Derivation of embryonic stem cells for therapy: new technologies

Embryonic stem cells are currently derived from the inner cell mass of human blastocysts, generated from spare embryos donated for research. To overcome ethical concerns raised by destruction of the embryo, two groups of workers have attempted to derive these cells from isolated blastomeres of 8- to 10-cell stage embryos using the embryo biopsy method akin to that used in preimplantation diagnosis. This paper briefly discusses these two techniques in relation to the routine derivation of stem cells from blastocysts. Some embryological aspects of using the inner cell mass of blastocysts in preference to early embryonic cells are presented. The paper also considers some pitfalls in therapeutic cloning, especially in non-human primates, since legislation to allow this procedure for stem cell research is currently being passed in Australia.