Apoptosis in acute pulmonary allograft rejection and cytomegalovirus infection.

Apoptosis is a form of programmed cell death, characterized by activation of endonucleases that cleave DNA into oligonucleosomal fragments, which can be identified by in situ terminal deoxyribonucleotide transferase-mediated dUTP nick-end labeling (TUNEL). This process has recently been implicated in cardiac and hepatic allograft rejection, and we investigated its contribution to acute pulmonary allograft rejection and cytomegalovirus (CMV) pneumonitis by in situ TUNEL of transbronchial biopsy specimens. In situ TUNEL was performed on 70 transbronchial biopsy samples collected from 25 pulmonary allograft recipients for diagnosis of acute rejection or CMV pneumonitis, and the number of apoptotic nuclei/mm2 was correlated with the rejection grade (International Society of Heart and Lung Transplantation classification). During acute pulmonary allograft rejection, apoptotic nuclei were demonstrated in pulmonary parenchymal cells and mononuclear infiltrating cells, and the number of apoptotic cells was positively correlated with the rejection grade. In addition, a marked increase in the density of apoptotic cells was found in pulmonary allografts with CMV pneumonitis. We conclude that apoptosis contributes to cell death during acute pulmonary allograft rejection and CMV infection.     

BILE DUCTAL AND DUCTULAR CHANGES OF THE LIVERS IN THE RENAL ALLOGRAFTED PATIENTS

Nine liver biopsies from six renal allografted patients suffering from liver injury were examined by light and electron microscope and immunostaining. The patients had never been on liver dysfunction prior to renal transplantation and after renal transplanatation had been administered azathioprine continuously. These patients had shown HBs antigen negative sera. Three of these patients restored normal liver function after withdrawal of azathioprine. Accordingly, the liver diseases of the three were supposedly caused by azathioprine. The liver biopsies of six patients were histologically diagnosed as follows: chronic active hepatitis with severe cholestasis (1 patient), liver cirrhosis with cholestasis (1 patient), acute hepatitis (1 patient), and mild hepatitis (3 patients). The common pathological findings of six patients were degeneration of interlobular bile ducts and ductules, as well as degeneration of liver cells, and mild to moderate inflammatory cell infiltration of portal tracts and sinusoids. The degeneration of bile ductal and ductular cells were classified into two types: light microscopical finding showed vacuolar or eosinophilic cytoplasm and electron microscopic compatible findings showed hydropic cytoplasm scant of free ribosome and organelles, or dense cytoplasm rich in free ribosome and degenerated organelles. The basement membranes of interlobular bile ducts and ductules were always preserved.     

Bile ductal and ductular changes of the livers in the renal allografted patients

Nine liver biopsies from six renal allografted patients suffering from liver injury were examined by light and electron microscope and immunostaining. The patients had never been on liver dysfunction prior to renal transplantation and after renal transplantation had been administered azathioprine continuously. These patients had shown HBs antigen negative sera. Three of these patients restored normal liver function after withdrawal of azathioprine. Accordingly, the liver diseases of the three were supposedly caused by azathioprine. The liver biopsies of six patients were histologically diagnosed as follows: chronic active hepatitis with severe cholestasis (1 patient), liver cirrhosis with cholestasis (1 patient), acute hepatitis (1 patient), and mild hepatitis (3 patients). The common pathological findings of six patients were degeneration of interlobular bile ducts and ductules, as well as degeneration of liver cells, and mild to moderate inflammatory cell infiltration of portal tracts and sinusoids. The degeneration of bile ductal and ductular cells were classified into two types: light microscopical finding showed vacuolar or eosinophilic cytoplasm and electron microscopic compatible findings showed hydropic cytoplasm scant of free ribosome and organelles, or dense cytoplasm rich in free ribosome and degenerated organelles. The basement membranes of interlobular bile ducts and ductules were always preserved.     

Apoptosis in the human liver during allograft rejection and end-stage liver disease

The contribution of apoptosis (programmed cell death) to cellular damage in human liver disease is unknown. Using the in situ DNA end labelling method (ISEL), evidence was sought of programmed cell death (PCD) in liver tissue from patients with various liver diseases. In particular, the study aimed to determine whether PCD is involved in either the loss of interlobular bile ducts (vanishing bile duct syndrome—VBDS) or the perivenular hepatocyte drop-out, both of which are characteristic of irreversible graft rejection. Large numbers of apoptotic hepatocytes were found in pervenular areas in tissues taken from patients with chronic graft rejection. Significant hepatocyte apoptosis, was not seen in long-term stable allografts, primary biliary cirrhosis, cholestasis, paracetamol-induced fulminant hepatic failure, or fulminant hepatic failure of indeterminate origin (non-A, non-B, non-C hepatitis). Bile ducts rarely stained positively, but mononuclear cells present in the post-transplant tissues were frequently positive, showing nuclear or cytoplasmic staining. The presence of cytoplasmic staining suggested that some mononuclear cells had ingested apoptotic DNA from other cellular sources. PCD may thus contribute to the perivenular hepatocyte loss in chronic rejection. The absence of ductular epithelial cell staining suggests that PCD is not involved significantly in the bile duct loss of VBDS. Furthermore, apoptosis of monomuclear cells implies that PCD may be involved in regulating the inflammatory cell infiltration of graft rejection.     

Paucity of interlobular bile ducts.

Paucity of interlobular bile ducts (PIBD) is defined as the reduction in the number of interlobular bile ducts. Paucity could be defined using the ratio of the number of portal tracts devoid of bile duct to the total number of portal tracts. At least 10 complete portal areas must be examined. In the past, only wedge biopsies could provide such samples, but now it can be achieved with needle biopsy. Usually, two types of PIBD, syndromatic and nonsyndromatic, are considered. In the syndromatic type, paucity is a major feature of the disease. In the nonsyndromatic type, paucity is only a part of the disease, as in peroxisomal disorders or alpha 1-antitrypsine (A1AT) deficiency, and is an inconstant finding. Opacification of the intrahepatic bile ducts in infants with nonsyndromatic paucity with no associated disorder demonstrates sclerosing cholangitis in at least half of patients in whom the diagnosis of "idiopathic paucity" would have been made a few years ago. The remaining patients must be considered as waiting for the identification of new disorders associated with paucity.     

Histological features of sclerosing cholangitis in patients with chronic ulcerative colitis.

Primary sclerosing cholangitis was diagnosed radiologically in 16 of 681 patients (2.2%) with chronic ulcerative colitis in a follow up study at the gastroenterology unit in Oxford. On the basis of established histological criteria, the liver biopsy was considered diagnostic in only half of the cases. The histological findings in these cases were therefore reassessed to determine whether the accuracy of biopsy diagnosis could be improved. The most common specific histological feature was periductal concentric fibrosis of small interlobular bile ducts, even in the absence of inflammation. Other common features were bile ductular proliferation associated with diminution or absence of interlobular bile ducts. Degeneration of bile duct epithelium and diffuse infiltration of portal tracts by mononuclear cells and polymorphonuclear leucocytes were accompanying features. Piecemeal necrosis without rosette formation was found in about half the biopsies. When all these features were considered together a biopsy diagnosis of primary sclerosing cholangitis was established in 14 of 16 cases.     

Expression of vimentin in proliferating and damaged bile ductules and interlobular bile ducts in nonneoplastic hepatobiliary diseases.

Biliary epithelial cells express characteristically cytokeratin in their cytoplasm in normal and diseased livers. The present study disclosed that vimentin was frequently expressed in the cytoplasm of proliferating and damaged bile ductules and interlobular bile ducts, while their normal counterparts were negative for vimentin. Although this expression itself seemed nonspecific to any of the hepatobiliary diseases examined, bile ductules and interlobular bile ducts were frequently positive in chronic cholestatic and necroinflammatory liver diseases. In biliary epithelial cells, vimentin was localized around the nucleus or in the subnuclear regions, when present. Immunoelectron microscopically, reaction products for vimentin and for cytokeratin were found on bundles of intermediate filaments in the cytoplasm of biliary epithelial cells. The former was found mostly in the paranuclear and subnuclear regions, while the latter detected around the desmosomes, in addition to the paranuclear cytoplasm. Vimentin and cytokeratin were also seen together under immunoelectron microscopy on the same intermediate filaments. It seems likely that aberrant expression of vimentin in bile ductules and interlobular bile ducts and heterogeneous antigenic expression of intermediate filaments in the same biliary epithelial cells may be related to proliferation of, reorganization of, or damage to the ductular and ductal biliary cells in a variety of hepatobiliary diseases.     

Apoptosis and cell proliferation in biliary atresia

Biliary atresia (BA), which is thought to result from progressive destruction of the bile ducts by a necroinflammatory process, is the most common cause of obstructive jaundice in infancy. Abnormalities in the cell turnover of remodelling ductal plates are considered one of the important aetiological factors in this disorder, but little work has been done on this topic. Programmed cell death or apoptosis was therefore examined by TdT-mediated dUTP biotin nick end labelling (TUNEL) and cell proliferation by Ki67 immunostaining in 34 cases of BA. The results were compared with normal control liver (five cases) and congenital dilatation of the bile ducts (CDB, five cases) in order to study the cell turnover or tissue dynamics of BA. The TUNEL labelling index (LI) in bile ducts (48.9 +/- 13.2 per cent) was significantly higher than that of the control normal liver (3.6 +/- 2.8 per cent) and of CDB (2.5 +/- 5.1 per cent). The Ki67 LI in the bile ducts of BA (15.0 +/- 5.57 per cent) was also significantly higher than that of CDB (8.6 +/- 5.4 per cent). No significant differences of the TUNEL and Ki67 LIs in hepatocytes were, however, observed between BA, CDB, and normal liver. The TUNEL LI was significantly higher than the Ki67 LI in the bile ducts of BA. BA is therefore associated with increased and disorganized cell turnover of the bile ducts, which is related to malformation of the ductal plate or abnormal bile duct development.     

Morphometric and immunohistochemical characterization of human liver regeneration.

Regeneration in human liver is characterized in part by the formation of ductular structures, so-called ductular hepatocytes in massive hepatic necrosis and bile ductules in mechanical biliary obstruction. In an attempt to characterize the liver regenerative process, we performed image analysis and immunohistochemical staining of the ductular structures in these well defined human liver disorders, 13 cases of massive hepatic necrosis and 9 cases of mechanical biliary obstruction. The proliferation index was determined and the expression of several antigens was localized by immunohistochemical staining using antibodies to alpha-fetoprotein, alpha-1-antitrypsin, albumin, and cytokeratin 19. The ductular structures in adult human liver were compared with the developing ductal plates in 11 fetal livers, ranging in age from 9 to 36 weeks of gestation. Image analysis demonstrated that the mean total area, mean nuclear area, and mean cell size of ductular hepatocytes were significantly larger than those of bile ductules (p < 0.05). The proliferation index of ductular hepatocytes and bile ductules was significantly higher than that of hepatocytes of normal livers (p < 0.02). Bile ducts, bile ductules in mechanical biliary obstruction, ductular hepatocytes in massive hepatic necrosis, and the ductal plate cells in fetal liver showed strong staining for cytokeratin 19, which characterizes intermediate filaments associated with bile duct epithelial cells. Albumin, a liver-specific protein, and alpha-1-antitrypsin, a protease inhibitor, were strongly expressed in ductal plate cells of fetal liver, hepatocytes, and ductular hepatocytes, whereas bile duct cells and bile ductules were negative for albumin. In summary, ductular hepatocytes demonstrate morphometric and immunophenotypic features of both hepatocytes and biliary epithelial cells, whereas bile ductules share characteristics primarily with fetal ductal plates and mature bile ducts. These findings suggest that ductular hepatocytes in massive hepatic necrosis may serve as bipotential progenitor cells, and bile ductules in mechanical biliary obstruction are related to ductal plates of fetal liver.     

Detection of apoptosis and expression of apoptosis-related proteins during human intrahepatic bile duct development.

We investigated apoptosis by nick end labeling and the expression of apoptosis-related proteins by immunohistochemistry in fetal development of human intrahepatic bile ducts and hepatocytes. During intrahepatic bile duct development, apoptosis was present at all stages, and its positive ratio was high in the remodeling ductal plate, moderate in the ductal plate, and relatively low in remodeled ducts. The cell proliferative activity as determined by proliferating cell nuclear antigen was also high in the remodeling ductal plate, and relatively low in the ductal plate and remodeled ducts. fas antigen and c-myc protein were constantly positive in the ductal plate, remodeling ductal plate and remodeled ducts. Bcl-2 protein was negative or faintly positive in the ductal plate and remodeling ductal plate, but was apparently positive in remodeled ducts. Lewisy as detected by the BM-1 antibody was present in the ductal plate, remodeling ductal plate, and remodeled ducts. p53 protein was not found in any cell types in the liver development. During hepatocyte development, many apoptotic and proliferating cell nuclear antigen-positive hepatocytes were noted. The developing hepatocytes expressed c-myc protein and fas antigen. Bcl-2 protein and Lewisy antigen were also weakly positive in the developing hepatocytes. These findings showed that balanced cell proliferation and apoptosis are involved in the normal development of intrahepatic bile ducts and hepatocytes, and suggest that c-myc protein, fas antigen, Bcl-2 protein, and Lewisy antigen modulate apoptosis of fetal intrahepatic biliary cells and hepatocytes, probably by stimulative (c-myc protein and fas and Lewisy antigens) or inhibitory (Bcl-2 protein) effects.     

Morphologic features resembling transplant rejection in core biopsies of native livers from patients with Hepatitis C

Morphologic differentiation of recurrent Hepatitis C from transplant rejection is a major problem in posttransplant liver biopsies. Although biopsies of the native livers from patients with Hepatitis C are known to display bile duct damage, other morphologic features similar to those seen in rejection, such as endotheliitis, portal eosinophils, and pericentral fibrosis, are not generally acknowledged. To determine the frequency with which features morphologically similar to rejection might be present, we examined 50 cases of core-needle biopsy from the native livers of patients with Hepatitis C for the presence of the following: bile duct damage, portal eosinophils, portal or central vein endotheliitis, ductopenia, vascular obliteration, pericentral fibrosis, and pericentral mononuclear cell infiltrate. Biopsy specimens with other concurrent disease processes were excluded. The frequency of each morphologic feature was as follows: bile duct damage (30%), portal eosinophils (42%), portal endotheliitis (20%), central vein endotheliitis (0%), pericentral mononuclear cell infiltrate (14%), ductopenia (2%), atrophic-looking bile ducts (2%), vascular obliteration (0%), and pericentral fibrosis (10%). Bile duct damage and portal endotheliitis were both more common with higher grade hepatitis (Fisher exact test, P = .001). None of the morphologic parameters correlated with biopsy stage, viral genotype, or liver function tests. We conclude that features similar to those found in acute rejection are common in Hepatitis C, whereas features resembling chronic rejection are less frequent. This study provides quantitative data that supports the need to interpret these features with great caution in posttransplant liver biopsies from patients with recurrent Hepatitis C who are suspected of rejection.     

The role of liver biopsy in evaluating acute allograft dysfunction following liver transplantation: a clinical histologic correlation of 34 liver transplants

One hundred six liver biopsy specimens from 34 orthotopic liver transplant (OLT) patients were examined and the histologic findings correlated with the clinical course of the patients to determine if specific morphologic patterns were associated with specific causes of acute allograft dysfunction. The principle causes of allograft injury in these patients appeared to be acute rejection and ischemic injury, with rarer cases of viral infection and biliary obstruction. Graft rejection causing transient liver dysfunction was associated with a mixed inflammatory infiltrate in the portal tracts and involving the interlobular bile ducts. Rejection resulting in severe, persistent dysfunction was associated with destruction and loss of the interlobular bile ducts or portal inflammation, followed by acute centrilobular hepatocyte necrosis. Ischemic liver injury was characterized by hepatocyte ballooning and/or hepatocyte necrosis. Ischemic injury causing transient graft dysfunction demonstrated focal, limited areas of hepatocyte necrosis or transient centrilobular hepatocyte ballooning. Severe ischemic injury resulting in persistent dysfunction caused diffuse hepatocyte necrosis or centrilobular ballooning followed by centrilobular hepatocyte loss and severe cholestasis with evidence of bile duct epithelial injury. The histologic patterns observed were not pathognomonic; radiologic studies, bile cultures, and other laboratory tests were necessary to rule out biliary or vascular obstruction and bacterial cholangitis. However, liver biopsies, especially serial biopsies, were helpful in suggesting the probable cause of liver dysfunction and in predicting subsequent allograft recovery or failure.     

Role of transforming growth factor beta 1 on hepatic regeneration and apoptosis in liver diseases.

AIMS--To investigate the effects of transforming growth factor beta 1 (TGF-beta 1) on regeneration and induction of apoptosis of liver cell and bile duct in various liver diseases. METHODS--Formalin fixed paraffin wax sections of 18 liver tissue samples were obtained by needle biopsy, surgery, or necropsy; these included six liver cirrhosis, three obstructive jaundice; five fulminant hepatitis, one subacute hepatitis, and three normal liver. Expression of TGF-beta 1, apoptosis related Le(y) antigen, Fas antigen, a receptor for tumour necrosis factor, and biotin nick end labelling with terminal deoxynucleotidyl transferase mediated dUTP (TUNEL) for locating DNA fragmentation, was investigated histochemically. RESULTS--TGF-beta 1 was expressed in areas of atypical bile duct proliferation, where bile duct continuously proliferated from liver cells. In occlusive jaundice and fulminant hepatitis, TUNEL was positive in nuclei and cytoplasm of metaplastic cells which formed incomplete bile ducts, and these cells appeared to extend from TGF-beta 1 expressing liver cells. Fas antigen was found only on the cell membrane of proliferated bile duct in fulminant hepatitis, which differed from TGF-beta 1 and TUNEL positive areas. Le(y) antigen was expressed in liver cell and bile duct at the areas with atypical bile duct proliferation, but its coexpression with TUNEL was rare. CONCLUSIONS--TGF-beta 1 plays a role in the arrest of liver cell regeneration and atypical bile duct proliferation, and in areas of rapidly progressing atypical bile duct proliferation, such as in fulminant hepatitis or bile retention. Apoptosis appears to be induced by TGF-beta 1. This phenomenon may account for the inadequate hepatic regeneration that occurs with liver disease.     

Destruction of canals of Hering in primary biliary cirrhosis

The canals of Hering (CoH), converging from the hepatic lobule onto the portal tract, connect bile canaliculi to the interlobular bile ducts, and represent the most proximal portion of the bile drainage pathway with a cholangiocyte lining. In this study we sought to ascertain whether this proximal pathway is involved by the disease process in primary biliary cirrhosis (PBC), which uniformly affects small bile ducts while sparing medium- and large-sized ducts. Ten biopsy specimens with early-stage PBC were compared with 6 normal control livers. Adjacent 4-micron-thick sections of routinely processed, formalin-fixed tissue were immunostained for CK19 and HLA-DR. Each terminal portal tract was assigned a stage: 0, normal; 1, bile duct damage or loss; 2, bile ductular proliferation; or 3, periportal fibrosis. The ratio of the number of CoH to number of portal tracts (i.e., the c/p ratio) was calculated for the control biopsies and individual portal tracts at each stage of PBC. The numbers of CoH were decreased in all stages of PBC (P <0.0001), with the fewest found around portal tracts at stages 0 and 1 and the most around portal tracts at stages 2 and 3, but never at normal levels. HLA-DR was expressed focally on bile ducts and CoH in PBC, but was absent in normal controls. We conclude that CoH are destroyed in PBC in concert with the destruction of small bile ducts. This destruction appears to be an early event, because CoH numbers are lowest around stage 0 portal tracts, which still contain normal bile ducts.     

The development of proliferating ductular structures in liver disease. An immunohistochemical study.

Proliferation of bile ductules or ductular hepatocytes occurs in a variety of liver diseases. The origin of these ductular structures and the mechanism of their proliferation are controversial. Using cytokeratin as marker for ductular structures, liver diseases in which ductular proliferation was a consistent and prominent feature were studied. Paraffin-embedded sections of livers (five cases each) with acute or chronic obstruction of extrahepatic bile ducts, primary biliary cirrhosis (stage II), drug-induced cholestatic liver disease, liver allograft rejection, vicinity of metastatic carcinoma, and massive hepatic necrosis were studied by immunohistochemical methods using three kinds of antiserum against cytokeratin polypeptides of different molecular weights. Bile ductules in diseases involving bile ducts and ductular hepatocytes in massive hepatic necrosis were closely associated with hepatocytes at the limiting plate or with injured hepatocytes. These findings suggest that hepatocytes play an important role in the proliferation of ductular structures or may represent their origin.     

Cytokeratin expression as an aid to diagnosis in medical liver biopsies

Bateman A C & Hübscher S G
(2010) Histopathology 56 , 415–425
Cytokeratin expression as an aid to diagnosis in medical liver biopsies The study of cytokeratin expression has provided a valuable insight into the biliary microanatomy of the liver in health and disease. The canals of Hering are a putative site of origin for progenitor cells, which may repopulate the liver after cellular damage and loss. Normal bile ducts and the bile ductular reaction that occurs in many chronic liver diseases – especially chronic biliary tract disease – express cytokeratin (CK) 7 and CK19. Therefore, both ductopenia and the process of bile ductular reaction can be highlighted with immunohistochemistry for these cytokeratins. Furthermore, CK7 is usually expressed in an increasingly widespread manner by hepatocytes as chronic cholestatic liver disease progresses. For these reasons, CK immunohistochemistry is a very useful adjunct to morphological assessment and histochemical stains for copper retention when a diagnosis of chronic biliary disease is being considered. This review describes the anatomical theory behind the use of CK immunohistochemistry for the assessment of bile duct number and distribution in the liver and provides practical advice for the application of this technique in the diagnostic setting of common medical liver diseases.     

Cytokeratin immunostaining for detection of biliary epithelium: its use in counting bile ducts in cases of liver allograft rejection.

AIMS--To see how useful the application of a bile duct specific cytokeratin antibody (AE1) was in identifying and counting bile ducts in liver allograft biopsy specimens. METHODS--Eighteen liver biopsy specimens showing acute rejection and 17 biopsy specimens plus six hepatectomy specimens showing chronic rejection were studied. Serial sections were cut and stained with haematoxylin and eosin and AE1 antibody. Two pathologists (RFH and KP) examined the sections with respect to a range of histological features. RESULTS--Similar numbers of bile ducts were identified on haematoxylin and eosin sections as on corresponding sections stained by AE1 in cases of acute rejection and end stage chronic rejection. Greater numbers of bile ducts were identified by AE1 during the early stages of chronic rejection, especially when dense portal inflammatory infiltrates were present. These were often incomplete structures or individual cells within portal tracts, and bile ducts subsequently disappeared in all cases. Ductular proliferation was clearly shown by AE1 in acute rejection and the extent seemed to correlate with the severity of rejection present. By contrast, no ductular proliferation was observed in chronic rejection. CONCLUSIONS--Haematoxylin and eosin stained sections are adequate for counting bile ducts in most biopsy specimens from patients with suspected chronic rejection. Immunostaining for biliary cytokeratins using AE1 is of limited use in occasional cases where bile ducts are obscured by inflammatory cells.     

Distribution of apoptotic cells and expression of apoptosis-related proteins along the intrahepatic biliary tree in normal and non-biliary diseased liver

AIMS: The cell kinetics and homeostasis of biliary epithelial cells may be maintained differently along the biliary tree. In this study, the role of apoptosis in the maintenance and homeostasis of the intrahepatic biliary tree was evaluated. METHODS AND RESULTS: By counting apoptotic biliary cells and by immunostaining apoptosis-related proteins in normal liver, fatty liver, and those with acute viral hepatitis, chronic viral hepatitis, and hepatitis virus-related cirrhosis, it was found that the larger the intrahepatic bile ducts became, the more biliary epithelial cells underwent apoptosis. bcl-2, an inhibitor of apoptosis, was diffusely expressed in the interlobular bile ducts, but rarely detectable in the large and septal bile ducts. bcl-XL and mcl-1, inhibitors of apoptosis, and bax, a promoter of apoptosis, were diffusely expressed along the intrahepatic biliary tree. CD95, a direct inducer of apoptosis, was present in the large and septal bile ducts, but rarely in the interlobular bile ducts. CONCLUSION: The ratio of bax to bcl-2, as well as the expression of CD95 which differed at the interlobular versus large and septal bile ducts, may be responsible for the unique distribution of apoptotic biliary cells and involved in the homeostasis of the intrahepatic biliary tree.     

Bax and apoptosis in acute and chronic rejection of rat cardiac allografts

Apoptosis is associated with acute rejection, transplant vascular disease, and the "Quilty effect" in cardiac allografts. However, the causality and mechanisms of apoptosis in the pathogenesis of vascular injury are poorly understood. In the current study, the Lewis-to-F344 rat cardiac allograft model was utilized as a means to immunohistochemically evaluate the expression of Bax, Bcl-2, and factor VIII-related antigen in transplant vascular disease. Apoptosis was detected by in situ labeling of fragmented DNA using in situ terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) in native hearts and grafted hearts of allogeneic and syngeneic recipients. Bax immunostaining was detected in 50% of endothelial cells, in 60% of infiltrating leukocytes associated with acute rejection in the myocardium, and in certain other parenchymal cells, considering all cardiac allografts. More than 75% of infiltrating leukocytes in the intima of vessel walls immunostained positive for Bax. Bcl-2 immunopositivity was not detected in native hearts, allo allo-, or syngrafts. On Days 2, 4, 7, and 14 after transplantation, TUNEL positivity was detected in only about 1% of leukocytes in the interstitial infiltrates, despite the fact that rather severe rejection was observed in Day 14 allografts. The number of apoptotic leukocytes increased significantly by Days 28 and 56 after transplantation, although the severity of histopathological rejection did not increase as compared with Day 14. The apoptotic leukocytes remained isolated or in small clusters, mainly perivascular. TUNEL positivity colocalized with Bax expression in these cells. TUNEL staining was also observed in certain parenchymal cells in the interstitium and in randomly distributed inflammatory cells in vessel walls. TUNEL positivity was detected in rare luminal endothelial cells in transverse sections of vessel walls (about 10% of cells in <1/10 of the vessels studied). Nuclear TUNEL positivity was observed in Bax-negative cardiomyocytes in ischemically damaged areas of myocardium in both allografts and syngrafts. In summary, increased expression of Bax was observed in rat cardiac allografts. The colocalization of TUNEL and Bax suggests that endothelial cell injury and infiltrating leukocyte apoptosis may be regulated in part by the apoptosis-promoting protein, Bax. In the current model, myocyte death due to ischemia and surgical injury in syngrafts and allografts does not seem to involve Bax.     

Expression of Bcl-2 familial proteins is reduced in small bile duct lesions of primary biliary cirrhosis

In primary biliary cirrhosis, biliary epithelial cell death by apoptosis results in progressive bile duct loss. We examined immunohistochemically 4 apoptosis-regulating bcl-2 familial proteins (bcl-2, mcl-1, bcl-X, and bax) in the biliary epithelium in 19 cases of primary biliary cirrhosis. Ten cases of chronic hepatitis C, 9 cases of extrahepatic biliary obstruction, and 10 cases of normal liver were used as a control. Bcl-2 and mcl-1 are inhibitors of apoptosis, bcl-X, probably bcl-XL in biliary epithelial cells, an inhibitor, and bax, a promoter of apoptosis. First, we clarified the distribution of bcl-2 familial proteins on the intrahepatic biliary tree in normal livers. Bcl-2 was detected in the interlobular bile ducts and bile ductules, but not in the large and septal bile ducts in all cases examined. Mcl-1, bcl-X, and bax were diffusely detectable at the any level of the intrahepatic biliary tree, with a staining pattern that was diffuse and cytoplasmic. This distribution pattern was preserved in extrahepatic biliary obstruction. Bcl-2 expression was lost or markedly reduced in the damaged interlobular bile ducts in primary biliary cirrhosis, whereas the reduction was only focal or mild in the bile ducts with hepatitis-associated damage in chronic hepatitis C. Expression levels of mcl-1, bcl-X, and bax were similarly reduced to that of bcl-2 in these 2 diseases. These findings suggest that bax is not important as a proapoptotic factor in the damaged bile ducts and that downregulation of bcl-2 and mcl-1, and probably that of bcl-XL, leads to a decrease in the threshold of apoptosis and increase in the vulnerability to apoptotic stimuli in these bile ducts, followed by the progressive apoptotic loss of interlobular bile ducts, in primary biliary cirrhosis.