Stem Cell Research Controversies

Stem cells are "blank" cells that have the potential to develop into any type of cell in the body -- nerve cells, heart cells, kidney cells. Scientists are trying to harvest the cells before they have differentiated, then coax them into becoming certain types. If they could grow cardiac cells, for instance, scientists one day might be able to replace damaged heart tissue in someone who has had a heart attack. By growing nerve cells they might be able to repair brain cells damaged by Alzheimer's or Parkinson's, or replace injured spinal cord cells in a paraplegic.

Stem cells have two important characteristics that distinguish them from other types of cells. First, they are unspecialized cells that renew themselves for long periods through cell division. The second is that under certain physiologic or experimental conditions, they can be induced to become cells with special functions, such as the beating cells of the heart muscle or the insulin-producing cells of the pancreas. Scientists primarily work with two kinds of stem cells from animals and humans: embryonic stem cells and adult stem cells. There are many ways in which human stem cells can be used in basic research and in clinical research. Studies of