Stem Cells Quick Reference
Embryonic Stem Cells
Embryonic stem (ES) cells are formed as a normal part of embryonic development. They can be isolated from an early embryo and grown in a dish.
Potential as therapy
ES cells have the potential to become any type of cell in the body, making them a promising source of cells for treating many diseases.
Special considerations
Without drugs that suppress the immune system, a patient's immune system will recognize transplanted cells as foreign and attack them.
Ethical considerations
When scientists isolate human embryonic stem (hES) cells in the lab, they destroy an embryo. The ethical and legal implications of this have made some relunctant to support research involving hES cells.
Learn more about the controversy behind embryonic stem cells, and why iPS cells may bring it to an end. The Stem Cell Debate: Is It Over?
Somatic Stem Cells
Somatic stem cells (also called adult stem cells) exist naturally in the body. They are important for growth, healing, and replacing cells that are lost through daily wear and tear.
Potential as therapy
Stem cells from the blood and bone marrow are routinely used as a treatment for blood-related diseases. However, under natural circumstances somatic stem cells can become only a subset of related cell types. Bone marrow stem cells, for example, differentiate primarily into blood cells. This partial differentiation can be an advantage when you want to produce blood cells; but it is a disadvantage if you're interested in producing an unrelated cell type.
Special considerations
Most types of somatic stem cells are present in low abundance and are difficult to isolate and grow in culture. Isolation of some types could cause considerable tissue or organ damage, as in the heart or brain. Somatic stem cells can be transplanted from donor to patient, but without drugs that suppress the immune system, a patient's immune system will recognize transplanted cells as foreign and attack them.
Ethical considerations
Therapy involving somatic stem cells is not controversial; however, it is subject to the same ethical considerations that apply to all medical procedures.
Induced Pluripotent Stem Cells
Induced pluripotent stem (iPS) cells are created artificially in the lab by "reprogramming" a patient's own cells. iPS cells can be made from readily available cells including fat, skin, and fibroblasts (cells that produce connective tissue).
Potential as therapy
Mouse iPS cells can become any cell in the body (or even a whole mouse). Although more analysis is needed, the same appears to be true for human iPS cells, making them a promising source of cells for treating many diseases. Importantly, since iPS cells can be made from a patient's own cells, there is no danger that their immune system will reject them.
Special considerations
iPS cells are much less expensive to create than ES cells generated through therapeutic cloning (another type of patient-specific stem cell; see below).
Ethical considerations
Therapy involving iPS cells is subject to the same ethical considerations that apply to all medical procedures.
Therapeutic Cloning
Therapeutic cloning is a method for creating patient-specific embryonic stem (ES) cells.
Potential as therapy
Therapeutic cloning can, in theory, generate ES cells with the potential to become any type of cell in the body. In addition, since these cells are made from a patient's own DNA, there is no danger of rejection by the immune system.
Special considerations
Scientists have not been able to grow a cloned human embryo to the blastocyst stage. In other animals, the cloning process has been time consuming, inefficient, and expensive.
Ethical considerations
Therapeutic cloning brings up considerable ethical considerations. It involves creating a clone of a human being and destroying the cloned embryo, and it requires a human egg donor.
Learn more about somatic cell nuclear transfer: Click and Clone
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