Authors:
Katrin E. Rhodes, Christos Gekas, Yanling Wang, Christopher T. Lux, Cameron S. Francis, David N. Chan, Simon Conway, Stuart H. Orkin, Mervin C. Yoder, and Hanna K.A. Mikkola
Summary:
The mouse placenta was unveiled as an important reservoir for hematopoietic stem cells (HSCs), yet the origin of placental HSCs was unknown. By tracking developing HSCs by expression of Runx1-lacZ and CD41, we have found that HSCs emerge in large vessels in the placenta. Analysis of Ncx1−/− embryos, which lack a heartbeat, verified that HSC development is initiated in the placental vasculature independent of blood flow. However, fewer CD41+ hematopoietic cells were found in Ncx1−/− placentas than in controls, implying that some HSCs/progenitors colonize the placenta via circulation and/or HSC emergence is compromised without blood flow. Importantly, placentas from Ncx1−/− embryos possessed equal potential to generate myelo-erythroid and B and T lymphoid cells upon explant culture, verifying intact multilineage hematopoietic potential, characteristic of developing HSCs. These data suggest that, in addition to providing a niche for a large pool of HSCs prior to liver colonization, the placenta is a true site of HSC generation.
Source:
Cell Stem Cell, Vol. 2, 252-263, (03/06/08).