Rat Mesentery Angiogenesis Assay

The adult rat mesentery window angiogenesis assay is biologically appropriate and is exceptionally well suited to the study of sprouting angiogenesis in vivo [see review papers], which is the dominating form of angiogenesis in human tumors and non-tumor tissues, as discussed in invited review papers1,2. Angiogenesis induced in the membranous mesenteric parts by intraperitoneal (i.p.) injection of a pro-angiogenic factor can be modulated by subcutaneous (s.c.), intravenous (i.v.) or oral (p.o.) treatment with modifying agents of choice. Each membranous part of the mesentery is translucent and framed by fatty tissue, giving it a window-like appearance

On Connective Tissue Mast Cells as Protectors of Life, Reproduction, and Progeny

The connective tissue mast cell (MC), a sentinel tissue-residing secretory immune cell, has been preserved in all vertebrate classes since approximately 500 million years. No physiological role of the MC has yet been established. Considering the power of natural selection of cells during evolution, it is likely that the MCs exert essential yet unidentified life-promoting actions. All vertebrates feature a circulatory system, and the MCs interact readily with the vasculature. It is notable that embryonic MC progenitors are generated from endothelial cells. The MC hosts many surface receptors, enabling its activation via a vast variety of potentially harmful exogenous and endogenous molecules and via reproductive hormones in the female sex organs. Activated MCs release a unique composition of preformed and newly synthesized bioactive molecules, like heparin, histamine, serotonin, proteolytic enzymes, cytokines, chemokines, and growth factors. MCs play important roles in immune responses, tissue remodeling, cell proliferation, angiogenesis, inflammation, wound healing, tissue homeostasis, health, and reproduction. As recently suggested, MCs enable perpetuation of the vertebrates because of key effects—spanning generations—in ovulation and pregnancy, as in life-preserving activities in inflammation and wound healing from birth till reproductive age, thus creating a permanent life-sustaining loop. Here, we present recent advances that further indicate that the MC is a specific life-supporting and progeny-safeguarding cell

2.5 kDa and 5.0 kDa heparin fragments specifically inhibit microvessel sprouting and network formation in VEGF165-mediated mammalian angiogenesis

Tumour growth is angiogenesis dependent. Thrombosis and thromboembolism are very common in cancer patients. These patients are often treated with heparin as an anti-coagulant. Many tumour angiogens, including VEGF165, and endogenous anti-angiogenesis factors bind heparin tightly. Using the non-surgical mesenteric-window angiogenesis assay, we studied in detail the systemic effect of heparin fractions with a mean MW of 2.5, 5.0 and 16.4 kDa on the microvessel sprouting and network formation in angiogenesis mediated by VEGF165 in rats. The microvessel network was assessed objectively in terms of the number and lengths of segments (the distance between two successive branching points), the number of branching points, the degree of tortuosity, the index of interconnecting loop formation, the index of intersection, as well as the number and lengths of sprouts. Compared with the saline control, the 2.5 kDa fraction significantly shortened the microvessel sprouts and the microvessel segments but increased the microvessel tortuosity in statistical terms; the 5.0 kDa fraction statistically significantly shortened the sprouts, decreased the number of segments and the number of microvessel branching points; whereas the 16.4 kDa fraction statistically significantly elongated the longest segments. Moreover, statistically significant differences were found between the three heparin fractions in terms of microvessel tortuosity (2.5 vs. 16.4 kDa), index of loop formation (5.0 vs. 2.5 + 16.4 kDa) and index of intersection (5.0 vs. 16.4 kDa). These findings demonstrate that heparin fragments size-specifically inhibit microvessel sprouting and network formation in VEGF165-mediated angiogenesis. As VEGF165 is a potent angiogen in human tumours, we suggest that heparin enriched in 2.5 kDa species and 5.0 kDa species especially should be exploited as a combined anti-coagulant and specific adjuvant anti-angiogenic agent in cancer patients who require anti-coagulant therapy