There are a number of sources for obtaining human stem cells. The first is IVF (In Vitro Fertilization) treatment, where surplus embryos (and unfertilized eggs for creating embryos) are donated for research with the consent of the donor rather than being destroyed following treatment. The second source is aborted tissues, which are used as stem cells taken from the aborted foetus. Another is umbilical cord blood, rich in stem cells. These cells are harvested following the baby's birth.
The most controversial is perhaps therapeutic cloning, where cells are created for research that is genetically identical to the donor (patient). This is done by removing the nucleus of an egg and fusing this egg with any enucleated cell from the donor. This will create an embryo genetically identical to the donor. Cells can then be harvested from this embryo for treatment. Being an exact replica, there is potentially less chance of rejection following transplantation.
The US President's Council on Bioethics recently published a whole white paper on Alternate Sources of Human Pluripotent Stem Cells (www.bioethics.gov). Sometimes these cells could be taken from the recipient patients themselves, avoiding any immune-rejection difficulties. At other times they are taken from donors. There are even proposals to create new non-embryonic organisms which can produce human stem-cells. What all these 'adult' stem-cells have in common is that they are derived from people without harming anyone. Umbilical cord blood, the placenta and even the amniotic fluid have in fact been found to be rich in stem-cells (McGuckin et al 245-255). Stem-cells have also been found in all the tissues found in our bodies such as the brain, pancreas, liver, skin, fat, muscle, blood, bone marrow, lungs, nose and tooth pulp.
There is substantial opposition from various religious groups on the ethical issues. One of the most important concerns is that embryonic stem-cells are taken from human embryos. It basically involves killing the embryos which is destined to become a complete human being if it is allowed to. These embryos are taken in the very early stages of their development and hence are very small, having only developed to the stage of 120 cells or so since their creation by IVF or, more recently, by cloning. They are still young-approximately 5 to 6 days old-and grown in a culture in some Petri dish; they might even be a few years old, having been stored in some freezer soon after their manufacture (Fisher 2005).
The main area of controversy surrounding this research arises from the harvesting of cells for research. The most flexible stem cells are obtained from embryos owing to their ability to become any type of tissue cell in the body. In fact it is a proven fact that adult stem cells also have similar possibilities. An embryonic stem cell is derived as follows- A fertilized egg forms a blastocyst 4 days after conception. This blastocyst has two types of cells; an outer layer (which becomes the placenta and other supporting tissues needed for foetal development) and an inner cell mass (the stem cells). In order to harvest these cells, they are removed from the blastocyst, a