Caveolae and caveolin-1 in reptilian liver

Relation between ultrastructural localization, changes in caveolin-1, and capillarization of liver sinusoidal endothelial cells in human hepatitis C-related cirrhotic liver

Most vascular endothelial cells are continuously exposed to shear stress in vivo. Caveolae are omega-shaped membrane invaginations in endothelial cells (ECs) and are enriched in cholesterol, caveolins, and signaling molecules. This study was designed to elucidate the ultrastructural localization and change in caveolin-1 expression within human liver sinusoidal endothelial cells (LSECs) during the progression of cirrhosis caused by hepatitis C, using tissue sections prepared via perfusion-fixation. Normal control liver specimens and hepatitis C-related Child-Pugh A and C cirrhotic liver specimens were studied. Caveolin-1 in the liver sinusoids was examined via immunohistochemistry, Western blotting, and immunoelectron microscopy. In control liver tissue, caveolin-1 was localized on caveolae mainly in arterial and portal endothelial cells of the portal tract and was also found on vesicles and some fenestrae in LSECs around the central vein. In cirrhotic liver tissue, aberrant caveolin-1 expression was observed on caveolae-like structures in LSECs. Caveolin-1 was especially overexpressed in late-stage cirrhosis. This study demonstrates that caveolin-1 is strongly expressed within caveolae-like structures and associated vesicles within LSECs of the hepatitis C-related cirrhotic liver. These findings suggest a direct association of caveolin-1 in the process of differentiation of LSECs in cirrhosis-mediated capillarization.

Imaging fluorescently labeled complexes by means of multidimensional correlative light and transmission electron microscopy: practical considerations

These days the common ground between structural biology and molecular biology continues to grow thanks to the biomolecular insights offered by correlative microscopy, even though the vision of combining insights from different imaging tools has been around for nearly four decades. The use of correlative imaging methods to dissect the cell's internal structure is progressing faster than ever as shown by the boom in the number of methodological approaches available for correlative microscopy studies, each designed to address a specific scientific question. In this chapter, we will present a relatively straightforward approach to combining information from fluorescence microscopy and electron microscopy at the supramolecular level. The method combines live-cell and/or confocal laser microscopy with classical sample preparation for transmission electron microscopy (TEM), thereby allowing the integration of dynamic details of subcellular processes with insights about the organelles and molecular machinery involved. We illustrate the applicability of this multidimensional correlative microscopy approach on cultured Caco-2 colorectal cancer cells exposed to fluorescently labeled cisplatin, and discuss how these methods can deepen our understanding of key cellular processes, such as drug uptake and cell fate.

Recent advances in liver sinusoidal endothelial ultrastructure and fine structure immunocytochemistry

Ultrastructure reports have described that liver sinusoidal endothelial cell (LSEC)s contain a cytoskeletal framework of filamentous actin. Small G protein has emerged as an important regulator of the actin cytoskeleton, and consequently, of cell morphology and motility. We investigated actin filaments in relation to SEF in LSECs using a heavy meromyosin-decorated reaction and thereby elucidated the roles of small G protein and actin cytoskeleton in the morphological and functional alterations of SEF. Caveolin-1 expression has also been found in fenestrations with many characteristics of liver sinusoidal endothelial cells. Currently, fenestral studies and human disease are revealing ways to increase the liver sieve's porosity, which is reduced through pathological mechanisms. Hepatic sinusoidal endothelial dysfunction, which is known to impair endothelium-dependent relaxation in the liver microcirculation, contributes to increased intrahepatic vascular resistance.