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STEM CELL is a cell from the embryo, fetus, or adult, that has the ability to reproduce itself for long periods. It can give rise to specialized cells that make up the tissues and organs of the body.
EMBRYONIC STEM CELL is derived from the blastocyst of an embryo, or from fetal tissue destined to become part of the gonads. In the laboratory, and only under such conditions, this type of stem cell can proliferate indefinitely. It is pluripotent, which means that it has an ability to give rise to all types of cells, which develop from any of the three germ layers, from which all the cells of the body arise. It remains in such uncommitted state until it receives a signal to develop into one of ~200 known specialized cell types. When maintained as a cell line embryonic stem cells have a normal number and shape of chromosomes.
FETAL STEM CELL is an undifferentiated cell that occurs within a differentiated tissue of the fetus, renews itself for the lifetime of the organism, and differentiates into all of the specialized cell types of the tissue from which it originated. But it does not replicate indefinitely in tissue culture. Up until now it has been difficult to identify, isolate and purify. It “homes” into its tissue of origin.
PRECURSOR (PROGENITOR) STEM CELL occurs in fetal tissues, rarely in adult tissues, and is partially differentiated. It divides and gives rise to a specialized cell of the tissue to which it belongs. It replaces damaged or dead cells, and thus maintains the integrity and function of the tissue of origin. It “homes” to the tissue it comes from.
DIFFERENTIATION is the process by which an unspecialized cell (such as stem cell) becomes specialized into one of ~200 cell types that make up the body.
HOMING is a process whereby a transplanted cell is attracted by and travels to the injury site within the tissue it originates from.
BLASTOCYST is a pre-implantation embryo of 30 – 150 cells.
IMMUNOGENICITY means producing an immune response.
ALLOTRANSPLANTATION is implantation of cells, tissues or organs within species, e.g. from man to man or from dog to dog, etc.
XENOTRANSPLANTATION is an implantation of cells, tissues or organs between species, e.g. from animal to man, from dog to cat, etc.
