Stiff substrates enhance cultured neuronal network activity

Abstract

The mechanical property of extracellular matrix and cell-supporting substrates is known to modulate neuronal growth, differentiation, extension and branching. Here we show that substrate stiffness is an important microenvironmental cue, to which mouse hippocampal neurons respond and integrate into synapse formation and transmission in cultured neuronal network. Hippocampal neurons were cultured on polydimethylsiloxane substrates fabricated to have similar surface properties but a 10-fold difference in Young's modulus. Voltage-gated Ca2+ channel currents determined by patch-clamp recording were greater in neurons on stiff substrates than on soft substrates. Ca2+ oscillations in cultured neuronal network monitored using time-lapse single cell imaging increased in both amplitude and frequency among neurons on stiff substrates. Consistently, synaptic connectivity recorded by paired recording was enhanced between neurons on stiff substrates. Furthermore, spontaneous excitatory postsynaptic activity became greater and more frequent in neurons on stiff substrates. Evoked excitatory transmitter release and excitatory postsynaptic currents also were heightened at synapses between neurons on stiff substrates. Taken together, our results provide compelling evidence to show that substrate stiffness is an important biophysical factor modulating synapse connectivity and transmission in cultured hippocampal neuronal network. Such information is useful in designing instructive scaffolds or supporting substrates for neural tissue engineering.

Matrix stiffness modulates formation and activity of neuronal networks of controlled architectures

“…6EeG) depends on the network activity and thus on synaptic inputs. In this context, one can assume that the more there are excitatory synapses, the more the intrinsic excitability of the network decreases [31]. This phenomenon allows a homeostatic regulation of the neuronal excitability that refers to the collective phenomena by which neurons alter their intrinsic or synaptic properties to maintain a target level of electrical activity.…”

Biomaterials for Enhancing Neuronal Repair

“…Such measurements of human brain tissue are highly dependent on frequency and region, and therefore variable. Additional studies have demonstrated that timing and duration of exposure to stiffness cues impacts stem cell differentiation to neural cell types, and that while neuritogenesis may be enhanced on soft substrates, network connectivity and signal transduction are enhanced by stiffer substrates (Balgude et al, 2001;Jiang et al, 2010;Keung et al, 2012;Zhang et al, 2014;Mosley et al, 2017). These findings emphasize that stiffness cues should be adjusted depending on the desired outcome, with close attention to the region of interest in the human body.…”

“…b Electrical References: (Jaffe and Stern, 1979;Patel and Poo, 1982;Hotary and Robinson, 1991;Davenport and McCaig, 1993;Metcalf and Borgens, 1994;Yao et al, 2008Yao et al, , 2009Yao et al, , 2011Graves et al, 2011;Koppes et al, 2014;Kim et al, 2016;Ma et al, 2016). c Mechanical Stiffness References: (Balgude et al, 2001;Discher et al, 2005;Jiang et al, 2010;Keung et al, 2012;Lee et al, 2013;Zhang et al, 2014;Mosley et al, 2017).…”

Neuronal Differentiation Modulated by Polymeric Membrane Properties

“…Neuronal cell-membrane interaction is also deeply influenced by the mechanical properties of the membranes that modulate neuronal growth, differentiation, extension, and branching [Zhang et al, 2014]. In particular, the brain, a soft tissue, requires polymeric materials with low elastic modulus [Clements et al, 2009], and a strategy to enhance the mechanical properties of polymeric membranes includes the blending of two or more polymers with differences in stiffness.…”

“…Our expectations are based on a recent report by Zhang et al [2014] in which it is evidenced how mechanical properties of neuron-supporting substrates have a great impact on cell behavior. Neurons can sense mechanical cues from their microenvironments and integrate them into synapse connectivity and transmission.…”