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by Jennifer Purdes
Imagine a world where one can simply stop by the cell bank, order a new liver, and drop in to pick it up a few days later. While it may never be quite as simple as this, the new and controversial field of stem cell research has been taking giant steps toward making this approach to medicine a reality.
Human stem cell research began making its way into mainstream medical research only in the past few years. In 1998, a pluripotent human stem cell, one that is able to differentiate into any type of cell in the body, was first isolated from human embryos donated by couples undergoing infertility treatment. Since then, scientists have been making steady progress toward discovering countless potential applications of stem cells in the treatment of common, and to date incurable, diseases such as Alzheimer's, Parkinson's, and diabetes.
The world of stem cell research is no further away than the 14th floor of Moos Tower, where the University of Minnesota's Stem Cell Institute resides. The Institute has been working to unlock the secrets of human stem cells, with the goal of applying this knowledge towards creating therapies to treat many debilitating diseases.
What is a stem cell?
There are two types of stem cells: embryonic and adult. An embryonic stem cell has the ability to self-replicate indefinitely as well as to differentiate into cells of any tissue in the body. Embryonic stem cells are taken from the inner mass (30-34 cells of the 200-250 cells making up the embryo) of the blastocyst stage five days after fertilization. The embryonic stem cells are known to be pluripotent.
While adult stem cells possess the ability to replicate in large quantities, they do not replicate indefinitely and exponentially like embryonic stem cells do. As for function, embryonic stem cells give rise to the rest of the body whereas adult stem cells generally maintain homeostasis and replace cells that die.
Adult stem cells are taken from tissues such as bone marrow, the retina, the cornea, dental pulp, the brain, the liver, and skin. These cells, found in specialized tissue, are still undifferentiated, though for the most part they are already "programmed" to differentiate into a certain line of cells. Those cells found in the bone marrow tend to develop into new blood cells among other cells, while those found in the liver tend to differentiate into liver cells. At least this had been the hypothesis held in the past. The ability of adult stem cells to differentiate into cells not typical for the tissue in which they are found, known as plasticity, is a hot topic in today's research and one being tackled by the Stem Cell Institute.
The Stem Cell Institute
The main focus of the Stem Cell Institute is to study the biology of human stem cells, how they grow, and how they differentiate. The Institute has grown more than 1050 cells from single mouse and rat stem cells over the course of the past two years. For human cells, the number is about 1035. One of the major breakthroughs that the Stem Cell Institute has made is the discovery that a single human stem cell from bone marrow can be introduced into foreign soft tissue, where it will survive and replicate.
Currently, the Institute is anxiously awaiting the approval of a recently submitted paper by the Institute's director, Dr. Catherine Verfaillie. This paper outlines recent experiments that have shown an adult stem cell placed into a mouse blastocyst will differentiate into cells types that make up all body tissues. This exciting result shows the possible pluripotency of adult stem cells, which have conventionally been thought as already set to differentiate in a specific direction.
Another goal of the Stem Cell Institute is to apply the information gained from its research to fashion therapies using these cells. At the moment, the Institute is attempting to differentiate adult stem cells into mature liver cells. Presently only the differentiation to early stage liver cells has been achieved. The Institute, however, has grown fully mature cells of all three types of tissues that comprise an artery. The remaining question is how to assemble these tissues so they form an actual artery.
The Future: What Does it Hold?
Where it was once thought impossible to repair damage to the nervous system, an experiment carried out by researchers at Johns Hopkins University has proven that new neurons can be grown out of adult stem cells and will function when inserted into an organism. A mouse was subjected to a virus that destroys the motor neurons and thus became paralyzed. After receiving stem call therapy, the mouse showed movement, while those that did not receive treatment remained paralyzed. Currently incurable problems such as neural diseases (including Alzheimer's) and paralysis may become a thing of the past.
Looking towards the future, Verfaillie paints a picture of what would seem to be science fiction. A person would have a culture of their own stem cells, retrieved earlier either from a sample of bone marrow or from their own embryonic stage, stored in a cell bank. These cells could later be used to grow entire new organs such as a bioartificial liver or create a "heart patch" to replace scar tissue that forms on the heart if the blood supply to the heart is cut off).
These examples are just a taste of what may be possible in the future thanks to stem cell research. Verfaille speculates, "Ten or twenty years from now, medical science is going to be a completely different ball game."
FOR MORE INFORMATION:
www.umn.edu/stemcell
www.news.wise.edu/packages/stemcells
www.nih.gov/news/stemcells/
