RESUMO
This paper describes the derivation of a blastocyst following heterologous nuclear transfer (NT) into a human oocyte. It also demonstrates that a major obstacle to continuing research in human NT is the availability of suitable human oocytes. In this study, 36 oocytes were donated by 11 women undergoing four different treatments and their developmental potential was evaluated after NT. The time from oocyte collection to NT seems to be crucial, and only oocytes that were enucleated within 1 h proved successful. After enucleation of oocytes, fusion with undifferentiated human embryonic stem cells and in-vitro culture, early cleavage and blastocyst development of fused complexes was observed. The DNA fingerprinting comparison of the donor cells and derived blastocyst revealed successful heterologous NT, since both oocytes and donor cells were recovered from different patients. It has therefore been demonstrated that NT can be achieved in humans, using heterologous donor nuclei and surplus and donated oocytes. However, if the promise of this new science is to achieve its potential in the foreseeable future, it will be necessary to identify new sources of oocytes that can be used immediately after retrieval.