Wednesday, February 15, 2006

Medicine - Stem Cells - A Primer

image : © 2005 Advanced Cell Technology

Stem cells have been at the heart of serious debates between all types of politicians, bio-ethicists, church groups, patient advocacy groups, liberals, conservatives and everyone in between. Unfortunately, many people don't understand what the hoopla is all about, so here's a quick introduction on the subject.

A stem cell is a generic type of cell that has the ability to renew itself for long periods of time (or indefinitely in some cases) and has the amazing ability to become one of a host of different cell types including heart cells, skin cells, liver cells, muscle cells, nerve cells and others. This "specialization" process that occurs when a "generic" stem cell becomes a specific type of cell - is called differentiation.

A large population of scientists, doctors and patients are very excited because they envision stem cells providing a nearly infinite supply of new cells that can help fight a variety of medical conditions and diseases that tend to destroy cells in their path - some examples include Parkinson's disease, diabetes, chronic heart disease, end-stage kidney disease, liver failure, and cancer.

So you're probably asking, "what the h@ll are we waiting for ... let's go cure some diseases" - well its not that simple. It seems that all stem cells are not created equal. Stem cells come in different flavors, we'll focus on the following 2 flavors:

  • pluripotent - this stem cell can become any type of cell in the human body.
  • unipotent - this stem cell can only become one type of cell or a small set of cell types of a particular tissue in the body (for example - only cells that are found in the liver)

Now, unipotent stem cells have been found in several areas of the adult body including the bone marrow, blood, the cornea and the retina of the eye, brain, skeletal muscle, dental pulp, liver, skin, the lining of the gastrointestinal tract, and pancreas. Even though several sources and types of unipotent stem cells have been found they are rare and difficult to isolate from the adult body.

It should be obvious that the pluripotent stem cell is much more valuable since it can become ANY type of cell in the human body versus only one type of cell but here's the catch !! -- this type of stem cell has only been found in embryonic tissue of early stage embryos.

To clarify, pluripotent stem cells are found in embryonic tissue and are usually referred to as embryonic stem cells while unipotent stem cells are found in adult tissues and are usually referred to as adult stem cells.

This is why the stem cells issue has been so contentious in America - because it ran smack into the middle of the entire pro-life / pro-choice debate and as we all know - no matter what side you're on -America is split right down the middle on this topic.

  • When does life begin? At conception (a fertilized egg)? or when the heart starts beating?
  • When does a fetus gain recognition as a citizen and afforded protections by the law?

Embryonic stem cells provide an interesting twist to this debate since they may hold the potential for significant medical breakthroughs that affect millions of diseased Americans today. We will delve deeper into the science, the politics and the major players involved in a future blog post.

Some additional resources:

National Institutes of Health - Stem Cells
University of Wisconsin
President Bush Stem Cell Speech - 2001
Advanced Cell Techonogy

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