Low Forces Push the Maturation of Neural Precursors into Neurons

Abstract

Mechanical stimulation modulates neural development and neuronal activity. In a previous study, magnetic “nano‐pulling” is proposed as a tool to generate active forces. By loading neural cells with magnetic nanoparticles (MNPs), a precise force vector is remotely generated through static magnetic fields. In the present study, human neural stem cells (NSCs) are subjected to a standard differentiation protocol, in the presence or absence of nano‐pulling. Under mechanical stimulation, an increase in the length of the neural processes which showed an enrichment in microtubules, endoplasmic reticulum, and mitochondria is found. A stimulation lasting up to 82 days induces a strong remodeling at the level of synapse density and a re‐organization of the neuronal network, halving the time required for the maturation of neural precursors into neurons. The MNP‐loaded NSCs are then transplanted into mouse spinal cord organotypic slices, demonstrating that nano‐pulling stimulates the elongation of the NSC processes and modulates their orientation even in an ex vivo model. Thus, it is shown that active mechanical stimuli can guide the outgrowth of NSCs transplanted into the spinal cord tissue. The findings suggest that mechanical forces play an important role in neuronal maturation which could be applied in regenerative medicine.

Nano-pulling stimulates axon regeneration in dorsal root ganglia by inducing stabilization of axonal microtubules and activation of local translation

“…A correlation between the acetylation of MTs and their stabilization has always been observed in various studies on neurons ( Morley et al, 2016 ; Yan et al, 2018 ; Teoh et al, 2022 ), as well as in other studies on non-neuronal models ( Swiatlowska et al, 2020 ; Coleman et al, 2021 ). Consistently, in previous works we found that the force-induced stabilization of the MTs in the shaft causes their accumulation in stretched axons ( De Vincentiis et al, 2020 , 2023 ; Falconieri et al, 2023b ). This mechanism seems to be independent on the technology used for force generation, as a similar trend was also observed with magnetic microposts, which are a different magnetically-activated technology that are capable of exerting higher forces extracellularly ( Falconieri et al, 2022 ).…”

“…We have thus shown that nano-pulling results in an increase in the number of mitochondria compared to the control conditions ( Figure 2C ). This data on mitochondria in stretched ganglia are in line with previous findings on mice, human and chick isolated neurons ( Lamoureux et al, 2010 ; De Vincentiis et al, 2023 ; Falconieri et al, 2023b ). Endoplasmic reticulum is another key component for the production of proteins required for axon regeneration.…”

“…Here we used NGF-free media to investigate if the mechanical stimulation is sufficient per se to promote a robust regeneration process. Previous studies have shown that nano-pulling is effective only if MNPs are within the axon where they can generate active mechanical force when exposed to a static magnetic field ( De Vincentiis et al, 2020 , 2023 ; Falconieri et al, 2023b ). Compared to 2D cultures, whole ganglia present additional barriers to the penetration of MNPs, being characterised by similar features and complexity to in vivo neural tissues.…”

“…Since the early 21st century, many groups have exploited MNPs to modulate axonal functions, such as axon specification and orientation ( Riggio et al, 2014 ; Kunze et al, 2015 ; Raffa et al, 2018 ), intracellular calcium dynamics ( Tay et al, 2016 ; Tay and Di Carlo, 2017 ; De Vincentiis et al, 2020 ), cytoskeletal dynamics ( Pita-Thomas et al, 2015 ; De Vincentiis et al, 2020 ; Falconieri et al, 2023b ) axonal transport ( Steketee et al, 2011 ; Chowdary et al, 2013 ; Kunze et al, 2017 ; Chowdary et al, 2019 ; Falconieri et al, 2023b ), elongation and branching ( Steketee et al, 2011 ; Riggio et al, 2014 ; Tay et al, 2016 ; Raffa et al, 2018 ; De Vincentiis et al, 2020 ; Wang et al, 2020 ; Falconieri et al, 2023b ), and neuron maturation ( De Vincentiis et al, 2020 , 2023 ; Falconieri et al, 2023b ).…”

3D-printed weight holders design and testing in mouse models of spinal cord injury

“…We were able to fulfill these requirements by minimizing the weight of a 3D-printed non-deformable structure that was essential to ensuring the steady and continuous positioning of a couple of magnets for long-term application of the desired and previously optimized (Riggio et al, 2014;De Vincentiis et al, 2023) In both cases, C57BL/6J mice were housed under controlled conditions, maintaining a temperature of 23 °C ± 1 °C, humidity 50% ± 5%, and a 12-hour light-dark cycle. Mice were given unrestricted access to both food and water.…”