Neha Bhat, PhD
Postdoctoral Associate, Yale Cardiovascular Research Center
Project Title: Characterizing the pathophysiology of metabolic syndrome upon genetic manipulation of Dyrk1b in the liver
Non Alcoholic Fatty Liver Disease (NAFLD) is the most prevalent liver disease afflicting nearly 25% of people in the United States. Identification of genes making individuals more susceptible to NAFLD are likely to be key targets to reduce its further deterioration to steatohepatitis and hepatocellular carcinoma. The major risk factors for NAFLD are central obesity, insulin resistance and type II diabetes, collectively called metabolic syndrome (MetS). The mutations in the Dyrk1b (dual specificity tyrosine regulated kinase 1b) kinase was associated with familial pattern of inheritance of metabolic syndrome in humans. We aim to further delineate the function and dissect the mechanism of Dyrk1b action using mouse as a model system. Our specific aims are to investigate the role of Dyrk1b in lipid metabolism, inflammation, steatohepatitis and cirrhosis. We have generated global Dyrk1b knockout mice and hepatic overexpression models to address these questions by employing physiological and molecular biology methods.
Yasuko Iwakiri, PhD
Associate Professor of Medicine, Digestive Diseases
Project Title: Lymphangiogenesis in the liver
The lymphatic vascular system is essential for the maintenance of tissue fluid homeostasis and immune surveillance system. The liver is the key organ for lymphatic fluid production. However, it is largely unknown how these lymphatic vessels are formed in the liver and how their functions are regulated. The goal of this proposed research is to establish an experimental model of hepatic lymphangiogenesis and determine its mechanism.
Nikhil Joshi, PhD
Assistant Professor, Immunobiology
Project Title: Understanding mechanisms of hepatocyte-induced T cell immunologic tolerance
The liver properties of immunological tolerogenesis, thanks to the capacity of its sinusoid endothelial cells and its parenchymal cells (the hepatocytes) to present antigens to circulating T lymphocytes. These properties allow liver cells to prevent aberrant T cell responses to innocuous antigens (like ingested food, drug metabolites and all the other harmless molecules entering the body through the gut). Limited knowledge has been acquired on the mechanisms that allow hepatocytes to regulate antigen-specific T cell responses. Understanding, the mechanisms of liver tolerogenesis is important because breakdown of these mechanisms leads to pathology in some autoimmune disorders and allergies. These mechanisms may also be important for chronic liver infections and transplant tolerance.
The study of tolerance has been limited mainly because of the lack of adequate experimental models. We developed NINJA, which allows a tight spatial and temporal regulation of the expression of a neoantigen. As a consequence, we are able to induce antigen expression and presentation only in a chosen tissue or cell in the absence of inflammatory signals. Upon neoantigen induction in hepatocytes, antigen-specific T cells localize and expand, but fail to acquire a complete effector phenotype. Unlike other organs like pancreas, this inability is not dependent the PD-1/PD-L1 pathway, suggesting regulation of T cell responses in liver may differ from other organs.
Our aim is to identify the molecular pathways involved in the regulation of T cells and the establishment of tolerance in the liver. By studying endogenous T cells into NINJA mice, in the context of infection or the absence of inflammation, we will compare the phenotype and function of antigen-specific T cells and test if unique pathways of tolerogenesis exist in liver. We will also identify candidate genes that could cause differences in function between liver and pancreas and test their importance with genetic knock-down in responding T cells. Thus, our goal is to use our genetic models to identify and test key genes in the development of hepatocyte-dependent tolerance, and to understand whether deficiency of these genes is involved in immune-mediated liver pathology.
Supriya Kulkarni, PhD, MS
Associate Research Scientist, Digestive Diseases
Project Title: Identification and characterization of OSTα/β inhibitors for drug therapy in cholestasis
Human cholestatic syndromes PBC, and PSC either have no accepted therapy, or are in need to alternative therapies due to intolerance or incomplete response to currently approved therapies, such as obeticholic acid, and Ursodeoxycholic acid. This pilot grant proposes to identify novel small molecule inhibitors to the bile acid transporter OSTα/β that could be developed clinically to alleviate cholestatic liver injury.
OSTα/β is a heteromeric bile acid and sterol transporter, expressed primarily in human and rodent ileum and kidney, as well as in human liver. Previous studies have demonstrated that mice deficient in OSTα are protected against cholestatic liver injury. The proposed pilot project aims to identify novel small molecule inhibitors of bile acid transporter OSTα/β using a unique in vitro, cell-based high throughput assay format that employs Förster resonance energy transfer (FRET) via fluorescence-activated cell sorting (FACS) as the end readout. Small molecule libraries available with the Yale Center for Molecular Discovery (YCMD) will be screened using the FRET/FACS based assay for their OSTα/β inhibition potential. Top 3 inhibitors identified will be assessed for toxicity potential in vitro, and the top hit inhibitor will be assessed forfunctional efficacy in well-described preclinical, oral bile acid feeding model of cholestasis in mice.
Carol Soroka, PhD
Senior Research Scientist in Medicine, Digestive Diseases
Project Title: Is olation of Organoids from Bile of Patients with Primary Sclerosing Cholangitis Provides a Unique Opportunity to Study Extrahepatic Biliary Cells Throughout the Progression of the Disease
Primary sclerosing cholangitis (PSC) is a rare, progressive, and often fatal cholestatic liver disease of unknown etiology. Understanding the mechanisms of the disease and how to treat it is hampered by the diversity seen in the clinical population, the rarity of the disease, and the lack of a reproducible in vitro culture system that can focus on the bile duct cell that represents a very small percent of all hepatic cells. In this Pilot grant study, I have developed a method to isolate and culture progenitor cells (organoids) directly from the bile of patients undergoing ERCP. These cells have a biliary genotype as assessed by RT QPCR and can be maintained long-term in culture or frozen down in a biobank for future studies, including pharmacotherapeutic testing of drugs. The ability to acquire these cells from bile collected during ERCP provides analysis of PSC patients throughout the course of their disease, well before the need for liver transplantation, and allows for a personalized approach to their therapy. It is the hope that the use of organoids will provide insight into the diversity seen in the patient population and allow future studies into the mechanisms of this rare disease.