| Stem cells are primal cells common to all | | | | making it unclear whether the cells will |
| multi-cellular organisms that retain the | | | | behave in a similar manner in vivo. |
| ability to renew themselves through cell | | | | Considerable debate exists whether some |
| division and can differentiate into a wide | | | | proposed adult cell populations are truly |
| range of specialized cell types. Research in | | | | stem cells. |
| the human stem cell field grew out of | | | | |
| findings by Canadian scientists Ernest A. | | | | • Totipotent stem cells are produced |
| McCulloch and James E. Till in the 1960s. | | | | from the fusion of an egg and sperm cell. |
| | | | Cells produced by the first few divisions of |
| A stem cell is a primitive type of cell that | | | | the fertilized egg are also totipotent. These |
| can be coaxed into developing into most of | | | | cells can differentiate into embryonic and |
| the 220 types of cells found in the human | | | | extraembryonic cell types. |
| body (e.g. blood cells, heart cells, brain | | | | |
| cells, etc). Some researchers regard them as | | | | • Pluripotent stem cells are the |
| offering the greatest potential for the | | | | descendants of totipotent cells and can |
| alleviation of human suffering since the | | | | differentiate into cells derived from the |
| development of antibiotics. Over 100 million | | | | three germ layers. |
| Americans and two billion other humans | | | | |
| worldwide suffer from diseases that may | | | | • Multipotent stem cells can produce |
| eventually be treated more effectively with | | | | only cells of a closely related family of |
| stem cells or even cured. These include heart | | | | cells. |
| disease, diabetes, and certain types of | | | | |
| cancer. | | | | • Unipotent cells can produce only one |
| | | | cell type, but have the property of |
| Stem cells can be extracted from very young | | | | self-renewal which distinguishes them from |
| human embryos -- typically from surplus | | | | non-stem cells. |
| frozen embryos left over from in-vitro | | | | |
| fertilization (IVF) procedures at fertility | | | | Treatments |
| clinics. A couple undergoing IVF is faced | | | | |
| with four alternatives for their 16 or so | | | | Medical researchers believe that stem cell |
| surplus embryos: | | | | therapy has the potential to radically change |
| | | | the treatment of human disease. A number of |
| There are very few parents willing to give | | | | adult stem cell therapies already exist, |
| their embryos to another couple for a variety | | | | particularly bone marrow transplants that are |
| of emotional reasons. There are very few | | | | used to treat leukaemia. In the future, |
| couples willing to receive them for emotional | | | | medical researchers anticipate being able to |
| reasons and because thawed embryos have such | | | | use technologies derived from stem cell |
| a low chance of starting a pregnancy. | | | | research to treat a wider variety of diseases |
| Preservation can be expensive. | | | | including cancer, parkinson's disease, spinal |
| | | | cord injuries, and muscle damage, amongst a |
| Stem cell properties | | | | number of other impairments and conditions. |
| | | | However, there still exists a great deal of |
| These properties can be illustrated in vitro, | | | | social and scientific uncertainty surrounding |
| using methods such as clonogenic assays, | | | | stem cell research, which could possibly be |
| where the progeny of single cell is | | | | overcome through public debate and future |
| characterized. However, in vitro culture | | | | research. |
| conditions can alter the behavior of cells, | | | | |