Stem cells are cells that are non-specialized cells that can become a specialized cell to help repair damage to the human body. Stem cells are derived from two main sources, embryos and adult tissues. Embryonic stem cells are less specialized than the adult stem cells and are currently easier for scientists to work with. The human body is constantly renewing itself and some areas do this better than others, such as bone marrow and the stomach, because of the stem cells that divide there and help renew the tissue.
Adult Tissue Stem Cells
Adult tissue stem cells are more specialized than embryonic stem cells and while scientists thought that stem cells could only become cells of their originating tissues new evidence shows that they can become other types of tissues as well. The first step in producing more stem cells starts with the isolation of the stem cells from other cells that are harvested. There are many different ways for scientists to extract and separate stem cells and each has its own positives and negatives. With blood stem cells, for example, the blood is drawn from the body and then run through a centrifuge, known as apheresis, in a process known as density gradient centrifugation-negative selection. The apheresis helps scientist separates the stem cells out of the blood where they then can be frozen until they are transplanted to the recipient. When extracting stem cells from bone marrow, general anesthesia is required and the donor can have a two to a three-day hospital stay. The extraction process for this method also requires a needle to be stuck into the donorship bone, where the bone marrow is then removed. There are some side effects for the donor in this method, mainly pain in the removal site and a sore back.
Embryonic Stem Cells
Embryonic stem cells are non-specialized and can become any tissue that the body needs to be repaired. After seven to ten days post-fertilization, embryonic stem cells appear and this is where these cells come from. Most harvesting of embryonic stem cells comes from in vitro fertilization clinics, or IVF, where doctors fertilize multiple eggs in a test tube and then harvest the stem cells when they are present. Umbilical cords are also a source for this type of stem cell and can be donated to a blood bank or stored at a private umbilical cord blood bank, should the child ever need it.
Stem cells are being studied further every day and scientists and doctors are learning more as time goes on. Adult tissue stem cells, which were once thought to only be able to help restore tissues from the organ in which they originated, have now been found to be able to become other tissues as well and thus able to repair other organs. There are many different ways for the stem cells to be extracted and separated for further use. Embryonic stem cells are mainly produced for medical uses at an IVF clinic where doctors fertilize embryos and wait until the stem cells are present to extract them.