IPAC integrates rewarding and environmental memory during the acquisition of morphine CPP.

The association between rewarding and drug-related memory is a leading factor for the formation of addiction, yet the neural circuits underlying the association remain unclear. Here, we showed that the interstitial nucleus of the posterior limb of the anterior commissure (IPAC) integrated rewarding and environmental memory information by two different receiving projections from ventral tegmental area (VTA) and nucleus accumbens shell region (NAcSh) to mediate the acquisition of morphine conditioned place preference (CPP). A projection from the VTA GABAergic neurons (VTAGABA) to the IPAC lateral region GABAergic neurons (IPACLGABA) mediated the effect of morphine rewarding, whereas the pathway from NAcSh dopamine receptor 1-expressing neurons (NAcShD1) to the IPAC medial region GABAergic neurons (IPACMGABA) was involved in the acquisition of environmental memory. These findings demonstrated that the distinct IPAC circuits VTAGABA→IPACLGABA and NAcShD1R→IPACMGABA were attributable to the rewarding and environmental memory during the acquisition of morphine CPP, respectively, and provided the circuit-based potential targets for preventing and treating opioid addiction.

Tail nerve electrical stimulation promoted the efficiency of transplanted spinal cord-like tissue as a neuronal relay to repair the motor function of rats with transected spinal cord injury.

Following transected spinal cord injury (SCI), there is a critical need to restore nerve conduction at the injury site and activate the silent neural circuits caudal to the injury to promote the recovery of voluntary movement. In this study, we generated a rat model of SCI, constructed neural stem cell (NSC)-derived spinal cord-like tissue (SCLT), and evaluated its ability to replace injured spinal cord and repair nerve conduction in the spinal cord as a neuronal relay. The lumbosacral spinal cord was further activated with tail nerve electrical stimulation (TNES) as a synergistic electrical stimulation to better receive the neural information transmitted by the SCLT. Next, we investigated the neuromodulatory mechanism underlying the action of TNES and its synergism with SCLT in SCI repair. TNES promoted the regeneration and remyelination of axons and increased the proportion of glutamatergic neurons in SCLT to transmit brain-derived neural information more efficiently to the caudal spinal cord. TNES also increased the innervation of motor neurons to hindlimb muscle and improved the microenvironment of muscle tissue, resulting in effective prevention of hindlimb muscle atrophy and enhanced muscle mitochondrial energy metabolism. Tracing of the neural circuits of the sciatic nerve and tail nerve identified the mechanisms responsible for the synergistic effects of SCLT transplantation and TNES in activating central pattern generator (CPG) neural circuits and promoting voluntary motor function recovery in rats. The combination of SCLT and TNES is expected to provide a new breakthrough for patients with SCI to restore voluntary movement and control their muscles.

Electroacupuncture facilitates the integration of a grafted TrkC-modified mesenchymal stem cell-derived neural network into transected spinal cord in rats via increasing neurotrophin-3.

AIMS: This study was aimed to investigate whether electroacupuncture (EA) would increase the secretion of neurotrophin-3 (NT-3) from injured spinal cord tissue, and, if so, whether the increased NT-3 would promote the survival, differentiation, and migration of grafted tyrosine kinase C (TrkC)-modified mesenchymal stem cell (MSC)-derived neural network cells. We next sought to determine if the latter would integrate with the host spinal cord neural circuit to improve the neurological function of injured spinal cord. METHODS: After NT-3-modified Schwann cells (SCs) and TrkC-modified MSCs were co-cultured in a gelatin sponge scaffold for 14 days, the MSCs differentiated into neuron-like cells that formed a MSC-derived neural network (MN) implant. On this basis, we combined the MN implantation with EA in a rat model of spinal cord injury (SCI) and performed immunohistochemical staining, neural tracing, electrophysiology, and behavioral testing after 8 weeks. RESULTS: Electroacupuncture application enhanced the production of endogenous NT-3 in damaged spinal cord tissues. The increase in local NT-3 production promoted the survival, migration, and maintenance of the grafted MN, which expressed NT-3 high-affinity TrkC. The combination of MN implantation and EA application improved cortical motor-evoked potential relay and facilitated the locomotor performance of the paralyzed hindlimb compared with those of controls. These results suggest that the MN was better integrated into the host spinal cord neural network after EA treatment compared with control treatment. CONCLUSIONS: Electroacupuncture as an adjuvant therapy for TrkC-modified MSC-derived MN, acted by increasing the local production of NT-3, which accelerated neural network reconstruction and restoration of spinal cord function following SCI.

Tissue-Engineered Neural Network Graft Relays Excitatory Signal in the Completely Transected Canine Spinal Cord.

Tissue engineering produces constructs with defined functions for the targeted treatment of damaged tissue. A complete spinal cord injury (SCI) model is generated in canines to test whether in vitro constructed neural network (NN) tissues can relay the excitatory signal across the lesion gap to the caudal spinal cord. Established protocols are used to construct neural stem cell (NSC)-derived NN tissue characterized by a predominantly neuronal population with robust trans-synaptic activities and myelination. The NN tissue is implanted into the gap immediately following complete transection SCI of canines at the T10 spinal cord segment. The data show significant motor recovery of paralyzed pelvic limbs, as evaluated by Olby scoring and cortical motor evoked potential (CMEP) detection. The NN tissue survives in the lesion area with neuronal phenotype maintenance, improves descending and ascending nerve fiber regeneration, and synaptic integration with host neural circuits that allow it to serve as a neuronal relay to transmit excitatory electrical signal across the injured area to the caudal spinal cord. These results suggest that tissue-engineered NN grafts can relay the excitatory signal in the completely transected canine spinal cord, providing a promising strategy for SCI treatment in large animals, including humans.

Electroacupuncture Facilitates the Integration of Neural Stem Cell-Derived Neural Network with Transected Rat Spinal Cord.

The hostile environment of an injured spinal cord makes it challenging to achieve higher viability in a grafted tissue-engineered neural network used to reconstruct the spinal cord circuit. Here, we investigate whether cell survival and synaptic transmission within an NT-3 and TRKC gene-overexpressing neural stem cell-derived neural network scaffold (NN) transplanted into transected spinal cord could be promoted by electroacupuncture (EA) through improving the microenvironment. Our results showed that EA facilitated the cell survival, neuronal differentiation, and synapse formation of a transplanted NN. Pseudorabies virus tracing demonstrated that EA strengthened synaptic integration of the transplanted NN with the host neural circuit. The combination therapy also promoted axonal regeneration, spinal conductivity, and functional recovery. The findings highlight EA as a potential and safe supplementary therapeutic strategy to reinforce the survival and synaptogenesis of a transplanted NN as a neuronal relay to bridge the two severed ends of an injured spinal cord.

A Modular Assembly of Spinal Cord-Like Tissue Allows Targeted Tissue Repair in the Transected Spinal Cord.

Tissue engineering-based neural construction holds promise in providing organoids with defined differentiation and therapeutic potentials. Here, a bioengineered transplantable spinal cord-like tissue (SCLT) is assembled in vitro by simulating the white matter and gray matter composition of the spinal cord using neural stem cell-based tissue engineering technique. Whether the organoid would execute targeted repair in injured spinal cord is evaluated. The integrated SCLT, assembled by white matter-like tissue (WMLT) module and gray matter-like tissue (GMLT) module, shares architectural, phenotypic, and functional similarities to the adult rat spinal cord. Organotypic coculturing with the dorsal root ganglion or muscle cells shows that the SCLT embraces spinal cord organogenesis potentials to establish connections with the targets, respectively. Transplantation of the SCLT into the transected spinal cord results in a significant motor function recovery of the paralyzed hind limbs in rats. Additionally, targeted spinal cord tissue repair is achieved by the modular design of SCLT, as evidenced by an increased remyelination in the WMLT area and an enlarged innervation in the GMLT area. More importantly, the pro-regeneration milieu facilitates the formation of a neuronal relay by the donor neurons, allowing the conduction of descending and ascending neural inputs.

Recovery of paralyzed limb motor function in canine with complete spinal cord injury following implantation of MSC-derived neural network tissue.

We have reported previously that bone marrow mesenchymal stem cell (MSC)-derived neural network scaffold not only survived in the injury/graft site of spinal cord but also served as a "neuronal relay" that was capable of improving the limb motor function in a complete spinal cord injury (SCI) rat model. It remained to be explored whether such a strategy was effective for repairing the large spinal cord tissue loss as well as restoring motor function in larger animals. We have therefore extended in this study to construct a canine MSC-derived neural network tissue in vitro with the aim to evaluate its efficacy in treating adult beagle dog subjected to a complete transection of the spinal cord. The results showed that after co-culturing with neurotropin-3 overexpressing Schwann cells in a gelatin sponge scaffold for 14 days, TrkC overexpressing MSCs differentiated into neuron-like cells. In the latter, some cells appeared to make contacts with each other through synapse-like structures with trans-synaptic electrical activities. Remarkably, the SCI canines receiving the transplantation of the MSC-derived neural network tissue demonstrated a gradual restoration of paralyzed limb motor function, along with improved electrophysiological presentation when compared with the control group. Magnetic resonance imaging and diffusion tensor imaging showed that the canines receiving the MSC-derived neural network tissue exhibited robust nerve tract regeneration in the injury/graft site. Histological analysis showed that some of the MSC-derived neuron-like cells had survived in the injury/graft site up to 6.5 months. Implantation of MSC-derived neural network tissue significantly improved the microenvironment of the injury/graft site. It is noteworthy that a variable number of them had integrated with the regenerating corticospinal tract nerve fibers and 5-HT nerve fibers through formation of synapse-like contacts. The results suggest that the transplanted MSC-derived neural network tissue may serve as a structural and functional "neuronal relay" to restore the paralyzed limb motor function in the canine with complete SCI.