Some of the organs in the body contain stem cells called adult stem cells. These persist throughout life and contribute to the maintenance and repair of those organs. Not every organ has been found to have these cells and generally adult stem cells have restricted development potential. This means that there capacity for proliferation is limited and they can only give rise to a few cell types.
Embryonic stem cells can divide almost indefinitely and can give rise to every cell type in the body. This suggests that they may be the most versatile source of cells for research and transplantation therapies.
Induced pluripotent stem cells are derived from somatic (adult, non-germaline) cells, that have been reverted to an embryonic stem cell-like state. Induced pluripotent stem cells are like embryonic stem cells in that they can be differentiated into any cell in the body. This makes them pluripotent.
The process of creating these cells is often referred as reprogramming and it involves introducing a combination of three or four genes for transcription factors delivered by retroviruses into the somatic cells. More recent methods for doing this have replaced and reduced the number of genes required for the transformation.
Alternative delivery methods to get the genes into the cell and replacing the genes with chemical factors have also been introduced. Cells can be taken from patients with specific diseases such as Parkinson’s or cardiovascular disease and induced to form iPS cells. There are multiple uses that can be derived from iPS cells when they are differentiated to more specialized cells types and this includes the development of assays for studying disease processes, testing new drugs for safety and effectiveness and being applied to regenerative medicine.
Stem cells can be used to generate cell lines specific to a particular patient with a particular disease. By matching the biological data from these cells with the clinical history of the patient, it could be possible to extract more relevant information on the linkage between molecular pathways and the cause of disease.
Cell lines can be derived from stem cells for specific tissues such as heart muscle, specific types of neurons, kidney cells, etc. and used in biological assays to screen thousands of chemical compounds for their safety and effectiveness in treating disease. Stem cells also play an important role in expanding our knowledge of embryonic and fetal development, helping researchers to identify the cells and molecules responsible for guiding the patterns of normal (and abnormal) tissue and organ formation.
Stem cells really are more than just a source of potential replacement parts, they provide researchers with an essential tool for better understanding normal and disease biology and evaluating other modes of treatment.