Embryonic vs. Adult
All stem cells are characterized by the ability to self-replicate (make themselves) and the ability to turn into other cell types. However, there are two main categories of stem cells, Stem Cells
Undifferentiated cells,
Undifferentiated Cells
Cells that can become other cell types. They have not yet decided their fate; what type of cell they will become.
that can give rise to more mature differentiated cells and have the ability to self-replicate. There are many kinds of stem cells - adult stem cells (AS), embryonic cells (ES), embryonic germ cells (EG).
Embryonic stem cells Embryonic Stem Cells Embryonic Stem Cells
Pluripotent cells that can differentiate into various tissues in the body.
Pluripotent Pluripotent Stem-Cells
Stem cells, which can develop into any of the three major tissue types: endoderm (interior gut lining), mesoderm (muscle, bone, blood), and ectoderm (epidermal tissues and nervous system). Pluripotent stem cells can eventually specialize in any bodily tissue, but they cannot themselves develop into a human being.
cells that can differentiate into various tissues in the body.
Morula
A morula (Latin "morus", mulberry) is an embryo at an early stage of embryonic development, consisting of approximately 12-32 cells (called blastomeres) in a solid ball contained within the zona pellucida.
Blastocysts
A preimplantation
embryo Embryo
Organisms in the early stages of growth and development. In human, “embryo” generally refers to the time from implantation to about eight to twelve weeks after conception.
of about 150 cells produced by cell division following fertilization. The blastocyst is a sphere made up of an outer layer of cells (the trophoblast), a fluid-filled cavity (the blastocoel), and a cluster of cells on the interior (the inner cell mass).
As ES cells grow and mature, they begin to differentiate into specific cell type. At that point cells have more limited potential, and therefore those are called multipotent. These adult stem cells Adult Stem Cells
Undifferentiated Stem cells found among
differentiated cells Differentiated Cells
Cells that have developed into a specific type, like a neuron or blood cell.
in a tissue or organ. It can renew itself and can differentiate to yield the major specialized cell types of that tissue or organ in which its found.
Multipotent
Ability of a single stem cell to develop into more than one cell type of the body. See also pluripotent.
The oldest cells are ones that are fully differentiated and mature. These cells are no longer able to make copies of themselves, and they will not change their identity.
Human embryonic stem cells (hESCs) hESCs
Human embryonic stem cells.
hESC
Human embryonic stem cells.
Large numbers of embryonic stem cells can be easily grown in culture, while adult stem cells are rare in mature tissues and methods for isolating those cells and expanding their numbers in cell culture have not yet been worked out. This is very important, as large numbers of cells are needed for stem cell replacement therapies. One advantage of using the adult stem cell is that patient's own cells could be expanded in culture and then reintroduced into the patient and would not be rejected by the immune system. However, through the process of SCNT, SCNT
Somatic Cell Nuclear Transfer (or Therapeutic cloning) - process of transferring a somatic nucleus into an enucleated cell.
Rejection
The process through which the body attacks and destroys foreign tissue.
