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. Copyright © 1998 John Wiley & Sons, Ltd.

Biliary atresia (BA) is the most common cause of obstructive jaundice in infancy. Although the etiology of BA remains unknown, the ductal plate malformation has been considered to play an important role in the development of BA. Cell-cell adhesion has long been recognized as one of the most important processes in organogenesis. E-cadherin is involved in cell-cell adhesion, together with the catenins. Abnormalities of E-cadherin and associated catenins have not been examined in detail in the liver with BA. We therefore examined immunolocalization of E-cadherin and alpha- and beta-catenins in the BA liver (n = 45) and compared the findings with those in non-BA (n = 11) and fetal liver (n = 21). We semiquantitatively evaluated the findings using H score, which were generated according to the percentage of immunopositive cells and their immunointensity. We also examined mRNA localization of E-cadherin using mRNA in situ hybridization. We then studied the correlation of E-cadherin immunoreactivity with apoptotic cells, and cyclin-dependent kinase inhibitor p27Kip1 immunolocalization of bile duct cells in BA liver (n = 10) and fetal liver (n = 10). In fetal liver, H score of E-cadherin, but not of alpha- and beta-catenins, was significantly lower in the remodeling stage than in the ductal plate (P = 0.0034) and remodeled stages (P = 0.0024). In addition, the H score of E-cadherin, but not alpha- and beta-catenin, in bile duct cells was significantly lower in BA liver than in non-BA liver (P = 0.0132). E-cadherin mRNA hybridization signals were relatively conserved in bile duct cells of BA liver, but decreased in remodeling ductal plate cells of fetal liver. An inverse correlation was detected between the H score of E-cadherin and the TUNEL labeling index (LI) in both fetal and BA liver. In contrast, a positive correlation was detected between the H score of E-cadherin and p27 LI in both fetal and BA liver. These findings suggest that impaired expression of E-cadherin in bile ducts may play an important role in the biological features of BA, possibly associated with cell cycle and apoptosis.

It is speculated that immune mechanisms are involved in bile duct damage in biliary atresia (BA), as in primary biliary cirrhosis (PBC). In BA, however, no reports have described the in situ distribution of cytotoxic T lymphocytes (CTLs) using specific markers, nor has the clinical association been clarified. The present study describes the immunohistochemical distribution of CD8+ T cells and the relevant markers [perforin, granzyme B, FasL (CD95L)] in 47 cases of BA operated upon at days 12-79. The results were compared with those of PBC. In BA, CD8+ T cells infiltrated bile ducts in a way similar to that observed in PBC. However, in sharp contrast to PBC, none of the inflammatory cells infiltrating into the bile ducts in BA expressed cytotoxic markers such as perforin, granzyme B, or Fas ligand (FasL). Clinical follow-up of patients with BA revealed that a greater degree of infiltration of bile ducts by CD8+ T cells is associated with better liver function. Taken together, these data suggest the absence of direct CTL activity against bile ducts in BA in the postnatal period.

Progressive fibrosis, despite successful surgical treatment, is one of the serious complications of biliary atresia. To understand the mechanism of this fibrosis, the in situ expression of fibrogenic growth factors (TGF-beta and PDGF) and their corresponding receptors was studied by immunohistochemistry using frozen sections. The results were compared between the early (n=12) and late (n=6) stages. The early stage was characterized by abundant expression of all ligands and receptors, together with type I procollagen (PC-I). The major cellular sources were activated fibroblasts/myofibroblasts distributed mostly in the portal tracts. Macrophages also expressed all the ligands and the receptors, but to a lesser degree. Bile duct cells strongly expressed TGF-beta RI and RII and PDGF AA and BB, but focally expressed TGF-beta. All of these decreased in the late stage of biliary atresia. These results suggest that TGF-beta and PDGF play important roles in the fibrogenesis of biliary atresia, especially in its early stage, acting either by autocrine or paracrine mechanisms involving activated fibroblasts/myofibroblasts, bile duct cells, and macrophages.

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