Intravital Fluorescence Facilitates Measurement of Multiple Physiologic Functions and Gene Expression in Tumors of Live Animals

Abstract

The purpose of this report is to present an overview of the use of fluorescence imaging in vivo, with particular emphasis on oncology. It is important to note, however, that many of the methods described herein have been applied to the study of non-malignant tissues as well. Modern medicine and biology research has benefited greatly from an ever-expanding assortment of fluorescent markers and labels. These markers and labels have allowed investigators to observe the behavior and properties of cell and molecular entities of interest in the context of complicated biological systems such as a mammalian cell or a whole mouse. Methods developed to image fluorescence in whole mice have been valuable in studying patterns of tumor growth and metastases. Alternatively, more detailed information and a wide variety of endpoints can be obtained using “intravital” preparations. This review focuses on use of fluorescence imaging for intravital preparations. For detail on fluorescence imaging of whole animals, refer to reviews on this subject [1,2]. For oncologic applications, studies have focused primarily on window chamber preparations that allow for real-time visualization of tumor growth, vascularity, vascular responses to stimulation, vascular permeability, vascular orientation, flow instability, and the like. These endpoints have been used to show that there are functional differences between tumor and normal tissues with respect to these functions under baseline conditions and after therapeutic manipulation. Examples of some of these differences are provided in this review as a means to illustrate how they can be used.

Tomographic Fluorescence Mapping of Tumor Targets

“…9L-GFP tumors were implanted in a dorsal skin chamber, 1 week before imaging session (2). Immediately before imaging, gas anesthetized animals received an i.v.…”

Intravital Microscopic Characterization of Suramin Effects in an Orthotopic Immunocompetent Rat Model of Pancreatic Cancer

“…[14][15][16][17][18] Briefly, the animals were anesthetized with Rompun and Ketamine as described above. Polyethylene catheters (inside diameter, 0.5 mm; B.Braun, Germany) were inserted into the right jugular vein and the left carotid artery for monitoring heart rate, blood pressure, and injection of substances needed for intravital microscopy.…”

The Role of Blood-Brain Barrier Permeability in Brain Tumor Imaging and Therapeutics

“…The animal is then monitored while tumor growth occurs, allowing visualization of blood vessel formation. Using fluorescent microscopy, the extravasation of fluorescent-labeled particles from vessels can be used to measure permeability in a quantitative manner [6] (Fig. 1).…”