Imaging of Thrombosis and Microcirculation in Mouse Lungs of Initial Melanoma Metastasis

Abstract

Microscopic bioimaging of blood flow and distribution of cancer cells in lungs are essential to analyze mechanism of lung metastasis. Such cancer metastasis has been well known to induce hypercoagulable states and thrombosis. In histopathological tissue sections, however, it has been difficult to capture rapid phenomenon of thrombus formation due to technical problems associated with much less retention of soluble serum components as well as dynamic histological features reflecting their living states. In this part, to develop the cryotechnique for human pathology, we achieved bioimaging of both hypercoagulable states and thrombosis induced by early metastasis of mouse B16-BL6 melanoma. Thus, to examine plasma flow with fluorescence emission, glutathione-coated quantum dots (QDs) were subsequently injected after melanoma cells via right ventricles. At 5 s after the melanoma injection, melanoma cells were mostly stacked and intruded in alveolar capillaries with changing their shapes. Platelets aggregated around the stacked melanoma cells at 5 min. Such aggregated platelets were partially activated because of phosphorylated tyrosine 418 and 527 of Src on paraffin sections. Fibrin monomers and fibrinogens were also immunolocalized around stacked melanoma cells, indicating initial thrombus formation. In those areas, QDs were rarely detected, probably because of the lack of blood supply. Thus, IVCT revealed histopathological features of initial thrombosis under their circulatory conditions.