In cancer and cardiovascular diseases (CVD), abnormal development of blood vessels plays a major role in disease progression. In case of cancer, abnormal angiogenesis promote tumour expansion and metastasis, which are characterized by formation of an abundant chaotic capillary network. In case of CVD, abnormal angiogenesis is characterised by obstruction of blood vessels, which results in hypoxia leading to cell apoptosis and necrosis in e.g. cardiac tissue. Many pathways of angiogenesis are still poorly understood and should be explored using gene function studies. In this thesis, we aim to identify novel molecular pathways involved in angiogenesis, which might shed light on failing gene therapy and offer novel perspectives on pro- and anti-angiogenic therapies.
To identify new genetic factors involved in angiogenesis, a genome-wide microarray screen was performed on the transcriptome of murine embryo`s. A list of genes that were significantly upregulated in FLK-positive cells was validated using whole-mount in situ hybridization in zebrafish larvae. Genes with a corresponding expression pattern in the vasculature were selected and silenced in an in vivo model of angiogenesis, in developing zebrafish larvae and in a mural retina model. In vitro knockdown assays were also performed in 3D-collagen based co-culture of EC and pericytes to assess blood vessel formation. In this thesis CMTM3, CMTM4, CGNL1, THSD1, and CECR1 were selected as candidate genes and their molecular pathways were investigated. For the first time to our knowledge we concluded that their properties in ECs are involved in the angiogenesis process. We also investigated the angiogenic property of the nucleotide Up4A as it is synthesised in response to VEGFR2 stimulation during stress conditions, such as hypoxia or in cancer conditions.
In conclusion, our fundamental findings of novel pathways involved in angiogenesis hold promising therapeutic perspectives to understand and treat vascular diseases.

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D.J.G.M. Duncker (Dirk) , C. Cheng (Caroline)
Erasmus University Rotterdam
Financial support by the Dutch Heart Foundation for the publication of this thesis is gratefully acknowledged
Department of Cardiology