A light-modulated hydrogel system to analyze cell durotaxic behavior in a dynamic manner

Castro Nava, Arturo; De Laporte, Laura (Thesis advisor); Möller, Martin (Thesis advisor)

Aachen : RWTH Aachen University (2021)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2021

Abstract

This doctoral thesis reports an in vitro light-responsive hydrogel system that rapidly actuates with spatial and temporal resolution using a NIR-light trigger. Accurate, temporal, and user-defined mechanical forces (~nN) are applied on a targeted group of cells cultured on the hydrogel surface with various frequencies and actuation times. The obtained insights reveal the effect of controlled mechanical actuation on cell migration, the kinetics of mechanosensor proteins, induction of pre-osteoblast differentiation in mesenchymal stem cells (MSC), and downregulation of pluripotency markers in induced pluripotent stem cells (iPSC) in combination with differentiation factors.Chapter 1 states the motivation of my scientific research and provides an overview of the doctoral thesis. Furthermore, it describes the current challenges of the state of the art and how the obtained results open new pathways to overcome certain limitations in the field of dynamic in vitro cell culture systems and cellular mechanotransduction. Chapter 2 describes the state of the art by focusing on the following topics: i) hydrogel design and ii) responsive polymer systems. Chapter 3 describes the building blocks and fabrication techniques that are required to engineer the light-modulated hydrogel platform and sets the foundations for the following chapters. It is shown that a NIR-light-triggered hydrogel system allows unrestricted cell growth and rapidly actuates with a spatio-temporal resolution, which ultimately has an effect on cellular mobility and the kinetics of the nuclear translocation of the mechanosensor protein MRTFA in mouse fibroblasts. Chapter 4 utilizes this engineered hybrid hydrogel platform and takes a step further by mechanically stimulating MSC. It is shown that these sub-cellular mechanical forces trigger changes in their cellular morphology and conformation. More importantly, without the addition of biochemical factors, the applied forces trigger pre-osteoblast differentiation, as well as nuclear translocation of the mechanosensor protein transcription factor YAP and upregulation of the osteogenic marker RUNX2. Chapter 5 illustrates how the surface topography of the hydrogel system affects the colony distribution of iPSC clusters. Furthermore, it is demonstrated that the synergistic effect of mechanical and biochemical cues affect iPSC fate by downregulating pluripotency markers OCT-4 and NANOG.