Date of Award

Fall 12-2017

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

Committee Chair

Yan-Lin Guo

Committee Chair Department

Biological Sciences

Committee Member 2

Fengwei Bai

Committee Member 2 Department

Biological Sciences

Committee Member 3

Alex Flynt

Committee Member 3 Department

Biological Sciences

Committee Member 4

Shahid Karim

Committee Member 4 Department

Biological Sciences

Committee Member 5

Hao Xu

Committee Member 5 Department

Biological Sciences

Abstract

Embryonic stem cells (ESCs) hold enormous promise for the goals of regenerative medicine and tissue engineering, and extraordinary progress has been made in defining conditions for differentiation to desired cell types. However, an often overlooked aspect of ESC biology is innate immunity, the ability of cells to detect and respond to pathogens and inflammatory cytokines. A number of recent studies by our lab and others have established that ESCs and other types of pluripotent cells from both mice and humans do not mount typical immune responses to viral or bacterial stimuli. There are also indications that various cell types differentiated from ESCs are also hyporesponsive, raising concerns for their suitability for therapeutic application. We have developed a model for the study of innate immunity during differentiation of mouse ESCs to fibroblasts (mESC-FBs). Using this model, the development of innate immune responses during in vitro differentiation was demonstrated by an increase in type I interferon (IFN) expression in response to viral stimuli, and an increased response to exogenous IFN, as compared with ESCs. The magnitude of responsiveness was further increased with continuous passaging, and this development could be accelerated by immune “priming” or exposure to low doses of immune stimulants during culturing. Differentiation correlated with a transition in functionality of the NFκB signaling pathway, a critical regulator of innate immune responses, from inactive in ESCs to a functioning state in differentiated cells. In addition to antiviral responses, responsiveness to inflammatory cytokines was acquired during in vitro differentiation, which again relied on a functional NFκB pathway, as well as increased expression of cytokine receptors. Preliminary characterization of mESC-FBs revealed several similarities with mesenchymal stem cells (MSCs), including morphology and marker expression, differentiation capacity, and production of trophic and immunosuppressive mediators. Thus mESC-FBs are not only a valuable model to study the mechanisms of innate immunity development, but could serve as an unlimited source for therapeutically valuable MSC-like cells.

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