Somatic cell nuclear transfer in its first and second decades: successes, setbacks, paradoxes and perspectives.

The present review gives a subjective outline of the past and future of somatic cell nuclear transfer (SCNT). The first decade was full of contradictions: amazing successes were followed by frustrating fiascos. Although the possibility of reversing somatic cell differentiation completely is a more or less acknowledged fact, the underlying mechanisms are obscure. Consequently, the advancement has been mostly empirical and rather slow. Efficiency is slowly increasing in some species while stagnating in others, and the technology is too expensive for most practical purposes. The number of cloning laboratories is rather small, and those with reasonable productivity are extremely rare. SCNT research is underfinanced because of the atmosphere of suspicion surrounding cloning and the controversial reputation of cloners. However, certain signs may indicate a more successful next decade. In some species, technical refinements have resulted in a considerable decrease in developmental anomalies. Even the actual efficiency seems to be suitable for special purposes with high scientific and commercial impact including transgenic domestic animal production for human disease models, xenotransplantation and biopharming. Human therapeutic cloning is now a realistic perspective, and certain responsible scientists have started to question the reasonableness of an eternal ban for human reproductive cloning. Just one fulfilled goal out of the many promises of SCNT would justify the invested efforts.