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This Article Free via Open Access: OA OA Full Text Full Text (PDF) OA All Versions of this Article: 2007-0876v1 26/10/2455    most recent Alert me when this article is cited Alert me if a correction is posted Citation Map Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints/Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Unger, C. Articles by Dilber, M. S. Search for Related Content PubMed PubMed Citation Articles by Unger, C. Articles by Dilber, M. S.

EMBRYONIC STEM CELLS/INDUCED PLURIPOTENT STEM CELLS

Lentiviral-Mediated HoxB4 Expression in Human Embryonic Stem Cells Initiates Early Hematopoiesis in a Dose-Dependent Manner but Does Not Promote Myeloid Differentiation

^aDepartment of Medicine, Karolinska University Hospital Huddinge, Karolinska Institutet, Stockholm, Sweden;
^bCenter for Oral Biology, Institute of Odontology, Karolinska Institutet, Stockholm, Sweden;
^cDepartment of Clinical Science, Intervention and Technology, Karolinska University Hospital Huddinge, Karolinska Institutet, Stockholm, Sweden,
^dDepartment of Woman and Child Health, Karolinska University Hospital Solna, Karolinska Institutet, Stockholm, Sweden

Key Words. Embryonic stem cells • HoxB4 • Transcription factors • Gene therapy • Hematopoiesis

Correspondence: Correspondence: M. Sirac Dilber, M.D., Ph.D., Department of Medicine, M54, Karolinska Institutet, Karolinska University Hospital Huddinge, SE-14186 Stockholm, Sweden. Telephone: 46-8-585-83855; Fax: 46-8-711-7684; e-mail: Sirac.Dilber{at}ki.se

Received on October 24, 2007; accepted for publication on June 26, 2008.

First published online in STEM CELLS EXPRESS  July 10, 2008.

The variation of HoxB4 expression levels might be a key regulatory mechanism in the differentiation of human embryonic stem cell (hESC)-derived hematopoietic stem cells (HSCs). In this study, hESCs ectopically expressing high and low levels of HoxB4 were obtained using lentiviral gene transfer. Quantification throughout differentiation revealed a steady increase in transcription levels from our constructs. The effects of the two expression levels of HoxB4 were compared regarding the differentiation potential into HSCs. High levels of HoxB4 expression correlated to an improved yield of cells expressing CD34, CD38, the stem cell leukemia gene, and vascular epithelium-cadherin. However, no improvement in myeloid cell maturation was observed, as determined by colony formation assays. In contrast, hESCs with low HoxB4 levels did not show any elevated hematopoietic development. In addition, we found that the total population of HoxB4-expressing cells, on both levels, decreased in developing embryoid bodies. Notably, a high HoxB4 expression in hESCs also seemed to interfere with the formation of germ layers after xenografting into immunodeficient mice. These data suggest that HoxB4-induced effects on hESC-derived HSCs are concentration-dependent during in vitro development and reduce proliferation of other cell types in vitro and in vivo. The application of the transcription factor HoxB4 during early hematopoiesis from hESCs might provide new means for regenerative medicine, allowing efficient differentiation and engraftment of genetically modified hESC clones. Our study highlights the importance of HoxB4 dosage and points to the need for experimental systems allowing controlled gene expression.

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