Pluripotent stem cells can turn into all types of cells that make up the tissues and organs in our body. The specific cell type (stem cell fate) depends on the biochemical and biophysical cues they experience. The biophysical cues depend on the surrounding scaffold's mechanical properties, such as the elastic modulus and the Poisson's ratio (which is the ratio of a material's lateral contraction to its increase in length upon stretching). This project seeks to understand how these mechanical properties determine stem cell fate by tuning both elastic modulus and Poisson's ratio to reveal the synergistic roles of biophysical and biochemical signaling on stem cell fate. This research will benefit bioengineering applications and biomanufacturing (e.g., novel microcarriers), leading to better drug screening and disease modeling for the biotechnology and pharmaceutical industries. The project will also establish an interactive learning platform to reduce gender disparity and increase the participation of minority students in engineering. Efforts will be made to stimulate African American and women students to pursue an advanced training and career by participating in the proposed research and educational activities. This project will include working with Women in Math, Science and Engineering organization, National Society of Black Engineers, Quality Education for Minorities Network, and the SciGirls program at National High Magnetic Field Laboratory to attract young girls and African American students for advanced science and engineering training and career.
The goal of this project is to elucidate the interactions between biophysical cues of elastic modulus and Poisson's ratio of 3D polyurethane (PU) scaffolds and their influence on the secretion of endogenous ECMs and Yes-associated protein (YAP) localization by iPSCs during lineage-specific commitment. The project's central hypothesis is that the scaffolds with tunable elastic modulus and Poisson's ratio affect cell organization and transduce biophysical signals to modulate the profile of endogenous ECMs and YAP expression and influence lineage commitment of iPSCs. This hypothesis is based on preliminary results that demonstrated enhanced neural and vascular differentiation of pluripotent stem cells (PSCs) using 3D scaffolds with re-entrant structures - structures with angles pointing inward that expand in all three directions if stretched in one direction, i.e., structures with negative Poisson's ratios. The research plan is organized under three objectives. The FIRST Objective is to fabricate and characterize scaffold arrays with different Poisson's ratio and elastic modulus. Regular PU scaffolds with reticulate structure will be heated/softened and controlled buckling will be used to produce a spectrum of auxetic scaffolds with varying Poisson's ratio (0.3 to -0.4) at a fixed elastic modulus. Likewise, auxetic scaffolds with different elastic modulus (1-100 kPa) at a fixed Poisson's ratio will be fabricated by compressing the regular scaffold with different modulus to the same degree of buckling. The scaffolds will be fabricated according to the prediction of finite element modeling with the inputs of temperature-dependent elastic modulus and on video data. The SECOND Objective is to examine the differential effects of Poisson's ratio and elastic modulus on iPSC lineage commitment. Undifferentiated iPSCs or iPSC-derived neural progenitor cells (NPCs) will be seeded into different scaffolds and induced toward neural lineage or vascular lineage. The cells will be characterized for neuronal markers or vascular markers with expectations that auxetic scaffolds that mimic tissue elasticity will promote neural differentiation of iPSCs and that elastic modulus and Poisson's ratio have differential effects on neural lineage commitment. The THIRD Objective is to determine the influences of Poisson's ratio and elastic modulus on YAP localization and the secretion of endogenous ECMs, which modulate canonical Wnt signaling and contribute to the lineage commitment of iPSCs. YAP localization will be examined and the influence of YAP on Wnt signaling will be revealed with expectations that auxetic scaffolds induce cytoplasmic YAP localization, that nuclear YAP localization activates Wnt signaling, that cells will secrete different profiles of ECMs in response to the scaffold elasticity and influence Wnt signaling and finally, that interactions of YAP with Wnt signaling contribute to the lineage commitment of iPSCs.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
