Neuronal Growth and Formation of Neuron Networks on Directional Surfaces

Abstract

The formation of neuron networks is a process of fundamental importance for understanding the development of the nervous system and for creating biomimetic devices for tissue engineering and neural repair. The basic process that controls the network formation is the growth of an axon from the cell body and its extension towards target neurons. Axonal growth is directed by environmental stimuli that include intercellular interactions, biochemical cues, and the mechanical and geometrical properties of the growth substrate. Despite significant recent progress, the steering of the growing axon remains poorly understood. In this paper, we develop a model of axonal motility, which incorporates substrate-geometry sensing. We combine experimental data with theoretical analysis to measure the parameters that describe axonal growth on micropatterned surfaces: diffusion (cell motility) coefficients, speed and angular distributions, and cell-substrate interactions. Experiments performed on neurons treated with inhibitors for microtubules (Taxol) and actin filaments (Y-27632) indicate that cytoskeletal dynamics play a critical role in the steering mechanism. Our results demonstrate that axons follow geometrical patterns through a contact-guidance mechanism, in which geometrical patterns impart high traction forces to the growth cone. These results have important implications for bioengineering novel substrates to guide neuronal growth and promote nerve repair.

Mathematical models of neuronal growth

“…While these works discuss mechanisms and constraints at play in chemotaxis or mechanical guidance, they do not seek to describe the path of the growth cone as a response to these stimuli. To that end, trajectories of growth cones seen as a random motion on a 2D substrate have been studied by multiple authors (Katz et al 1984;Mortimer et al 2010;Maskery et al 2004;Van Ooyen 1999, 2000;Krottje and Van Ooyen 2007;Borisyuk et al 2008;Buettner et al 1994;Wang et al 2003;Pearson et al 2011;Ben-Jacob 2000, 2001;Basso et al 2019;Yurchenko et al 2019Yurchenko et al , 2021Davis et al 2017;Roberts et al 2014); see also the review by Maskery and Shinbrot (2005). The main focus in these works is not the mechanism of elongation, as treated before, but rather the shape and statistical properties of growth cone trajectories, as a function of external cues.…”

Combined Traction Force–Atomic Force Microscopy Measurements of Neuronal Cells

“…The brain tissue isolation protocol was approved by Tufts University Institutional Animal Care and Use Committee in accordance with the NIH Guide for the Care and Use of Laboratory Animals. For cell dissociation and culture, we used established protocols reported in our previous work [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. Cortical neurons were cultured on poly acrylamide (PAA) substrates coated with poly D-lysine (PDL), at a density of 5000 cells/cm 2 .…”

“…To date, despite important recent advances, researchers still lack a fully quantitative description of growth dynamics, which incorporates the physical interactions between the neuron and the surrounding environment. In particular, there are still numerous basic unanswered questions about the mechanisms that determine neuron biomechanical behavior, such as neuron-substrate interactions, cellular response to various external cues, and how these interactions affect the formation and function of neuronal networks [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. A detailed knowledge of these interactions is essential, because these stimuli together control the wiring of neuronal circuits and their function, from growth to homeostasis and cellular health.…”

Engineering Tissues of the Central Nervous System: Interfacing Conductive Biomaterials with Neural Stem/Progenitor Cells

“…Hyaluronic acid [ 410] 1 × 10 −13 -1 × 10 −6 influenced by the chemistry, porosity, and stiffness of conductive biomaterials. [31,[170][171][172][173] Chemistry, porosity, and stiffness also determine cell-material interactions. For example, size scale and interconnectivity of pores within biomaterial scaffolds are key to their ability to integrate functionally with host tissues.…”

“…[ 176 ] For example, biomaterial implants with an interconnected network of uniform pores on the order of tens of microns, which are large enough to permit host cell infiltration yet small enough to still provide some guidance via confinement, promote the formation of a seamless tissue interface with minimal scarring in the rodent spinal cord. [ 177 ] Alternatively, single axons have been reported to align well with features on the order of 1 µm [ 178,179 ] and bundles of spinal cord axons regenerate robustly through guidance tubes on the order of 100's of µm. [ 180–182 ]…”