What Is an Embryonic Stem Cell
The stem cells generated from early embryo is a vertebrate, are potent enough to self-renewal and can generate each of the different cell types of a fetus and the adult organism. These are described as embryonic (ES) stem cells and are generally derived from the inner cell mass of a blastocyst. In early 1980s, ES cell lines in culture were first obtained from mouse blastocyst. Later in early 1990s, primordial germ cell culture were shown to give rise to cells with characteristic of ES cells and were designated as embryonic germ cells to distinguish their source of origin relative to that of ES cells. Similarly, embryonic stem cells derived from teratocarcinoma are described as embryonic carcinoma cells. ES and EG cells were later derived from embryos of other mammals including humans. In November 1998, two groups in USA, independently produced immortal human ES cell lines for the first time.
James Thomson and his team at the university of Wisconsin, used stem cells from human embryos produced in vitro from a fertility clinic and established five immortal ES cell lines. John Gearhart and his team at Johns Hopkins University, instead used primordial germ cells (precursors of sperms and oocytes), kept apart from abortive fetuses and established an ES cell line. According to the two reports, the ES cells could be conserved in their undifferentiated state for several months. Since ES cells in culture have a natural inclination to secernate into various kinds of cells. The conservation of ES cells in unsecrnated state for several months was described as a chief breakthrough both for basic science and for biotechnological applications involving transplantation therapies.
Ethical issues for ESC therapy are one new subject of research and debate. It involves transfer of somatic nuclei from non-reproductive cells of patient’s body to enucleated donated eggs and production of embryos from these fused cells. The embryos produced thus are used for collecting pluripotent embryonic stem cells, which can differentiate into any cell type identical to that of a part of the body of the patient. Cells and tissues derived from such embryonic stem cells for the purpose of transplantation will not be rejected by the patient’s body, since the nucleus was derived from the patient.
Although embryo research and therefore ESC research is banned in some countries, there are countries like France, UK and Japan, which are lifting the ban and will permit the use of frozen surplus embryos derived from in vitro fertilization for research; thousands of these surplus embryos will be destroyed every day, if not used. However, the use of these embryos for stem cells will be allowed with several conditions, eg. Embryos only 14 days old; no money is paid to donors, etc.