Regulation of cell reprogramming by matrix stiffness

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Project Summary Cell reprogramming represents a major advancement in biology, and has wide applications in regenerative medicine, disease modeling and drug screening. During cell reprogramming, cells experience epigenetic changes that result in a cell phenotype switch. However, whether and how biophysical factors regulate cell reprogramming through epigenetic modifications are not well understood. We have found that biophysical factors, specifically extracellular matrix (ECM) stiffness, has profound effects on epigenetic state and the conversion of fibroblasts into induced neuronal (iN) cells, with the highest efficiency at an intermediate ECM stiffness, which is regulated by focal adhesions and the cytoskeleton. In addition, we have discovered that actin assembly and transport into nucleus plays an important role in epigenetic modulation. Based on our preliminary data, we hypothesize that (1) biophysical cues such as ECM stiffness regulates FAs, actin assembly/disassembly, nuclear transport of actin, and thus, HAT activity to modulate the epigenetic state and cell reprogramming process and (2) an intermediate level of stiffness is optimal for epigenetic remodeling and cell reprogramming. To test our hypothesis, we propose three Specific Aims: (1) Investigate how matrix stiffness regulates iN reprogramming through FAs and actin cytoskeleton, (2) Elucidate how matrix stiffness modulates HAT and the epigenetic state to turn on neuronal genes during iN reprogramming, and (3) Determine the role of actin nuclear transport in matrix stiffness- modulation of HAT and epigenetic state during iN reprogramming. We have assembled a multidisciplinary team with expertise on mechanobiology, cell engineering, high throughput genomic and epigenomic analysis, and live cell imaging to work together and investigate the underlying biophysical and biological mechanisms. Our proposed studies will be one of the first to elucidate how ECM stiffness regulates transcriptomic and epigenetic changes for cell reprogramming, and how ECM stiffness modulates focal adhesions and the cytoskeleton for cell reprogramming. Findings from this project will unravel new mechanisms of cell fate determination, which will have wide applications in cell and tissue engineering, disease modeling and drug discovery, and provide a rational basis for the optimization and development of novel biomaterials for somatic cell reprogramming.