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TISSUE-SPECIFIC STEM CELLS

Endoglin Is Not Critical for Hematopoietic Stem Cell Engraftment and Reconstitution but Regulates Adult Erythroid Development

^aMolecular Medicine and Gene Therapy, Institute of Laboratory Medicine, Lund Strategic Research Center for Stem Cell Biology and Cell Therapy, Lund University Hospital, Lund, Sweden;
^bImmunology Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden

Key Words. Hematopoiesis • Stem cells • RNA interference • Erythropoiesis

Correspondence: Stefan Karlsson, M.D., Ph.D., Molecular Medicine and Gene Therapy, Lund University Hospital, BMC A12, 221 84 Lund, Sweden. Telephone: 46-46-222-0577; Fax: 46-46-222-05-78; e-mail: Stefan.Karlsson{at}med.lu.se

Received October 27, 2006; accepted for publication July 19, 2007.
First published online in STEM CELLS EXPRESS   August 2, 2007.



Endoglin is a transforming growth factor-β (TGF-β) accessory receptor recently identified as being highly expressed on long-term repopulating hematopoietic stem cells (HSC). However, little is known regarding its function in these cells. We have used two complementary approaches toward understanding endoglin's role in HSC biology: one that efficiently knocks down expression via lentiviral-driven short hairpin RNA and another that uses retroviral-mediated overexpression. Altering endoglin expression had functional consequences for hematopoietic progenitors in vitro such that endoglin-suppressed myeloid progenitors (colony-forming unit-granulocyte macrophage) displayed a higher degree of sensitivity to TGF-β-mediated growth inhibition, whereas endoglin-overexpressing cells were partially resistant. However, transplantation of transduced bone marrow enriched in primitive hematopoietic stem and progenitor cells revealed that neither endoglin suppression nor endoglin overexpression affected the ability of stem cells to short-term or long-term repopulate recipient marrow. Furthermore, transplantation of cells altered in endoglin expression yielded normal white blood cell proportions and peripheral blood platelets. Interestingly, decreasing endoglin expression increased the clonogenic capacity of early blast-forming unit-erythroid progenitors, whereas overexpression compromised erythroid differentiation at the basophilic erythroblast phase, suggesting a pivotal role for endoglin at key stages of adult erythropoietic development.

Disclosure of potential conflicts of interest is found at the end of this article.