Exploration of the Effects of Substrate Stiffness on Biological Responses of Neural Cells and Their Mechanisms

Abstract

Substrate stiffness, as a critical mechanical factor, has been proven to be an important regulator of biological responses, cellular functions, and disease occurrence. However, the effects of substrate stiffness on the phenotypes and drug responses of neural cells remain largely unknown. In this study, polydimethylsiloxane (PDMS) substrates with different stiffnesses were employed to establish the mechanical microenvironment of tissues of different organs. We studied the influences of stiffness on neural cell phenotypes, including cell viability, cell cycle, cytoskeleton structures, cell stiffness, and drug responses of neural cells for hormesis and therapeutic efficacy in neurodegenerative disorders (NDD). The results showed that the greater the range of maximum stimulatory responses, the bigger the width of the stimulatory dosage and the higher the range of maximum neuroprotective activities of hormetic chemicals in neural cells grown on the soft substrate commensurable to the stiffness of the brain, indicating that neural cells on a rigid substrate are resistant to hormetic and neuroprotective effects of hormetic chemicals against 6-hydroxydopamine (6-OHDA)-induced Parkinson’s disease (PD) model. The sensitivity of neural cells on the soft substrate to drug response was attributed to the increased cell viability rate, cell cycle progression, actin stress fibers, focal adhesion formation, and decreased cell stiffness. The promoting effect of the soft substrate and the enhanced hormetic and neuroprotective effect of hormetic chemicals on soft substrates in PC12 cells were confirmed to be mediated by the upregulated EGFR/PI3K/AKT signaling pathway by RNA-Seq and bioinformatics analysis. This study demonstrates that the biomechanical properties of the neural microenvironment play important roles in cell phenotypes and drug responses of neural cells in vitro and suggests that substrate stiffness should be considered in the anti-NDD drug design and treatment.

TiO2 Nano‐Biopatterning Reveals Optimal Ligand Presentation for Cell–Matrix Adhesion Formation

“…[ 50 ] However, substrate rigidity was used to control integrin clustering in these experiments, which also leads to activation of substrate‐rigidity‐dependent signaling pathways such as Akt, Src family kinase, Mitogen‐activated protein kinase (MAPK), RhoA pathway, and various other receptor tyrosine kinases. [ 51‐54 ] Thus, empirically it remains unclear how integrin nanoclustering may depend on FAK activation independent of the substrate rigidity changes. Here, we hypothesized that on rigid substrates, FAK activation would also depend on integrin cluster size, and inhibiting FAK should lead to the loss of integrin cluster size mechanosensing.…”

Biomaterials-based strategies for in vitro neural models

“…294 This results from the evidence showing that neurons display more accurate responses to external treatments in a native tissue-like biomechanical microenvironment favoring a neuronal phenotype. 295 Hydrogels take the lead in this regard with their waterretaining architectures that are intrinsically similar to the neural ECM. Moreover, most hydrogels offer some degree of tunability with respect to their mechanical properties, 296 allowing mechanobiology models and freedom in experimental design.…”

Changes in Physiological Tendon Substrate Stiffness Have Moderate Effects on Tendon-Derived Cell Growth and Immune Cell Activation

“…While the mechanisms driving the observed changes in TDC growth were not explored as part of this study, there is evidence that cell response to stiffer substrates tend to be driven by Rho-ROCK pathways ( Paszek et al, 2005 ; Mih et al, 2012 ; Sridharan et al, 2019 ; Doss et al, 2020 ). Neural cells, meanwhile, have been shown to respond to softer substrates through the EGFR/PI3K/AKT pathway ( Zhang et al, 2020 ). Understanding the mechanisms regulating TDC response to substrate stiffness could play an important role in directing future therapeutics for tendinopathy.…”