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- Barkefors, Irmeli, 1981-
(författare)
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Directing Angiogenesis : Cellular Responses to Gradients in vitro
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Blood vessels are essential for the delivery of nutrients and oxygen to tissues, as well as for the removal of waste products. Patients with tumors, wounds or diabetes all have active angiogenesis, formation and remodeling of blood vessels, a process that is initiated and manipulated by gradients of secreted signaling proteins. This thesis describes the development of new microfluidic in vitro assays where directed migration of single endothelial cells and three dimensional vascular structures can be monitored in real time. Combining these assays with live imaging microscopy we have studied the behavior of endothelial cells in gradients of proangiogenic factors as well as directed sprouting in embryonic kidneys and stem cell cultures. With the 2D assay we have quantified endothelial cell chemotaxis towards FGF2, VEGFA165 and VEGFA121 and we also demonstrate that constant levels of VEGFA165, but not of FGF2, are able to reduce chemokinesis of endothelial cells. In the 3D migration chamber we have studied directed endothelial cell sprouting in mouse embryonic kidneys and embryoid bodies in response to VEGFA gradients. In both models directed angiogenesis is detected towards increasing levels of growth factor. Using the microarray technique on differentiating embryonic stem cells we have been able to identify the gene exoc3l2 as potentially involved in angiogenesis and endothelial cell migration and we present evidence that ExoC3l2 is associated with the exocyst complex; an important regulator of cell polarity. We have also shown that siRNA mediated gene silencing of exoc3l2 results in impaired VEGFR2 phosphorylation as well as loss of directionality in response to a VEGFA gradient.
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| 3. |
- Fredlund Fuchs, Peder, 1984-
(författare)
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Myofibroblasts and the Vascular Endothelium : Impact of Fibrin Degradation Products and miRNA on Vascular Motility and Function
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Angiogenesis is the formation of new blood vessels from pre-existing vasculature and is important during development as well as wound healing and tissue remodeling. Angiogenesis also occurs during pathological conditions such as diabetic retinopathy and cancer. This thesis is centered on the biology of endothelial cells, lining the blood vessels, and myofibroblasts, important for wound healing.We investigated an endothelial cell specific gene, ExoC3l2, and its role in VEGFR2 signaling and migration. EXOC3L2 co-localize with members of the exocyst complex, involved in vesicular transport, as well as VEGFR2. Reducing the level of EXOC3L2 in microvascular endothelial cells results in reduced VEGFR2 signaling and subsequently reduced chemotactic response to VEGF-A.MicroRNA (miRNA) have been shown to be regulators of gene transcription and cell type specific miRNAs have been identified. We investigated two miRNAs, miR-145 and miR-24. miR-145 is expressed in pericytes and fibroblasts but was shown to regulate fli1, an endothelial transcription factor. miR-145 overexpression reduced chemotaxis in both fibroblasts and endothelial cells, as did suppression of the endogenous miR-145 level in fibroblasts.miR-24 in contrast is expressed by endothelial cells and are able to target Ndst1, important for heparan sulfate (HS) sulfation. Sulfation of HS is important for many processes, amongst them growth factor signaling. Overexpression of miR-24 resulted in lower sulfation of HS chains, decreasing the ability of HS to interact with VEGF-A. Overexpressing miR-24 resulted in disturbed chemotaxis, similar to suppressing Ndst1 using siRNA.Myofibroblast recruitment is an important step in wound healing. The myofibroblasts contract the wound, synthesize new extracellular matrix and contribute to revascularization by looping angiogenesis. Maturation from resting fibroblast to myofibroblast is dependent on TGF-β. We found that fibrin fragment E (FnE), a degradation product of fibrin, potentiated the response of fibroblasts to TGF-β thus enhancing TGF-β-induced myofibroblast differentiation. FnE was also found to influence the migration of fibroblasts. These responses are dependent on integrins and toll-like receptors.These findings may serve to further increase the understanding of angiogenesis and wound healing to develop new therapies against pathological conditions.
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| 4. |
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| 5. |
- Gerwins, Pär, et al.
(författare)
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Function of fibroblast growth factors and vascular endothelial growth factors and their receptors in angiogenesis
- 2000
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Ingår i: Critical reviews in oncology/hematology. - 1040-8428 .- 1879-0461. ; 34:3, s. 185-194
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Tidskriftsartikel (refereegranskat)abstract
- Angiogenesis, formation of new vessels from pre-existing ones, results from stimulation of endothelial cells, which line the vessel wall. These cells will leave their resting state and start to digest the basement membrane, proliferate, migrate and eventually differentiate to form a hollow tube. All these steps can be induced by growth factors and this review will focus on two important types of angiogenic growth factors, vascular endothelial growth factor (VEGF; also denoted vascular permeability factor, VPF) and fibroblast growth factor (FGF). Both types of factors bind to cell surface expressed receptors, which are ligand-stimulatable tyrosine kinases. Binding of the growth factors to their receptors leads to activation of the intrinsic tyrosine kinase and signal transduction to downstream signalling cascades. This results in transcriptional changes and biological responses. The molecular aspects of signalling cascades critical for endothelial cell proliferation and migration are beginning to be delineated. In contrast, signalling cascades leading to endothelial cell differentiation remain to be determined. Angiogenesis is essential for a number of physiological events such as embryonic development, ovulation, and wound healing. It has become increasingly clear that a number of diseases depend on angiogenesis. For future development of therapeutic tools, it is important to understand the molecular mechanisms that regulate angiogenesis.
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| 7. |
- Heindryckx, Femke, et al.
(författare)
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Endoplasmic reticulum stress enhances fibrosis through IRE1α-mediated degradation of miR-150 and XBP-1 splicing
- 2016
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Ingår i: EMBO Molecular Medicine. - : Wiley-Blackwell. - 1757-4676 .- 1757-4684. ; 8:7, s. 729-744
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Tidskriftsartikel (refereegranskat)abstract
- ER stress results in activation of the unfolded protein response and has been implicated in the development of fibrotic diseases. In this study, we show that inhibition of the ER stress-induced IRE1α signaling pathway, using the inhibitor 4μ8C, blocks TGFβ-induced activation of myofibroblasts in vitro, reduces liver and skin fibrosis in vivo, and reverts the fibrotic phenotype of activated myofibroblasts isolated from patients with systemic sclerosis. By using IRE1α(-/-) fibroblasts and expression of IRE1α-mutant proteins lacking endoribonuclease activity, we confirmed that IRE1α plays an important role during myofibroblast activation. IRE1α was shown to cleave miR-150 and thereby to release the suppressive effect that miR-150 exerted on αSMA expression through c-Myb. Inhibition of IRE1α was also demonstrated to block ER expansion through an XBP-1-dependent pathway. Taken together, our results suggest that ER stress could be an important and conserved mechanism in the pathogenesis of fibrosis and that components of the ER stress pathway may be therapeutically relevant for treating patients with fibrotic diseases.
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| 9. |
- Heindryckx, Femke, et al.
(författare)
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Targeting the tumor stroma in hepatocellular carcinoma
- 2015
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Ingår i: World Journal of Hepatology. - : Baishideng Publishing Group Inc.. - 1948-5182. ; 7:2, s. 165-176
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Tidskriftsartikel (refereegranskat)abstract
- Hepatocellular carcinoma (HCC) is one of the most common and deadly cancers worldwide. In ninety percent of the cases it develops as a result of chronic liver damage and it is thus a typical inflammation-related cancer characterized by the close relation between the tumor microenvironment and tumor cells. The stromal environment consists out of several cell types, including hepatic stellate cells, macrophages and endothelial cells. They are not just active bystanders in the pathogenesis of HCC, but play an important and active role in tumor initiation, progression and metastasis. Furthermore, the tumor itself influences these cells to create a background that is beneficial for sustaining tumor growth. One of the key players is the hepatic stellate cell, which is activated during liver damage and differentiates towards a myofibroblast-like cell. Activated stellate cells are responsible for the deposition of extracellular matrix, increase the production of angiogenic factors and stimulate the recruitment of macrophages. The increase of angiogenic factors (which are secreted by macrophages, tumor cells and activated stellate cells) will induce the formation of new blood vessels, thereby supplying the tumor with more oxygen and nutrients, thus supporting tumor growth and offering a passageway in the circulatory system. In addition, the secretion of chemokines by the tumor cells leads to the recruitment of tumor associated macrophages. These tumor associated macrophages are key actors of cancer-related inflammation, being the main type of inflammatory cells infiltrating the tumor environment and exerting a tumor promoting effect by secreting growth factors, stimulating angiogenesis and influencing the activation of stellate cells. This complex interplay between the several cell types involved in liver cancer emphasizes the need for targeting the tumor stroma in HCC patients.
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