Mechanotransductive Engineering of Neural Stem Cell Behavior

Abstract

the target species. A significant limitation of previous low-penetration methods arises from the very character that provides their utility: the low penetration depth also means they can only probe molecular events very close to the substrate surface. We have fabricated vertical silicon dioxide nanopillars which, at a height of up to one micron, carry that low penetration depth up into the cell environment where the relevant molecular processes occur. The pillars can also be specifically functionalized with molecules of interest for either delivery into the local environment or study while tethered in the observation volume. With single molecule detection at biologically-relevant concentrations and biologically-applicable locations, these nanopillars provide a template on which to study a multitude of biological processes in a controlled, dynamic, and localized fashion.

Microelastic mapping of the rat dentate gyrus

“…Our measurements also validate the physiological relevance of engineered ECM substrates to drive NSC neurogenesis in culture. We show that the stiffness of living DG tissue lies within a range of 50-150 Pa, which is consistent with past AFM measurements of bulk hippocampal tissue [16] and closely matches stiffness regimes previously identified (200 Pa in two-dimensional culture [12,13] and 180 Pa in three-dimensional culture [24]) to be pro-neurogenic in vitro for NSCs, mesenchymal stem cells [11] and human pluripotent stem cells [17]. However, it is important to note some caveats that accompany our measurements.…”

“…For example, mechanical signalling through cell-extracellular matrix (ECM) interactions has been shown to play a role in regulating NSC differentiation. In particular, the elastic modulus (E) of the ECM substrate has been shown to regulate NSC lineage in vitro [11,12], with soft ECMs promoting NSC neurogenesis and stiff ECMs suppressing it [12,13]. Despite the clear instructive effects of elastic modulus on stem cell behaviour in vitro, and the in vivo regulation of stem cell behaviour by signals that are modulated in vitro by stiffness differences [13], the degree to which E may vary in the in vivo niche is unknown.…”

“…Such measurements have informed the design of in vitro assay platforms capable of recapitulating in vivo behaviour. Synthetic polyacrylamide matrix culture systems have shown stiffness-dependent instruction of NSC differentiation [12,13], neurogenic instruction of pluripotent stem cell differentiation [17] and full neuronal maturation and subtype differentiation with physiological stiffness values [18]. That said, these seminal AFM indentation measurements focused on large size scale variations in stiffness across the entire hippocampus, rather than high-resolution investigation of the specific regions in which hippocampal NSCs reside.…”

Tissue mechanics, an important regulator of development and disease

“…R. Soc. B 374: 20180215 stiffness increases RhoA and Cdc42 expression and actomyosin contractility, directly increasing cell stiffness and suppressing neurogenesis during differentiation of neural stem cells [132].…”

Microarraying for Mechanosensivitity

“…Cell source is a current limitation of muscle stem cellbased therapies, given that MuSCs have been difficult to expand in culture, whereas more committed myoblasts can be expanded yet often progressively lose myodifferentiation potential. This work thus further demonstrates that engineered biomaterials have the potential not only to address fundamental biological questions but potentially also to serve as culture systems to expand and differentiate cells for biomedical applications (Keung et al, 2010).…”