embrionic stem cells and medical application

Embryonic stem cells are pluripotent, meaning they are able to grow (i.e.

differentiate) into all derivatives of the three primary germ layers: ectoderm, endoderm and mesoderm.

In other words, they can develop into each of the more than 200 cell types of the adult body as long as they are specified to do so stem cells derived from the inner cell mass of an early stage embryo known as a blastocyst. Human embryos reach the blastocyst stage 4–5 days post fertilization, at which time they consist of 50–150 cells.


Embryonic Stem (ES) cells are pluripotent. This means they are able to differentiate into all derivatives of the three primary germ layers: ectoderm, endoderm, and mesoderm. These include each of the more than 220 cell types in the adult body. Pluripotency distinguishes ES cells from multipotent progenitor cells found in the adult; these only form a limited number of cell types. When given no stimuli for differentiation, (i.e. when grown in vitro), ES cells maintain pluripotency through multiple cell divisions. The presence of pluripotent adult stem cells remains a subject of scientific debate; however, research has demonstrated that pluripotent stem cells can be directly generated from adult fibroblast cultures.


Stem Cell Research
There has been a lot of discussion about embryonic stem cell research lately. Has the debate left you with questions about the medical potential for control and cures for diseases like Parkinson's, diabetes, and Alzheimer's? Pathologist Michael Shelanski, MD, PhD, joined us on Sept. 22, 2004, to discuss what he and other researchers might find down the stem cell path.
There is also ongoing research to reduce the potential for rejection of the differentiated cells derived from ES cells once researchers are capable of creating an approved therapy from ES cell research. One of the possibilities to prevent rejection is by creating embryonic stem cells that are genetically identical to the patient via therapeutic cloning.

An alternative solution for rejection by the patient to therapies derived from non-cloned ES cells is to derive many well-characterized ES cell lines from different genetic backgrounds and use the cell line that is most similar to the patient; treatment can then be tailored to the patient, minimizing the risk of rejection.

The thing that makes stem cells different is that they are cells that have no defined characteristics and that you can cause to grow in number. So if you start with one stem cell and keep it as a stem cell, over time you can have 10 cells or 10,000 cells. Then by providing the proper signals to those cells you can turn all 10,000 cells into a nerve, a kidney, or pancreas cell.

Therapeutic application

On January 23, 2009, Phase I clinical trials for transplantation of a human-ES-derived cell population into spinal cord-injured individuals received approval from the U.S. Food and Drug Administration (FDA), marking it the world's first human ES cell human trial . The study leading to this scientific advancement was conducted by Hans Keirstead and colleagues at the University of California, Irvine and supported by Geron Corporation of Menlo Park, CA. The results of this experiment suggested an improvement in locomotor recovery in spinal cord-injured rats after a 7-day delayed transplantation of human ES cells that were pushed towards an oligodendrocytic lineage.