Stem cells are biological cells found in all multicellular organisms that can divide through mitosis and differentiate into diverse specialized cell types or can self renew to produce more stem cells. In mammals, there are two broad types of stem cells: embryonic stem cells that are isolated from the inner cell mass of blastocysts, and adult stem cells that are found in various tissues. In adult organisms stem cells and progenitor cells act as a repair system for the body; however, in a developing embryo, they can differentiate into all the specialized cells but also maintain the normal turnover of regenerative organs.
Embryonic stem cell lines are cultures of cells derived from the epiblast tissue of the inner cell mass of a blastocyst or an early stage embryo ( usually 3-5 days old). Embryonic stem cells are pluripotent and give rise during development to all derivatives of the three primary germ layers: ectoderm, endoderm, and mesoderm. In other words, they can develop into each of the the more than 200 cell types in the adult body. In July 2008 an update on the subject of stem cell research has a potentially revolutionary development. Japanese researcher Shinua Yamanaka discovered how to take ordinary skin cells from and adult mouse, turn back the genetic clock, and transform them into an equivalent of embryonic stem cells. All research to date has taken place using mouse embryonic stem cells or human embryonic stem cells (both have essential stem cell characteristics but need different environments in order to maintain and undifferentiated state); but, after nearly ten years of research there are no approved treatments using embryonic stem cells.Adult stem cells, also known as somatic stem cells, are different. They are rare but can be found in a number of tissues including umbilical cord blood. A great deal of adult stem cell research had focused on clarifying their capacity to divide or self renew indefinitely. Adult stem cell treatments have been successful for many years to treat leukemia and related blood/bone cancers through bone marrow transplants. Also the use of Adult stem cells in research and therapy is not as controversial as Embryonic stem cells because their production does not require the destruction of an embryo.
In 1981, scientists discovered ways to derive embryonic stem cells from early mouse embryos. The study of the biology of the mouse's stem cells led to the discovery of a method to derive stem cells form human embryos and grow them cells in a laboratory. Embryos used in these studies were created for reproductive purposes through vitro fertilization procedures. Then in 2006 researchers made a breakthrough by identifying conditions that would allow some specialized adult cells to be reprogrammed genetically to assume a stem cell like state. This new type of stem cells are called induced pluripotent stem cells. Because of their generative abilities, they offer a new potential for treating diseases like diabetes and heart disease. Cells can also now be artificially grown and transformed into specialized cell types using cells that can be taken from a variety of sources like an umbilical cord or blood and bone marrow.As for treatments, medical researches believe that stem cells have the potential to dramatically change the treatment of human disease. New stem cells therapies exist like bone marrow transplants for leukemia and in the future researches anticipate being able to use technologies from stem cell research to treat a wider variety of diseases like other cancers, Parkinson's disease, spinal chord injuries etc; however, there is a great deal of of social and scientific uncertainty surrounding stem cell research. Once concern of treatment is the possible risk that the transplanted cells could form tumors and have the possibility of becoming cancerous if cell if cell division continues uncontrollably.
