Where do stem cells come from?
Embryonic stem cells are derived from the inner cell mass of a blastocyst: the fertilized egg, called the zygote, divides and forms two cells; each of these cells divides again, and so on. Soon there is a hollow ball of about 150 cells called the blastocyst that contains two types of cells, the trophoblast and the inner cell mass. Embryonic stem cells are obtained from the inner cell mass.
A stem cell is a cell that has the ability to continuously divide and differentiate (develop) into various other kind(s) of cells and tissues. Like a blank microchip that can ultimately be programmed to perform any one of a number of specialized tasks, stem cells are undifferentiated, ‘blank’ cells that do not yet have a specific physiological function. When the proper conditions occur in the body or in the laboratory, stem cells begin to develop into specialized tissues and organs. Stem cells are also self-sustaining, replicating through cell division. These unique characteristics are why stem cell research holds such great promise for the treatment of life-threatening and debilitating diseases such as Alzheimer’s disease, cancer, Parkinson’s disease, and juvenile diabetes. Understanding what the genetic and biochemical signs are that trigger stem cell differentiation may allow researchers to one day program new cells to repair damaged tissues and organs, and to better understand dise
Researchers have discovered several sources of stem cells: Embryonic stem cells. These stem cells come from embryos that are four to five days old. At this stage, an embryo is called a blastocyst and has about 150 cells. These are pluripotent (ploo-RIP-uh-tunt) stem cells, meaning they can divide into more stem cells or they can specialize and become any type of body cell. Because of this versatility, embryonic stem cells have the highest potential for use to regenerate or repair diseased tissue and organs in people. Adult stem cells. These stem cells are found in small numbers in most adult tissues, such as bone marrow. Adult stem cells are also found in children and in placentas and umbilical cords. Because of that, a more precise term is somatic stem cell, meaning “of the body.” Until recently, it was felt that adult stem cells could only create similar types of cells. For instance, it was thought that stem cells residing in the bone marrow could give rise only to blood cells. Howev
There are several sources of stem cells. Pluripotent stem cells can be isolated from human embryos that are a few days old. Cells from these embryos can be used to create pluripotent stem cell “lines” —cell cultures that can be grown indefinitely in the laboratory. Pluripotent stem cell lines have also been developed from fetal tissue (older than 8 weeks of development).
Pluripotent stem cells are isolated from human embryos that are a few days old. Cells from these embryos can be used to create pluripotent stem cell “lines” cell cultures that can be grown indefinitely in the laboratory. Pluripotent stem cell lines have also been developed from fetal tissue obtained from fetal tissue (older than 8 weeks of development).
