Basic question about stem cells

A 14 year old reader wondered about the basics of stem cell biology. Here's a repeat of a prior post that addresses some of this:

Some Basics on Adult Stem Cells

All information on this page is summarized from the website of the International Society for Stem Cell Research. Since it’s a slow news day, I thought it might be useful to update the blog with some VERY basic information about non-embryonic stem cells. Any errors in the science are my own.

There are several types of stem cells besides embryonic stem cells that are being studied and/or used in therapies throughout the world.

Adult stem cells have different properties depending upon where they are derived from. Their ability to differentiate and the extent of such differentiation is still not well understood.

Hematopoietic stem cells are a type of adult stem cell produced by human bone marrow. They can be used to produce different kinds of blood cells, are easily obtained from bone marrow or directly from the blood, and have been used in therapies for blood cancers and other diseases for years. It is unknown at present if they can differentiate into cells other than blood cells. (See the 9-18-05 Post “Stem Cell Recipients Mostly Healthy 10 Years Later” for a discussion of a study on HCTs.)

Mesenchymal stem cells are also adult stem cells which are produced by the bone marrow, but they are able to differentiate into several different kinds of cells, including fat cells, muscles cells, bone and cartilage cells, tendon and ligament cells, skin cells, and nerve cells. (The ability to differentiate into a variety of cells is known as pluripotency.) They are easily cultured in the laboratory and can be preserved by freezing. Animal trials on tissue repair with mesenchymal stem cells have shown promise.

Umbilical cord stem cells (also known as neo-natal stem cells) are a different form of hematopoietic stem cells. They are obtained from the blood of a newborn infant’s umbilical cord and are less mature than stem cells obtained from the bone marrow of children or adults. In the treatment of blood cancers and diseases, cord blood grafts are less likely to produce an immune system response from the recipient than bone marrow grafts. However, the use of cord blood cells for tissue regeneration is probably subject to the same risk of rejection as regular organ donations.

All stem cells, whether embronic or adult, work through basic cell division. They split into two: one cell remains an exact copy of the original stem cell and is able to further divide into more stem cells. The other cell, known as the daughter cell, is larger than the copied stem cell and it is the one that differentiates into a cell of a specific body types. Embryonic stem cells are much more flexible in what they differentiate into than adult stem cells. (It's easy to see why--the single cell that is a fertilized egg eventually divides into every cell in the body, so embryonic stem cells have the capacity to do the same thing. Adult stem cells, on the other hand, can be understood through our body's healing process; when we cut a skin or break a bone, we grow new cells of the apporpiate type. The adult cells already have jobs, so to speak.)

What makes a stem cell differentiate into a particular kind of cell? That's the million dollar question that researchers are working on.

Besides the link above, another good basic source is the National Institute of Health Stem Cell Information, http://stemcells.nih.gov/index.asp. There are also some links under Other Resources on this blog that have stem cell info.

Good luck to you!