Hikoharu Kanaoka

Intermediate filaments of hepatocytes and biliary epithelial cells in bile duct obstruction: Transmission and scanning electron microscopy study

SummaryThe cytoskeletons of hepatocytes and biliary epithelial cells in bile duct ligated rate livers were investigated by transmission and scanning electron microscopy. The three dimensional organization of the intermediate filaments (IFs) of hepatocytes and biliary epithelial cells was clearly demonstrated by scanning electron microscopy. Cell borders and dilated bile canaliculi were well preserved after perfusion with detergent solution. A very dense filamentous network of IFs was seen throughout the cytoplasm, especially around the dilated bile canaliculi and at the cell borders. IFs in biliary epithelial cells were more numerous compared with hepatocytes. Morphometric analysis showed that the IFs of hepatocytes significantly (p>.001) increased in amount in bile duct ligated rats. The IFs of biliary epithelial cells showed no significant changes in bile duct ligated rats compared to controls. These results suggest that the increase in IFs in hepatocytes results from the adaptation of the hepatocytes to the stress imposed by bile duct ligation. It may be that the resulting intracanalicular pressure and back diffusion of bile induces a metaplastic change in hepatocytes so that they acquire more IFs to function like the bile duct epithelium to conduct bile flow.

Role of Sinusoidal Endothelial Cells in Alcoholic Liver Disease

We investigated the role of sinusoidal endothelial cells (SECs) in alcoholic liver disease (ALD) using cases of ALD and experimental rat models. In ALD, ballooning of hepatocytes was noted, and in alcoholic liver fibrosis sinusoidal endothelial fenestrae (SEFs) had decreased in size and in number. In chronic ethanol-fed rats (E-rats), ballooned hepatocytes compressed sinusoids, especially in zone 3. However, the porosity of SEFs in zone 3 significantly increased, and hepatic blood flow also increased, resulting in compensating hypoxia of hepatocytes in zone 3 in E-rats. Thioacetoamide-administrated-rats demonstrated that defenestration developed in proportion to the progress of hepatic fibrosis, resulting in liver injury by hypoxia. The present studies using an in vitro flow system demonstrated that adhesion molecules on SECs and their ligands were very important in the adhesion and migration of polymorphonuclear leukocytes (PMNs). Dexamethasone inhibited the adhesion and migration of PMNs.

Immuoelectron microscopic localization of actin in normal and cholestatic rat hepatocytes

SummaryThe immunoelectron microscopic localization of actin in hepatocytes was studied in normal, common bile duct-ligated, and phalloidin treated rats. We used the low temperature embedding procedure with Lowicryl K4M and protein A-gold technique was applied to demonstrate the localization of actin. The tissues embeded in Lowicryl K4M at low temperature provided good preservation of ultrastructure and antigenicity of actin. In control rats bile canaliculi were clearly visualized and most of the gold particles were observed on the bile canalicular microvilli, at the pericanalicular ectoplasm, at the cell border, and on the sinusoidal microvilli. In common bile duct-ligated rats and phalloidin treated rats, pericanalicular ectoplasm was thickened and many gold particles were seen there.

The effects of ethanol on the sinusoidal endothelial fenestration of rat liver.

走査電顕を用いて急性,慢性エタノール投与および断酒後のラット肝の類洞内皮細胞小孔(SEF)の変化を観察し,正常ラットのSEFと比較検討した.10cmH2Oの灌流圧で門脈より灌流し,SEFの直径,数,有孔度の定量的解析を行った.正常ラットの肝小葉内においてheterogeneityが存在しており,zone 1のSEFの直径はzone 3より有意(p<0.001)に大きく,その数はzone 3の方が有意(p<0.001)に多かった. SEFの有孔度はzone 1よりzone 3の方が有意(p<0.05)に大きかった.慢性エタノール投与によりzone 3でSEFの直径,有孔度は有意(p<0.001, p<0.01)に増大し,数は有意(p<0.001)に減少していた.断酒後,これらのSEFの変化は比較的短期間で正常ラットの状態に復した.今回の成績はアルコール性肝障害の初期病変であるアルコール性脂肪肝の成因にSEFの変化が関与する可能性を示唆するものである.

Transmission and scanning electron microscopy of the human liver cell cytoskeleton.

光顕的に正常肝組織像を呈するヒト肝組織片6個を対象とした.試料採取直後に細切し,凍結割断の後にdetergentで処理する方法と,採取した肝組織片に静注針を刺入しdetergentで潅流する2つの方法を用いた.得られた試料を透過電顕,走査電顕で観察し,肝細胞細胞骨格(H-CS)の二次元的,三次元的存在様式を明らかにした.細胞質全体に亘って中間径フィラメント(IFs)が多数存在し,IFsは接着・吻合を示し,微小管やマイクロフィラメントも観察できた.肝細胞と肝細胞の間で割断された試料では,毛細胆管周囲や細胞境界部が明瞭で,多くのCSが存在し,マイクロフィラメントも多数残存していた.今回の研究成績は,今後ヒトの肝細胞細胞骨格病理の研究に有用であると考えた.