When they originally hit the media scene, stem cells sparked discussions ranging from promises of a new age in medicine to ethical complaints from various human rights groups. Since the initial ethical controversy, stem cell research continued quietly over the past decade. But the topic is heating up again: in the past year, there have been experimental results which may promise a new field of regenerative medicine after all, allowing scientists to begin growing transplant organs and studying certain diseases in unique ways.
Given its various subtypes, what defines a stem cell? There are three types of stem cells: embryonic, adult, and induced pluripotent (iPS). Scientists can remove embryonic stem cells from human fetuses, but since this procedure destroys the fetus, this consequence has contributed to moral debate. Embryonic cells are pluripotent and can thus transform into any type of body cell. Adult stem cells, which are tissue-specific and cannot transform into cells of a different organ, lack this versatility. Yet out of these three types, scientists find growing iPS cells the most useful option. Scientists can reprogram any cell, typically a skin cell to be pluripotent. In other words, iPS cells are human, non-embryonic cells that behave like embryonic stem cells . The relative simplicity and ethical soundness of producing iPS cells over other types suggest that stem cell research really does have a future in regenerative medicine.
Though the better alternative, iPS cells could not be produced at a feasible volume for medical research. Low conversion rates from skin cells to pluripotent cells stagnated research. Even successfully converted cells did so at different times, creating problems with isolation. In September 2013, scientists found a way to finally overcome these issues with a surprisingly simple change. They removed a single protein known as Mbd3 from the cells, leading to a nearly 100% conversion rate “on a synchronized schedule” . In January 2014, a simplistic yet unexplained technique found mouse blood cells suddenly morphing into iPS cells when shocked with acid. Specifically, by introducing such stressors to the blood cells as “perforation of the cell membrane, exposure to an acidic solution, and physical squeezing,” the cells would become pluripotent. This method could ultimately produce stem cells ten times faster than normal. Despite the simplicity of this mass production technique, scientists still have little clue as to the mechanism .
Besides increasing rate of production, recent stem cell research promises a solution to a common issue with organ transplantation. The immune system of the patient often attacks the foreign, donor organ, creating a problem of compatibility. iPS cells overcome this challenge by following a very complex procedure designed by Dr. Mitalipov in 2013. A somatic cell nuclear transfer replaces DNA of a human egg cell with that of a skin cell, effectively tricking the egg cell to form an embryo, which is a genetic copy of the donor . Organs that are genetic copies of the individual, such as those grown using human embryonic stem cells, circumvent this problem.
If stem cell research changes the practice of organ transplantation, which organs can be feasibly produced? Hans-Willem Snoeck, M.D., Ph.D., professor of medicine from Columbia University recently stated, “Researchers have had relative success in turning human stem cells into heart cells, pancreatic beta cells, intestinal cells, liver cells, and nerve cells, raising all sorts of possibilities for regenerative medicine…”  Japanese scientists first produced human liver buds from iPS cells which, when mixed with certain cells, organized themselves into a structure resembling a functioning liver. Through a similar mechanism, Austrian scientists created structural parts of the human brain, such as the ventral forebrain or the choroid plexus, from both adult and embryonic stem cells.  Lastly, scientists from Columbia University produced lung epithelial cells from human embryonic and iPS cells which contained markers of at least six different types of lung epithelial cells, including one that produces surfactant, a necessary structural component of lung alveoli.  These three examples demonstrate the level of success that scientists have indeed achieved with producing human organs.
Collectively these research advances imply two impacts on medicinal application. The first regards organ transplantation. If entire organs could be produced from these cells, then transplantation would no longer require a donor. Organ transplant lists are tremendously long: on average 16,000 Americans are on a liver transplant list at any given time. Eliminating the need for a donor would mean instantly giving Americans the treatment they must normally wait for. This would also remove the financial burden on the patient of relying on medical treatment to stay alive while waiting for his or her organ on the transplant list.
The second application of these findings to medicine is in the study of disease. For example, in the case of the brain, scientists grew organoids from the skin cells of someone with microcephaly—a genetic disorder where the brain grows to be smaller than normal—and found that these organoids indeed grew to be smaller than normal due to premature cell division and the resulting depletion of normal cells . In the case of the lung, scientists can learn more about idiopathic pulmonary fibrosis by creating laboratory models of the disease and screening drugs on these cells for a possible cure . With organ production becoming more feasible and novel techniques for studying diseases, stem cell research is living up to its promise to transform medicine.
Over the past year alone, scientists have discovered techniques for both improving the efficiency and rate of stem cell production and successfully creating functional tissues of certain organs from stem cells. These findings together have strong applicability to medicine in terms of organ regeneration and the study of disease. As a result, stem cell research is more relevant to medicine than ever before and should no longer lie under the radar. It is time for the media to educate the public about this evolving field, because stem cell research’s transformative effects on medicine will likely be seen in the near future.
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- CUMC. Human Stem Cells Converted to Functional Lung Cells. [Internet]. 2013 Dec 1 [cited 02 Feb 2014]. Available from: http://newsroom.cumc.columbia.edu/blog/2013/12/01/human-stem-cells-converted-functional-lung-cells/
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