Neuronal contact guidance and YAP signaling on ultra-small nanogratings

Abstract

contact interaction of neuronal cells with extracellular nanometric features can be exploited to investigate and modulate cellular responses. By exploiting nanogratings (nGs) with linewidth from 500 nm down to 100 nm, we here study neurite contact guidance along ultra-small directional topographies. the impact of nG lateral dimension on the neuronal morphotype, neurite alignment, focal adhesion (fA) development and YAp activation is investigated in nerve growth factor (nGf)differentiating PC12 cells and in primary hippocampal neurons, by confocal and live-cell total internal reflection fluorescence (TIRF) microscopy, and at molecular level. We demonstrate that loss of neurite guidance occurs in NGs with periodicity below 400 nm and correlates with a loss of FA lateral constriction and spatial organization. We found that YAP intracellular localization is modulated by the presence of nGs, but it is not sensitive to their periodicity. nocodazole, a drug that can increase cell contractility, is finally tested for rescuing neurite alignment showing mild ameliorative effects. Our results provide new indications for a rational design of biocompatible scaffolds for enhancing nerveregeneration processes.With its chemical and physical complexity, the extracellular environment can drive cell morphogenesis, migration and differentiation 1-4 , In particular, the contact interaction of cells with extracellular nanometric features has a primary role in regulating many physiological 5-12 and pathological processes 13 in vivo, and can be exploited to modulate cell responses in vitro [14][15][16][17] . Cells gather morphological information about the Extracellular matrix (ECM) through integrin-mediated adhesion clusters, called the focal adhesions (FAs), which act as topographical sensors. FAs can integrate multiple nanotopographical details into specific biomolecular instructions via the cytoskeletal signaling, which lastly regulates cell contractility, morphology and migration 9,18,19 , Artificial scaffolds with controlled micro/nano-topographies are definitively the apparatus of choice to better understand the response mechanisms of cells to external stimuli. They indeed allow to select and finely tune specific topographical aspects and selectively study their interaction with living system in vitro. The scientific literature reports many examples of nanostructures that can, for example, direct stem cell fate 20-22 , neuronal and glial adhesion 23-25 , differentiation 26 , polarization, and neurite orientation 14,18 , Our previous studies have demonstrated that plastic nanogratings (NGs) (i.e. alternating lines of sub-micron grooves and ridges, in the range between 500 and 2000 nm in linewidth) can promote neurite alignment and bipolarity of PC12 neuronal cells upon administration of nerve grow factor (NGF), simply by the contact guidance mechanism 27,28 , In these studies, adhesion on the ridges imposes a geometrical and directional constraint to FAs that results in neuronal polarization via the ROCK-mediated pathway 14,29-31 ...

Cellular and Subcellular Contact Guidance on Microfabricated Substrates

“…No change in cell alignment was visible after treatment with siRNA against YAP, but siRNA against TAZ led to an increased alignment (Raghunathan et al, 2014). More recently, Tonazzini et al (2020) similarly reported only a slight increase in YAP nuclear/cytoplasmic ratio in PC12 cells on nanogrooves, and no change in YAP expression levels (Tonazzini et al, 2020). Overall, these two studies suggest that YAP/TAZ pathway is only partially involved in contact guidance, at least in the response to grooves for these cell types.…”

Cell contact guidance via sensing anisotropy of network mechanical resistance

“…Contact guidance on 2D substrata like parallel grooves or adhesive ligand stripes has been intensively studied (recent examples include refs. [4][5][6] because in these experiments, the guidance field can be precisely defined and easily manipulated. However, it is the case of aligned fibrils that has the preponderance of physiological relevance.…”

Guidelines for a Morphometric Analysis of Prokaryotic and Eukaryotic Cells by Scanning Electron Microscopy

“…On the other hand, when it is greater than 75°, the neurite is scored as perpendicular to the cues. In the case of substrates without a topographic pattern, a random direction can be selected as the axis [ 71 , 80 ].…”