Date of Award

1-1-2018

Embargo Period

4-20-2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Regenerative Medicine and Cell Biology

College

College of Graduate Studies

First Advisor

Michele A. Battle

Second Advisor

John J. Lemasters

Third Advisor

Robin Muise-Helmericks

Fourth Advisor

Paula Traktman

Abstract

Studies on liver development and disease traditionally relied on using animal models. However, the difference in liver biology between human and animals prevented the animal models from fully recapitulating human liver dieases. Human induced pluripotent stem cells (iPSC) reprogramed from human somatic cells can self-renew and are capable of being differentiated into various cell types that originate from endoderm, mesoderm or ectoderm. Our lab previously developed a procedure to differentiate iPSCs into cells that resemble mature human hepatocytes. Here we aim to explore the application of iPSC-derived hepatocyte-like cells for the study of basic developmental biology, the generation of new disease models, and identification of therapeutics. Hepatic specification is the conversion of endoderm cell into hepatic progenitor cells. Previous studies have identified a series of pathways regulating hepatic specification. However, these studies were performed using animal models, and the throughput was low. We hypothesized that the differentiation of iPSCs could be used to model hepatic specification and enable unbiased, high-throughput analysis to identify new players regulating this process. Our results showed that a protein chaperone, heat shock protein 90 beta (HSP90β), plays a pivotal role in the formation of hepatic progenitors by stabilizing hepatocyte nuclear factor 4 alpha (HNF4a), which is a master regulator of hepatocyte differentiation. We next explored whether iPSC-derived hepatocyte-like cells could be used to model liver diseases. Mitochondria DNA depletion syndrome 3 (MTDPS3) is a mitochondrial disease caused by mutations in deoxyguanosine kinase (DGUOK) gene. The MTDPS3 patients suffer from liver diseases and usually die from liver failure due to insufficient ATP production by the hepatocytes. The studies on the MTDPS3 were hindered by the lack of a model that mimics the hepatic phenotypes, because primary hepatocytes are difficult to maintain or expand in vitro. To overcome this limitation, we generated iPSC-derived hepatocyte-like cells from DGUOK-deficient iPSCs and found that the DGUOK-deficient hepatocytes recapitulate the pathophysiology of MTDPS3. We then performed a drug screen and revealed that Nicotinamide adenine dinucleotide (NAD) could rescue the mitochondria dysfunction and ATP reduction in DGUOK-deficient hepatocytes and, therefore, holds promise for treating MTDPS3.

Rights

All rights reserved. Copyright is held by the author.

Download

Share

COinS