Vinsamlegast notið þetta auðkenni þegar þið vitnið til verksins eða tengið í það: http://hdl.handle.net/1946/13894
Since human embryonic stem cells (hES cells) were discovered they have been studied intensively, revealing hES cells as a powerful research tool for understanding early embryonic development in humans. Furthermore, hES cells are promising candidates in therapeutic treatments and stem cell therapies. hES cells have been differentiated into cells of all the three germ layers that at later stages of development form the human body.
During human embryonic development, the embryo is dependent on blood supply for nurture and growth. Blood supply is also vital for the adult human body, as almost all tissues depend on blood flow. Since blood is supplied via blood vessels, formation of blood vessels is an essential process both during human embryonic development and during postnatal stages of life. Blood vessel formation is also crucial for tumors in cancer, as tumors are dependent on nutrition via blood supply for them to be able to grow and metastasize. Endothelial cells line the interior surface of blood vessels and they are necessary in formation of blood vessels, as they proliferate, migrate and invade the extracellular matrix (ECM) to form vascular structures throughout the human body. Members of the TGFβ superfamily have been shown to play a role in blood vessel formation. In most cell types, TGFβ signals through the TGFβ type I receptor activin receptor-like kinase 5 (ALK5) but endothelial cells express the endothelial specific TGFβ type I receptor ALK1. TGFβ can therefore signal via the ALK1 and the ALK5 receptor in endothelial cells.
The aim of this project was to study the role of ALK1 and ALK5 in blood vessel formation, both in the adult human body and during human embryonic development, using human umbilical vein endothelial cells (HUVECs) and hES cell derived endothelial cells, respectively. Constitutively active (ca) ALK1 and caALK5 were overexpressed in HUVECs before their biological effects on tube-like formation and invasion were evaluated. Efforts were made to identify novel genes activated by ALK1 and ALK5. It was shown that ALK1 promotes tube-like formation and invasion by upregulating Id1, while ALK5 has a negative effect on blood vessel formation, likely through upregulation of thrombospondin-1 (TSP-1). To study the role of ALK1 and ALK5 in vascular development of hES cell derived cells, a method was set up to differentiate hES cells into endothelial cells. The endothelial properties of the differentiated cells were determined by evaluating protein expression and by performing biological assays recapitulating angiogenesis in vivo. A neutralizing antibody specifically raised against ALK1 was used to determine the importance of ALK1 in vascular embryonic development. The differentiation method resulted in a cell population with endothelial properties. Results indicate the importance of ALK1 in hES cell derived vascular development, although the findings are preliminary. Taken together, this study provides further insight into the role of ALK1 and ALK5 in blood vessel formation, both during human embryonic development and in the adult human body.