In vivo effects of vascular endothelial growth factor on the chicken chorioallantoic membrane

Ambrosy

Wilting

et al. 1995

Developmental Dynamics

Self Cite

Section: Effects Of Vegfsupporting

confidence: 75%

Proliferation pattern of capillary endothelial cells in chorioallantoic membrane development indicates local growth control, which is counteracted by vascular endothelial growth factor application

Ambrosy

Wilting

et al. 1995

Developmental Dynamics

Self Cite

“…Differences between various controls or between various VEGF isoforms were not significant. We conclude that (1) the carrier material was well suited for the CAM assay because it did not induce changes of the vascular pattern as compared with the situation when no carrier was present; (2) the endothelium-specific mitogenic effect of the 165 (Wilting et al, 1993 and 121 (Wilting et al, 1996) amino acid isoforms induced a greater complexity of the vascular pattern at the site of application, which corresponded to the histologically verified multiple layers of capillaries and precapillary vessels, and to the visual impression of a higher bifurcation density; (3) the XCM was superior to the BCM because of its stability and reduced variance. …”

Section: Complexity Of Cam Blood Vessel Pattern Is Increased By Vegfmentioning

confidence: 96%

“…This can be verified by time-consuming histological techniques, or much faster by image analysis of the altered vessel arrangement in whole mounts. For details on CAM structure and histology, and on the CAM assay for angiogenesis, the reader is referred to Wilting et al (1993Wilting et al ( , 1996, and references therein, and to Kurz et al (1994, 1995). We here provide only brief information in specimens and growth factors.…”

Section: Application To Angiogenesis Researchmentioning

confidence: 99%

Measuring fractal dimension and complexity — an alternative approach with an application

Sandau¹,

1997

Journal of Microscopy

SummaryFractal dimension has often been applied as a parameter of complexity, related to, for example, surface roughness, or for classifying textures or line patterns. Fractal dimension can be estimated statistically, if the pattern is known to be self-similar. However, the fractal dimension of more general patterns cannot be estimated, even though the concept may be retained to characterize complexity. We here show that the usual statistical methods, e.g. the box counting method, are not appropriate to measure complexity. A recently developed approach, the extended counting method, whose properties are closer to what fractal dimension means, is considered here in more detail. The methods are applied to geometric and to blood vessel patterns. The weak assumptions about the structure, and the lower variance of the estimate, suggest that the extended counting method has beneficial properties for comparing complexity of naturally occurring patterns.

“…The former has been implicated in vascular remodeling within adult tissues (Maisonpierre et al, 1997), whereas the latter is known to be essential for pericyte recruitment in the retina (Benjamin et al, 1998), brain (Hellstrom et al, 1999, and placenta (Ohlsson et al, 1999). Notably, the application of PDGF-B to fully developed CAMs leads to an abundant formation of larger pre-and postcapillary microvessels but does not amplify capillary meshes (Oh et al, 1998), whereas exogenous VEGF-A affects the capillary plexus and terminal feeding vessels, but has no influence on larger microvessels (Wilting et al, 1993;Kurz et al, 1995). Our assumption that endothelial cells respond to local challenges when initiating IBR is strongly supported by two recent observations: endothelial grafting in the chick-quail system showed that expression of the arterial marker ephrin-B2 depends on hemodynamics or local environment (Othman-Hassan et al, 2001); and serial section histology demonstrated intussusceptive remodeling in conditions of severely altered blood flow during tissue repair or tumor angiogenesis (Patan et al, 2001a,b).…”

Section: Possible Molecular Mechanisms Involved In Vascular Remodelingmentioning

confidence: 99%

Optimality in the developing vascular system: Branching remodeling by means of intussusception as an efficient adaptation mechanism

Djonov

Burri

2002

Developmental Dynamics

189

218

The theory of bifurcating vascular systems predicts vessel diameters that are related to optimality criteria like minimization of pumping energy or of building material. However, mechanisms for producing the postulated optimality have not been described so far, and quantitative data on bifurcation diameters during development are scarce. We used an embryonic vascular bed that rapidly grows and adapts to changing hemodynamic conditions, the chicken chorioallantoic membrane (CAM), and correlated vascular cast and tissue section morphology with in vivo time-lapse video monitoring. The bifurcation exponent ⌬ and associated parameters were quantitatively assessed in arterial and venous microvessels ranging in diameter from 30 to 100 m. We observed emergence of optimality by means of intussusception, i.e., formation of transvascular tissue pillars. In addition to intussusceptive microvascular growth (IMG ‫؍‬ expansion of capillary networks) and intussusceptive arborization (IAR ‫؍‬ formation of feeding vessels from capillaries) the observed intussusception at bifurcations represents a third variant of nonsprouting angiogenesis. We call it intussusceptive branching remodeling (IBR). IBR occurred in vessels of considerable diameter by means of two alternative mechanisms: either through pillars arising close to a bifurcation, which increased in girth until they merged with the connective tissue in the bifurcation angle; or through pillars arising at some distance from the bifurcation point, which then expanded by formation of ingrowing tissue folds until they became connected to the tissue of the bifurcation angle. Morphologic evidence suggests that IBR is a wide-spread phenomenon, taking place also in lung, intestinal, kidney, eye, etc., vasculature. Irrespective of the mode followed, IBR led to a branching pattern close to the predicted optimum, ⌬ ‫؍‬ 3.0. Significant differences were observed between ⌬ at arterial bifurcations (2.70 to 2.90) and ⌬ at venous bifurcations (2.93 to 3.75). IBR, by means of eccentric pillar formation and fusion, was also involved in vascular pruning. Experimental changes in CAM hemodynamics (by locally increasing blood flow) induced onset of IBR within less than 1 hr. Our study provides morphologic and quantitative evidence that a similar cellular machinery is used for all three variants of vascular intussusception, IMG, IAR, and IBR. It thus provides a mechanism of efficiently generating complex blood transport systems from limited genetic information. Differential quantitative outcome of IBR in arteries and veins, and the experimental induction of IBR strongly suggest that hemodynamic factors can instruct embryonic vascular remodeling toward optimality.