Stem Cell Types
Different Types of Stem Cells
There are several main categories: the “pluripotent” stem cells (embryonic stem cells and induced pluripotent stem cells) and nonembryonic or somatic stem cells (commonly called “adult” stem cells). Pluripotent stem cells have the ability to differentiate into all of the cells of the adult body. Adult stem cells are found in a tissue or organ and can differentiate to yield the specialized cell types of that tissue or organ. The following cell types are the most common that we research here in our labs and utilize in our Stem Cell Treatments.
Adult Stem Cells (ASCs):
ASCs are undifferentiated cells found living within specific differentiated tissues in our bodies that can renew themselves or generate new cells that can replenish dead or damaged tissue. You may also see the term “somatic stem cell” used to refer to adult stem cells. The term “somatic” refers to non-reproductive cells in the body (eggs or sperm). ASCs are typically scarce in native tissues which have rendered them difficult to study and extract for research purposes.
Resident in most tissues of the human body, discrete populations of ASCs generate cells to replace those that are lost through normal repair, disease, or injury. ASCs are found throughout ones lifetime in tissues such as the umbilical cord, placenta, bone marrow, muscle, brain, fat tissue, skin, gut, etc. The first ASCs were extracted and used for blood production in 1948. This procedure was expanded in 1968 when the first adult bone marrow cells were used in clinical therapies for blood disease.
Studies proving the specificity of developing ASCs are controversial; some showing that ASCs can only generate the cell types of their resident tissue whereas others have shown that ASCs may be able to generate other tissue types than those they reside in. More studies are necessary to confirm the dispute.
Types of Adult Stem Cells:
- Hematopoietic Stem Cells (Blood Stem Cells)
- Mesenchymal Stem Cells
- Neural Stem Cells
- Epithelial Stem Cells
- Skin Stem Cells
Embryonic Stem Cells (ESCs):
During days 3-5 following fertilization and prior to implantation, the embryo (at this stage, called a blastocyst), contains an inner cell mass that is capable of generating all the specialized tissues that make up the human body. ESCs are derived from the inner cell mass of an embryo that has been fertilized in vitro and donated for research purposes following informed consent. ESCs are not derived from eggs fertilized in a woman’s body.
These pluripotent stem cells have the potential to become almost any cell type and are only found during the first stages of development. Scientists hope to understand how these cells differentiate during development. As we begin to understand these developmental processes we may be able to apply them to stem cells grown in vitro and potentially regrow cells such as nerve, skin, intestine, liver, etc for transplantation.
Induced Pluripotent Stem Cells (iPSCs)
Induced pluripotent stem cells are stem cells that are created in the laboratory, a happy medium between adult stem cells and embryonic stem cells. iPSCs are created through the introduction of embryonic genes into a somatic cell (a skin cell for example) that cause it to revert back to a “stem cell like” state. These cells, like ESCs are considered pluripotent Discovered in 2007, this method of genetic reprogramming to create embryonic like cells, is novel and needs many more years of research before use in clinical therapies.
Types of stem cells
The full classification includes:
- Totipotent: These stem cells can differentiate into all possible cell types. The first few cells that appear as the zygote starts to divide are totipotent.
- Pluripotent: These cells can turn into almost any cell. Cells from the early embryo are pluripotent.
- Multipotent: These cells can differentiate into a closely related family of cells. Adult hematopoietic stem cells, for example, can become red and white blood cells or platelets.
- Oligopotent: These can differentiate into a few different cell types. Adult lymphoid or myeloid stem cells can do this.
- Unipotent: These can only produce cells of one kind, which is their own type. However, they are still stem cells because they can renew themselves. Examples include adult muscle stem cells.
*Embryonic stem cells are considered pluripotent instead of totipotent because they cannot become part of the extra-embryonic membranes or the placenta. Embryonic stem cells are the most potent, as their job is to become every type of cell in the body.
It is important to note that these treatments are still considered experimental and have not yet received approval from Western medical standards. While there have been promising results and anecdotal evidence of positive outcomes, there is currently no definitive scientific proof of a cure for any specific condition using stem cell therapy. It is crucial to understand that what works for one patient or in a small sample size may not necessarily be applicable to others or prove effective in larger clinical trials. Patients considering stem cell therapy should be aware of the experimental nature of these treatments and exercise caution when evaluating potential benefits.