Читать книгу The SAGE Encyclopedia of Stem Cell Research - Группа авторов - Страница 362
Origins of Stem Cells
ОглавлениеStem cells are precursors to the somatic cells that make up functional adult tissue types, and are classified by their plasticity. Totipotent cells are found in embryonic tissue and are capable of giving rise to an entire organism and all of its various tissue types. Pluripotent cells can also mature into any tissue type but cannot result in a complete organism, whereas multipotent cells (aka adult stem cells) develop into only a very specific set of tissue types and are usually found only within that existing tissue type.
iPSC and iASC are adult stem cells that have been induced from a multipotent state to a pluripotency and are themselves subclassified by origin. Totipotent stem cells can be created in the lab by use of somatic cell nuclear transfer (SCNT), where the complete genetic material of an adult donor cell is inserted into the nucleus of an egg (oocyte). The use of SCNT remains volatile as some argue the implanted oocyte becomes a viable, independent embryo and defeats many of the ethical benefits of iASC.
Allogeneic iASC are cells collected from a donor, with the best-known being those collected from neonate umbilical cords and cord blood. When used therapeutically, the same precautions against immune rejection must be taken as with organ transplants. Conversely, autologous stem cells (or syngeneic stem cells) are collected and induced directly from the receiving patient’s own body or from an identical twin (respectively). Because they do not require immune suppressive therapy after implantation, and skirt most stem cell controversies, this is where much of the current research is focused.