Abstract

I. Introduction stem cells were first isolated from the internal cell mass of blastocyst and grown in vitro. Variants of these techniques for obtaining and cultivation are used today in laboratories around the world. The most important publications related to stem cells have been centralized in the years 2001 and 2002 by R. Edwards. In vitro growth of the embryo is the subject of many research teams, the first one realizing it was Heope in 1980, which won the doe produced after embryo transfer to recipient. (Gottlieb, D.I. and Huettner, J.E., 1999). Early research on stem cells in vitro cultivation (Fig. 1) were made in 1963 by J. Paul and E. Edwards, who prepared for a group of cells growing rabbit embryo preimplantaţional in drops of NCTC 109 , 199, F10. (Theia, N.D., 2000). A stem cell has two main properties: long-term capacity autoreînnoire without senescence and pluripotenţă and ability to differentiate into one or more specialized cell types. These cells can provide an inexhaustible source of cells for transplantation. Totipotente stem cells that have the ability to generate all types of tissue plays a critical role in human development, providing material for the development of all tissues and organs in the embryo and in all extra embryonic tissues. At first it was thought that these adult stem cells regenerate only a very limited set of cell lines, but they demonstrated during a much greater plasticity.