stem cell phenotype while other progeny cells commit to differentiation. They are not stem cells by the rule of “self-renewal OR differentiation” (as is the case for pluripotent stem cells). They are stem cells by the unique rule of “self-renewal AND differentiation.” The distinction in these two important rules underpins the reason why tissue stem cells like hematopoietic stem cells can be transplanted directly into the body without tumor formation, and pluripotent stem cells cannot.
Memory B-cells and memory T-cells may persist by such an asymmetric self-renewal program, but the the cell kinetics basis for their longevity after production has not been clearly defined.
Kind regards,
James @ Asymmetrex®
Not all stem cells divide asymmetrically. That’s just one idea and mechanism. I get your company is somewhat focused on asymmetry but it’s not a universal rule.