Formation of endothelial cell networks

Helmlinger, Gabriel; Endo, Masatoshi; Ferrara, Napoleone; Hlatky, Lynn; Jain, Rakesh K.

doi:10.1038/35012132

Cited by 149 publications

(117 citation statements)

References 7 publications

Supporting

Mentioning

112

Contrasting

Unclassified

Order By: Relevance

“…Interestingly, the K m values that we have measured for VEGF up-regulation are similar to the oxygen concentrations which stimulate the ability of endothelial cells to form capillary networks (Helmlinger and Jain, 1998). They are also low enough that, if oxygen concentration were the only deteminant for VEGF production, most tumours should contain areas which are hypoxic enough to have large areas which stain for VEGF.…”

Section: Discussionsupporting

confidence: 63%

A quantitative analysis of the reduction in oxygen levels required to induce up-regulation of vascular endothelial growth factor (VEGF) mRNA in cervical cancer cell lines

Chiarotto

Hill

1999

Br J Cancer

View full text Add to dashboard Cite

Regions of hypoxia, or low oxygen tension, are known to exist within tumours (Raleigh et al, 1996;Brown and Giaccia, 1998;Dewhirst, 1998). Since radiotherapy and some forms of chemotherapy are less effective at killing cancer cells in hypoxic environments, much effort has been directed toward identifying tumours containing such regions. Measurement of oxygen tension by needle electrodes in lymph node metastasis of cancer of the head and neck found that radiation was less effective at inducing regression when the lymph nodes were hypoxic (Gatenby et al, 1988) and such measurements have been reported to identify patients with poor locoregional tumour control (Nordsmark et al, 1996). Similar work in advanced cancer of the uterine cervix (Hockel et al, 1993(Hockel et al, , 1996Fyles et al, 1998;Hockel and Vaupel, 1998) showed that increased levels of hypoxia in the primary tumour mass correlated with poorer treatment outcome. These results suggested that hypoxia in cervical cancers correlated with a greater likelihood of both local failure and nodal metastasis. Metastases were also found to be more frequent in patients with the most hypoxic soft tissue sarcoma of the extremities (Brizel et al, 1996). Furthermore, exposure of cancer cells to hypoxia (Young et al, 1988;Jang and Hill, 1997) and hypoxia-induced increases in vascular endothelial growth factor (VEGF) secretion have been associated with an increased metastatic ability (Danielsen and Rofstad, 1998).VEGF is the most selective vascular endothelial cell mitogen known . In cancer cells, the four VEGF isoforms which have been most frequently described contain 121, 165, 189 and 206 amino acids (Tischer et al, 1991). In some studies, increased intra-tumoural VEGF mRNA and protein has been associated with poor prognosis (Berger et al, 1995;Toi et al, 1995), increased metastasis Takahashi et al, 1995), and increased microvessel density Toi et al, 1995;Fontini et al, 1997). Antibodies directed towards VEGF can inhibit angiogenesis and the proliferation of cancer cells in vivo (Kim et al, 1993;Kondo et al, 1993). Cancer cells constitutively produce VEGF and can up-regulate its expression under hypoxic stress (Shweiki et al, 1992) via the transcription factor hypoxia-inducible factor 1 (Forsythe et al, 1996) and by stabilization of the mRNA (Levy et al, 1996(Levy et al, , 1998. The qualitative relationship between oxygen level and VEGF up-regulation has been examined in a variety of different tumour systems but has not been quantitatively documented in most of the studies performed (Shweiki et al, 1992;Minchenko et al, 1994;Leith and Michelson, 1995;Mukhapadhyay et al, 1995). The purpose of the present work was to examine the relationship between VEGF mRNA level and oxygen concentration in detail and to determine the extent of its variation between different tumour cells of similar histopathological type. Cell lines derived from human cancer of the uterine cervix were chosen for the study based on the abundance of clinical data relating tumour A quantitative analysis ...

show abstract

Section: Discussionsupporting

confidence: 63%

A quantitative analysis of the reduction in oxygen levels required to induce up-regulation of vascular endothelial growth factor (VEGF) mRNA in cervical cancer cell lines

Chiarotto

Hill

1999

Br J Cancer

View full text Add to dashboard Cite

show abstract

“…Hypoxia and TGF-␤ are known to regulate angiogenesis, a process where VEGF plays a critical role promoting the formation of blood vessels, by inducing proliferation, migration, elongation, network formation, and branching of endothelial cells (40,41,48). Involvement of individual components of the TGF-␤ and hypoxia pathways in the angiogenic process has been demonstrated during recent years by gene ablation experiments in mice.…”

Section: Discussionmentioning

confidence: 99%

Synergistic Cooperation between Hypoxia and Transforming Growth Factor-β Pathways on Human Vascular Endothelial Growth Factor Gene Expression

Sánchez-Elsner¹,

Botella²,

Velasco³

et al. 2001

Journal of Biological Chemistry

350

248

View full text Add to dashboard Cite

Signaling by transforming growth factor (TGF)-␤ family members is mediated by Smad proteins that regulate gene transcription through functional cooperativity and association with other DNA-binding proteins. The hypoxia-inducible factor (HIF)-1 is a transcriptional complex that plays a key role in oxygen-regulated gene expression. We demonstrate that hypoxia and TGF-␤ cooperate in the induction of the promoter activity of vascular endothelial growth factor (VEGF), which is a major stimulus in the promotion of angiogenesis. This cooperation has been mapped on the human VEGF promoter within a region at ؊1006 to ؊954 that contains functional DNA-binding sequences for HIF-1 and Smads. Optimal HIF-1␣-dependent induction of the VEGF promoter was obtained in the presence of Smad3, suggesting an interaction between these proteins. Consistent with this, co-immunoprecipitation experiments revealed that HIF-1␣ physically associates with Smad3. These results demonstrate that both TGF-␤ and hypoxia signaling pathways can synergize in the regulation of VEGF gene expression at the transcriptional level.

show abstract

“…In vitro models have demonstrated that hypoxic conditions enhance tube formation, as do hypoxic regions formed by the O 2 consumption of the cells in threedimensional (3D) structures (3,19,32). Research has shown that the rate of O 2 consumption of cells follows the Michaelis-Menten kinetics and depends on the cell type, cell density (15), and dissolved oxygen (DO) levels (1).…”

mentioning

confidence: 99%

“…Research has shown that the rate of O 2 consumption of cells follows the Michaelis-Menten kinetics and depends on the cell type, cell density (15), and dissolved oxygen (DO) levels (1). Variations in DO levels strongly affect angiogenesis (19,48) through different vascular cell responses, such as viability, differentiation, migration, and remodeling of the extracellular matrix (4,27,40).…”

mentioning

confidence: 99%

Unforeseen decreases in dissolved oxygen levels affect tube formation kinetics in collagen gels

Abaci

Truitt

Tan

et al. 2011

American Journal of Physiology-Cell Physiology

View full text Add to dashboard Cite

The availability of oxygen (O2) is a critical parameter affecting vascular tube formation. In this study, we hypothesize that dissolved oxygen (DO) levels in collagen gels change during the three-dimensional (3D) culture of human umbilical vein endothelial cells (HUVECs) in atmospheric conditions and that such changes affect the kinetics of tube formation through the production of reactive oxygen species (ROS). We demonstrate a decrease in O2 tension during 3D cultures of HUVECs. Noninvasive measurements of DO levels during culture under atmospheric conditions revealed a profound decrease that reached as low as 2% O2 at the end of 24 h. After media replacement, DO levels rose rapidly and equilibrated at ϳ15% O 2, creating a reoxygenated environment. To accurately estimate DO gradients in 3D collagen gels, we developed a 3D mathematical model and determined the Michaelis-Menten parameters, V max and K m, of HUVECs in collagen gels. We detected an increase in ROS levels throughout the culture period. Using diphenyliodonium to inhibit ROS production resulted in the complete inhibition of tube formation. Interference RNA studies further showed that hypoxiainducible factors (HIFs)-1␣ and -2␣ are not involved in the formation of 3D tubes in collagen gels. We conclude that ROS affect the tubulogenesis process through HIF␣-independent pathways, where the levels of ROS are influenced by the uncontrolled variations in DO levels. This study is the first demonstration of the critical and unexpected role of O 2 during 3D in vitro culture models of tubulogenesis in atmospheric conditions. microvasculature; reactive oxygen species; hypoxia-inducible factors AN UNDERSTANDING OF THE MECHANISMS controlling how blood vessels form from endothelial cells (ECs) is crucial for developmental biology and vascular tissue engineering. In recent decades, our understanding of the molecular regulation underlying vascular development has vastly expanded, primarily because of newly available, well-defined in vitro models. One common model is the culturing of ECs in gels made of the extracellular matrix component collagen, which has enabled us to investigate the effects of many factors on tubulogenesis (24,38,39).The availability of oxygen (O 2 ) is a critical parameter affecting how vascular cells form tubes. In vitro models have demonstrated that hypoxic conditions enhance tube formation, as do hypoxic regions formed by the O 2 consumption of the cells in threedimensional (3D) structures (3,19,32). Research has shown that the rate of O 2 consumption of cells follows the Michaelis-Menten kinetics and depends on the cell type, cell density (15), and dissolved oxygen (DO) levels (1). Variations in DO levels strongly affect angiogenesis (19, 48) through different vascular cell responses, such as viability, differentiation, migration, and remodeling of the extracellular matrix (4, 27, 40).Hypoxia-inducible factors (HIFs) and reactive oxygen species (ROS) are among the effectors responsible for cellular responses to changing DO levels. HIF1␣ and HI...

show abstract

Formation of endothelial cell networks

Cited by 149 publications

References 7 publications

A quantitative analysis of the reduction in oxygen levels required to induce up-regulation of vascular endothelial growth factor (VEGF) mRNA in cervical cancer cell lines

A quantitative analysis of the reduction in oxygen levels required to induce up-regulation of vascular endothelial growth factor (VEGF) mRNA in cervical cancer cell lines

Synergistic Cooperation between Hypoxia and Transforming Growth Factor-β Pathways on Human Vascular Endothelial Growth Factor Gene Expression

Unforeseen decreases in dissolved oxygen levels affect tube formation kinetics in collagen gels

Contact Info

Product

Resources

About