Review: What we know about stem cells

The Journal, Stem Cells, has published a free open access article about those cells that become the different blood cells, including red blood cells, white blood cells and platelets, entitled "Concise Review: Hematopoietic Stem Cells and Tissue Stem Cells: Current Concepts and Unanswered Questions" by Donald Metcalf, MD, of Australia.

An interesting point from this article is the current controversy about the definition of "stem cells." Dr. Metcalf gives his definition and notes that some cells now called stem cells are actually better described as "self proliferative" progenitor cells, which have been committed to only fewer lines of cells.

Which will be important to understand the controversy that surrounds another type of stem cell, which is described in another, newer article published this week online in advance, entitled, "Concise Review: Mesenchymal Stem/Multi-Potent Stromal Cells (MSCs): The State of Transdifferentiation and Modes of Tissue Repair - Current Views" by Donald G. Phinney and Darwin J. Prockop of the Center for Gene Therapy, Tulane University Health Sciences Center, New Orleans, LA.

These adult stem cells are found in most organs and tissues in the body including umbilical cord blood, skeletal, muscle, fat, joint fluid, blood and the cells surrounding the blood vessels, the pulp in teeth, and amniotic fluid. (They have also been harvested from aborted infants.) In the body, they are known to become bone cells, fat cells, and cartilage. When they are grown in the lab, they form a wide variety of tissues depending on the conditions in which they are grown. They can be induced to form cells that function as nerve, lung tissue, retinal pigment cells, blood vessel cells, and repair kidneys and hearts.

However, you may read that these cells are not as "plastic" as embryonic stem cells, that it's hard to study them and cause them to form the exact cells that are desired. While it's true that they do not form "all the cells in the body," they can be induced to form a wide range of cells and tissues and it's no harder to control the development of these cells than it is to control embryonic stem cells. They may in fact be different types of progenitor cells, depending on the source, but there are an awful lot of sources. And they don't require the destruction of a human life.