Submitted June 21, 2006
Accepted September 19, 2006
Non-hematopoietic/endothelial SSEA-1pos cells defines the most primitive progenitors in the adult murine bone marrow mesenchymal compartment
Fernando Anjos-Afonso and Dominique Bonnet*
Haematopoietic Stem Cell Lab, Cancer Research UK, London Research Unit, London, UK
* Corresponding author; email: dominique.bonnet{at}cancer.org.uk.
It is believed that in the bone marrow a primitive cell-type that maintains the mesenchymal compartment exists. However, this putative mesenchymal stem/progenitor cell is yet to be identified and isolated. We are reporting the identification, isolation and detailed characterization of the most primitive mesenchymal progenitor cells in the adult murine bone marrow, based on the expression of Stage Specific Embryonic Antigen-1 (SSEA-1). This primitive subset can be identified in mesenchymal cell cultures and also directly in the bone marrow, thus ascertaining for the first time their existence in an adult organism. Characterization of SSEA-1pos mesenchymal cells revealed that upon purification, these cells gave rise to SSEA-1neg mesenchymal cells, whereas the reverse could not be observed. Also, these SSEA-1pos cells have a much higher capacity to differentiate than their negative counterparts, not only to several mesenchymal cell-types but also to unconventional cell-types such as astrocyte-, endothelial- and hepatocyte-like cells in vitro. Most importantly, single-cell derived population was capable of differentiating abundantly into different mesenchymal cell-types in vivo. Altogether we are proposing a hierarchical organization of the mesenchymal compartment placing SSEA-1pos cells at the apex of this hierarchy.
