Rat Mesentery Exteriorization: A Model for Investigating the Cellular Dynamics Involved in Angiogenesis

Abstract

Microvacular network growth and remodeling are critical aspects of wound healing, inflammation, diabetic retinopathy, tumor growth and other disease conditions 1,2 . Network growth is commonly attributed to angiogenesis, defined as the growth of new vessels from pre-existing vessels. The angiogenic process is also directly linked to arteriogenesis, defined as the capillary acquisition of a perivascular cell coating and vessel enlargement. Needless to say, angiogenesis is complex and involves multiple players at the cellular and molecular level 3 . Understanding how a microvascular network grows requires identifying the spatial and temporal dynamics along the hierarchy of a network over the time course of angiogenesis. This information is critical for the development of therapies aimed at manipulating vessel growth.The exteriorization model described in this article represents a simple, reproducible model for stimulating angiogenesis in the rat mesentery. It was adapted from wound-healing models in the rat mesentery [4][5][6][7] , and is an alternative to stimulate angiogenesis in the mesentery via i.p. injections of pro-angiogenic agents 8,9 . The exteriorization model is attractive because it requires minimal surgical intervention and produces dramatic, reproducible increases in capillary sprouts, vascular area and vascular density over a relatively short time course in a tissue that allows for the two-dimensional visualization of entire microvascular networks down to single cell level. The stimulated growth reflects natural angiogenic responses in a physiological environment without interference of foreign angiogenic molecules. Using immunohistochemical labeling methods, this model has been proven extremely useful in identifying novel cellular events involved in angiogenesis. Investigators can readily correlate the angiogenic metrics during the time course of remodeling with time specific dynamics, such as cellular phenotypic changes or cellular interactions 4,5,7,10,11 .

Anti‐VEGFR agents ameliorate hepatic venous dysregulation/microcirculatory dysfunction, splanchnic venous pooling and ascites of NASH‐cirrhotic rat

“…In another one set of rats, the splanchnic (superior mesenteric artery) blood flow and angiogenesis (mesenteric window vascular length and area) were measured with flow probes and FITC‐labelled CD31 immunoflurensence (IF) staining as previous studies to confirm the in vivo image finding of anti‐VEGFR agents chronic treatment . In splanchnic angiogenesis measurement, 6–8 vascularized mesenteric windows were identified and a mesenteric window is defined as the thin translucent membrane in between the artery/vein pairs feeding the small intestine . In addition, splanchnic (mesentery and intestines) tissue was collected to measurement various angiogenic (PDGFRβ and α‐SMA), vasodilatory [VEGFR2, PI3K(p85), eNOS] protein expressions with antibodies as in Experiment 2 .…”

VEGF‐C Induces Lymphangiogenesis and Angiogenesis in the Rat Mesentery Culture Model

“…Such a response has been associated with the aortic ring model . Given that chronic angiogenesis in the rat mesentery in vivo can be stimulated by simply exteriorizing the tissue , a sham‐like response in our culture system is not surprising. This effect, however, on the time duration for angiogenesis and lymphangiogenesis studies remains to be investigated.…”

Concomitant inhibition of oxidative stress and angiogenesis by chronic hydrogen‐rich saline and N‐acetylcysteine treatments improves systemic, splanchnic and hepatic hemodynamics of cirrhotic rats

“…In the same set of rats in Experiment 4, the splanchnic (superior mesenteric artery) angiogenesis (mesenteric window vascular length and area) were measured with flow probes and fluorescein isothiocyanate‐labeled CD31 immunofluorescent staining as per a previous study …”