Appendix N. 
403 
envisaged (Fig. 7). Fertilized embryos that are “left over" from IVF 
have three potential fates: disposal, generation of normal embryonic 
stem cells or generation of a normal baby when implanted into the 
womb. Similarly, the cloned embryo has three potential fates; it can 
be destroyed or could be used to generate a normal ntES cell line 
that has the same potential for therapy as an ES cell derived from a 
fertilized embryo. In contrast to the fertilized embryo, the cloned 
embryo has little if any potential to ever generate a normal baby. An 
embryonic stem cell line derived by nuclear may, however, help 
sustain existing life when used as a source for cell therapy that is 
"tailored" to the need of the patient who served as its nuclear donor. 
If SCNT were accepted as a valid therapeutic option, a major 
concern of its implementation as medical procedure would be the 
problem of how to obtain sufficient numbers of human eggs that 
could be used as recipients. Commercial interests may pressure 
women into an unwanted role as egg donors. The recent 
demonstration that embryonic stem cells can be coaxed into a 
differentiation pathway that yields oocyte-like cells (Hubner et al., 
2003) may offer a solution to this dilemma. If indeed functional 
oocytes could be generated from a generic human ES cell line, 
sufficient eggs could be generated in culture and serve as recipients 
for nuclear transfer without the need of a human egg donor. It seems 
that technical issues, not fundamental biological barriers, need to be 
overcome so that transplantation therapy can be carried out without 
the use of human oocytes. 
PRE -PUBLICATION VERSION 
