Engineering human hepatic tissue for modeling liver-stage malaria

Abstract

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biological Engineering, 2014.Cataloged from PDF version of thesis. Vita.Includes bibliographical references (pages 132-153).The Plcsmodium liver stage is an attractive target for the development of antimalarial drugs and vaccines, as it provides an opportunity to interrupt the life cycle of the parasite at a critical early stage. However, targeting the liver stage has been difficult due to a lack of human liver models that robustly recapitulate host-pathogen interactions in a physiologically relevant cell type. Through the application of hepatic tissue engineering concepts and techniques, this thesis sought to develop advanced models of liver-stage malaria that will allow the facile interrogation of potential antimalarial drugs in primary human hepatocytes. In the first part of this work, we established liver-stage Plasmodium infection in an engineered microscale human liver platform based on micropatterned cocultures of primary human hepatocytes and supportive stromal cells, enabling medium-throughput phenotypic screens for potential antimalarial drugs in a more authentic host cell, and demonstrated the utility of this model for malaria vaccine testing. We further hypothesized and showed that recapitulation of a more physiologically relevant oxygen tension that is experienced by hepatocytes in vivo improved infection rates and parasite growth in vitro. Next, we demonstrated the feasibility of establishing liver-stage malaria infections in human induced pluripotent stem cell-derived hepatocyte-like cells (iHLCs), thus enabling the study of host genetic variation on liver-stage malaria infection and antimalarial drug responses. We also applied recently discovered small molecules to induce further hepatic maturation, thus increasing the utility of using iHLCs for antimalarial drug development. Finally, we designed and provided a proof-of-concept for a humanized mouse model of liver-stage malaria that involves the fabrication and ectopic implantation of PEG-cryogel-based engineered human artificial livers, and can be generated in a facile, rapid and scalable fashion for future preclinical antimalarial drug testing in vivo. The results of this research represent a three-pronged approach towards engineering scalable human liver models that recapitulate liver-stage malaria infection which may ultimately facilitate antimalarial drug discovery at various stages of the drug development pipeline.by Shengyong Ng.Ph. D