Simultaneous measurement of RBC velocity, flux, hematocrit and shear rate in vascular networks

Abstract

Not all tumor vessels are equal. Tumor-associated vasculature includes immature vessels, regressing vessels, transport vessels undergoing arteriogenesis and peritumor vessels influenced by tumor growth factors. Current techniques for analyzing tumor blood flow do not discriminate between vessel subtypes and only measure average changes from a population of dissimilar vessels. We have developed methodologies for simultaneously quantifying blood flow (velocity, flux, hematocrit and shear rate) in extended networks at single capillary resolution in vivo. Our approach relies on deconvolution of signals produced by labeled red blood cells as they move relative to the scanning laser of a confocal or multiphoton microscope and provides fully-resolved three-dimensional flow profiles within vessel networks. Using this methodology, we show that blood velocity profiles are asymmetric near intussusceptive tissue structures in tumors in mice. Furthermore, we show that subpopulations of vessels, classified by functional parameters, exist in, around a tumor and in normal brain.

Vascular Normalization as a Therapeutic Strategy for Malignant and Nonmalignant Disease

“…The haphazard and bizarre distribution of vessels leads to heterogeneous blood flow, sluggish in some regions and excessive in others (Jain 1988(Jain , 2005bKamoun et al 2010). In addition, reduced PVC coverage, EC dissociation, and an excess of vesiculo-vaculor organelles (VVOs) results in marked tumor vessel permeability, with excess extravasation of fluid and protein into the extracellular compartment (Jain 2005b).…”

Image-based modelling of skeletal muscle oxygenation

“…For the validation of a blood haemodynamics model Liu et al [152] perfused the muscle of an anesthetized rat with Tyrode's solution. Similarly, in an effort to validate computational modelling results for tissue oxygen supply, the vasculature could be perfused with fluorescent nanoparticles and their diffusion into the tissue could be recorded visually, similar to the work of Kamoun et al [9]. Another, likely more robust approach is to make use of in vivo imaging techniques that are able to capture oxygenation and blood vessel morphology.…”

“…However, this approach was limited to 2D and to an isolated environment. For 3D imaging in vivo of RBCs, Kamoun et al [9] proposed the use of CLSM or multiphoton laser scanning microscopy (a method similar to CLSM, however not using a pinhole aperture but the laser beam itself for optical sectioning of the sample) to capture fluorescently labelled RBCs. Phase-contrast SR CT can also be extended to image the RBC distribution within a 3D tissue sample; however, the information will then still be intrinsically ex vivo, but closer to the in vivo case than in any existing image-based tissue oxygenation model.…”

Real-time intravital microscopy of individual nanoparticle dynamics in liver and tumors of live mice

“…Dynamic biological processes for which quantitative IVM procedures have been implemented include the assessment of vascular morphology 8 , permeability 9 , flow 10 , and response to therapy 11 . IVM is also well suited for imaging the dynamics of nanoparticles in vivo, and as result, IVM is increasingly leveraged for the design and optimization of nanotherapeutics [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] .…”

“…Tip Liver IVM may also be performed on an inverted microscope while maintaining adequate blood flow 10,[53][54][55] . We find an upright microscope to be more flexible for advanced tissue preparations, since it does not require custom stages for each new preparation and allows users to directly visualize where the tissue is being illuminated.…”