In this study, gelatin and graphene-based nerve regeneration conduits/scaffolds possessing tailored 3D microstructures and mechanical properties were fabricated using 3D printing. The effect of 3D conduit microstructure and mechanical properties along with the applied electrical stimuli on mesenchymal stem cell (MSCs) behavior and transdifferentiation into Schwann cell (SC)-like phenotypes were investigated. The results indicated that the gelatin conduits/scaffolds had favorable 3D microstructural and mechanical properties for MSC attachment and growth. Immunocytochemistry results demonstrated that the application of electrical stimuli through the conductive graphene within the gelatin-based 3D microstructure had a profound effect on the differentiation of MSCs to SC-like phenotypes and their paracrine activity. 80% of the cells exhibited SC marker staining, and the cells showed significantly enhanced nerve growth factor (NGF) secretion. These results suggest that the electrical stimuli applied within the 3D gelatin matrix enables enhanced differentiation and paracrine activity compared to transdifferentiation procedures involving electrical stimuli applied on 2D substrates and chemical stimuli applied in 3D gelatin scaffolds, leading to promising nerve regeneration strategies.

In this study, a novel method based on the transfer of graphene patterns from a rigid or flexible substrate onto a polymeric film surface via solvent casting was developed. The method involves the creation of predetermined graphene patterns on the substrate, casting a polymer solution, and directly transferring the graphene patterns from the substrate to the surface of the target polymer film via a peeling-off method. The feature sizes of the graphene patterns on the final film can vary from a few micrometers (as low as 5 µm) to few millimeters range. This process, applied at room temperature, eliminates the need for harsh post-processing techniques and enables creation of conductive graphene circuits (sheet resistance: ~0.2 kΩ/sq) with high stability (stable after 100 bending and 24 h washing cycles) on various polymeric flexible substrates. Moreover, this approach allows precise control of the substrate properties such as composition, biodegradability, 3D microstructure, pore size, porosity and mechanical properties using different film formation techniques. This approach can also be used to fabricate flexible biointerfaces to control stem cell behavior, such as differentiation and alignment. Overall, this promising approach provides a facile and low-cost method for the fabrication of flexible and stretchable electronic circuits.

Small Rho GTPases are molecular switches that are involved in multiple processes including regulation of the actin cytoskeleton. These GTPases are activated (turned on) and inactivated (turned off) through various upstream effector molecules to carry out many cellular functions. One such upstream modulator of small Rho GTPase activity is delta-catenin, which is a protein in the p120-catenin subfamily that is enriched in the central nervous system. Delta-catenin affects small GTPase activity to assist in the developmental formation of dendrites and dendritic spines and to maintain them once they mature. As the dendritic arbor and spine density are crucial for synapse formation and plasticity, delta-catenin’s ability to modulate small Rho GTPases is necessary for proper learning and memory. Accordingly, the misregulation of delta-catenin and small Rho GTPases has been implicated in several neurological and non-neurological pathologies. While links between delta-catenin and small Rho GTPases have yet to be studied in many contexts, known associations include some cancers, Alzheimer’s disease (AD), Cri-du-chat syndrome, and autism spectrum disorder (ASD). Drawing from established studies and recent discoveries, this review explores how delta-catenin modulates small Rho GTPase activity. Future studies will likely elucidate how PDZ proteins that bind delta-catenin further influence small Rho GTPases, how delta-catenin may affect small GTPase activity at adherens junctions when bound to N-cadherin, mechanisms behind delta-catenin’s ability to modulate Rac1 and Cdc42, and delta-catenin’s ability to modulate small Rho GTPases in the context of diseases, such as cancer and AD.

This study investigated the effect of electrical stimuli parameters using graphene-based devices for the transdifferentiation of genetically engineered brain-derived neurotrophic factor (BDNF) hypersecreting mesenchymal stem cells (BDNF-MSCs) into neuronal or glial lineages. The results suggest that BDNF-MSCs have the tendency to transdifferentiate into both neuronal and Schwann cell (SC)-like phenotypes at lower voltages (25-50 mV). However, as the applied voltage changed from 25 to 100 mV at 50 Hz, the transdifferentiation of BDNF-MSCs yielded more into SC-like phenotypes and resulted in complete transdifferentiation into SC-like phenotypes at 100 mV and 50 Hz. With an increase in voltage to 100 mV, the complete transdifferentiation to SC-like phenotypes also resulted in enhanced paracrine activity leading to total secretion of nerve growth factor (NGF) up to 50 ng/mL with pronounced biological activity, causing neurite extension of 4 μm/cell on PC12-TrkB cells. Moreover, 90% of the transdifferentiated cells demonstrated significant myelination potential. The contact co-culture of BDNF-MSCs with adult hippocampal progenitor cells (AHPCs) in the presence of electrical stimuli resulted in differentiation of BDNF-MSCs into SC-like phenotypes accompanied by synergistic neurite extension of AHPCs. Overall, this study demonstrates the possibility of controlling simultaneous and spatial differentiation of MSCs into selected neuronal and glial lineages at desired ratios via changes in electrical stimuli through graphene-based devices and can contribute to the development of novel cell-based strategies for nervous system rescue and repair. Lay Summary This work evaluates the effect of different electrical stimuli conditions applied through inkjet-printed and laser-annealed graphene-based interdigitated circuits on the differentiation behavior of mesenchymal stem cells. Our results suggested that it is possible to spatially and locally control the differentiation of mesenchymal stem cells into final lineage type (glial or neuronal) by manipulating the electrical stimuli. The future work will include the control of stem cell differentiation and fate commitment in an in vivo model using electrical stimuli.

Dendritic arborization is essential for proper neuronal connectivity and function. Conversely, abnormal dendrite morphology is associated with several neurological pathologies like Alzheimer’s disease and schizophrenia. Among major intrinsic mechanisms that determine the extent of the dendritic arbor is cytoskeletal remodeling. Here, we characterize and compare the impact of the four proteins involved in cytoskeletal remodeling–vertebrate members of the p120-catenin subfamily–on neuronal dendrite morphology. In relation to each of their own distributions, we find that p120-catenin and delta-catenin are expressed at relatively higher proportions in growth cones compared to ARVCF-catenin and p0071-catenin; ARVCF-catenin is expressed at relatively high proportions in the nucleus; and all catenins are expressed in dendritic processes and the soma. Through altering the expression of each p120-subfamily catenin in neurons, we find that exogenous expression of either p120-catenin or delta-catenin correlates with increased dendritic length and branching, whereas their respective depletion decreases dendritic length and branching. While increasing ARVCF-catenin expression also increases dendritic length and branching, decreasing expression has no grossly observable morphological effect. Finally, increasing p0071-catenin expression increases dendritic branching, but not length, while decreasing expression decreases dendritic length and branching. These distinct localization patterns and morphological effects during neuron development suggest that these catenins have both shared and distinct roles in the context of dendrite morphogenesis.