Automatiserad Mätning av blodcirkulationens Blood Flow Velocity i Lung Metastaser av råttor
Summary
A method is presented to measure microcirculatory blood flow velocity in pulmonary cancer metastases of the pleural surface in rats in an automated fashion, using closed-chest pulmonary intravital microscopy. This model has potential to be used as a widespread tool to perform physiologic research on pulmonary metastases in rodents.
Abstract
Because the lung is a major target organ of metastatic disease, animal models to study the physiology of pulmonary metastases are of great importance. However, very few methods exist to date to investigate lung metastases in a dynamic fashion at the microcirculatory level, due to the difficulty to access the lung with a microscope. Here, an intravital microscopy method is presented to functionally image and quantify the microcirculation of superficial pulmonary metastases in rats, using a closed-chest pulmonary window and automated analysis of blood flow velocity and direction. The utility of this method is demonstrated to measure increases in blood flow velocity in response to pharmacological intervention, and to image the well-known tortuous vasculature of solid tumors. This is the first demonstration of intravital microscopy on pulmonary metastases in a closed-chest model. Because of its minimized invasiveness, as well as due to its relative ease and practicality, this technology has the potential to experience widespread use in laboratories that specialize on pulmonary tumor research.
Introduction
The lung is one of the most important target organs of metastatic disease, and because this condition is difficult to treat successfully with chemo- and radiation therapy, a cure is still rare1,2. Specific pathophysiological and microcirculatory features of solid primary and metastatic tumors, such as microregional hypoxia, diffusion limitation and inefficient tumor vasculature, greatly contribute to their resistance to anticancer treatment3,4. Due to the microscopic scale and dynamic nature of parameters such as microvascular blood flow, intravital microscopy of the tumor in the living animal has become a very important research tool in the field5. While intravital microscopy models have been applied to tumors in different organ sites, including the metastatic lung within an open rib cage, no protocol has been developed yet for the research of pulmonary metastases in a physiologically preserving, closed-chest environment6,7. Such an endeavor is particularly hampered by the necessity to surgically access the rib cage without affecting the overall function of the lung7-9. Recently, a method was introduced to image pulmonary microcirculatory blood flow in a close-chest setting in live rats, using fluorescence intravital microscopy10. This protocol enables the systematic quantification of blood flow velocity from injected, fluorescently labeled red blood cells, using computerized analysis, while keeping the animal physiologically stable and preserving the integrity of the lung11. In this present study, it is shown how this technology can be modified to image and quantify microcirculatory blood flow in tail vein-inoculated pulmonary metastases on the pleural surface in the immunocompromised rat. This model is also the first one to study metastatic lung tumors in a closed-chest intravital microscopy setting.
Protocol
Representative Results
Discussion
En modell presenteras som är möjligt att bildförändringar blodcirkulationens blodflödet och andra dynamiska processer i lungmetastaser av råttor, med hjälp intravital mikroskopi och beräkningsanalys blodflödet. Medan andra metoder finns för att utföra mikroskopi på utsatta lungor i öppna bröstkorgar av gnagare, är denna modell också den första att avbilda lungmetastaser genom en bröstväggen perforering i en miljö med sluten bröstet. Med denna metod är möjligheten visat att mäta farmakologiskt ind…
Disclosures
The authors have nothing to disclose.
Acknowledgements
The scientific advice of Drs. Timothy McMahon and Siqing Shan is appreciated. The presenters thank Drs. David Kirsch and Patricia Steeg for the generous gift of the fluorescently labeled Mouse Sarcoma and metastatic MDAMB-231 cells, respectively. This work was funded in part by the U.S. Defense Advanced Research Projects Agency (DARPA) Prime Award Number N66001-10-C-2134, and in part by the Department of Radiation Oncology, Duke University Medical Center.
Materials
| Name of Material/ Equipment | Company | Catalog Number | Comments/Description |
| Athymic nude rats | Charles River | Strain code 316 | Female 10 week-old athymic nude rats |
| micro-CT/micro-Irradiator | Precision X-ray Inc. | Xrad 225Cx | Use MicroCT to detect metastases |
| DiI (1,1=-dioctadecyl-3,3,3=,3=-tetramethyl-indocarbocyanine perchlorate) | Sigma Aldrich | 468495-100MG | Mix 100 ul packed red blood cells with 100 ul of 0.5 mg/ml DiI in 200 proof ethanol, 2 ml of 5% dextrose solution in water, and fill up to a 10-ml final volume with saline |
| Rodent ventilator | Kent Scientific | TOPO Small Animal Ventilator | Device is important to maintain positive lung pressure after application of pneumothorax |
| Zeiss Axioskop fluorescence microscope upright | Zeiss | Axioskop | Microscope for intravital imaging |
| Andor CCD camera | Andor | iXonEM 885 | CCD camera for live imaging of blood flow |
| Pulse oximeter | StarrLife | MouseOx | Pulse oximeter |
| Fluorescence microscope | Zeiss | Axioskop | Fluorescence microscope |
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