The effect of neurotrophin-3/chitosan carriers on the proliferation and differentiation of neural stem cells

GABAergic neurons differentiated from BDNF- and Dlx2-modified neural stem cells restore disrupted neural circuits in brainstem stroke

BACKGROUND

Brainstem stroke causes severe and persistent neurological impairment. Due to the limited spontaneous recovery and regeneration of the disrupted neural circuits, transplantation of exogenous neural stem cells (NSCs) was an alternative, while there were limitations for primitive NSCs.

METHODS

We established a mouse model of brainstem stroke by injecting endothelin in the right pons. Brain-derived neurotrophic factor (BDNF)- and distal-less homeobox 2 (Dlx2)-modified NSCs were transplanted to treat brainstem stroke. Transsynaptic viral tracking, immunostaining, magnetic resonance imaging, behavioral testing, and whole-cell patch clamp recordings were applied to probe the pathophysiology and therapeutic prospects of BDNF- and Dlx2-modified NSCs.

RESULTS

GABAergic neurons were predominantly lost after the brainstem stroke. No endogenous NSCs were generated in situ or migrated from the neurogenesis niches within the brainstem infarct region. Co-overexpressions of BDNF and Dlx2 not only promoted the survival of NSCs, but also boosted the differentiation of NSCs into GABAergic neurons. Results from transsynaptic virus tracking, immunostaining, and evidence from whole-cell patch clamping revealed the morphological and functional integration of the grafted BDNF- and Dlx2-modified NSCs-derived neurons with the host neural circuits. Neurological function was improved by transplantation of BDNF- and Dlx2-modified NSCs in brainstem stroke.

CONCLUSIONS

These findings demonstrated that BDNF- and Dlx2-modified NSCs differentiated into GABAergic neurons, integrated into and reconstituted the host neural networks, and alleviated the ischemic injury. It thus provided a potential therapeutic strategy for brainstem stroke.

A hyaluronic acid/silk fibroin/poly-dopamine-coated biomimetic hydrogel scaffold with incorporated neurotrophin-3 for spinal cord injury repair

Bio-factor stimulation is essential for axonal regeneration in the central nervous system. Thus, persistent and efficient factor delivery in the local microenvironment is an ideal strategy for spinal cord injury repair. We developed a biomimetic hydrogel scaffold to load biofactors in situ and release them in a controlled way as a promising therapeutic modality. Hyaluronic acid and silk fibroin were cross-linked as the basement of the scaffolds, and poly-dopamine coating was used to further increase the loading of factors and endow the hydrogel scaffolds with ideal physical and chemical properties and proper biocompatibility. Notably, neurotrophin-3 release from the hydrogel scaffolds was prolonged to 28 days. A spinal cord injury model was constructed for hydrogel scaffold transplantation. After eight weeks, significant NF200-positive nerve fibers were observed extending across the glial scar to the center of the injured area. Due to the release of neurotrophin-3, spinal cord regeneration was enhanced, and the cavity area of the injury graft site and inflammation associated with CD68 positive cells were reduced, which led to a significant improvement in hind limb motor function. The results show that the hyaluronic acid/silk fibroin/poly-dopamine-coated biomimetic hydrogel scaffold achieved locally slow release of neurotrophin-3, thus facilitating the regeneration of injured spinal cord. STATEMENT OF SIGNIFICANCE: Hydrogels have received great attention in spinal cord regeneration. Current research has focused on more efficient and controlled release of bio-factors. Here, we adopted a mussel-inspired strategy to functionalize the hyaluronic acid/silk fibroin hydrogel scaffold to increase the load of neurotrophin-3 and extend the release time. The hydrogel scaffolds have ideal physiochemical properties, proper release rate, and biocompatibility. Owing to the continuous neurotrophin-3 release from implanted scaffolds, cavity formation is reduced, inflammation alleviated, and spinal cord regeneration enhanced, indicating great potential for bio-factor delivery in soft tissue regeneration applications.

Activating Endogenous Neurogenesis for Spinal Cord Injury Repair: Recent Advances and Future Prospects

After spinal cord injury (SCI), endogenous neural stem cells are activated and migrate to the injury site where they differentiate into astrocytes, but they rarely differentiate into neurons. It is difficult for brain-derived information to be transmitted through the injury site after SCI because of the lack of neurons that can relay neural information through the injury site, and the functional recovery of adult mammals is difficult to achieve. The development of bioactive materials, tissue engineering, stem cell therapy, and physiotherapy has provided new strategies for the treatment of SCI and shown broad application prospects, such as promoting endogenous neurogenesis after SCI. In this review, we focus on novel approaches including tissue engineering, stem cell technology, and physiotherapy to promote endogenous neurogenesis and their therapeutic effects on SCI. Moreover, we explore the mechanisms and challenges of endogenous neurogenesis for the repair of SCI.

Proper wiring of newborn neurons to control bladder function after complete spinal cord injury

Activation of endogenous neurogenesis by bioactive materials enables restoration of sensory/motor function after complete spinal cord injury (SCI) via formation of new relay neural circuits. The underlying wiring logic of newborn neurons in adult central nervous system (CNS) is unknown. Here, we report neurotrophin3-loaded chitosan biomaterial substantially recovered bladder function after SCI. Multiple neuro-circuitry tracing technologies using pseudorabies virus (PRV), rabies virus (RV), and anterograde adeno-associated virus (AAV), demonstrated that newborn neurons were integrated into the micturition neural circuits and reconnected higher brain centers and lower spinal cord centers to control voiding, and participated in the restoration of the lower urinary tract function, even in the absence of long-distance axonal regeneration. Opto- and chemo-genetic studies further supported the notion that the supraspinal control of the lower urinary tract function was partially recovered. Our data demonstrated that regenerated relay neurons could be properly integrated into disrupted long-range neural circuits to restore function of adult CNS.

Circuit reconstruction of newborn neurons after spinal cord injury in adult rats via an NT3-chitosan scaffold

An implanted neurotrophin-3 (NT3)-chitosan scaffold can recruit endogenous neural stem cells to migrate to a lesion region and differentiate into mature neurons after adult spinal cord injury (SCI). However, the identities of these newborn neurons and whether they can form functional synapses and circuits to promote recovery after paraplegia remain unknown. By using combined advanced technologies, we revealed here that the newborn neurons of several subtypes received synaptic input from the corticospinal tract (CST), rubrospinal tract (RST), and supraspinal tracts. They formed a functional neural circuit at the injured spinal region, further driving the local circuits beneath the lesion. Our results showed that the NT3-chitosan scaffold facilitated the maturation of spinal neurons and the reestablishment of the spinal neural circuit in the lesion region 12 weeks after SCI. Transsynaptic virus experiments revealed that these newborn spinal neurons received synaptic connections from the CST and RST and drove the neural circuit beneath the lesion via newly formed synapses. These re-established circuits successfully recovered the formation and function of the neuromuscular junction (NMJ) beneath the lesion spinal segments. These findings suggest that the NT3-chitosan scaffold promotes the formation of relay neural circuits to accommodate various types of brain descending inputs and facilitate functional recovery after paraplegia.

Recognition of necrotic regions in MRI images of chronic spinal cord injury based on superpixel

BACKGROUND AND OBJECTIVE

The cystic cavity and its surrounding dense glial scar formed in chronic spinal cord injury (SCI) hinder the regeneration of nerve axons. Accurate location of the necrotic regions formed by the scar and the cavity is conducive to eliminate the re-growth obstacles and promote SCI treatment. This work aims to realize the accurate and automatic location of necrotic regions in the chronic SCI magnetic resonance imaging (MRI).

METHODS

In this study, a method based on superpixel is proposed to identify the necrotic regions of spinal cord in chronic SCI MRI. Superpixels were obtained by a simple linear iterative clustering algorithm, and feature sets were constructed from intensity statistical features, gray level co-occurrence matrix features, Gabor texture features, local binary pattern features and superpixel areas. Subsequently, the recognition effects of support vector machine (SVM) and random forest (RF) classification model on necrotic regions were compared from accuracy (ACC), positive predictive value (PPV), sensitivity (SE), specificity (SP), Dice coefficient and algorithm running time.

RESULTS

The method is evaluated on T1- and T2-weighted MRI spinal cord images of 24 adult female Wistar rats. And an automatic recognition method for spinal cord necrosis regions was established based on the SVM classification model finally. The recognition results were 1.00±0.00 (ACC), 0.89±0.09 (PPV), 0.88±0.12 (SE), 1.00±0.00 (SP) and 0.88±0.07 (Dice), respectively.

CONCLUSIONS

The proposed method can accurately and noninvasively identify the necrotic regions in MRI, which is helpful for the pre-intervention assessment and post-intervention evaluation of chronic SCI research and treatments, and promoting the clinical transformation of chronic SCI research.

Enhancing Stem Cell-Based Therapeutic Potential by Combining Various Bioengineering Technologies

Stem cell-based therapeutics have gained tremendous attention in recent years due to their wide range of applications in various degenerative diseases, injuries, and other health-related conditions. Therapeutically effective bone marrow stem cells, cord blood- or adipose tissue-derived mesenchymal stem cells (MSCs), embryonic stem cells (ESCs), and more recently, induced pluripotent stem cells (iPSCs) have been widely reported in many preclinical and clinical studies with some promising results. However, these stem cell-only transplantation strategies are hindered by the harsh microenvironment, limited cell viability, and poor retention of transplanted cells at the sites of injury. In fact, a number of studies have reported that less than 5% of the transplanted cells are retained at the site of injury on the first day after transplantation, suggesting extremely low (<1%) viability of transplanted cells. In this context, 3D porous or fibrous national polymers (collagen, fibrin, hyaluronic acid, and chitosan)-based scaffold with appropriate mechanical features and biocompatibility can be used to overcome various limitations of stem cell-only transplantation by supporting their adhesion, survival, proliferation, and differentiation as well as providing elegant 3-dimensional (3D) tissue microenvironment. Therefore, stem cell-based tissue engineering using natural or synthetic biomimetics provides novel clinical and therapeutic opportunities for a number of degenerative diseases or tissue injury. Here, we summarized recent studies involving various types of stem cell-based tissue-engineering strategies for different degenerative diseases. We also reviewed recent studies for preclinical and clinical use of stem cell-based scaffolds and various optimization strategies.

Chronic spinal cord injury repair by NT3-chitosan only occurs after clearance of the lesion scar

Spinal cord injury (SCI) is a severe damage usually leading to limb dysesthesia, motor dysfunction, and other physiological disability. We have previously shown that NT3-chitosan could trigger an acute SCI repairment in rats and non-human primates. Due to the negative effect of inhibitory molecules in glial scar on axonal regeneration, however, the role of NT3-chitosan in the treatment of chronic SCI remains unclear. Compared with the fresh wound of acute SCI, how to handle the lesion core and glial scars is a major issue related to chronic-SCI repair. Here we report, in a chronic complete SCI rat model, establishment of magnetic resonance-diffusion tensor imaging (MR-DTI) methods to monitor spatial and temporal changes of the lesion area, which matched well with anatomical analyses. Clearance of the lesion core via suction of cystic tissues and trimming of solid scar tissues before introducing NT3-chitosan using either a rigid tubular scaffold or a soft gel form led to robust neural regeneration, which interconnected the severed ascending and descending axons and accompanied with electrophysiological and motor functional recovery. In contrast, cystic tissue extraction without scar trimming followed by NT3-chitosan injection, resulted in little, if any regeneration. Taken together, after lesion core clearance, NT3-chitosan can be used to enable chronic-SCI repair and MR-DTI-based mapping of lesion area and monitoring of ongoing regeneration can potentially be implemented in clinical studies for subacute/chronic-SCI repair.

Transplantation of bioengineered Reelin-loaded PLGA/PEG micelles can accelerate neural tissue regeneration in photothrombotic stroke model of mouse

Ischemic stroke is characterized by extensive neuronal loss, glial scar formation, neural tissue degeneration that leading to profound changes in the extracellular matrix, neuronal circuitry, and long-lasting functional disabilities. Although transplanted neural stem cells (NSCs) can recover some of the functional deficit after stroke, retrieval is not complete and repair of lost tissue is negligible. Therefore, the current challenge is to use the combination of NSCs with suitably enriched biomaterials to retain these cells within the infarct cavity and accelerate the formation of a de novo tissue. This study aimed to test the regenerative potential of polylactic-co-glycolic acid-polyethylene glycol (PLGA-PEG) micelle biomaterial enriched with Reelin and embryonic NSCs on photothrombotic stroke model of mice to gain appropriate methods in tissue engineering. For this purpose, two sets of experiments, either in vitro or in vivo models, were performed. In vitro analyses exhibited PLGA-PEG plus Reelin-induced proliferation rate (Ki-67⁺ NSCs) and neurite outgrowth (axonization and dendritization) compared to PLGA-PEG + NSCs and Reelin + NSCs groups (p < 0.05). Besides, neural differentiation (Map-2⁺ cells) was high in NSCs cultured in the presence of Reelin-loaded PLGA-PEG micelles (p < 0.05). Double immunofluorescence staining showed that Reelin-loaded PLGA-PEG micelles increased the number of migrating neural progenitor cells (DCX⁺ cells) and mature neurons (NeuN⁺ cells) around the lesion site compared to the groups received PLGA-PEG and Reelin alone after 1 month (p < 0.05). Immunohistochemistry results showed that the PLGA/PEG plus Reelin significantly decreased the astrocytic gliosis and increased local angiogenesis (vWF-positive cells) relative to the other groups. These changes led to the reduction of cavity size in the Reelin-loaded PLGA-PEG+NSCs group. Neurobehavioral tests indicated Reelin-loaded PLGA-PEG+NSCs promoted neurological outcome and functional recovery (p < 0.05). These results indicated that Reelin-loaded PLGA-PEG is capable of promoting NSCs dynamic growth, neuronal differentiation, and local angiogenesis following ischemic injury via providing a desirable microenvironment. These features can lead to neural tissue regeneration and functional recovery.

Neurotrophin-3 attenuates human peripheral blood T cell and monocyte activation status and cytokine production post stroke

BACKGROUND AND PURPOSE

Stroke therapy still lacks successful measures to improve post stroke recovery. Neurotrophin-3 (NT-3) is one promising candidate which has proven therapeutic benefit in motor recovery in acute experimental stroke. Post stroke, the immune system has opposing pathophysiological roles: pro-inflammatory cascades and immune cell infiltration into the brain exacerbate cell death while the peripheral immune response has only limited capabilities to fight infections during the acute and subacute phase. With time, anti-inflammatory mechanisms are supposed to support recovery of the ischemic damage within the brain parenchyma. However, interestingly, NT-3 can improve recovery in chronic neurological injury when combined with the pro-inflammatory stimulus lipopolysaccharide (LPS).

AIM

We elucidated the impact of NT-3 on human monocyte and T cell activation as well as cytokine production ex vivo after stroke. In addition, we investigated the age-dependent availability of the high affinity NT-3 receptor TrkC upon LPS stimulation.

METHODS

Peripheral blood mononuclear cells (PBMCs) were isolated from acute stroke patients and controls and incubated with different dosages of NT-3 (10 and 100 ng/mL) and with or without LPS or anti-CD3/CD28 for 48 h. Total TrkC expression and cell activation (CD25, CD69 and HLA-DR) were assessed by FACS staining. IFN-γ, TNF-α, IL-2, IL-4, IL-5, IL-6, IL-9, IL-10, IL-13, IL-17A, IL-17F, IL-21 and IL-22 were quantified by cytometric bead array.

RESULTS

Most monocytes and only a small proportion of T cells expressed TrkC in blood from humans without stroke. Activation of cells from young humans (without strokes) using anti-CD3/CD28 or LPS partially reduced the proportion of monocytes expressing TrkC whilst they increased the proportion of T cells expressing TrkC. In contrast, activation of cells from elderly humans (without strokes) did not affect the proportion of monocytes expressing TrkC and only anti-CD3/CD28 led to an increase in the proportion of CD4+ T cells expressing TrkC. In blood from stroke patients or controls, NT-3 treatment reduced the percentage of monocytes and CD4+ and CD8+ T cells that were activated and reduced all cytokines investigated besides IL-21.

CONCLUSIONS

NT-3 attenuated immune responses in cells from stroke patients and controls. The mechanism whereby human immune cells respond to NT-3 may be via TrkC receptors whose levels are regulated by stimulation. Further work is required to determine whether the induction of sensorimotor recovery in rodents by NT-3 after CNS injury is caused by this attenuation of the immune response.

The Beneficial Potential of Genetically Modified Stem Cells in the Treatment of Stroke: a Review

The last two decades have witnessed a surge in investigations proposing stem cells as a promising strategy to treat stroke. Since growth factor release is considered as one of the most important aspects of cell-based therapy, stem cells over-expressing growth factors are hypothesized to yield higher levels of therapeutic efficiency. In pre-clinical studies of the last 15 years that were investigating the efficiency of stem cell therapy for stroke, a variety of stem cell types were genetically modified to over-express various factors. In this review we summarize the current knowledge on the therapeutic efficiency of stem cell-derived growth factors, encompassing techniques employed and time points to evaluate. In addition, we discuss several types of stem cells, including the recently developed model of epidermal neural crest stem cells, and genetically modified stem cells over-expressing specific factors, which could elevate the restorative potential of naive stem cells. The restorative potential is based on enhanced survival/differentiation potential of transplanted cells, apoptosis inhibition, infarct volume reduction, neovascularization or functional improvement. Since the majority of studies have focused on the short-term curative effects of genetically engineered stem cells, we emphasize the need to address their long-term impact.

Immunomodulatory biomaterials and their application in therapies for chronic inflammation-related diseases

The degree of tissue injuries such as the level of scarring or organ dysfunction, and the immune response against them primarily determine the outcome and speed of healing process. The successful regeneration of functional tissues requires proper modulation of inflammation-producing immune cells and bioactive factors existing in the damaged microenvironment. In the tissue repair and regeneration processes, different types of biomaterials are implanted either alone or by combined with other bioactive factors, which will interact with the immune systems including immune cells, cytokines and chemokines etc. to achieve different results highly depending on this interplay. In this review article, the influences of different types of biomaterials such as nanoparticles, hydrogels and scaffolds on the immune cells and the modification of immune-responsive factors such as reactive oxygen species (ROS), cytokines, chemokines, enzymes, and metalloproteinases in tissue microenvironment are summarized. In addition, the recent advances of immune-responsive biomaterials in therapy of inflammation-associated diseases such as myocardial infarction, spinal cord injury, osteoarthritis, inflammatory bowel disease and diabetic ulcer are discussed.

Neurotrophin-3 stimulates stem Leydig cell proliferation during regeneration in rats

Neurotrophin‐3 (NT‐3) acts as an important growth factor to stimulate and control tissue development. The NT‐3 receptor, TRKC, is expressed in rat testis. Its function in regulation of stem Leydig cell development and its underlying mechanism remain unknown. Here, we reported the role of NT‐3 to regulate stem Leydig cell development in vivo and in vitro. Ethane dimethane sulphonate was used to kill all Leydig cells in adult testis, and NT‐3 (10 and 100 ng/testis) was injected intratesticularly from the 14th day after ethane dimethane sulphonate injection for 14 days. NT‐3 significantly reduced serum testosterone levels at doses of 10 and 100 ng/testis without affecting serum luteinizing hormone and follicle‐stimulating hormone levels. NT‐3 increased CYP11A1‐positive Leydig cell number at 100 ng/testis and lowered Leydig cell size and cytoplasmic size at doses of 10 and 100 ng/testis. After adjustment by the Leydig cell number, NT‐3 significantly down‐regulated the expression of Leydig cell genes (Lhcgr, Scarb1, Star, Cyp11a1, Hsd3b1, Cyp17a1, Hsd17b3, Hsd11b1, Insl3, Trkc and Nr5a1) and the proteins. NT‐3 increased the phosphorylation of AKT1 and mTOR, decreased the phosphorylation of 4EBP, thereby increasing ATP5O. In vitro study showed that NT‐3 dose‐dependently stimulated EdU incorporation into stem Leydig cells and inhibited stem Leydig cell differentiation into Leydig cells, thus leading to lower medium testosterone levels and lower expression of Lhcgr, Scarb1, Trkc and Nr5a1 and their protein levels. NT‐3 antagonist Celitinib can antagonize NT‐3 action in vitro. In conclusion, the present study demonstrates that NT‐3 stimulates stem Leydig cell proliferation but blocks the differentiation via TRKC receptor.

Analysis of neurite length of hippocampal neurons cultured into 3D artificial network patterned microfluidic chips

Purpose: The study aims to lay a foundational probe for the thorough application microfluidic chips in brain function research with microfluidic chips. Neuron slide culture is a common culture method in vitro, and the microfluidic chip with the artificial network pattern not only can realize neuron cells 3 D culture in vitro, but also limit the extension space of neurite outgrow.Materials and Methods: In order to analyze the differences of hippocampal cells neurite growth length between the 3 D chips and the common 2 D culture, the experiments utilized statistical analysis method analyzing the length of the hippocampus neuron neurite of 3 days, 5 days and 7 days, respectively, with the common glass slide 2 D culture method and the microfluidic chip 3 D culture in vitro.Results: The results showed that there was no significant difference in the neurite length after 3 days. However, there was a significant difference after 5 days and 7 days. It can be seen that the microfluidic chip with artificial network pattern has limitations to the growth of neurite after 5 days.Conclusions: We concluded that the growth state of hippocampal cells in the restricted 3 D space is different from that of conventional 2 D culture.It showed that the artificial network pattern design has limited the growth space of the dendrites but also affected its growth.

Neural stem cell transplantation therapy for brain ischemic stroke: Review and perspectives

Brain ischemic stroke is one of the most common causes of death and disability, currently has no efficient therapeutic strategy in clinic. Due to irreversible functional neurons loss and neural tissue injury, stem cell transplantation may be the most promising treatment approach. Neural stem cells (NSCs) as the special type of stem cells only exist in the nervous system, can differentiate into neurons, astrocytes, and oligodendrocytes, and have the abilities to compensate insufficient endogenous nerve cells and improve the inflammatory microenvironment of cell survival. In this review, we focused on the important role of NSCs therapy for brain ischemic stroke, mainly introduced the methods of optimizing the therapeutic efficacy of NSC transplantation, such as transfection and overexpression of specific genes, pretreatment of NSCs with inflammatory factors, and co-transplantation with cytokines. Next, we discussed the potential problems of NSC transplantation which seriously limited their rapid clinical transformation and application. Finally, we expected a new research topic in the field of stem cell research. Based on the bystander effect, exosomes derived from NSCs can overcome many of the risks and difficulties associated with cell therapy. Thus, as natural seed resource of nervous system, NSCs-based cell-free treatment is a newly therapy strategy, will play more important role in treating ischemic stroke in the future.

Validation study of neurotrophin-3-releasing chitosan facilitation of neural tissue generation in the severely injured adult rat spinal cord

It was previously reported that a tube holding chitosan carriers loaded with neurotrophin-3 (NT-3), after insertion into a 5 mm long transection gap in the adult rat spinal cord, triggered de novo neural tissue generation and functional recovery. Here, we report an effort to validate these findings using stringent blinding methodologies, which are crucial for robustness in reproducing biomedical studies. Radio frequency identification (RFID) chips were utilized to label rats that were randomly assigned into three experimental groups: transection with chitosan-NT-3 implant (C-NT3), transection only (T-controls), and laminectomy only (S-controls), blinding the experimenters to the treatments. Three months after surgery, animals only known by their RFID were functionally, electrophysiologically, and anatomically assessed. The data were then collected into the proper groups and statistically analyzed. Neural tissue with nestin-, Tuj1-, and NeuN-positive cells was found bridging the transection gap in C-NT3 rats, but not in T-controls. Motor- and somatosensory-evoked potentials were detected in C-NT3 rats and S-controls, but not in T-controls. Hind limb movement was significantly better in C-NT3 rats compared with T-controls. Our validation study indicates that C-NT3 implants facilitate neural tissue generation, at least in part, by eliciting endogenous neurogenesis. Our data support the use of C-NT3 implants for tissue remodeling in the injured spinal cord.

NT3-chitosan enables de novo regeneration and functional recovery in monkeys after spinal cord injury

Spinal cord injury (SCI) often leads to permanent loss of motor, sensory, and autonomic functions. We have previously shown that neurotrophin3 (NT3)-loaded chitosan biodegradable material allowed for prolonged slow release of NT3 for 14 weeks under physiological conditions. Here we report that NT3-loaded chitosan, when inserted into a 1-cm gap of hemisectioned and excised adult rhesus monkey thoracic spinal cord, elicited robust axonal regeneration. Labeling of cortical motor neurons indicated motor axons in the corticospinal tract not only entered the injury site within the biomaterial but also grew across the 1-cm-long lesion area and into the distal spinal cord. Through a combination of magnetic resonance diffusion tensor imaging, functional MRI, electrophysiology, and kinematics-based quantitative walking behavioral analyses, we demonstrated that NT3-chitosan enabled robust neural regeneration accompanied by motor and sensory functional recovery. Given that monkeys and humans share similar genetics and physiology, our method is likely translatable to human SCI repair.

Functional hyaluronate collagen scaffolds induce NSCs differentiation into functional neurons in repairing the traumatic brain injury

The traumatic brain injury (TBI) usually causes brain tissue defects, including neuronal death or loss, which ultimately results in dysfunction in some degree. The cell replacement therapy is now one of the most promising methods for such injury. There are currently various methods to induce the differentiation of stem cells into neurons, but all extremely complex, slow and unstable. Here we report that the sodium hyaluronate collagen scaffold loaded with bFGF (bFGF-controlled releasing system, bFGF-CRS) can induce neural stem cells (NSCs) to differentiate into multi-type and mature functional neurons at a high percentage of 82±1.528% in two weeks. The quantitative real-time (QRT) PCR results reveal that a long-term activation of bFGF receptors could up-regulate ERK/MAPK signal pathways, thus facilitating the formation of presynaptic and postsynaptic structure among the induced neuronal cells (iN cells). The functional synaptic connections established among iN cells were detected by the planar multielectrode dish system. When jointly transplanting the bFGF-CRS and NSCs into the CA1 zone of the rat TBI area, the results suggested that bFGF-CRS provided an optimal microenvironment, which promoted survival, neuronal differentiation of transplanted NSCs and functional synapse formation not only among iN cells but also between iN cells and the host brain tissue in TBI rats, consequently leading to the cognitive function recovery of TBI rats. These findings in vitro and in vivo may lay a foundation for the application of bFGF-CRS and shed light on the delivery of exogenous cells or nutrients to the CNS injury or disease area.

STATEMENT OF SIGNIFICANCE

A sodium hyaluronate collagen scaffold was specifically functionalized with nutrient-bFGF which can induce the differentiation of neural stem cells (NSCs) into multi-type and mature functional neurons at a high percentage in two week. When jointly transplanting the bFGF-CRS and NSCs into the CA1 zone of the traumatic brain injured area of adult rats, the bFGF-CRS could provide an optimal microenvironment, which promoted survival, migration and neuronal differentiation of transplanted NSCs and functional synapse formation among iN cells, as well as between iN cells and host brain tissue in TBI rats, consequently leading to the cognitive function recovery of TBI rats.

Effect of controlled release of brain-derived neurotrophic factor and neurotrophin-3 from collagen gel on neural stem cells

This study aimed to examine the effect of controlled release of brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) from collagen gel on rat neural stem cells (NSCs). With three groups of collagen gel, BDNF/collagen gel, and NT-3/collagen gel as controls, BDNF and NT-3 were tested in the BDNF-NT-3/collagen gel group at different time points. The enzyme-linked immunosorbent assay results showed that BDNF and NT-3 were steadily released from collagen gels for 10 days. The cell viability test and the bromodeoxyuridine incorporation assay showed that BDNF-NT-3/collagen gel supported the survival and proliferation of NSCs. The results also showed that the length of processes was markedly longer and differentiation percentage from NSCs into neurons was much higher in the BDNF-NT-3/collagen gel group than those in the collagen gel, BDNF/collagen gel, and NT-3/collagen gel groups. These findings suggest that BDNF-NT-3/collagen gel could significantly improve the ability of NSCs proliferation and differentiation.

Regeneration strategies after the adult mammalian central nervous system injury-biomaterials

The central nervous system (CNS) has very restricted intrinsic regeneration ability under the injury or disease condition. Innovative repair strategies, therefore, are urgently needed to facilitate tissue regeneration and functional recovery. The published tissue repair/regeneration strategies, such as cell and/or drug delivery, has been demonstrated to have some therapeutic effects on experimental animal models, but can hardly find clinical applications due to such methods as the extremely low survival rate of transplanted cells, difficulty in integrating with the host or restriction of blood–brain barriers to administration patterns. Using biomaterials can not only increase the survival rate of grafts and their integration with the host in the injured CNS area, but also sustainably deliver bioproducts to the local injured area, thus improving the microenvironment in that area. This review mainly introduces the advances of various strategies concerning facilitating CNS regeneration.

NT3-chitosan elicits robust endogenous neurogenesis to enable functional recovery after spinal cord injury

Neural stem cells (NSCs) in the adult mammalian central nervous system (CNS) hold the key to neural regeneration through proper activation, differentiation, and maturation, to establish nascent neural networks, which can be integrated into damaged neural circuits to repair function. However, the CNS injury microenvironment is often inhibitory and inflammatory, limiting the ability of activated NSCs to differentiate into neurons and form nascent circuits. Here we report that neurotrophin-3 (NT3)-coupled chitosan biomaterial, when inserted into a 5-mm gap of completely transected and excised rat thoracic spinal cord, elicited robust activation of endogenous NSCs in the injured spinal cord. Through slow release of NT3, the biomaterial attracted NSCs to migrate into the lesion area, differentiate into neurons, and form functional neural networks, which interconnected severed ascending and descending axons, resulting in sensory and motor behavioral recovery. Our study suggests that enhancing endogenous neurogenesis could be a novel strategy for treatment of spinal cord injury.

Transcriptome analyses reveal molecular mechanisms underlying functional recovery after spinal cord injury

Spinal cord injury (SCI) is considered incurable because axonal regeneration in the central nervous system (CNS) is extremely challenging, due to harsh CNS injury environment and weak intrinsic regeneration capability of CNS neurons. We discovered that neurotrophin-3 (NT3)-loaded chitosan provided an excellent microenvironment to facilitate nerve growth, new neurogenesis, and functional recovery of completely transected spinal cord in rats. To acquire mechanistic insight, we conducted a series of comprehensive transcriptome analyses of spinal cord segments at the lesion site, as well as regions immediately rostral and caudal to the lesion, over a period of 90 days after SCI. Using weighted gene coexpression network analysis (WGCNA), we established gene modules/programs corresponding to various pathological events at different times after SCI. These objective measures of gene module expression also revealed that enhanced new neurogenesis and angiogenesis, and reduced inflammatory responses were keys to conferring the effect of NT3-chitosan on regeneration.

Effect of an Epineurial-Like Biohybrid Nerve Conduit on Nerve Regeneration

A novel approach of making a biomimetic nerve conduit was established by seeding adipose-derived adult stem cells (ADSCs) on the external wall of porous poly(d,l-lactic acid) (PLA) nerve conduits. The PLA conduits were fabricated using gas foaming salt and solvent-nonsolvent phase conversion. We examined the effect of two different porous structures (GS and GL) on ADSC growth and proliferation. The GS conduits had better structural stability, permeability, and porosity, as well as better cell viability at 4, 7, and 10 days. The epineurial-like tissue was grown from ADSC-seeded conduits cultured for 7 days in vitro and then implanted into 10-mm rat sciatic nerve defects for evaluation. The regeneration capacity and functional recovery were evaluated by histological staining, electrophysiology, walking track, and functional gait analysis after 6 weeks of implantation. Experimental data indicated that the autograft and ADSC-seeded GS conduits had better functional recovery than the blank conduits and ADSC-seeded GL conduits. The area of regenerated nerve and number of myelinated axons quantified based on the histology also indicated that the autograft and AGS groups performed better than the other two groups. We suggested that ADSCs may interact with endogenous Schwann cells and release neurotrophic factors to promote peripheral nerve regeneration. The design of the conduit may be critical for producing a biohybrid nerve conduit and to provide an epineurial-like support.

Synthetic Extracellular Microenvironment for Modulating Stem Cell Behaviors

The innate ability of stem cells to self-renew and differentiate into multiple cell types makes them a promising source for tissue engineering and regenerative medicine applications. Their capacity for self-renewal and differentiation is largely influenced by the combination of physical, chemical, and biological signals found in the stem cell niche, both temporally and spatially. Embryonic and adult stem cells are potentially useful for cell-based approaches; however, regulating stem cell behavior remains a major challenge in their clinical use. Most of the current approaches for controlling stem cell fate do not fully address all of the complex signaling pathways that drive stem cell behaviors in their natural microenvironments. To overcome this limitation, a new generation of biomaterials is being developed for use as three-dimensional synthetic microenvironments that can mimic the regulatory characteristics of natural extracellular matrix (ECM) proteins and ECM-bound growth factors. These synthetic microenvironments are currently being investigated as a substrate with surface immobilization and controlled release of bioactive molecules to direct the stem cell fate in vitro, as a tissue template to guide and improve the neo-tissue formation both in vitro and in vivo, and as a delivery vehicle for cell therapy in vivo. The continued advancement of such an intelligent biomaterial system as the synthetic extracellular microenvironment holds the promise of improved therapies for numerous debilitating medical conditions for which no satisfactory cure exists today.

Advances in regenerative therapies for spinal cord injury: a biomaterials approach

Spinal cord injury results in the permanent loss of function, causing enormous personal, social and economic problems. Even though neural regeneration has been proven to be a natural mechanism, central nervous system repair mechanisms are ineffective due to the imbalance of the inhibitory and excitatory factors implicated in neuroregeneration. Therefore, there is growing research interest on discovering a novel therapeutic strategy for effective spinal cord injury repair. To this direction, cell-based delivery strategies, biomolecule delivery strategies as well as scaffold-based therapeutic strategies have been developed with a tendency to seek for the answer to a combinatorial approach of all the above. Here we review the recent advances on regenerative/neural engineering therapies for spinal cord injury, aiming at providing an insight to the most promising repair strategies, in order to facilitate future research conduction.

Neural ECM mimetics

The consequence of numerous neurological disorders is the significant loss of neural cells, which further results in multilevel dysfunction or severe functional deficits. The extracellular matrix (ECM) is of tremendous importance for neural regeneration mediating ambivalent functions: ECM serves as a growth-promoting substrate for neurons but, on the other hand, is a major constituent of the inhibitory scar, which results from traumatic injuries of the central nervous system. Therefore, cell and tissue replacement strategies on the basis of ECM mimetics are very promising therapeutic interventions. Numerous synthetic and natural materials have proven effective both in vitro and in vivo. The closer a material's physicochemical and molecular properties are to the original extracellular matrix, the more promising its effectiveness may be. Relevant factors that need to be taken into account when designing such materials for neural repair relate to receptor-mediated cell-matrix interactions, which are dependent on chemical and mechanical sensing. This chapter outlines important characteristics of natural and synthetic ECM materials (scaffolds) and provides an overview of recent advances in design and application of ECM materials for neural regeneration, both in therapeutic applications and in basic biological research.

Functional recoveries of sciatic nerve regeneration by combining chitosan-coated conduit and neurosphere cells induced from adipose-derived stem cells

Suboptimal repair occurs in a peripheral nerve gap, which can be partially restored by bridging the gap with various biosynthetic conduits or cell-based therapy. In this study, we developed a combination of chitosan coating approach to induce neurosphere cells from human adipose-derived stem cells (ASCs) on chitosan-coated plate and then applied these cells to the interior of a chitosan-coated silicone tube to bridge a 10-mm gap in a rat sciatic nerve. Myelin sheath degeneration and glial scar formation were discovered in the nerve bridged by the silicone conduit. By using a single treatment of chitosan-coated conduit or neurosphere cell therapy, the nerve gap was partially recovered after 6 weeks of surgery. Substantial improvements in nerve regeneration were achieved by combining neurosphere cells and chitosan-coated conduit based on the increase of myelinated axons density and myelin thickness, gastrocnemius muscle weight and muscle fiber diameter, and step and stride lengths from gait analysis. High expressions of interleukin-1β and leukotriene B4 receptor 1 in the intra-neural scarring caused by using silicone conduits revealed that the inflammatory mechanism can be inhibited when the conduit is coated with chitosan. This study demonstrated that the chitosan-coated surface performs multiple functions that can be used to induce neurosphere cells from ASCs and to facilitate nerve regeneration in combination with a cells-assisted coated conduit.

Neo-innervation of a bioengineered intestinal smooth muscle construct around chitosan scaffold

Neuromuscular disorders of the gut result in disturbances in gastrointestinal transit. The objective of this study was to evaluate the neo-innervation of smooth muscle in an attempt to restore lost innervation. We have previously shown the potential use of composite chitosan scaffolds as support for intestinal smooth muscle constructs. However, the constructs lacked neuronal component. Here, we bioengineered innervated colonic smooth muscle constructs using rabbit colon smooth muscle and enteric neural progenitor cells. We also bioengineered smooth muscle only tissue constructs using colonic smooth muscle cells. The constructs were placed next to each other around tubular chitosan scaffolds and left in culture. Real time force generation conducted on the intrinsically innervated smooth muscle constructs showed differentiated functional neurons. The bioengineered smooth muscle only constructs became neo-innervated. The neo-innervation results were confirmed by immunostaining assays. Chitosan supported (1) the differentiation of neural progenitor cells in the constructs and (2) the neo-innervation of non-innervated smooth muscle around the same scaffold.

Evaluation of the Effect of NT-3 and Biodegradable Poly-L-lactic Acid Nanofiber Scaffolds on Differentiation of Rat Hair Follicle Stem Cells into Neural Cells In Vitro

Recent improvement in neuroscience has led to new strategies in neural repair. Hair follicle stem cells are high promising source of accessible, active, and pluripotent adult stem cells. They have high affinity to differentiate to neurons. Aside from using cell-scaffold combinations for implantation, scaffolds can provide a suitable microenvironment for cell proliferation, migration, and differentiation. NT-3 is the most interesting neurotrophic factors being an important regulator of neural survival and differentiation. Since treatment duration in neural repair is very important, this study aims to evaluate the effect of NT-3 and poly-L-lactic acid (PLLA) on differentiation time of bulge stem cells of rat hair follicle to neural-like cells. HFSCs of rat whisker was isolated and cultured on PLLA and differentiated with 10 ng/mL NT-3. Biological features of cultured cells were evaluated with immunocytochemistry and flowcytometry methods by using CD34, nestin, and βІІІ-tubulin markers. For cell viability and morphological assessment, MTT assay and SEM were performed. Our results showed that bulge stem cells of hair follicle can express CD34 and Nestin before differentiation. By using NT-3 during differentiation process, the cells showed positive reaction to βІІІ-tubulin antibody. MTT results demonstrated that PLLA significantly increased cell viability. Finally, HFSCs adhesion was confirmed by SEM results. The results indicate that 10 ng/mL NT-3 and PLLA have significant effect on differentiation time of rat HFSCs to neural cells even in 10 days.

Scaffolds to promote spinal cord regeneration

Substantial research effort in the spinal cord injury (SCI) field is directed towards reduction of secondary injury changes and enhancement of tissue sparing. However, pathway repair after complete transections, large lesions, or after chronic injury may require the implantation of some form of oriented bridging structure to restore tissue continuity across a trauma zone. These matrices or scaffolds should be biocompatible and create an environment that facilitates tissue growth and vascularization, and allow axons to regenerate through and beyond the implant in order to reconnect with "normal" tissue distal to the injury. The myelination of regrown axons is another important requirement. In this chapter, we describe recent advances in biomaterial technology designed to provide a terrain for regenerating axons to grow across the site of injury and/or create an environment for endogenous repair. Many different types of scaffold are under investigation; they can be biodegradable or nondegradable, natural or synthetic. Scaffolds can be designed to incorporate immobilized signaling molecules and/or used as devices for controlled release of therapeutic agents, including growth factors. These bridging structures can also be infiltrated with specific cell types deemed suitable for spinal cord repair.

The effect of amino density on the attachment, migration, and differentiation of rat neural stem cells in vitro

Artificial extracellular matrices play important roles in the regulation of stem cell behavior. To generate materials for tissue engineering, active functional groups, such as amino, carboxyl, and hydroxyl, are often introduced to change the properties of the biomaterial surface. In this study, we chemically modified coverslips to create surfaces with different amino densities and investigated the adhesion, migration, and differentiation of neural stem cells (NSCs) under serum-free culture conditions. We observed that a higher amino density significantly promoted NSCs attachment, enhanced neuronal differentiation and promoted excitatory synapse formation in vitro. These results indicate that the amino density significantly affected the biological behavior of NSCs. Thus, the density and impact of functional groups in extracellular matrices should be considered in the research and development of materials for tissue engineering.

Neurotrophin-induced migration and neuronal differentiation of multipotent astrocytic stem cells in vitro

Hypoxic ischemic encephalopathy (HIE) affects 2-3 per 1000 full-term neonates. Up to 75% of newborns with severe HIE die or have severe neurological handicaps. Stem cell therapy offers the potential to replace HIE-damaged cells and enhances the autoregeneration process. Our laboratory implanted Multipotent Astrocytic Stem Cells (MASCs) into a neonatal rat model of hypoxia-ischemia (HI) and demonstrated that MASCs move to areas of injury in the cortex and hippocampus. However, only a small proportion of the implanted MASCs differentiated into neurons. MASCs injected into control pups did not move into the cortex or differentiate into neurons. We do not know the mechanism by which the MASCs moved from the site of injection to the injured cortex. We found neurotrophins present after the hypoxic-ischemic milieu and hypothesized that neurotrophins could enhance the migration and differentiation of MASCs. Using a Boyden chamber device, we demonstrated that neurotrophins potentiate the in vitro migration of stem cells. NGF, GDNF, BDNF and NT-3 increased stem cell migration when compared to a chemokinesis control. Also, MASCs had increased differentiation toward neuronal phenotypes when these neurotrophins were added to MASC culture tissue. Due to this finding, we believed neurotrophins could guide migration and differentiation of stem cell transplants after brain injury.

Effect of BDNF-plasma-collagen matrix controlled delivery system on the behavior of adult rats neural stem cells

The neurogenesis amount in central nervous system (CNS) stimulated by the injury or diseases is so small that neural stem cells (NSCs) cannot specifically differentiate into the ideal phenotypes to repair the injured CNS. The transplanted exogenous NSCs also have such problems as poor survival and insufficient neuronal differentiation. In this study, the behavior of NSCs from the spinal cord of adult rats was compared at the neurosphere level after the respective addition of the brain-derived neurotrophic factor (BDNF) daily, the BDNF-loaded plasma-collagen matrix, the plasma-collagen matrix alone, or the defined medium alone. The results suggested that the BDNF, either in the control release form or in the soluble form, initiated NSCs proliferation and differentiation by activating receptors Trk B and p75NTR. BDNF also increased the differentiation percentage of adult NSCs into neurons and supported the long-term cell survival and growth. The BDNF was stably released by the plasma-collagen matrix for up to 21 days. The plasma-collagen matrix alone showed its biocompatibility with cells by facilitating the adhesion, survival, and differentiation of NSCs. The NSCs in the defined medium alone group showed poor survival and a very low level of neuronal differentiation and proliferation abilities than above three groups. This study suggested that the BDNF-loaded plasma-collagen matrix may provide a promising means to resolve either the poor survival and insufficient neuronal differentiation of transplanted exogenous NSCs, or stimulating the intrinsic NSCs to proliferate and differentiate into neurons so as to repair the injured adult CNS.

Optimal time-point for neural stem cell transplantation to delay denervated skeletal muscle atrophy

INTRODUCTION

Transplantation of neural stem cells (NSCs) is a promising treatment to delay denervated skeletal muscle atrophy; however, the optimal time-point between peripheral nerve injury and NSC transplantation needs to be determined.

METHODS

Improvement in rat gastrocnemius muscle function was evaluated after NSCs were transplanted into sectioned distal tibial nerves. We also assessed survival and differentiation. ANOVA was used to compare the mean value of the number of neuron-like cells, cross-sectional area amelioration, the amount of activated fibers, and latency and amplitude of the gastrocnemius compound muscle action potential.

RESULTS

The group in which the NSCs were transplanted 1 week after tibial nerve transection had the largest number of neuron-like cells, maximum cross-sectional area amelioration, and maximum amount of activated gastrocnemius fibers compared with all other groups (P < 0.01).

CONCLUSIONS

The optimal time-point for NSC transplantation for delaying denervated skeletal muscle atrophy is 1 week after severing the nerve.

Modification of the Neurotrophin-3 Gene Promotes Cholinergic Neuronal Differentiation and Survival of Neural Stem Cells Derived from Rat Embryonic Spinal Cord In Vitro and In Vivo

OBJECTIVE: To investigate the effects of the neurotrophin-3 ( NTF3) gene on the survival and differentiation of neural stem cells (NSCs) in vitro and in vivo. METHODS: The NTF3 gene was isolated from rats, amplified by polymerase chain reaction (PCR) and subcloned into the lentiviral vector pWPXL-MOD to construct a lentiviral expression vector pWPXL-MOD— NTF3. Reverse transcription—PCR and Western blotting were used to analyse NTF3 mRNA and protein levels, respectively. Adult rats with sectioned tibial nerves received implants of NSCs transfected with either pWPXL-MOD— NTF3 ( n = 30) or an empty expression vector ( n = 30). In vitro and in vivo cell differentiation and survival were determined by fluorescence immunohistochemistry. RESULTS: Expression of NTF3 significantly increased the differentiation of NSCs into cholinergic neurons both in vitro and in vivo. NTF3-expressing NSCs implanted into the tibial nerve also survived longer than cells without NTF3 gene modification. CONCLUSIONS: The NTF3 gene promoted differentiation of NSCs into cholinergic neurons and enhanced neuronal cell survival. These findings may have clinical implications for cell transplantation therapy in patients with nerve injury.

Neuroprotection of neurotrophin-3 against focal cerebral ischemia/reperfusion injury is regulated by hypoxia-responsive element in rats

Exogenous delivery of the neurotrophin-3 (NT-3) gene may provide a potential therapeutic strategy for ischemic stroke. To investigate the neuroprotective effects of NT-3 expression controlled by 5HRE after focal cerebral ischemia, we constructed a recombinant retrovirus vector (RV) with five copies of hypoxia-responsive elements (5HRE or 5H) and NT-3 and delivered it to the rat brain. Three groups of rats received RV-5H-NT3, RV-5H-EGFP or saline injection. Three days after gene transfer, the rats underwent 90min of transient middle cerebral artery occlusion (tMCAO), followed by 1-28days of reperfusion. Three days after tMCAO, brain NT-3 expression was significantly increased in the RV-5H-NT3-transduced animals compared with the RV-5H-EGFP or saline group, and brain infarct volume was smaller in the RV-5H-NT3-transduced group than the RV-5H-EGFP or saline group. The percentage of TUNEL-positive cells was reduced in RV-5H-NT3-transduced brains compared with the RV-5H-EGFP or saline group 3 and 7days after tMCAO. Furthermore, the neurological status of RV-5H-NT3-transduced rats was better than that of RV-5H-EGFP- or saline-transduced animals from 1day to 4weeks after tMCAO. Our results demonstrated that 5HRE could modulate NT-3 expression in the ischemic brain environment and that the up-regulated NT-3 could effectively improve neurological status following tMCAO due to decreased initial damage. To avoid unexpected side effects, 5HRE-controlled gene expression might be a useful tool for gene therapy of ischemic disorders in the central nervous system.

Hyaluronic acid-based scaffold for central neural tissue engineering

Central nervous system (CNS) regeneration with central neuronal connections and restoration of synaptic connections has been a long-standing worldwide problem and, to date, no effective clinical therapies are widely accepted for CNS injuries. The limited regenerative capacity of the CNS results from the growth-inhibitory environment that impedes the regrowth of axons. Central neural tissue engineering has attracted extensive attention from multi-disciplinary scientists in recent years, and many studies have been carried out to develop cell- and regeneration-activating biomaterial scaffolds that create an artificial micro-environment suitable for axonal regeneration. Among all the biomaterials, hyaluronic acid (HA) is a promising candidate for central neural tissue engineering because of its unique physico-chemical and biological properties. This review attempts to outline current biomaterials-based strategies for CNS regeneration from a tissue engineering point of view and discusses the main progresses in research of HA-based scaffolds for central neural tissue engineering in detail.

Protoplasmic astrocytes enhance the ability of neural stem cells to differentiate into neurons in vitro

Protoplasmic astrocytes have been reported to exhibit neuroprotective effects on neurons, but there has been no direct evidence for a functional relationship between protoplasmic astrocytes and neural stem cells (NSCs). In this study, we examined neuronal differentiation of NSCs induced by protoplasmic astrocytes in a co-culture model. Protoplasmic astrocytes were isolated from new-born and NSCs from the E13-15 cortex of rats respectively. The differentiated cells labeled with neuron-specific marker β-tubulin III, were dramatically increased at 7 days in the co-culture condition. Blocking the effects of brain-derived neurotrophic factor (BDNF) with an anti-BDNF antibody reduced the number of neurons differentiated from NSCs when co-cultured with protoplasmic astrocytes. In fact, the content of BDNF in the supernatant obtained from protoplasmic astrocytes and NSCs co-culture media was significantly greater than that from control media conditions. These results indicate that protoplasmic astrocytes promote neuronal differentiation of NSCs, which is driven, at least in part, by BDNF.

Coseeded Schwann cells myelinate neurites from differentiated neural stem cells in neurotrophin-3-loaded PLGA carriers

Biomaterials and neurotrophic factors represent promising guidance for neural repair. In this study, we combined poly-(lactic acid-co-glycolic acid) (PLGA) conduits and neurotrophin-3 (NT-3) to generate NT-3-loaded PLGA carriers in vitro. Bioactive NT-3 was released stably and constantly from PLGA conduits for up to 4 weeks. Neural stem cells (NSCs) and Schwann cells (SCs) were coseeded into an NT-releasing scaffold system and cultured for 14 days. Immunoreactivity against Map2 showed that most of the grafted cells (>80%) were differentiated toward neurons. Double-immunostaining for synaptogenesis and myelination revealed the formation of synaptic structures and myelin sheaths in the coculture, which was also observed under electron microscope. Furthermore, under depolarizing conditions, these synapses were excitable and capable of releasing synaptic vesicles labeled with FM1-43 or FM4-64. Taken together, coseeding NSCs and SCs into NT-3-loaded PLGA carriers increased the differentiation of NSCs into neurons, developed synaptic connections, exhibited synaptic activities, and myelination of neurites by the accompanying SCs. These results provide an experimental basis that supports transplantation of functional neural construction in spinal cord injury.

Spheroid formation and neural induction in human adipose-derived stem cells on a chitosan-coated surface

The application of stem cells appears to have great therapeutic potential to facilitate nerve regeneration in patients with neurodegenerative disease or spinal cord injury. Human adipose-derived stem cells (hADSCs), a subset of multipotent mesenchymal stem cells, possess the great advantages of an abundant amount of cells, less ethical conflict and minimal invasive surgical procedures to obtain the cells. Chitosan, a naturally derived polysaccharide from chitin, has been widely studied to facilitate and guide the direction of nerve regeneration as a biomaterial for the neural tube. Chitosan also serves as a three-dimensional culture substrate to facilitate cellular sphere formation among various cells but is as yet unexplored in hADSCs. In this study, the ability of hADSCs to transdifferentiate from the mesenchymal into the neural lineage by seeding hADSCs on a chitosan-coated surface to form therapeutic cell spheres was investigated. The optimal seeding density (2 × 10(4) cells/cm(2)) and harvesting time (72 h) to obtain sphere formation were determined by cell viability on a chitosan-coated surface. Expression of neural lineage markers was observed by immunofluorescent staining of nestin, neurofilament heavy chain and glial fibrillary acidic protein. The neural induction potentials were also provoked by replating spheres from primary to tertiary passages. The effect of neural induction in hADSCs on a chitosan-coated surface may help to provide cell sources for facilitating nerve regeneration in future clinical applications.

The effects of different phenotype astrocytes on neural stem cells differentiation in co-culture

Astrocytes were reported to show neuroprotective effects on neurons, but there was no direct evidence for a functional relationship between astrocytes and neural stem cells (NSCs). In this experiments, we examined neuronal differentiation of NSCs induced by protoplasmic and fibrous astrocytes in a co-culture model respectively. Two types of astrocytes and NSCs were isolated from E13 to 15 cortex of rats. The neuronal differentiation of NSCs was examined after co-culture with two kinds of astrocytes. There were more neuronal marker β-tublin III positive cells from NSCs co-cultured with protoplasmic astrocytes. However the differentiated neurons, whether co-cultured with protoplasmic astrocytes or fibrous astrocytes, both expressed glutamate AMPA receptor subunit GluR2 protein and exhibited biological electrical reactivity after stimulated by glutamine. Therefore, these findings indicated that two types of astrocytes could induce the differentiation of NSCs and also possibly induce functional maturation of differentiated neurons, among which protoplasmic astrocytes have the ability to promote neuronal differentiation of NSCs compared with fibrous astrocytes.

Optimal time for passaging neurospheres based on primary neural stem cell cultures

Cultured neural stem cells (NSCs) provide a powerful means for investigating central nervous system disease, neuron development, differentiation, and regeneration. To obtain sufficient neurospheres, subculturing is essential following establishment of the primary NSC culture. Passaging the primary neurospheres is a key issue that is often ignored. We evaluated the influence of different passaging schedules on primary cultured NSCs. Passaging was performed on day 5, 7 or 9. We observed more neurospheres with diameters of 200-250 μm on day 7 than on day 5 or 9. Prolonging the time of primary culture reduced the cell metabolic activity by the MTT assay and cell proliferation by colony-forming assay and the differentiation to neurons from cells at P2 and later decreased. Additionally, more cells were in G0/G1 phase, and higher expression of p16 ( INK4a ) and lower expression of cyclin D1 was found when the time of primary culture was prolonged to 9 days compared to 7-days cultures. Thus, in this study, we established that the optimal time for subculturing aggregated NSCs was on day 7 based on the primary culture.