What exactly does Stem Cell Research involve?

Stem cells are precursor cells: that is they have the potential to change into (differentiate) every specialised cell type in the body (eg nerve, heart, muscle, bone, liver etc). Many scientists are trying to find out how to reproducibly turn stem cells into a particular cell type and in large numbers, and just as importantly keep the cells as that type. If that can be done then the possibility of using them for transplant or repair of damaged or diseased organs/tissues is enormous!

(Not an answer, but a followup question.)

There is a lot of ethical controversy regarding stem-cell research because the cells are (usually?) harvested from human embryos.  My question is: is there another source of stem cells?  Also, when salamanders and other such animals are able to regenerate lost limbs, is that because they still produce stem cells in adulthood?

I assume your question is: is there another source of human [adult] stem cells? If so the answer is very definitely yes - the main source is the bone marrow and some parts of the brain. However these adult "stem" cells would more accurately be called precursor cells since they are not totipotent (able to differentiate into all cell types). Hardly a week goes by without a new advance and sceptical as I am about the field I have a real expectation that transplants will be a reality for a range of conditions (not just the very rare single gene recessive mutations) within the next 5-years (you heard it first here folks).

as to salamaders and tails - the answer is yes but again it is precursor rather than stem cells.

As a final year undergrad student I worked in a lab that worked on hemopoietic (blood-forming) stem cells. Although they're called stem-cells, like David mentioned, these are blood-forming precursor cells usually developed in the bone marrow and are already destined to become blood cells (i.e. red blood cells and different types of white blood cells). But they have the ability to become any of the blood cells they are capable of depending on the substances they are subjected to during maturation, hence they are known as multipotent. Hemopoietic stem cells differentiate through cell-to-cell interactions with bone marrow stromal cells (connective tissue cells). Our lab focused on these cell-to-cell interactions that determined cell differentiation and researched which surface molecules were responsible.

The great thing about precursor cells is that you can get them from adults and thus could avoid any ethical issues usually associated with embryonic stem cells. It's been some time since I was involved in any of this but the last I heard was that researchers are trying to find a way to revert these precursor cells into a totipotent stem cell that can be manipulated into differentiating into any desired cell type.

So, it's actually somewhat misleading when someone addresses the ethical problems of stem cell research because there are many multipotent stem cells in our body besides embryonic stem cells. They may not be completely totipotent as embryonic stem cells but they are good candidates for engineering into such a state.

Last edited by Manabu Sakamoto (9th Jul 2007 12:17:05)