Cancer Biology

Nuclear blood pool imaging using radiolabeled red blood cells has been used in the clinical setting for the evaluation of a number of medical conditions including gastrointestinal hemorrhage, impaired cardiac contractility, and altered cerebrovascular blood flow. Nuclear blood pool imaging is typically performed using Technetium-99m-labeled (^99mTc) human erythrocytes (i.e., the “tagged RBC” scan) and gamma camera-based planar scintigraphic imaging. When compared to typical clinical planar scintigraphy and single-photon emission computed tomographic (SPECT) imaging platforms, positron emission tomography (PET) provides superior image quality and sensitivity. A number of PET-based radionuclide agents have been proposed for blood pool imaging, but none have yet to be used widely in the clinical setting. In this protocol, we described a simple and fast procedure for imaging the vasculature of immunodeficient mice through a combination of a small animal positron emission tomography/computed tomography (PET/CT) scanner and human erythrocytes labeled with the PET tracer 2-deoxy-2-(¹⁸F)fluoro-D-glucose (¹⁸F-FDG). This technique is expected to have significant advantages over traditional ^99mTc -labeled erythrocyte scintigraphic nuclear imaging for these reasons.

Angiogenesis is a multifactorial event which requires the migration, proliferation, differentiation and structure rearrangement of endothelial cells. This angiogenic process has been commonly studied using in vitro assays such as Boyden chamber assay, wound healing assay and tube formation assay. These assays mainly use monolayers of endothelial cells which are modified by repeated passages and are fully proliferative, a situation far away from physiology. In addition, not only endothelial cells are involved in this process but surrounding cells (such as pericytes, smooth muscle cells, fibroblasts) and the supporting matrix are also major players.

The three-dimensional ex vivo aortic ring model recapitulates the complexities of angiogenesis and combines the advantages of in vitro and in vivo models. The aortic ring is cultivated in a chemically defined culture environment. Microvessels which grow in this system are lumenized vessels with surrounding supporting cells and are essentially indistinguishable from microvessels formed during angiogenesis in vivo. The efficacy of pro-or anti-angiogenic factors can be determined in the absence of serum molecules which may otherwise interfere with the substances being tested (Nicosia and Ottinetti, 1990). However, this system requires access to fresh rat tissue but several samples can be prepared from one aorta.