Critics, on the other hand, say that nobody gives us the right to use embryos as a spare part factory. They see embryos as human beings. Killing them after a few days is morally wrong. They say that stem cells should only be taken from adult tissue.
Adult stem cells are found in the skin, liver, bone marrow and other places. These natural stem cells repair damaged cells and replace them when they are needed. However, in contrast to embryos, adult stem cells are harder to get and may not last as long.
Medical experts point out possible risk factors in changing stem cells and transplanting them into an ill person’s body. Such transplants may transmit other diseases and stem cells may risk turning into cancer cells.
Scientists have recently conducted experiments that make stem cells out of blood cells. This could offer a fast and easy way of producing stem cells, but it may take many years until such a treatment is widely available.