Suresh K. Nayar

Yes-Associated Protein Regulates the Hepatic Response After Bile Duct Ligation

Human chronic cholestatic liver diseases are characterized by cholangiocyte proliferation, hepatocyte injury, and fibrosis. Yes‐associated protein (YAP), the effector of the Hippo tumor‐suppressor pathway, has been shown to play a critical role in promoting cholangiocyte and hepatocyte proliferation and survival during embryonic liver development and hepatocellular carcinogenesis. Therefore, the aim of this study was to examine whether YAP participates in the regenerative response after cholestatic injury. First, we examined human liver tissue from patients with chronic cholestasis. We found more‐active nuclear YAP in the bile ductular reactions of primary sclerosing cholangitis and primary biliary cirrhosis patient liver samples. Next, we used the murine bile duct ligation (BDL) model to induce cholestatic liver injury. We found significant changes in YAP activity after BDL in wild‐type mice. The function of YAP in the hepatic response after BDL was further evaluated with liver‐specific Yap conditional deletion in mice. Ablating Yap in the mouse liver not only compromised bile duct proliferation, but also enhanced hepatocyte necrosis and suppressed hepatocyte proliferation after BDL. Furthermore, primary hepatocytes and cholangiocytes isolated from Yap‐deficient livers showed reduced proliferation in response to epidermal growth factor in vitro. Finally, we demonstrated that YAP likely mediates its biological effects through the modulation of Survivin expression. Conclusion: Our data suggest that YAP promotes cholangiocyte and hepatocyte proliferation and prevents parenchymal damage after cholestatic injury in mice and thus may mediate the response to cholestasis‐induced human liver disease. (HEPATOLOGY 2012;56:1097–1107)

Hypoxia inducible factor 2 alpha inhibits hepatocellular carcinoma growth through the transcription factor dimerization partner 3/ E2F transcription factor 1–dependent apoptotic pathway

Hypoxia inducible factors (HIFs) are activated in many tumors and show either promoter or suppressor activity, depending on tumor cell biology and background. However, the role of HIF member HIF‐2α remains unclear in hepatocellular carcinoma (HCC). Here, HIF‐2α expression was measured in HCC and paired peritumoral tissues by quantitative real‐time polymerase chain reaction, western blotting, and immunofluorescence assays, and the clinical significance was explored in 246 HCC patients. In cell culture, HIF‐2α levels were up‐regulated or down‐regulated by use of expression or short hairpin RNA recombinant plasmid, respectively. Cells were analyzed by immunoblotting, chromatin immunoprecipitation coupled with microarray, coimmunoprecipitation, and immunohistochemical staining. In vivo tumor growth was analyzed in nude mice. We found that the average expression of HIF‐2α was relatively low in HCC tissues, and the decreased level was associated with lower overall survival (P = 0.006). High HIF‐2α expression in HCC cells induced higher levels of apoptosis and expression of proapoptotic proteins and inhibited cell and tumor growth. Furthermore, HIF‐2α inhibited expression of the novel target gene, transcription factor dimerization partner 3 (TFDP3). TFDP3 protein was found to bind with E2F transcription factor 1 (E2F1) and inhibit its transcriptional activity through both p53‐dependent and ‐independent pathways. Reintroduction of TFDP3 expression reversed HIF‐2α‐induced apoptosis. Conclusions: Data gathered from cell lines, tumorigenicity studies, and primary HCC samples demonstrate a negative role of HIF‐2α in tumors, which is mediated by the TFDP3/E2F1 pathway. Our study provides evidence supporting a possible tumor‐suppressor role for HIF‐2α and has uncovered a mechanism that links HIF‐2α to a fundamental biological regulator, E2F1. (HEPATOLOGY 2013)

The frequency of KRAS and BRAF mutations in intrahepatic cholangiocarcinomas and their correlation with clinical outcome

The incidence of intrahepatic cholangiocarcinoma is increasing worldwide. The prognosis of intrahepatic cholangiocarcinoma is poor, and a better understanding of intrahepatic cholangiocarcinoma tumor biology is needed to more accurately predict clinical outcome and to suggest potential targets for more effective therapies. v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) and BRAF are frequently mutated oncogenes that promote carcinogenesis in a variety of tumor types. In this study, we analyze a large set of intrahepatic cholangiocarcinoma tumors (n = 54) for mutations in these genes and compare the clinical outcomes of wild type versus KRAS and BRAF mutant cases. Of 54 cases, 7.4% were mutant for KRAS, 7.4% were mutant for BRAF, and these were mutually exclusive. These mutant cases were associated with a higher tumor stage at time of resection and a greater likelihood of lymph node involvement. These cases were also associated with a worse long-term overall survival. Therefore, testing for KRAS and BRAF mutations could be a valuable adjunct in improving both prognosis and outcome stratification among patients with intrahepatic cholangiocarcinoma.

Isolated spinal cord contusion in rats induces chronic brain neuroinflammation, neurodegeneration, and cognitive impairment. Involvement of cell cycle activation.

Cognitive dysfunction has been reported in patients with spinal cord injury (SCI), but it has been questioned whether such changes may reflect concurrent head injury, and the issue has not been addressed mechanistically or in a well-controlled experimental model. Our recent rodent studies examining SCI-induced hyperesthesia revealed neuroinflammatory changes not only in supratentorial pain-regulatory sites, but also in other brain regions, suggesting that additional brain functions may be impacted following SCI. Here we examined effects of isolated thoracic SCI in rats on cognition, brain inflammation, and neurodegeneration. We show for the first time that SCI causes widespread microglial activation in the brain, with increased expression of markers for activated microglia/macrophages, including translocator protein and chemokine ligand 21 (C–C motif). Stereological analysis demonstrated significant neuronal loss in the cortex, thalamus, and hippocampus. SCI caused chronic impairment in spatial, retention, contextual, and fear-related emotional memory—evidenced by poor performance in the Morris water maze, novel objective recognition, and passive avoidance tests. Based on our prior work implicating cell cycle activation (CCA) in chronic neuroinflammation after SCI or traumatic brain injury, we evaluated whether CCA contributed to the observed changes. Increased expression of cell cycle-related genes and proteins was found in hippocampus and cortex after SCI. Posttraumatic brain inflammation, neuronal loss, and cognitive changes were attenuated by systemic post-injury administration of a selective cyclin-dependent kinase inhibitor. These studies demonstrate that chronic brain neurodegeneration occurs after isolated SCI, likely related to sustained microglial activation mediated by cell cycle activation.

Expression of Yes-associated protein modulates Survivin expression in primary liver malignancies

Hepatocellular carcinoma and intrahepatic cholangiocarcinoma account for 95% of primary liver cancer. For each of these malignancies, the outcome is dismal; incidence is rapidly increasing, and mechanistic understanding is limited. We observed abnormal proliferation of both biliary epithelium and hepatocytes in mice after genetic manipulation of Yes-associated protein, a transcription coactivator. Here, we comprehensively documented Yes-associated protein expression in the human liver and primary liver cancers. We showed that nuclear Yes-associated protein expression is significantly increased in human intrahepatic cholangiocarcinoma and hepatocellular carcinoma. We found that increased Yes-associated protein levels in hepatocellular carcinoma are due to multiple mechanisms including gene amplification and transcriptional and posttranscriptional regulation. Survivin, a member of the inhibitors-of-apoptosis protein family, has been reported as an independent prognostic factor for poor survival in both hepatocellular carcinoma and intrahepatic cholangiocarcinoma. We found that nuclear Yes-associated protein expression correlates significantly with nuclear Survivin expression for both intrahepatic cholangiocarcinoma and hepatocellular carcinoma. Furthermore, using mice engineered to conditionally overexpress Yes-associated protein in the liver, we found that Survivin messenger RNA expression depends upon Yes-associated protein levels. Our findings suggested that Yes-associated protein contributes to primary liver tumorigenesis and likely mediates its oncogenic effects through modulating Survivin expression.

The Student Curriculum Review Team: How we catalyze curricular changes through a student-centered approach.

Abstract Student feedback is a valuable asset in curriculum evaluation and improvement, but many institutions have faced challenges implementing it in a meaningful way. In this article, we report the rationale, process and impact of the Student Curriculum Review Team (SCRT), a student-led and faculty-supported organization at the Johns Hopkins University School of Medicine. SCRT’s evaluation of each pre-clinical course is composed of a comprehensive three-step process: a review of course evaluation data, a Town Hall Meeting and online survey to generate and assess potential solutions, and a thoughtful discussion with course directors. Over the past two years, SCRT has demonstrated the strength of its approach by playing a substantial role in improving medical education, as reported by students and faculty. Furthermore, SCRT’s uniquely student-centered, collaborative model has strengthened relationships between students and faculty and is one that could be readily adapted to other medical schools or academic institutions.

Basic Science Research Trends in Orthopedic Surgery: An Analysis of the Top 100 Cited Articles

BackgroundMuch of current clinical orthopedics traces its origin to basic science investigation of cellular and biochemical pathways, tissue engineering, and biomechanics of bone and joint physiology in animal and cadaveric models.Questions/PurposesWe sought to describe research trends in highly cited basic science studies in orthopedics.MethodsBy searching Web of Science, we identified the 100 most cited basic science orthopedics articles and focused on author position and degree (PhD, MD, or MD/PhD), topic, type of study, country, institution, and citation trends.ResultsThese articles were published from 1970 to 2008 (citation range, 330 to 2111), with the majority from the USA (78). While there was no correlation between years since publication and total citations, more recent articles had higher citation rates. There were 38 unique first authors represented, with Caplan, Harris, Mankin, Noyes, and Warren as primary authors or co-authors of four articles each. Twelve journals published these 100 articles, with the majority in Journal of Bone and Joint Surgery (46) and Clinical Orthopaedics and Related Research (18). Frequent topics included biomechanics (31), healing/regeneration (21), and cellular/molecular biology (13). The Hospital for Special Surgery/Cornell University (10) published the most, followed by the Hospital for Joint Diseases/New York University (6), and University of Pittsburgh (6). No difference was observed in total citations and average citation rate by author degree. Eight articles were contributed from privately owned institutions or industry, with the rest from academic hospitals.ConclusionThis review may aid those seeking insight into landmark studies and future direction of basic science research in orthopedics.