title: Human embryonic stem cells: the real challenge for research as well as for bioethics is still ahead of us.
abstract: Research on human embryonic stem cells (ESCs) has aroused a lot of controversy for years. Stimulated by recent work on mammalian embryology and new developments in stem cell research, an International Symposium entitled 'Stem Cell Research: A Challenge for Embryology, Regenerative Medicine and Bioethics' was held in Bonn (Germany) in 2006, bringing together embryologists, stem cell researchers and ethicists interested in human ESC research and the ensuing ethical debate. Two contributions to this Symposium are being published in Cells Tissues Organs, and the present paper aims to provide an introduction to these as well as personal impressions of the author about the perspectives that surfaced at the meeting, confronting them with relevant reports about stem cell research published recently. This paper highlights discussions about the mechanisms of specification of the main body axes during development, the role of extrinsic or intrinsic signals, and about the remarkable potential of ESCs to develop a basic body plan (individuation capacity) resembling properties of early embryonic cells (as shown by the formation of embryoid bodies and entire embryos if tetraploid complementation is performed). Another topic is 'alternative sources for human ESCs' recently proposed by the US President's Council on Bioethics ('organismically dead embryos', biopsied blastomeres or 'biological artifacts', e.g. created by 'altered nuclear transfer' and reprogramming of somatic cells). The possibility to rescue such (epi)genetically handicapped cells shows that this is not a way leading out of the ethical cul-de-sac. Recent reports about reprogramming somatic cells (fibroblasts) to gain ES-like potential highlight again the importance of focusing on the developmental potentiality as the major challenge for ethical considerations. Such a change of focus may be the only way out of the ethical impasse.
authors.forename: Hans-Werner
authors.initials: HW
authors.lastname: Denker
mesh_terms: D000818:Animals; D026688:Bioethical Issues; D002460:Cell Line; D033041:Embryo Research / Q000941:ethics*; D053595:Embryonic Stem Cells / Q000166:cytology; D006801:Humans; D051379:Mice; D011123:Polyploidy