What Induced Pluripotent Stem Cells Can Tell Us About Disease - Printable Version
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What Induced Pluripotent Stem Cells Can Tell Us About Disease - bridgettpayseur - 05-02-2013
Updates From Experimental Biology Expo 2013
For many years, stem cells have been touted as a potential cure for a variety of human diseases and injuries. Stem cells are immature cells that are able to mature into a wide variety of fully developed cells. There are two main types of stem cells considered for medical research. Embryonic stem cells are obtained from early stage embryos. Adult stem cells are obtained from tissue from adults, such as bone marrow. Embryonic stem cells are more plastic than adult stem cells, which means they have the potential to mature into a broader range of cell types. However, because obtaining embryonic stem cells involves destruction of a human embryo, there are many ethical concerns to using embryonic stem cells. Because adult stem cells can be obtained from a living person, there is no such ethical concern. In addition, adult stem cells can be obtained from a patient, matured into the desired cell type, and re-injected into the patient, removing any possibility of transplant rejection.
The use of stem cells has been controversial, largely due to the use of embryos to produce the stem cells. Originally, cloning of embryonic stem cells was performed as a way for scientists to learn about diseases. In order to study these diseases, scientists began trying to understand the process of therapeutic cloning. The first successful cloning of a mammal was Dolly the sheep in the 1990s, an achievement that paved the way for researching the growth of embryonic origin cells from mammals. This achievement also proved that animal egg cells could be manipulated to help develop stem cells that could develop into every type of body cell.
One of the original goals researchers had was to be able to eventually grow organs in tissue culture to study disease states. Another long term goal of cloning was to be able to produce organs for human transplant. However, because of the nature of obtaining stem cells from embryos and the controversy involved, studies such as these were not widely accepted by the public. Researchers also wanted to grow stem cells in tissue culture dishes in order to study how normal tissue develops. Understanding how these developments occur can help researchers determine what goes wrong during the disease process.
In the past few years, researchers have discovered how to reprogram matured adult cells into a less mature state. These cells are called induced pluripotent stem cells (iPSCs). The reprogramming involves sending signals to the nucleus of the cell that tells the cell to revert to an immature, undeveloped state. iPSCs can be developed into many more types of cells than adult stem cells, and are therefore more versatile. iPSCs are very similar to embryonic stem cells, but because of their adult origin, production of these cells does not have as many ethical considerations.
iPSCs have many advantages to both embryonic stem cells as well as adult stem cells. As mentioned above, iPSCs do not pose any of the ethical dilemmas that embryonic stem cells do. In additional, because of Bush era funding restrictions, many of the embryonic stem cell lines in use today have been around for many years. These cell lines were grown with mouse origin feeder cells, meaning they are no longer consider pure human cell lines. Because of this, any mature cells derived from these embryonic stem cell lines would not be suitable for human transplantation. In addition, because of their rapid replication and the large number of generations they have been grown in culture, embryonic stem cells are prone to mutations. These mutations may also cause problems when transplanted into humans, as the cells would be highly prone to developing cancerous tumors. Because iPSCs could be developed directly from cells obtain from the patient, they would not been grown for long periods of times in mouse feeder cells, and they would not have had a chance to acquire as many mutations. This would make adult stem cells matured from iPSCs much safer for use in transplantation than cells matured from embryonic stem cells. In addition, many scientists now believe that instead of growing entire organs, such as a kidney or liver, in tissue culture, they can simply inject matured iPSCs into the patient in order to repair damaged organs. The overall desire to use stem cells to treat a multitude of human diseases remain the same, but the methods being explored have changed a great deal since studies of therapeutic cloning began.