The use of Yes-associated protein expression in the diagnosis of persistent neonatal cholestatic liver disease

Abstract

Although physiologic jaundice of neonates is common, persistent neonatal cholestasis is life-threatening and has multiple etiologies. Among these etiologies, biliary atresia (BA) requires rapid diagnosis and treatment. In diagnosing BA, the surgical pathologist must recognize subtle histologic changes, often with only a small core liver biopsy. To aid in the differential diagnosis of neonatal cholestasis, we investigated Yes-associated protein (YAP), a regulator of organ size and bile duct development. We examined whether a YAP immunostain can highlight emerging hepatobiliary epithelium in BA [n=28] versus other causes of persistent cholestasis (non-BA) [n=15] and thus serve as a useful diagnostic marker in persistent neonatal jaundice. We show significantly (p≤0.01) more high-grade (≤2) fibrosis and ductular proliferation among BA versus non-BA cases. Likewise, there was significantly more high-grade (2–3/3) cytoplasmic and nuclear YAP staining in BA (97% and 89%) versus non-BA (20% and 13%). High-grade nuclear YAP staining was both sensitive (88%) and specific (87%) for the diagnosis of BA. In contrast to neonatal cholestasis, the differences in YAP localization in cholestatic/obstructed vs. non-obstructed adult livers were not significant. Lastly, we found that pharmacological inhibition of the YAP complex in both cholangiocyte and cholangiocarcinoma cell lines blocked compensatory bile duct proliferation, an early marker of BA that requires nuclear YAP expression, in a time- and dose-dependent manner. In summary, we show that YAP expression modulates both bile duct proliferation and liver damage/fibrosis while acting as a sensitive and specific marker in the differential diagnosis of persistent neonatal cholestasis.

Taurocholate Induces Connective Tissue Growth Factor Expression in Hepatocytes Through ERK-YAP Signaling

“…Consistent with previous reports, JNK signaling was not activated in hepatocytes in BDL-induced cholestasis [46]. Furthermore, YAP was reported to be involved in cholestasis-related liver fibrosis and liver cancer progression, and served as a classical upstream regulator of CTGF/CCN2 in mammalian cells [29,30]. Thus, we investigated whether BAs regulate CTGF/CCN2 levels through YAP and found that TC increased YAP levels in hepatocytes.…”

“…TGF-β can induce CTGF/CCN2 expression in a Smaddependent manner in hepatocytes [26], whereas it regulates the expression of CTGF/CCN2 through Smad-independent signaling in hepatic progenitor cells [27]. CTGF/CCN2 also acts as a downstream gene of Yes-associated protein (YAP) [28], which has been reported to be involved in cholestasis [29,30]. Moreover, enhanced expression of CTGF/CCN2 was observed in liver tissues of cholestatic patients [31].…”

Hippo Pathway Regulation of Gastrointestinal Tissues

“…A series of studies have demonstrated a close association between cholestasis and Hippo signaling (133)(134)(135). Cholestasis is usually caused by the disruption of enterohepatic circulation and overload of bile acids, which results in diseases such as primary sclerosing cholangitis (PSC) and primary biliary cirrhosis (PBC).…”

Yes-associated protein in the liver: Regulation of hepatic development, repair, cell fate determination and tumorigenesis

“…Additionally, VP treatment reduced cell proliferation more pronouncedly in HuCCT1 cholangiocarcinoma cell line than it did to normal cholangiocyte cell line H69, suggesting the potential of VP in treating cholangiocarcinoma [62].…”

“…Elevated nuclear YAP expression was found in ductular reactions of primary sclerosing cholangitis (PSC) and primary biliary cirrhosis (PBC) [26] as well as in bile duct epithelium of neonates with biliary atresia [62]. In cholestatic livers of young patients, hepatocytes also display robust YAP staining [63].…”