In a scientific breakthrough, researchers in South Korea have become the first to successfully clone human embryos and extract stem cells from them. The scientists said their goal was to further understanding of the causes and treatment of disease, and not for reproductive purposes.
But the achievement, published in this month’s journal Science, raises the possibility of making a cloned human baby more feasible. The development rekindles the debate about whether all human cloning should be banned, even if it were strictly for medical purposes. Cloning to create babies has been banned in numerous countries, including South Korea, but “therapeutic cloning” for stem cells could potentially lead to cures for crippling diseases and is still being considered by many governments.
Click on the gallery to see how stem cells are extracted from a cloned human embryo.
Embryonic stem cells hold great promise for medical research, as they can be manipulated into many other human cells that may provide cures for conditions such as Parkinson’s, Alzheimer’s, diabetes, heart disease and spinal cord injuries. But some critics say that using stem cells from embryos, even those newly created in a petri dish, is equivalent to taking human life, since embryos are destroyed when stem cells are removed.
Scientists in South Korea took donor eggs and removed their nuclei, which contains the egg cells' genetic code.
Prior to becoming an embryo, egg cells have only half of the genetic code needed to begin growing.
An adult cell-- with a full genetic code-- was fused with the egg cell. The adult cell and egg came from the same donor.
With a complete set of genetic material, the egg begins to divide, its cells subdividing beneath the casing of the egg.
A growing embryo first becomes a blastocyst, which takes about 4-5 days. Blastocysts are formed of several hundred cells encased in a sphere, including the building blocks of the body known as stem cells. The embryo at this point is very tiny-- about the size of the dot on an "i"-- and its stem cells aren't yet committed to becoming particular organ or tissue cells.
In this image, the stem cells are represented as purple cells.
Using a microscopic needle, scientists remove stem cells from the blastocyst.
About 242 unfertilized eggs were donated for the South Korean experiment, and 30 blastocysts were formed. Of the blastocysts, 20 yielded stem cells for culture.
The stem cells are placed in a culture dish, where they are coaxed into multiplying. In the South Korea experiment, one stem cell line was successfully grown from the material removed from a blastocyst.
The stem cells grown from the line can be manipulated into other types of cells, such as nerve, muscle and organ cells, and used for research. Scientists say that in addition to furthering understanding of the causes and treatment of disease, stem cells may be used to grow replacement tissue for patients as well.