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Fate and Performance of flk1-/- Endothelial Precursors
Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Genetics and Pathology.
Manuscript (Other academic)
URN: urn:nbn:se:uu:diva-96916OAI: oai:DiVA.org:uu-96916DiVA: diva2:171650
Available from: 2008-03-20 Created: 2008-03-20 Last updated: 2010-01-13Bibliographically approved
In thesis
1. VEGFR-2 in Endothelial Differentiation and Vascular Organization
Open this publication in new window or tab >>VEGFR-2 in Endothelial Differentiation and Vascular Organization
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The cardiovascular system is the first functional organ to develop during embryogenesis. As the embryo reaches above a certain size, passive diffusion of gases and nutrients is no longer compatible with efficient growth. During embryogenesis, endothelial progenitor cells (angioblasts) are recruited from the primitive streak mesoderm and instructed to express vascular endothelial growth factor receptor-2 (VEGFR-2). This thesis examines the roles played by VEGFR-2 in the events through which a subpopulation of embryonic stem (ES) cells differentiate into endothelial cells and form the vasculature.

We show that ES cells gene targeted for VEGFR-2 (flk1-/-) develop immature endothelial cells (ECs), precursors, when differentiated in vitro as embryoid bodies (EBs). The flk1-/- ECs are unresponsive to VEGF-stimulation and consistently fail to form vessels. However, when co-cultured with wild type ES cells in chimeric EBs, flk1-/- endothelial precursors are guided by wild type ECs to form transient, chimeric vascular structures. Use of lentivirus in an add-back approach allowed reconstitution of VEGFR-2 expression in flk1-/- ES cells, and rescue of vasculogenesis and sprouting angiogenesis. We propose that recruitment to the endothelial lineage is not dependent on VEGFR-2, although this receptor tyrosine kinase appears indispensible for EC integrity, survival and for differentation of endothelial precursors into mature ECs formating a stable vasculature.

Neuropilin-1 (NRP1) and heparan sulfate proteoglycans (HSPGs) function as co-receptors for VEGFs. The co-receptors influence, qualitatively and quantitatively, the intracellular signal relayed by VEGFR-2 but it is unclear how. We examined the contribution of NRP1 to VEGFR-2 signaling in EB cultures, in zebrafish and in mice. Only NRP1-binding VEGFs were able to promote sprouting angiogenesis and formation of properly branched vascular tubes, supported by pericytes. Downstream of VEGFR-2/NRP1 activation, we identified recruitment of p38MAPK in signal transduction regulating sprouting angiogenesis.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 48 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 322
Molecular medicine, Embryonic stem, VEGFR-2, Flk1, KDR, VEGF, vasculogenesis, angiogenesis, embryoid body, Molekylärmedicin
urn:nbn:se:uu:diva-8579 (URN)978-91-554-7133-0 (ISBN)
Public defence
2008-04-11, Rudbecksalen, Rudbecklaboratoriet, Dag Hammarskjölds väg 20, Uppsala, 13:15 (English)
Available from: 2008-03-20 Created: 2008-03-20 Last updated: 2009-05-07Bibliographically approved

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