(240c) Pluripotent Stem Cell Expansion and Neural Differentiation in 3-D Polyurethane Scaffolds after Auxetic Conversion

Auxetic scaffolds (i.e. scaffolds that can display negative Poisson’s ratio) could match both the elastic stiffness and the Poisson's ratio of the target tissue, and thus would likely better resemble native tissues and promote tissue regeneration.  Poisson’s ratio describes the degree of a material that contracts (or expands) transversally when axially strained.  While the brain has Poisson’s ratio close to zero, neural differentiation from pluripotent stem cells in auxetic scaffolds with tunable Poisson’s ratio has not been demonstrated.  In this study, the unique auxetic materials of polyurethane foam were fabricated by ingenious structure design in isotropic compression.  To establish a 3-D model system for neural differentiation, the polyurethane foam scaffolds were seeded with mouse embryonic stem cells and human induced pluripotent stem cells.  The cell organization was revealed by scanning electron microscopy and confocal microscopy.  Auxetic scaffolds supported smaller aggregate formation compared to the scaffolds prior to auxetic conversion, affecting the self-assembly process of the pluripotent stem cells.  The cells in the scaffolds exhibited the doubling time of 20-24 hours at the expansion stage and expressed high level of pluripotent markers such as Oct-4 and alkaline phosphatase.  Upon neural differentiation, differential expressions of neural markers of Nestin, Musashi-1, beta-tubulin type III and NCAM were observed for the cells grown in the scaffolds before and after auxetic conversion.  Compared to mouse embryonic stem cells, the aggregation process of human induced pluripotent stem cells when grown in the scaffolds was slower and lower percentages of aggregates were observed.  This study provides a novel 3-D model system with a spectrum of biophysical microenvironments to study the cellular differentiation from pluripotent stem cells.  This model system can be used for the generation of pluripotent stem cell-derived neural cells for disease modeling, drug screening, and regenerative medicine.