Engineered hydrogels for tracking cell signaling from the outside-in

An exciting new strategy for regenerative therapies involves the conversion of somatic cells back into an embryonic stem cell (ES)-like state, termed induced pluripotent stem cells (iPS). iPS cells have the same potential for differentiation as ES cells and hold immense promise for tissue engineering, regenerative medicine, and fundamental developmental biology research. However, the introduction of these reprogramming factors leads to epigenetic changes which are not yet fully understood but are of great concern in clinical usages as epigenetic markers are heritable. The propagation of mechanochemical signals from the extracellular matrix (ECM) to the cell nucleus has emerged as a central feature in regulating cellular differentiation and de-differentiation. We hypothesize that reprogramming can be influenced in vitro by tuning extracellular matrix signals such as substrate stiffness. However, while the influence of ECM on cell function and gene expression is well documented, it remains less clear how mechanotransduction influences the activity of chromatin modifying enzymes that direct gene expression programs. In this thesis, we demonstrate a platform to study how signals from biophysical interaction in extracellular space are propagated into the cell nucleus to influence epigenetics and use this platform to further understand the process of reprogramming. In chapter 2, we present an in vitro system to decouple the effect of stiffness on epigenetics in order to understand the propagation of signal from the cytoplasm to the nucleus of the cell. With this model system, we investigate how histone deacetylase (HDAC) expression level and localization changes in response to changes in stiffness in order to understand the propagation of signal from the cytoplasm to the nucleus. In chapter 3, we combine our polyacrylamide model system with spatial light interference microscopy (SLIM) in order to design a novel patterning approach to simultaneously measure cell traction force along with cell growth and migration. This allows us to study the interaction between cells and ECM to understand the propagation of signal across the cell boundary into the cytoskeleton. Finally, in chapter 4 we utilize these tools to understand cellular reprogramming and demonstrate an influence of ECM matrix elasticity and microconfinement on cellular processes underlying reprogramming. In Chapter 5, we summarize these works in the context of using in vitro systems to decipher cell signaling from the outside in and cellular reprogramming. Overall, we believe the work presented here gives new insight to the propagation of signal from a cell’s microenvironment to epigenetic changes within the cell nucleus. We also demonstrate the potential for extracellular properties to influence somatic cell reprogramming which may aid in the development of new biomaterials for use in regenerative therapies.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Bioengineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2018

Author dc:creator

• Li, Yanfen

Contributors dc:contributor

• Kilian, Kristopher A.
• Popescu, Gabriel
• Harley, Brendan A.
• Perez-Pinera, Pablo

• Tissue engineering
• Epigenetics
• Biomaterials
• Extracellular Matrix
• Reprogramming
• Stem Cells
• Stiffness

Statement dc:rights

• Copyright 2018 Yanfen Li

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/101811

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/101811