Reproducible and persistent weakness in adult rats after surgical resection of motor cortex: evaluation with limb placement test

Therapeutic Efficiency of Proteins Secreted by Glial Progenitor Cells in a Rat Model of Traumatic Brain Injury

Traumatic brain injuries account for 30-50% of all physical traumas and are the most common pathological diseases of the brain. Mechanical damage of brain tissue leads to the disruption of the blood-brain barrier and the massive death of neuronal, glial, and endothelial cells. These events trigger a neuroinflammatory response and neurodegenerative processes locally and in distant parts of the brain and promote cognitive impairment. Effective instruments to restore neural tissue in traumatic brain injury are lacking. Glial cells are the main auxiliary cells of the nervous system, supporting homeostasis and ensuring the protection of neurons through contact and paracrine mechanisms. The glial cells' secretome may be considered as a means to support the regeneration of nervous tissue. Consequently, this study focused on the therapeutic efficiency of composite proteins with a molecular weight of 5-100 kDa secreted by glial progenitor cells in a rat model of traumatic brain injury. The characterization of proteins below 100 kDa secreted by glial progenitor cells was evaluated by proteomic analysis. Therapeutic effects were assessed by neurological outcomes, measurement of the damage volume by MRI, and an evaluation of the neurodegenerative, apoptotic, and inflammation markers in different areas of the brain. Intranasal infusions of the composite protein product facilitated the functional recovery of the experimental animals by decreasing the inflammation and apoptotic processes, preventing neurodegenerative processes by reducing the amounts of phosphorylated Tau isoforms Ser396 and Thr205. Consistently, our findings support the further consideration of glial secretomes for clinical use in TBI, notably in such aspects as dose-dependent effects and standardization.

The Alteration of Brain Interstitial Fluid Drainage with Myelination Development

The integrity of myelination is crucial for maintaining brain interstitial fluid (ISF) drainage in adults; however, the mechanism of ISF drainage with immature myelin in the developing brain remains unknown. In the present study, the ISF drainage from the caudate nucleus (Cn) to the ipsilateral cortex was studied at different developmental stages of the rat brain (P 10, 20, 30, 40, 60, 80, 10-80). The results show that the traced ISF drained to the cortex from Cn and to the thalamus in an opposite direction before P30. From P40, we found impeded drainage to the thalamus due to myelin maturation. This altered drainage was accompanied by enhanced cognitive and social functions, which were consistent with those in the adult rats. A significant difference in diffusion parameters was also demonstrated between the extracellular space (ECS) before and after P30. The present study revealed the alteration of ISF drainage regulated by myelin at different stages during development, indicating that a regional ISF homeostasis may be essential for mature psychological and cognitive functions.

Neural stem cell delivery using brain-derived tissue-specific bioink for recovering from traumatic brain injury

Traumatic brain injury is one of the leading causes of accidental death and disability. The loss of parts in a severely injured brain induces edema, neuronal apoptosis, and neuroinflammation. Recently, stem cell transplantation demonstrated regenerative efficacy in an injured brain. However, the efficacy of current stem cell therapy needs improvement to resolve issues such as low survival of implanted stem cells and low efficacy of differentiation into respective cells. We developed brain-derived decellularized extracellular matrix (BdECM) bioink that is printable and has native brain-like stiffness. This study aimed to fabricate injured cavity-fit scaffold with BdECM bioink and assessed the utility of BdECM bioink for stem cell delivery to a traumatically injured brain. Our BdECM bioink had shear thinning property for three-dimensional (3D)-cell-printing and physical properties and fiber structures comparable to those of the native brain, which is important for tissue integration after implantation. The human neural stem cells (NSCs) (F3 cells) laden with BdECM bioink were found to be fully differentiated to neurons; the levels of markers for mature differentiated neurons were higher than those observed with collagen bioinkin vitro. Moreover, the BdECM bioink demonstrated potential in defect-fit carrier fabrication with 3D cell-printing, based on the rheological properties and shape fidelity of the material. As F3 cell-laden BdECM bioink was transplanted into the motor cortex of a rat brain, high efficacy of differentiation into mature neurons was observed in the transplanted NSCs; notably increased level of MAP2, a marker of neuronal differentiation, was observed. Furthermore, the transplanted-cell bioink suppressed reactive astrogliosis and microglial activation that may impede regeneration of the injured brain. The brain-specific material reported here is favorable for NSC differentiation and suppression of neuroinflammation and is expected to successfully support regeneration of a traumatically injured brain.

Efficient induction of neural progenitor cells from human ESC/iPSCs on Type I Collagen

A stable, rapid and effective neural differentiation method is essential for the clinical applications of human embryonic stem cells (ESCs) or induced pluripotent stem cells (iPSCs) in treating neurological disorders and diseases. Herein, we established a novel and robust monolayer differentiation method to produce functional neural progenitor cells (NPCs) from human ESC/iPSCs on Type I Collagen. The derived cells not only displayed the requisite markers, but also behaved similarly to classic NPCs both in vitro and in vivo. Upon transplantation into traumatic brain injury model, the derived NPCs facilitated recovery from injury. We also found that SMAD signaling stayed down throughout the differentiation process on Type I Collagen, and the pluripotent signals were rapidly downregulated along with raising up of neural early markers on the third day. Meanwhile, ATAC-seq data showed the related mediation of distinct transcriptome and global chromatin dynamics during NPC induction. Totally, our results thus provide a convenient way to generate NPCs from human ESC/iPSCs for neural diseases' treatment.

Proteomic analysis of trans-hemispheric motor cortex reorganization following contralateral C7 nerve transfer

Nerve transfer is the most common treatment for total brachial plexus avulsion injury. After nerve transfer, the movement of the injured limb may be activated by certain movements of the healthy limb at the early stage of recovery, i.e., trans-hemispheric reorganization. Previous studies have focused on functional magnetic resonance imaging and changes in brain-derived neurotrophic factor and growth associated protein 43, but there have been no proteomics studies. In this study, we designed a rat model of total brachial plexus avulsion injury involving contralateral C₇ nerve transfer. Isobaric tags for relative and absolute quantitation and western blot assay were then used to screen differentially expressed proteins in bilateral motor cortices. We found that most differentially expressed proteins in both cortices of upper limb were associated with nervous system development and function (including neuron differentiation and development, axonogenesis, and guidance), microtubule and cytoskeleton organization, synapse plasticity, and transmission of nerve impulses. Two key differentially expressed proteins, neurofilament light (NFL) and Thy-1, were identified. In contralateral cortex, the NFL level was upregulated 2 weeks after transfer and downregulated at 1 and 5 months. The Thy-1 level was upregulated from 1 to 5 months. In the affected cortex, the NFL level increased gradually from 1 to 5 months. Western blot results of key differentially expressed proteins were consistent with the proteomic findings. These results indicate that NFL and Thy-1 play an important role in trans-hemispheric organization following total brachial plexus root avulsion and contralateral C₇ nerve transfer.

Reduction of Cerebral Edema via an Osmotic Transport Device Improves Functional Outcome after Traumatic Brain Injury in Mice

Traumatic brain injury (TBI), the foremost cause of morbidity and mortality in persons under 45 years of age worldwide, leads to about 200,000 victims requiring hospitalization and approximately 52,000 deaths per year in the United States. TBI is characterized by cerebral edema leading to raised intracranial pressure, brain herniation, and subsequent death. Current therapies for TBI treatment are often ineffective, thus novel therapies are needed. Recent studies have shown that an osmotic transport device (OTD) is capable of reducing brain water content and improving survival in mice with severe cerebral edema. Here we compare the effects of a craniectomy and an OTD plus craniectomy on neurological function in mice after TBI. Animals treated with a craniectomy plus an OTD had significantly better neurological function 2 days after TBI compared with those treated with craniectomy only. This study suggests that an OTD for severe brain swelling may improve patient functional outcome. Future studies include a more comprehensive neurological examination, including long-term memory tests.

Effect of Erythropoietin and Stem Cells on Traumatic Brain Injury

OBJECTIVE

To investigate the healing effects of erythropoietin (EPO) and stem cells (SCs) in traumatic brain injury (TBI).

METHODS

Twenty-nine Wistar albino rats were used and separated into the following groups: control (C), EPO, SC, and SC+EPO. Group C received a TBI only, with no treatment. In the EPO group, 1000 U/kg EPO was given intraperitoneally at 30 minutes after TBI. In SC group, immediately after formation of TBI, 3 × 10,000 CD34(+) stem cells were injected into the affected area. In the SC+EPO group, half an hour after TBI and the injection of stem cells, 1000 U/kg EPO was injected. Before and after injury, trauma coordination performance was measured by the rotarod and inclined plane tests.

RESULTS

Seven weeks after trauma, rat brains were examined by radiology and histology. Rotarod performance test did not change remarkably, even after the injury. Compared with group C, the SC+EPO group was found to have significant differences in the inclined plane test results.

CONCLUSIONS

Separately given, SCs and EPO have a positive effect on TBI, and our findings suggest that their coadministration is even more powerful.

Enhancement of Contralesional Motor Control Promotes Locomotor Recovery after Unilateral Brain Lesion

There have been controversies on the contribution of contralesional hemispheric compensation to functional recovery of the upper extremity after a unilateral brain lesion. Some studies have demonstrated that contralesional hemispheric compensation may be an important recovery mechanism. However, in many cases where the hemispheric lesion is large, this form of compensation is relatively limited, potentially due to insufficient connections from the contralesional hemisphere to the paralyzed side. Here, we used a new procedure to increase the effect of contralesional hemispheric compensation by surgically crossing a peripheral nerve at the neck in rats, which may provide a substantial increase in connections between the contralesional hemisphere and the paralyzed limb. This surgical procedure, named cross-neck C7-C7 nerve transfer, involves cutting the C7 nerve on the healthy side and transferring it to the C7 nerve on the paretic side. Intracortical microstimulation, Micro-PET and histological analysis were employed to explore the cortical changes in contralesional hemisphere and to reveal its correlation with behavioral recovery. These results showed that the contralesional hemispheric compensation was markedly strengthened and significantly related to behavioral improvements. The findings also revealed a feasible and effective way to maximize the potential of one hemisphere in controlling both limbs.

A comparison of different models with motor dysfunction after traumatic brain injury in adult rats

The aim of this study was to evaluate the validity of the model that could produce reproducible and persistent motor weakness and define the accurate tasks and testing parameters for longitudinal assessment of neurological deficits after traumatic brain injury (TBI). We compared the effects of two rat models that suffered different controlled cortical impact (CCI) injury, as well as extensive motor cortex resection model, on behavior recovery and brain morphology. Behavioral tests including the skilled reaching task, limb-use asymmetry test and the grasping test were employed to evaluate neurofunctional recovery from pre- to 12 weeks after the injury. The results demonstrated that all the rats in four groups showed spontaneous functional improvement with the past of time after surgery, especially in rats with mild and moderate CCI injury. At the end of the experiment, the animals' performance reached preoperative base lines on reaching task and limb-use asymmetry test in mild and moderate groups, while severe motor weakness could be observed in rats with severe CCI injury, as well as rats with extended motor cortex resection. Overall, the results of this study indicated that both models with severe CCI injury and extended resection of the motor cortex developed reproducible and long-lasting motor weakness, comparable in severity and duration and identified skilled reaching task, as well as limb-use asymmetry test, as sensitive assessments for slight neurological deficits after brain injury. This will help to provide the basis for further research of the processes after the TBI and development of novel therapies.

In vivo bioluminescence imaging for prolonged survival of transplanted human neural stem cells using 3D biocompatible scaffold in corticectomized rat model

Stem cell-based treatment of traumatic brain injury has been limited in its capacity to bring about complete functional recovery, because of the poor survival rate of the implanted stem cells. It is known that biocompatible biomaterials play a critical role in enhancing survival and proliferation of transplanted stem cells via provision of mechanical support. In this study, we noninvasively monitored in vivo behavior of implanted neural stem cells embedded within poly-l-lactic acid (PLLA) scaffold, and showed that they survived over prolonged periods in corticectomized rat model. Corticectomized rat models were established by motor-cortex ablation of the rat. F3 cells expressing enhanced firefly luciferase (F3-effLuc) were established through retroviral infection. The F3-effLuc within PLLA was monitored using IVIS-100 imaging system 7 days after corticectomized surgery. F3-effLuc within PLLA robustly adhered, and gradually increased luciferase signals of F3-effLuc within PLLA were detected in a day dependent manner. The implantation of F3-effLuc cells/PLLA complex into corticectomized rats showed longer-lasting luciferase activity than F3-effLuc cells alone. The bioluminescence signals from the PLLA-encapsulated cells were maintained for 14 days, compared with 8 days for the non-encapsulated cells. Immunostaining results revealed expression of the early neuronal marker, Tuj-1, in PLLA-F3-effLuc cells in the motor-cortex-ablated area. We observed noninvasively that the mechanical support by PLLA scaffold increased the survival of implanted neural stem cells in the corticectomized rat. The image-guided approach easily proved that scaffolds could provide supportive effect to implanted cells, increasing their viability in terms of enhancing therapeutic efficacy of stem-cell therapy.

Surfactant reduction of cerebral infarct size and behavioral deficit in a rat model of cerebrovascular arterial gas embolism

Gas embolism occurs commonly in cardiac and vascular surgery and decompression sickness. The goals of this study were to develop a new in vivo rat model of cerebrovascular arterial gas embolism and to determine the effects of exogenous surfactants on resultant brain infarct volume and accompanying long-term neurological dysfunction using the model. Unilateral cerebral arterial gas embolism was induced in Sprague Dawley rats, including groups receiving intravenous Pluronic F-127 (PF-127) and Oxycyte perflourocarbon surfactant pretreatment. Magnetic resonance imaging (MRI) was performed at 24 and 72 h postembolism to determine infarct volume. The elevated body swing test (EBST), limb-placement test, proprioception forelimb and hindlimb tests, whisker tactile test, and Morris Water Maze test were performed to assess motor behavior, somatosensory deficit, and spatial cognitive function out to 29 days after embolization. A stable stroke model was developed with MRI examination revealing infarction in the ipsilateral cerebral hemisphere. Gas embolized rats had significant cognitive and sensorimotor dysfunction, including approximately threefold increase in Morris Water Maze latency time, ∼20% left-sided biasing in EBST performance, 0.5 to 1.5 (mean) point score elevations in the proprioception and whisker tactile tests, and 3.0 point (mean) elevation in the limb-placement test, all of which were persistent throughout the postembolic period. Surfactant prophylaxis with either PF-127 or Oxycyte rendered stroke undetectable by MRI scanning and markedly reduced the postembolic deficits in both cognitive and sensorimotor performance in treated rats, with normalization of EBST and whisker tactile tests within 7 days.

Functional recovery after injury of motor cortex in rats: effects of rehabilitation and stem cell transplantation in a traumatic brain injury model of cortical resection

PURPOSE

Experimental studies and clinical trials designed to help patients recover from various brain injuries, such as stroke or trauma, have been attempted. Rehabilitation has shown reliable, positive clinical outcome in patients with various brain injuries. Transplantation of exogenous neural stem cells (NSCs) to repair the injured brain is a potential tool to help patient recovery.

METHODS

This study aimed to evaluate the therapeutic efficacy of a combination therapy consisting of rehabilitation and NSC transplantation compared to using only one modality. A model of motor cortex resection in rats was used to create brain injury in order to obtain consistent and prolonged functional deficits. The therapeutic results were evaluated using three methods during an 8-week period with a behavioral test, motor-evoked potential (MEP) measurement, and measurement of the degree of endogenous NSC production.

RESULTS

All three treatment groups showed the effects of treatment in the behavioral test, although the NSC transplantation alone group (CN) exhibited slightly worse results than the rehabilitation alone group (CR) or the combination therapy group (CNR). The latency on MEP was shortened to a similar extent in all three groups compared to the untreated group (CO). However, the enhancement of endogenous NSC proliferation was dramatically reduced in the CN group compared not only to the CR and CNR groups but also to the CO group. The CR and CNR groups seemed to prolong the duration of endogenous NSC proliferation compared to the untreated group.

CONCLUSIONS

A combination of rehabilitation and NSC transplantation appears to induce treatment outcomes that are similar to rehabilitation alone. Further studies are needed to evaluate the electrophysiological outcome of recovery and the possible effect of prolonging endogenous NSC proliferation in response to NSC transplantation and rehabilitation.