Angiogenesis, the formation of new blood vessels from existing ones, is an essential process for successful bone regeneration. Further, angiogenesis is a key factor for the development of bone-related disorders like osteosarcoma or arthritis. Fucoidans, sulfated polysaccharides from brown algae, have been shown to affect angiogenesis as well as a series of other physiological processes including inflammation or infection. However, the chemical properties of fucoidan which define the biological activity vary tremendously, making a prediction of the bioactivity or the corresponding therapeutic effect difficult. In this study, we compare the effect of four chemically characterized high molecular weight fucoidan extracts from Fucus distichus subsp. evanescens (FE_crude and fractions F1, F2, F3) on angiogenic and osteogenic processes in bone-related primary mono- and co-culture cell systems. By determining the gene expression and protein levels of the regulatory molecules vascular endothelial growth factor (VEGF), angiopoietin-1 (ANG-1), ANG-2 and stromal-derived factor 1 (SDF-1), we show that the extracted fucoidans negatively influence angiogenic and osteogenic processes in both the mono- and co-culture systems. We demonstrate that purer fucoidan extracts with a high fucose and sulfate content show stronger effects on these processes. Immunocytochemistry of the co-culture system revealed that treatment with FE_F3, containing the highest fucose and sulfate content, impaired the formation of angiogenic tube-like structures, indicating the anti-angiogenic properties of the tested fucoidans. This study highlights how chemical properties of fucoidan influence its bioactivity in a bone-related context and discusses how the observed phenotypes can be explained on a molecular level-knowledge that is indispensable for future therapies based on fucoidans.

Protein tyrosine nitration is considered one of the most relevant disease biomarkers of oxidative stress. The mechanism of nitration, target protein and functional consequences remain often unclear. We focus on a prominent protein band surprisingly nitrotyrosine immunopositive under basal conditions in mouse, rat and pig heart and more so in diabetes and myocardial stress. Upon purification, we identify it as lactate dehydrogenase (LDH) and its basal nitration depending on NO synthase (NOS) and myeloperoxidase (MPO), respectively. Surprisingly, we locate LDH nitration by MALDI-TOF mass spectrometry not to a tyrosine but the C-terminal tryptophan, Trp-324. Molecular dynamics simulations suggested that Trp-324 nitration restricts the interaction of the active site loop with the C-terminal alfa-helix essential for activity, which was corroborated by an apparent lower Vmax. In summary, here we first extend protein nitration from pathology to physiology as an additional mechanism of post-translational regulation.

Background. The polysaccharide fucoidan is widely investigated as an anti-cancer agent. Here, we tested the effect of fucoidan on uveal melanoma cell lines. Methods. The effect of 100 µM fucoidan was investigated on five cell lines (92.1, Mel270 OMM1, OMM2.3, OMM2.5) and of 1 µg/mL–1 mg/mL fucoidan in two cell lines (OMM1, OMM2.3). Cell proliferation and viability were investigated with a WST-1 assay, migration in a wound healing (scratch) assay. Vascular Endothelial Growth Factor (VEGF) was measured in ELISA. Angiogenesis was evaluated in co-cultures with endothelial cells. Cell toxicity was induced by hydrogen-peroxide. Protein expression (Akt, ERK1/2, Bcl-2, Bax) was investigated in Western blot. Results. Fucoidan increased proliferation in two and reduced it in one cell line. Migration was reduced in three cell lines. The effect of fucoidan on VEGF was cell type and concentration dependent. In endothelial co-culture with 92.1, fucoidan significantly increased tubular structures. Moreover, fucoidan significantly protected all tested uveal melanoma cell lines from hydrogen-peroxide induced cell death. Under oxidative stress, fucoidan did not alter the expression of Bcl-2, Bax or ERK1/2, while inducing Akt expression in 92.1 cells but not in any other cell line. Conclusion. Fucoidan did not show anti-tumorigenic effects but displayed protective and pro-angiogenic properties, rendering fucoidan unsuitable as a potential new drug for the treatment of uveal melanoma.

The marine origin polysaccharide fucoidan combines multiple biological activities. As demonstrated by various studies in vitro and in vivo, fucoidans show anti-viral, anti-tumor, anti-oxidant, anti-inflammatory and anti-coagulant properties, although the detailed molecular action remains to be elucidated. The aim of the present study is to assess the impact of crude fucoidan extracts, on the formation of vascular structures in co-culture models relevant for bone vascularization during bone repair and for vascularization processes in osteosarcoma. The co-cultures consisted of bone marrow derived mesenchymal stem cells, respectively the osteosarcoma cell line MG63, and human blood derived outgrowth endothelial cells (OEC). The concentration dependent effects on the metabolic activity on endothelial cells and osteoblast cells were first assessed using monocultures of OEC, MSC and MG63 suggesting a concentration of 100 µg/mL as a suitable concentration for further experiments. In co-cultures fucoidan significantly reduced angiogenesis in MSC/OEC but also in MG63/OEC co-cultures suggesting a potential application of fucoidan to lower the vascularization in bone tumors such as osteosarcoma. This was associated with a decrease in VEGF (vascular endothelial growth factor) and SDF-1 (stromal derived factor-1) on the protein level, both related to the control of angiogenesis and furthermore discussed as crucial factors in osteosarcoma progression and metastasis. In terms of bone formation, fucoidan slightly lowered on the calcification process in MSC monocultures and MSC/OEC co-cultures. In summary, these data suggest the suitability of lower fucoidan doses to limit angiogenesis for instance in osteosarcoma.

Sufficient vascularization of the implant construct is required for tissue regeneration to ensure the supply of oxygen and nutrients. In our previous work, we established sonication-induced silk fibroin hydrogel to load neural stem cells for brain tissue engineering applications. In this study, we explored the application of silk fibroin as an injectable hydrogel for vascularization of soft tissues. We investigated the ability of outgrowth endothelial cells (OECs) in mono-culture or in co-culture with human bone marrow-derived mesenchymal stem cells (BM-MSCs) to form capillary networks in silk fibroin hydrogels. Furthermore, the silk fibroin hydrogel was modified with IKVAV peptide revealing a sequence derived from the extracellular matrix component laminin-1 to test its effects on angiogenesis, using unmodified and VVIAK modified silk fibroin hydrogel as controls. In monocultures of OECs, no angiogenic structures were observed in silk fibroin hydrogels. In contrast, vascular structures were abundant and increased in co-culture, as confirmed by immunocytochemistry and scanning electron microscopy (SEM) over 10 d of culture in silk fibroin-based hydrogels. Although no significant differences in angiogenic activity seem to be caused by the IKVAV peptide in our experimental settings, these results indicate that sonication-induced silk fibroin-based hydrogels support the formation of functional endothelial tubes and vascularization networks in the presence of mesenchymal cells supporting the vascular sprouting of endothelial cells.

According to present knowledge, blood derived endothelial progenitor cells (EPC) might act as proangiogenic myeloid cells, which play a fundamental role in the regulation of angiogenesis and blood vessel reorganisation. In this context, we have evaluated the contribution of endogenous myeloid cells in co-cultures of blood derived outgrowth endothelial cells (OEC) and osteogenic cells. In addition, we investigated the role of EPC as a potential source of myeloid cells in the formation of vascular structures in an in vitro model consisting of mesenchymal stem cells (MSC) and OEC. For this purpose, we added EPCs to co-cultures of MSC and OECs. Vascular structures and the co-localisation of myeloid cells were analysed by confocal laser microscopy (CLSM) for endothelial and myeloid markers and quantitative image analysis. The molecular effects of myeloid cells were evaluated by quantitative real time PCR, ELISA and protein arrays from cell culture supernatants and lysates. Endogenous myeloid cells were significantly co-localised with angiogenic structures in co-cultures of OEC and osteogenic cells. The active addition of EPC to co-cultures of OEC and MSC resulted in a statistically approved increase in the formation of prevascular structures at early stages of the co-culture process. In addition, we observed an increase of endothelial markers, indicating beneficial effects of EPC or myeloid cells on endothelial cell growth. Furthermore, real time PCR indicated high expression levels of CD68, CD11b and CD163 in co-cultures of EPC and MSC indicating that EPC act at least partly as macrophage like-cells.

Fucoidan is a polysaccharide isolated from brown algae which is of current interest for anti-tumor therapy. In this study, we investigated the effect of fucoidan on the retinal pigment epithelium (RPE), looking at physiology, vascular endothelial growth factor (VEGF) secretion, and angiogenesis, thus investigating a potential use of fucoidan for the treatment of exudative age-related macular degeneration. For this study, human RPE cell line ARPE-19 and primary porcine RPE cells were used, as well as RPE/choroid perfusion organ cultures. The effect of fucoidan on RPE cells was investigated with methyl thiazolyl tetrazolium--assay, trypan blue exclusion assay, phagocytosis assay and a wound healing assay. VEGF expression was evaluated in immunocytochemistry and Western blot, VEGF secretion was evaluated in ELISA. The effect of fucoidan on angiogenesis was tested in a Matrigel assay using calcein-AM vital staining, evaluated by confocal laser scanning microcopy and quantitative image analysis. Fucoidan displays no toxicity and does not diminish proliferation or phagocytosis, but reduces wound healing in RPE cells. Fucoidan decreases VEGF secretion in RPE/choroid explants and RPE cells. Furthermore, it diminishes VEGF expression in RPE cells even when co-applied with bevacizumab. Furthermore, fucoidan reduces RPE-supernatant- and VEGF-induced angiogenesis of peripheral endothelial cells. In conclusion, fucoidan is a non-toxic agent that reduces VEGF expression and angiogenesis in vitro and may be of interest for further studies as a potential therapy against exudative age-related macular degeneration.

Stem cells are used to generate differentiated somatic cells including neuronal cells. Synthesis and release of acetylcholine, a neurotransmitter and widely expressed signaling molecule, were investigated in the murine embryonic stem cell line CGR8 during early differentiation, i.e. in the presence of leukemia inhibitory factor (LIF) to maintain pluripotency and in the absence of LIF to induce early differentiation. CGR8 cells express choline acetyltransferase (ChAT) as demonstrated by measurement of enzyme activity and substantial inhibition by bromoacetylcholine. Pluripotent CGR8 cells showed a ChAT activity of 250 pmol acetylcholine/mg/h, contained 1.1 pmol acetylcholine/10⁶ cells and released about 12.00 pmol acetylcholine/1 x 10⁶ cells/6 h. Removal of LIF induced early differentiation as evidenced by reduced transcription factors Oct-4 and Nanog and a substantial slowing of the proliferation rate. Under this condition acetylcholine synthesis increased to 1640 pmol/mg/h; related to the pluripotent state the content of acetylcholine increased 10-fold and the release to about 32 pmol acetylcholine/1 x 10⁶ cells/6 h. Enzyme kinetic analysis showed a significant increase of the K(m) for the precursor acetyl-CoA and of V(max) without a change of the K(m) for the precursor choline. In conclusion, early differentiation of the stem cell line CGR8 is associated with a substantial increase in ChAT activity and acetylcholine release.

The repair and regeneration of large bone defects, including the formation of functional vasculature, represents a highly challenging task for tissue engineering and regenerative medicine. Recent studies have shown that vascularization and ossification can be stimulated by mild heat stress (MHS), which would offer the option to enhance the bone regeneration process by relatively simple means. However, the mechanisms of MHS-enhanced angiogenesis and osteogenesis, as well as potential risks for the treated cells are unclear. We have investigated the direct effect of MHS on angiogenesis and osteogenesis in a co-culture system of human outgrowth endothelial cells (OECs) and primary osteoblasts (pOBs), and assessed cytotoxic effects, as well as the levels of various heat shock proteins (HSPs) synthesized under these conditions. Enhanced formation of microvessel-like structures was observed in co-cultures exposed to MHS (41°C, 1 h), twice per week, over a time period of 7-14 days. As shown by real-time polymerase chain reaction (PCR), the expression of vascular endothelial growth factor (VEGF), angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2), and tumor necrosis factor-alpha was up-regulated in MHS-treated co-cultures 24 h post-treatment. At the protein level, significantly elevated VEGF and Ang-1 concentrations were observed in MHS-treated co-cultures and pOB mono-cultures compared with controls, indicating paracrine effects associated with MHS-induced angiogenesis. MHS-stimulated co-cultures and OEC mono-cultures released higher levels of Ang-2 than untreated cultures. On the other hand MHS treatment of co-cultures did not result in a clear effect regarding osteogenesis. Nevertheless, real-time PCR demonstrated that MHS increased the expression of mitogen-activated protein kinase, interleukin-6, and bone morphogenetic protein 2, known as HSP-related molecules in angiogenic and osteogenic regulation pathways. In agreement with these observations, the expression of some selected HSPs also increased at both the mRNA and protein levels in MHS-treated co-cultures.

The morphogen sonic hedgehog (Shh) seems to mediate adult repair processes in bone regeneration and vascularisation. In this study we investigated the effects of Shh on co-cultures consisting of human primary osteoblasts and outgrowth endothelial cells in terms of angiogenic activation and vessel maturation in comparison to the treatment with the commonly used proangiogenic factor, VEGF. Both, stimulation with VEGF or Shh, leads to an increase in the formation of microvessel-like structures compared to untreated controls. In contrast to VEGF, proangiogenic effects by Shh could already be observed after 24 h of treatment. Nevertheless, after 14 days the angiogenic activity of OEC was comparable in VEGF- or Shh-treated co-cultures. Furthermore, Shh and VEGF resulted in different growth factor expression or release profiles. Compared to VEGF, Shh stimulates also the expression and secretion of angiopoietins which was detected as early as 24 h of treatment. Moreover, smooth muscle cell-related markers, such as alpha-smooth muscle actin, desmin and myocardin, as well as basement membrane components were clearly upregulated in response to Shh treatment compared to VEGF- or untreated controls. In terms of growth factors relevant for vessel stabilisation and maturation increased levels of PDGF-BB, angiopoietin-1 and TGF-beta were observed in cell culture supernatants when treated with Shh. This was in accordance with higher levels of smooth muscle actin in Shh-treated samples indicating the potential of Shh to improve the angiogenic activity and vessel stabilisation of human tissue engineered constructs. Experiments using cyclopamine, a Shh pathway inhibitor, blocked the effects of Shh.

A number of previous studies documented the angiogenic potential of outgrowth endothelial cells in vitro and in vivo and provided evidence that therapeutic success could depend on coculture or coimplantation strategies. Thus, deeper insight into the molecular mechanisms underlying this pro-angiogenic effect of cocultures might provide new translational options for tissue engineering and regenerative medicine. One promising signaling pathway in bone repair involved in neoangiogenesis and bone formation is the sonic hedgehog (Shh) pathway. In this article, we focus on the effect of Shh on the formation of microvessel-like structures and osteoblastic differentiation in cocultures of primary osteoblasts and outgrowth endothelial cells. Already after 24 h of treatment, Shh leads to a massive increase in microvessel-like structures compared with untreated cocultures. Increased formation of angiogenic structures seems to correlate with the upregulation of vascular endothelial growth factor or angiopoietins (Ang-1 and Ang-2) studied at both the mRNA and protein levels. In addition, treatment with cyclopamine, an inhibitor of hedgehog signaling, blocked the formation of microvessel-like structures in the cocultures. However, exogenous Shh also resulted in the upregulation of several osteogenic differentiation markers in real-time polymerase chain reaction, as well as in an increased mineralization and alkaline phosphatase activity. The present data highlight the central role of the Shh pathway in bone regeneration and vascularization. Further, Shh might have the potential to improve both angiogenesis and osteogenesis in clinical applications in the future.

For successful bone regeneration tissue engineered bone constructs combining both aspects, namely a high osteogenic potential and a rapid connection to the vascular network are needed. In this study we assessed the formation of pre-vascular structures by human outgrowth endothelial cells (OEC) from progenitors in the peripheral blood and the osteogenic differentiation of primary human osteoblasts (pOB) on micrometric silk fibroin scaffolds. The rational was to gain more insight into the dynamic processes involved in the differentiation and functionality of both cell types depending on culture time in vitro. Vascular tube formation by OEC was assessed quantitatively at one and 4 weeks of culture. In parallel, we assessed the temporal changes in cell ratios by flow cytometry and in the marker profiles of endothelial and osteogenic markers by quantitative real-time PCR. In terms of OEC, we observed an increase in tube length, tube area, number of nodes and number of vascular meshes within a culture period of 4 weeks, but a decrease in endothelial markers in real-time PCR. At the same time early osteogenic markers were downregulated, while marker expression associated with progressing mineralized matrix was upregulated in later stages of the culture. In addition, deposition of matrix components, such as collagen type I, known as a pro-angiogenic substrate for endothelial cells, appeared to increase with time indicated by immunohistochemistry. In summary, the study suggests a progressing maturation of the tissue construct with culture time which seems to be not effected by culture conditions mainly designed for outgrowth endothelial cells.

Chapter 2 Material-Induced Cellular Interactions Thomas K. Monsees, Thomas K. Monsees University of Technology Dresden, Medical Faculty Carl Gustav Carus, Department of Anatomy, Fetscherstrasse 74, 01307 Dresden, GermanySearch for more papers by this authorRichard H. W. Funk, Richard H. W. Funk University of Technology Dresden, Medical Faculty Carl Gustav Carus, Department of Anatomy, Fetscherstrasse 74, 01307 Dresden, GermanySearch for more papers by this authorHartwig Wolburg, Hartwig Wolburg University of Tübingen, Institute of Pathology, Liebermeisterstrasse 8, 72076 Tübingen, GermanySearch for more papers by this authorFriederike Pfeiffer, Friederike Pfeiffer University of Bern, Theodor Kocher Institute, Freiestrasse 1, 3012 Bern, SwitzerlandSearch for more papers by this authorAndreas Heeren, Andreas Heeren University of Tübingen, Institute of Applied Physics, Auf der Morgenstelle 10, 72076 Tübingen, GermanySearch for more papers by this authorWolfgang Henschel, Wolfgang Henschel University of Tübingen, Institute of Applied Physics, Auf der Morgenstelle 10, 72076 Tübingen, GermanySearch for more papers by this authorJürgen Geis-Gerstorfer, Jürgen Geis-Gerstorfer University of Tübingen, Department of Prosthodontics, Section Medical Materials and Technology, Osianderstrasse 2–8, 72076 Tübingen, GermanySearch for more papers by this authorLutz Scheideler, Lutz Scheideler University of Tübingen, Department of Prosthodontics, Section Medical Materials and Technology, Osianderstrasse 2–8, 72076 Tübingen, GermanySearch for more papers by this authorDieter Kern, Dieter Kern University of Tübingen, Institute of Applied Physics, Auf der Morgenstelle 10, 72076 Tübingen, GermanySearch for more papers by this authorKirsten Peters, Kirsten Peters University of Rostock, Junior Research Group, Department of Cell Biology, Schillingallee 69, 18057 Rostock, GermanySearch for more papers by this authorRonald E. Unger, Ronald E. Unger Johannes Gutenberg University, Institute of Pathology, REPAIR-Lab, Langenbeckstrasse 1, 55101 Mainz, GermanySearch for more papers by this authorRoman Tsaryk, Roman Tsaryk Johannes Gutenberg University, Institute of Pathology, REPAIR-Lab, Langenbeckstrasse 1, 55101 Mainz, GermanySearch for more papers by this authorHarald Schmidt, Harald Schmidt Laboratory for Applied Molecular Physiology, Becherweg 11, 55099 Mainz, GermanySearch for more papers by this authorGünter Kamp, Günter Kamp Johannes Gutenberg University, Institute of Zoology, Becherweg 9, 55099 Mainz, GermanySearch for more papers by this authorProf. Dr. C. James Kirkpatrick, Prof. Dr. C. James Kirkpatrick Johannes Gutenberg University, Institute of Pathology, REPAIR-Lab, Langenbeckstrasse 1, 55101 Mainz, GermanySearch for more papers by this author Thomas K. Monsees, Thomas K. Monsees University of Technology Dresden, Medical Faculty Carl Gustav Carus, Department of Anatomy, Fetscherstrasse 74, 01307 Dresden, GermanySearch for more papers by this authorRichard H. W. Funk, Richard H. W. Funk University of Technology Dresden, Medical Faculty Carl Gustav Carus, Department of Anatomy, Fetscherstrasse 74, 01307 Dresden, GermanySearch for more papers by this authorHartwig Wolburg, Hartwig Wolburg University of Tübingen, Institute of Pathology, Liebermeisterstrasse 8, 72076 Tübingen, GermanySearch for more papers by this authorFriederike Pfeiffer, Friederike Pfeiffer University of Bern, Theodor Kocher Institute, Freiestrasse 1, 3012 Bern, SwitzerlandSearch for more papers by this authorAndreas Heeren, Andreas Heeren University of Tübingen, Institute of Applied Physics, Auf der Morgenstelle 10, 72076 Tübingen, GermanySearch for more papers by this authorWolfgang Henschel, Wolfgang Henschel University of Tübingen, Institute of Applied Physics, Auf der Morgenstelle 10, 72076 Tübingen, GermanySearch for more papers by this authorJürgen Geis-Gerstorfer, Jürgen Geis-Gerstorfer University of Tübingen, Department of Prosthodontics, Section Medical Materials and Technology, Osianderstrasse 2–8, 72076 Tübingen, GermanySearch for more papers by this authorLutz Scheideler, Lutz Scheideler University of Tübingen, Department of Prosthodontics, Section Medical Materials and Technology, Osianderstrasse 2–8, 72076 Tübingen, GermanySearch for more papers by this authorDieter Kern, Dieter Kern University of Tübingen, Institute of Applied Physics, Auf der Morgenstelle 10, 72076 Tübingen, GermanySearch for more papers by this authorKirsten Peters, Kirsten Peters University of Rostock, Junior Research Group, Department of Cell Biology, Schillingallee 69, 18057 Rostock, GermanySearch for more papers by this authorRonald E. Unger, Ronald E. Unger Johannes Gutenberg University, Institute of Pathology, REPAIR-Lab, Langenbeckstrasse 1, 55101 Mainz, GermanySearch for more papers by this authorRoman Tsaryk, Roman Tsaryk Johannes Gutenberg University, Institute of Pathology, REPAIR-Lab, Langenbeckstrasse 1, 55101 Mainz, GermanySearch for more papers by this authorHarald Schmidt, Harald Schmidt Laboratory for Applied Molecular Physiology, Becherweg 11, 55099 Mainz, GermanySearch for more papers by this authorGünter Kamp, Günter Kamp Johannes Gutenberg University, Institute of Zoology, Becherweg 9, 55099 Mainz, GermanySearch for more papers by this authorProf. Dr. C. James Kirkpatrick, Prof. Dr. C. James Kirkpatrick Johannes Gutenberg University, Institute of Pathology, REPAIR-Lab, Langenbeckstrasse 1, 55101 Mainz, GermanySearch for more papers by this author Book Editor(s):Prof. Dr. Jürgen Breme, Prof. Dr. Jürgen Breme Saarland University, Department of Metallic Materials, Postfach 151150, 66041 Saarbrücken, GermanySearch for more papers by this authorProf. Dr. C. James Kirkpatrick, Prof. Dr. C. James Kirkpatrick Johannes Gutenberg University, Institute of Pathology, REPAIR-Lab, Langenbeckstrasse 1, 55101 Mainz, GermanySearch for more papers by this authorProf. Dr. Roger Thull, Prof. Dr. Roger Thull Bayerische Julius-Maximilians-Universität Würzburg, Department of Functional Materials in Medicine and Dentistry, Pleicherwall 2, 97070 Würzburg, GermanySearch for more papers by this author First published: 20 February 2008 https://doi.org/10.1002/9783527622603.ch11 AboutPDFPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShareShare a linkShare onFacebookTwitterLinked InRedditWechat Summary This chapter contains sections titled: Cell-Specific Compatibility with Materials Endothelial Cell-Specific Aspects in Biocompatibility Testing In Vitro References Metallic Biomaterial Interfaces RelatedInformation

Divalent cobalt ions (Co2+) induce the expression of hypoxia responsive genes and are often used in cell biology to mimic hypoxia. In this in vitro study we compared the effects of hypoxia and Co2+ on human endothelial cells and examined processes that are stimulated in hypoxia in vivo (proliferation and angiogenesis). We analyzed the expression of the hypoxia-inducible factor-1α (HIF-1α) under different hypoxic conditions (3% and nearly 0% O2) and Co2+-concentrations (0.01–0.7 mM). As in hypoxia, the amount of HIF-1α protein was enhanced by exposure to Co2+ (did not correlate with mRNA amount). However, contrary to the results of hypoxia, in vitro-angiogenesis was inhibited after exposure to even low Co2+-concentrations (≥0.01 mM). This led to the conclusion that although hypoxia signaling after Co2+-exposure took place, further yet unknown Co2+-induced event(s) must have occurred. (Mol Cell Biochem 270: 157–166, 2005)

Endothelial cells line the intimal surface of blood vessels forming the interface between blood and tissue. Endothelial cells are unique in that they can form new capillaries from preexisting blood vessels (angiogenesis). Angiogenesis in vivo is a complex and highly regulated process, which becomes dysregulated under pathological conditions such as tumor growth, diabetic retinopathy and psoriasis. The fundamental significance of angiogenesis in these diseases has resulted in extensive research for pharmaceuticals affecting angiogenesis. We have established an in vitro model of angiogenesis which utilizes human endothelial cells (Figure 1) and have defined criteria for a software-supported image quantification (SSIQ) for analyzing the effects of compounds on angiogenesis.