Nuclear Cloning, Embryonic Stem Cells and the Promise for Transplantation Therapy

An emerging consensus is that somatic cell nuclear transfer (SCNT) for the purpose of creating a child (also called ‘reproductive cloning’) is not acceptable for both moral and scientific reasons. In contrast, SCNT with the goal of generating an embryonic stem cell line (‘therapeutic cloning’) remains a controversial issue. Although therapeutic cloning holds the promise of yielding new ways of treating a number of degenerative diseases, it is not acceptable to many because the derivation of an embryonic stem cell line from the cloned embryo (an essential step in this process) necessarily involves the loss of an embryo and hence the destruction of potential human life. In this article, I will develop two main arguments that are based on the available scientific evidence. 1) In contrast to an embryo derived by in vitro fertilization (IVF), a cloned embryo has little if any potential to ever develop into a normal human being. This is because, by circumventing the normal processes of gametogenesis and fertilization, nuclear cloning prevents the proper reprogramming of the clone’s genome, which is a prerequisite for development of an embryo to a normal individual. It is unlikely that these biological barriers to normal development can be solved in the foreseeable future. Therefore, from a biologist’s point of view, the cloned human embryo, used for the derivation of an embryonic stem cell and the subsequent therapy of a needy patient, has little if any potential to create a normal human life. 2) Embryonic stem cells developed from a cloned embryo are functionally indistinguishable from those that have been generated from embryos derived by in vitro fertilization (IVF). Both types of embryonic stem cells have an identical potential to serve as a source for therapeutically useful cells. 8_Jaenisch.qxd:MASTER GABRIELLA.qxd 10-07-2007 13:33 Pagina 114