Lectin Intravital Perfusion Studies in Tumor-bearing Mice: Micrometer-resolution, Wide-area Mapping of Microvascular Labeling, Distinguishing Efficiently and Inefficiently Perfused Microregions in the Tumor

Intravital lectin perfusion was combined with computer-guided scanning digital microscopy to map the perfused elements of the vasculature in tumor-bearing mice. High-precision composite images (spatial precision 1.3 μm and optical resolution 1.5 μm) were generated to permit exact positioning, reconstruction, analysis, and mapping of entire tumor cross-sections (c. 1 cm in diameter). Collation of these mosaics with nuclear magnetic resonance maps in the same tumor plane identified sites of rapid contrast medium uptake as tumor blood vessels. Digitized imaging after intravital double labeling allowed polychromatic visualization of two different types of mismatched staining. First, simultaneous application of two lectins, each bearing a different fluorochrome, revealed organ-specific differential processing in the microvascular wall. Second, sequential application of two boluses of one lectin, bearing different fluorochromes successively, distinguished between double-labeled microvessels, representing efficiently perfused vascular segments, and single-labeled microvessels, with inefficient or intermittent perfusion. Intravital lectin perfusion images of blood vessels in the vital functional state thus highlighted biologically significant differences in vessel function and served as high-resolution adjuncts to MR imaging.