"Therapeutic Cloning:" What It's Done For
Cell division in the human experiments has thus far not proceeded past the four-cell stage. Further cell divisions would produce, by the fourth or fifth day of development, a hollow blastocyst of roughly 100 cells. The blastocyst includes a group of cells, the inner cell mass, that would eventually develop into a fetus. Dissociation of the blastocyst, extraction and culture of the inner cell mass would provide stem cells for major organ systems, such as nerve cells, blood cells, pancreatic islets, and cardiac muscle cells.
Potential applications include cloning
of a patient's own cells in a donated egg, so that the genotype of the
stem cells will be identical to that of the patient. This might for example
assist in successful transplantation of blood-forming cells into the bone
marrow, following radiation therapy to kill cancerous cells, so as to start
a new hematopoetic cell line free of cancer.