Hematopoietic role of the placenta Volume 12, issue 4, Juillet-Août 2006


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Laboratoire d’embryologie cellulaire et moléculaire du CNRS et du Collège de France, Nogent-sur-Marne, adresse actuelle : CNRS, UPR 2197, Bâtiment 32-33, avenue de la Terrasse, 91498 Gif-sur-Yvette, Institut Cochin, département d’hématologie, INSERM U567, CNRS UMR 8104, Université Paris Descartes, Faculté de Médecine René Descartes, UM3, 123, boulevard de Port-Royal 75014 Paris

During ontogeny, blood cells are sequentially produced by several organs. In mammals, fetal liver has a major role, as it is the site where a population of extrinsic hematopoietic stem cells (HSC) becomes amplified and differentiates into all blood cell lineages, T lymphocytes excepted. Another key organ, whose role has failed to be appreciated, is the placenta, which is much richer in HSC and early progenitors than the liver. Like the para-aortic region, the placenta produces intrinsic progenitors since, at stages preceding vascularisation, these can be obtained from the allantois prior to its fusion to the chorionic plate. To know whether this site is truly more important than the AGM (Aorta/Gonads/Mesonephros) in producing HSCs, it is still required to analyze the long term restauration potential of allantoic cells.