Angiogenesis and blood flow

Magnetic resonance angiography (MRA) is a method of imaging blood vessels in the presence of certain diseases, such as angiogenesis, tumors, atherosclerosis, coronary arteries [100], myocardium infarction, vascular injury, and blood flow reduction. Blood pool CA enhanced MRA increases the vessel-to-background ratio [101]. Blood pool CAs can be classified into two types, namely, low molecular weight Gd-based CAs and macromolecular CAs. 

Warren BA (1979) The vascular morphology of tumors. In Peterson H-I (ed) Tumor Blood Circulation Angiogenesis, Vascular Morphology and Blood Flow of Experimental Human Tumors CRC Press, Florida, pp. 1-47. 

At the simplest level, the successful delivery of cytotoxic agents, either as small molecules or associated with polymers or liposomes, to a soUd tumour depends on the relationship between the tumour cells and the blood vessels supporting their growth. Therefore the first requirement for effective delivery is a fully functional vasculature with respect to perfusion function. For those strategies of treatment where blockade of the tumour blood flow or inhibition of tumour growth is associated with angiogenesis, other considerations need to be taken into account as will be discussed in Chapter 9. 

Lipid A can also inhibit angiogenesis, blood flow in the tumor and the secretion of immunosuppressive TGF-P by the tumor cells. 

Compound efficacy has been correlated with the inhibition of angiogenesis in a variety of assays (endothelial capillary tube formation, aortic ring assay, chorioallantoic membrane assay, real-time tumor blood flow and PO2 measurements, tumor blood vessel density, and tumor hypoxic and apoptotic fractions) [35]. 

Increases in vascular density, tissue blood volume, or blood flow may be useful outcome measures of angiogenesis. However, vascular density is also modulated by vascular regression and changes in the perivascular tissue such as edema matrix synthesis and cellular proliferation, infiltration, and apoptosis. Blood flow is particularly confounded by vascular tone, and many angiogenic factors are also vasodilators. It may be difficult to distinguish angiogenesis from the increased blood flow that is associated with inflammation. 

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