Micro/nanoengineering Tools for Stem Cell Mechanobiology

Research on human pluripotent stem cells (hPSCs) has expanded rapidly over the last two decades, owing to their promise for applications in regenerative medicine, disease modeling, and developmental biology studies. However, most hPSC studies have so far focused on identifying extrinsic soluble factors, intracellular signaling pathways, and transcriptional networks involved in regulating hPSC behaviors. Leveraging some novel synthetic biomimetic systems developed in my group, we have for the first time explicitly demonstrated mechano-sensitive and -responsive properties of hPSCs and functional regulation of survival, proliferation, and directed differentiation of hPSCs by their dynamic cell-matrix and cell-cell interactions with the local cell microenvironment. In this talk, I will first specifically discuss a study where we have leveraged mechanosensitive properties of hPSCs to apply microengineered compliant (soft) cell culture surfaces to promote differentiation of hPSCs toward neuroepithelial cells possessing intrinsic posterior identities. Functional specification of motor neurons (MNs) from neuroepithelial cells is significantly accelerated and promoted on compliant cell culture surfaces. Mechanistic studies have revealed a multi-targeted mechanotransductive process in hPSCs involving Smad phosphorylation and nucleocytoplasmic shuttling, regulated by rigidity-dependent Hippo-YAP activities and actomyosin cytoskeleton integrity and contractility. In this talk, I will further discuss our most recent effort in constructing microengineered stem cell models of early human neurological developmental processes. Specifically, we have utilized microscale patterned hPSC cultures to successfully develop autonomously regionalized neuroectoderm tissues in vitro. Importantly, our mechanistic study has suggested that induction and regionalization of neuroectoderm tissues involve mechanically gated BMP and Wnt signaling at the cellular level through regulations of cell shape and cytoskeleton contractility to reinforce spatial patterning of cell fates in neuroectoderm tissues. Together, our data provides strong evidence supporting critical involvements of cellular mechanics and mechanobiology as control mechanisms in ensuing robust formation of regionalized neuroectoderm tissues.