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Nanofibrous Electrospun Polymers for Reprogramming Human Cells


Forced expression of transcription factors epigenetically reprograms somatic cells harvested from routine skin biopsies into induced pluripotent stem cells (iPSCs). Human iPSCs are key resources for drug discovery, regenerative medicine and tissue engineering. Here we developed a materials approach to explore how culture substrates could impact factor-mediated reprogramming of human fibroblasts. A materials library consisting of nanofibrous substrates with randomly oriented and aligned structures was prepared by electrospinning four polymers [polylactic acid (PLA), polycaprolactone (PCL), thermoplastic polyurethane (TPU) and polypropylene carbonate (PPC)] into nanofiber orientations. Adsorbing protein to each substrate permitted robust attachment of fibroblasts to all substrates. Fibroblasts on aligned substrates had elongated nuclei, but after reprogramming factor expression, nuclei became more circular. Reprogramming factors could override the nuclear shape constraints imposed by nanofibrous substrates, and the majority of substrates supported full reprogramming. Early culture on PCL and TPU substrates promoted reprogramming, and TGF-β repressed substrate effects. Partial least squares modeling of the biochemical and biophysical cues within our reprogramming system identified TGF-β and polymer identity as important cues governing cellular reprogramming responses. We believe that our approach of using a nanofibrous materials library can be used to dissect molecular mechanisms of reprogramming and generate novel substrates that enhance epigenetic reprogramming.

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We acknowledge generous financial support from the Wisconsin Institute for Discovery (T.C. and K.S.), a Grainger Fellowship (J.C-S.) and the Society in Science Foundation (K.S.). We also would like to thank all members of the Saha lab and BIONATES theme for advice and support throughout this project. We acknowledge Dr. Rob McClain and the University of Wisconsin-Madison Biochemistry department for the use and expertise in collecting surface area data via the BET Micromeritics Gemini VII instrument.

Conflict of interest

Travis Cordie, Ty Harkness, Xin Jing, Jared Carlson-Stevermer, Hao-Yang Mi, Lih-Sheng Turng and Krishanu Saha declare that they have no conflicts of interest. Dr. Saha reports grants from Society in Science Foundation during the conduct of the study.

Ethical Standards

No human and animal studies were carried out by the authors for this article. All work with human embryonic stem cell lines was carried out in accordance with institutional, national, and international guidelines and approved by the Stem Cell Research Oversight Committee at the University of Wisconsin-Madison.

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Correspondence to Krishanu Saha.

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Associate Editor David Mooney oversaw the review of this article.

This paper is part of the 2014 Young Innovators Issue.

Travis Cordie and Ty Harkness have contributed equally to this work.

Krishanu Saha is an Assistant Professor in the Department of Biomedical Engineering at the University of Wisconsin-Madison. He is also a member of the Wisconsin Institute for Discovery in the bionanocomposite tissue engineering scaffolds (BIONATES) theme. Prior to his arrival in Madison, Dr. Saha studied Chemical Engineering at Cornell University and at the University of California in Berkeley. In his dissertation with Professors David Schaffer and Kevin Healy, he worked on experimental and computational analyses of neural stem cell development, as well as the design of new materials for adult stem cell culture. In 2009 he became a Society in Science: Branco-Weiss fellow in the laboratory of Professor Rudolf Jaenisch at the Whitehead Institute for Biomedical Research at MIT and in the Science and Technology Studies program at Harvard University with Professor Sheila Jasanoff in Cambridge, Massachusetts. Since then, he has performed research on human pluripotent stem cells, disease modeling and synthetic biology.

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Cordie, T., Harkness, T., Jing, X. et al. Nanofibrous Electrospun Polymers for Reprogramming Human Cells. Cel. Mol. Bioeng. 7, 379–393 (2014).

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  • Pluripotent stem cells
  • Reprogramming
  • Biomaterials
  • Electrospinning
  • Nuclear shape