Nanotopographical regulation of pancreatic islet-like cluster formation from human pluripotent stem cells using a gradient-pattern chip.

Bioengineering approaches to regulate stem cell fates aim to recapitulate the in vivo microenvironment. In recent years, manipulating the micro- and nano-scale topography of the stem cell niche has gained considerable interest for the purposes of controlling extrinsic mechanical cues to regulate stem cell fate and behavior in vitro. Here, we established an optimal nanotopographical system to improve 3-dimensional (3D) differentiation of pancreatic cells from human pluripotent stem cells (hPSCs) by testing gradient-pattern chips of nano-scale polystyrene surface structures with varying sizes and shapes. The optimal conditions for 3D differentiation of pancreatic cells were identified by assessing the expression of developmental regulators that are required for pancreatic islet development and maturation. Our results showed that the gradient chip of pore-part 2 (Po-2, 200-300 nm diameter) pattern was the most efficient setting to generate clusters of pancreatic endocrine progenitors (PDX1+ and NGN3+) compared to those of other pore diameters (Po-1, 100-200 or Po-3, 300-400 nm) tested across a range of pillar patterns and flat surfaces. Furthermore, the Po-2 gradient pattern-derived clusters generated islet-like 3D spheroids and tested positive for the zinc-chelating dye dithizone. The spheroids consisted of more than 30% CD200 + endocrine cells and also expressed NKX6.1 and NKX2.2. In addition, pancreatic β- cells expressing insulin and polyhormonal cells expressing both insulin and glucagon were obtained at the final stage of pancreatic differentiation. In conclusion, our data suggest that an optimal topographical structure for differentiation to specific cell types from hPSCs can be tested efficiently by using gradient-pattern chips designed with varying sizes and surfaces. STATEMENT OF SIGNIFICANCE: Our study provides demonstrates of using gradient nanopatterned chips for differentiation of pancreatic islet-like clusters. Gradient nanopatterned chips are consisted of two different shapes (nanopillar and nanopore) in three different ranges of nano sizes (100-200, 200-300, 300-400 nm). We found that optimal nanostructures for differentiation of pancreatic islet-like clusters were 200-300 nm nano pores. Cell transplantation is one of the major therapeutic option for type 1 diabetes mellitus (DM) using stem cell-derived β-like cells. We generated 50 um pancreatic islet-like clusters in size, which would be an optimal size for cell transplantation. Futuremore, the small clusters provide a powerful source for cell therapy. Our findings suggest gradient nanopatterned chip provides a powerful tool to generate specific functional cell types of a high purity for potential uses in cell therapy development.