by Alicia M Prater PhD

Created on: April 14, 2008   Last Updated: March 23, 2011

Stem cells are important in natural development and occur as two types: embryonic and adult. In general, embryonic stem cells have the potential of becoming any cell in the human body, whereas adult stem cells are specialized to become a certain type of tissue, though they can be manipulated to take on the aspects of embryonic stem cells (induced pluripotency). Because of this capacity to create new cells, stem cells have the potential to regenerate tissue, heal wounds, and cure disease, as well as illuminate the mechanisms underlying human

development.

Characteristics of the Different Types of Stem Cells

Embryonic stem cells are present after fertilization, and the first cellular divisions begin to produce an organism as the embryo transitions through 4- and 8-cell blastocyst stages. These few cells eventually become every tissue and structure in the body through cell division and differentiation, a property called pluripotency. Stem cells are also present in these differentiated tissues (adult stem cells). Because these stem cells occur in differentiated tissue, there is some question as to whether they still hold pluripotent capacity, though the research into this has been ongoing.

Adult stem cells do potentially have the capacity to regenerate or heal the particular tissue of which they are a component, making them potentially useful for medical applications. The pluripotency of embryonic stem cells make them ideal candidates for applications in diseases affecting multiple organ systems or systems that lack their own stem cells. However, the use of one's own stem cells (i.e. adult or induced pluripotent stem cells) would minimize the potential for rejection by the body after treatment. The main question lies in discerning the signals that make stem cells become a particular type of cell. It is not for certain that such signals exist in both embryonic and adult stem cells. However, one problem with pluripotent cells is that they have the capacity to form tumors, so inducing a cell without knowledge of the particular signals, or placing an induced cell in a cellular environment conducive to undirected division, may result in tumor formation, an unwanted byproduct. A major test for stem cells before they can be applied clinically is to determine their potential for such unattractive side effects.

Potential to Cure Disease

The main research question being addressed in today's laboratories is the potential of stem cells to cure disease. Non-diseased cells being

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