What are stem cells?
The cells in our body are specialized to be able to fulfill different roles in different tissues — fixed to a specific fate through a process called differentiation. Once differentiated, a cell generally cannot change into a different type of cell, and can only fulfill a specific role.
Stem cells are unusual in this regard. They are undifferentiated and have the potential to become various types of cells. Because of this, they may have the potential to “reset” the damaging immune response seen in scleroderma.
Replacing a patient’s immune cells with new ones produced from transplanted stem cells may help rebuild the immune system. Stem cells could also potentially help repair damage to parts of the body caused by scleroderma. However, for good reasons, their use in clinical trials is heavily regulated by the U.S. Food and Drug Administration (FDA).
Stem cells are collected from a donor or patient and cultured, or purified and increased in numbers, in the laboratory. Stem cells that come from a healthy donor they are called “allogenic,” those harvested from a patien are called “autologous.”
Embryonic stem cells
Embryonic stem cells are normally taken from an egg that has been fertilized in vitro (outside of the body), and then cultured in the laboratory. The egg will have been donated with explicit consent for this purpose.
As these cells are collected in very early developmental stages, they are called “pluripotent” cells, meaning that they have the potential to become any type of cell.
Embryonic stem cells are tightly regulated, and ethical issues surround their use. Concerns also exist that these cells may develop into tumors once transplanted.
No trials involving embryonic stem cells to treat scleroderma have been carried out to date.
Adult stem cells
Adult stem cells are considered “multipotent,” as generally there is a limited range of cell types that they can become. In the body, they replace cells in tissues that have continual turnover, such as the skin, small intestine, and blood.
Their source can define the types of cells they can become.
Hematopoietic stem cells
Hematopoietic stem cells are those found in the bone marrow. These constantly replenish the blood.
They can be harvested directly from bone marrow or from the peripheral (circulating) blood and umbilical cord blood.
Hematopoietic stem cells have been investigated in a number of clinical trials for the treatment of scleroderma. A recent trial (NCT00114530), which ended in January 2018, suggested that treatment with hematopoietic stem cells holds promise for scleroderma patients compared to standard immunosuppressive therapy.
Mesenchymal stem cells
Mesenchymal stem cells can be found in several tissues and can become bone, cartilage, muscle, tendon, and fat cells.
These cells are generally harvested from bone marrow, but can be obtained from tissues that include fat tissue, umbilical cord blood, and the placenta.
Neural stem cells
Neural stem cells are found in the central nervous system. They have the potential to become nerve cells and cells supporting the nervous system, such as oligodendrocytes and astrocytes. These cells are harvested from brain tissue, and are used in studies aiming to repair damage to the nervous system. They have not been investigated in scleroderma to date.
Other types of adult stem cells
Other types of adult stem cells include skin stem cells, and epithelial stem cells from other organs such as the intestine. These have not been considered for use in scleroderma patients at this time.
Induced pluripotent stem cells
Induced pluripotent stem cells, or iPSCs, are an experimental type of adult cell that has been reprogrammed to behave like an embryonic stem cell. These cells also have the potential to become any type of cell. There are fewer ethical issues surrounding the use of iPSCs compared to embryonic stem cells. However, they have not yet been considered as a potential scleroderma therapy.
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