The significance of human jagged 1 mutations detected in severe cases of extrahepatic biliary atresia

Biliary atresia

Biliary atresia (BA) remains a devastating disease of infants. It is still a disease of largely unknown etiology although many hypotheses such as an aberrant early bile duct development, perinatal viral infection, aberrant immune response, and abnormalities of bile acids have all been suggested as possibly etiologically important. Although recent studies, using the techniques of molecular biology and immunohistochemistry, have improved the understanding of some of the inflammatory elements of BA, there is a lack of understanding of how many such disparate elements interact and relate. Clinically, the management in the majority of cases should consist of a primary portoenterostomy (Kasai procedure) to try and restore bile flow and alleviate jaundice. Transplantation should be reserved for those who develop chronic liver disease and its attendant complications. Recent series would suggest that over 50% of infants in large centers will be able to clear their jaundice and therefore have a reasonable expectation of long-term survival with a good quality-of-life.

Limited role for CXC chemokines in the pathogenesis of alpha-naphthylisothiocyanate-induced liver injury

Alpha-naphthylisothiocyanate (ANIT) is a hepatotoxin that causes severe neutrophilic inflammation around portal tracts and bile ducts. The chemotactic signals that provoke this inflammatory response are unknown. In this study, we addressed the possibility that ANIT upregulates CXC chemokines in the liver and that these compounds mediate hepatic inflammation and tissue injury after ANIT treatment. Mice treated with a single dose of ANIT (50 mg/kg) exhibited rapid hepatic induction of the CXC chemokine macrophage inflammatory protein-2 (MIP-2). MIP-2 derived primarily from hepatocytes, with no apparent contribution by biliary cells. In ANIT-treated mice, the induction of MIP-2 coincided with an influx of neutrophils to portal zones; this hepatic neutrophil recruitment was suppressed by 50% in mice that lack the receptor for MIP-2 (CXCR2(-/-)). Interestingly, despite their markedly reduced degree of hepatic inflammation, CXCR2(-/-) mice displayed just as much hepatocellular injury and cholestasis after ANIT treatment as wild-type mice. Moreover, after long-term exposure, ANIT CXCR2(-/-) mice developed liver fibrosis that was indistinguishable from that in wild-type mice. In summary, our data show that CXC chemokines are responsible for some of the hepatic inflammation that occurs in response to ANIT but that these compounds are not essential to the pathogenesis of either acute or chronic ANIT hepatotoxicity.

Notch function in the vasculature: insights from zebrafish, mouse and man

Vascular development entails multiple cell-fate decisions to specify a diverse array of vascular structures. Notch proteins are signaling receptors that regulate cell-fate determination in a variety of cell types. The finding that Notch genes are robustly expressed in the vasculature suggests roles for Notch in guiding endothelial and associated mural cells through the myriad of cell-fate decisions needed to form the vasculature. In fact, mice with defects in genes encoding Notch, Notch ligands, and components of the Notch signaling cascade invariably display vascular defects. Human Notch genes are linked to Alagille's Syndrome, a developmental disorder with vascular defects, and CADASIL, a cerebral arteriopathy. Studies in zebrafish, mice and humans indicate that Notch works in conjunction with other angiogenic pathways to pattern and stabilize the vasculature. Here, we will focus on established functions for Notch in vascular remodeling and arterial/venous specification and more speculative roles in vascular homeostasis and organ-specific angiogenesis.

Prenatal diagnosis of liver and biliary tract disease

The diagnosis and detection of some forms of liver and bile duct disease have become possible since the adoption of routine fetal ultrasound scanning in the UK, and the remarkable advances in molecular biological techniques. Nevertheless, although antenatal detection may well have improved, it remains difficult to offer a specific diagnosis, much less a prognosis, in most cases. Cystic dilatation of the biliary tree is probably the most common finding. This may be due to cystic choledochal malformations or, occasionally but crucially, biliary atresia. Postnatal investigations (such as ultrasonography, magnetic resonance cholangiography and liver histology) must take the latter possibility into account, as early surgery is the key to a successful outcome following reconstructive biliary surgery. Antenatally diagnosed liver tumours are usually of vascular origin and have an unpredictable natural history. Some may cause fetal cardiac failure and are candidates for in-utero intervention, but in all likelihood, a large proportion will resolve without specific therapy.

Biliary atresia revisited

Extrahepatic biliary atresia (EHBA) is an inflammatory fibrosing process affecting the extrahepatic and intrahepatic biliary tree resulting in fibrous obliteration of the extrahepatic biliary tract, ductopenia of intrahepatic bile ducts, and biliary cirrhosis. EHBA is divided into a correctable and a noncorrectable type with focal patency of the otherwise atretic biliary tree in the former and no patency of the biliary tree in the noncorrectable type. EHBA is divided in a fetal, prenatal or embryonic, and a more common, perinatal, acquired form. The symptoms of the former start shortly after birth and there is frequently an association with a variety of congenital anomalies. Children with the perinatal form become jaundiced several weeks after birth; no associated congenital anomalies are present. Morphologically, an inflammatory and fibrosing process of the extrahepatic biliary tree leads to complete lumenal obliteration. The liver is characterized by a nonspecific giant cell transformation, and portal expansion by fibrous connective tissue with marked ductular proliferation. With time, ductopenia and biliary cirrhosis develop. The diffential diagnosis with other conditions with similar microscopic patterns such as as alpha-1 antitrypsin deficiency, total parental nutrition, obstruction by a choledochal cyst, arteriohepatic dysplasia, familial progressive intrahepatic cholestasis, and alteration of the bile acid metabolism is discussed. In the fetal group, abnormalities in different genes seem to play a role; ductal plate malformation is another possibility. Different etiologies have been postulated in the perinatal form of EHBA: genetic susceptibility, vascular factors, toxins, and infections mainly by rotavirus and reovirus. The pathogenesis is complex. EHBA is a heterogenous disease, resulting from a combination of genetic factors, insults, and activation of different genetic and immunologic pathways. The treatment of EHBA is surgical, with anastomosis between the biliary tree and the intestine in the correctable type and a hepatic portoenterostomy (HPE) for the noncorrectable group. HPE is a temporizing treatment allowing the infant to develop and grow, followed in the majority of the patients by liver transplantation.

Bile ducts and ductules are positive for CD56 (N-CAM) in most cases of extrahepatic biliary atresia

The diagnosis of extrahepatic biliary atresia can be challenging as the histologic features can overlap with other pediatric cholestatic liver diseases. Several previous studies have noted that biliary epithelium is positive for CD56 in the setting of extrahepatic biliary tract disease. Thus, we explored the use of CD56 in evaluating liver biopsy specimens for extrahepatic biliary atresia. A total of 22 cases were selected and immunostained for CD56, including 14 cases of confirmed extrahepatic biliary atresia and 8 cases of other cholestatic liver diseases in which the differential diagnosis included extrahepatic biliary atresia. Bile ducts and proliferating ductules were positive for CD56 in 13 of 14 cases of extrahepatic biliary atresia. The staining intensity was generally strong with most cases showing positivity in more than two thirds of portal tracts. The one negative case was a very small biopsy (<0.3 cm), and sampling may have played a role. In contrast, 4 of 8 cases in the control group were completely negative for CD56, with the remaining cases showing weak and focal positivity. In conclusion, bile ducts and ductules are CD56 positive in most cases of extrahepatic biliary atresia, and CD56 immunostaining can be a useful supplemental stain for diagnosing extrahepatic biliary atresia in its early, ductular proliferative phase when used in conjunction with traditional hematoxylin and eosin morphology and clinical information.

Biliary atresia

BA is a rare disease of unclear etiology; nevertheless, its impact in the field of pediatric hepatology is significant. It is the most common surgically correctable cause of neonatal cholestasis and is the most common pediatric disease referred for liver transplantation. Little progress has been made with regard to improving outcome or understanding its pathogenesis in the past decade. Fortunately, however, a national, government-sponsored collaborative endeavor has begun that will hopefully make a significant impact upon the progress of designing new treatments for BA and develop a better understanding of its pathogenesis.

Cholestatic syndromes

Further insights into the cellular and molecular mechanisms underlying hepatobiliary transport function and its regulation now permit a better understanding of the pathogenesis and treatment options of cholestatic liver diseases. Identification of the molecular basis of hereditary cholestatic syndromes will result in an improved diagnosis and management of these conditions. New insights into the pathogenesis of extrahepatic manifestations of cholestasis (eg, pruritus) have facilitated new treatment strategies. Important new studies have been published about the pathogenesis, clinical features, diagnosis, and treatment of primary biliary cirrhosis, primary sclerosing cholangitis, cholestasis of pregnancy, total parenteral nutrition-induced cholestasis, drug-induced cholestasis, and viral cholestatic syndromes.