Human Embryonic Stem Cells

One of the most exciting frontiers in medicine is the potential use of stem cells for treating a host of congenital, developmental, or degenerative diseases for which there are no cures. Cell replacement strategies are particularly relevant in tissues and organs that have little capacity for self-repair. One such organ is the brain; nerve cells or neurons are known to be very restricted in their capacity to regenerate following damage or disease, and the adult brain and spinal cord appear to have only a limited ability to produce new neurons. This is one reason why recovery is often limited when the nervous system is injured.

The goal of cell replacement is to develop therapies where stem cells are first induced to differentiate into specified cells of choice, then transplanted into patients to replace damaged or dysfunctional tissues. It is hoped that the replacement and integration of lost cells will be able to restore functions and behaviors compromised by the disease condition.

Embryonic stem cells possess two properties that make them especially well suited for cell therapy. First, because embryonic stem cells are obtained from early blastocysts, they are at a very early developmental stage, and retain the flexibility to become any one of the more than 200 cell types that make up the human body. Given the right combination of signals, embryonic stem cells will develop into mature cells that can function as neurons, muscles, bone, blood or other needed cell types. Stem cells with such flexibility are described as "pluripotent," to indicate their high potential to differentiate into a wide variety of cell types.

A second feature of embryonic stem cells is their ability to remain in an undifferentiated state and to divide indefinitely. This property of "self-renewal" means that essentially unlimited numbers of identical, well-defined, genetically and genomically characterized stem cells can be produced in culture for medical use.

Watch the animation to learn more about embryonic stem cells, and their potential for the treatment of type I diabetes.