Collagen nanofibers facilitated presynaptic maturation in differentiated neurons from spinal-cord-derived neural stem cells through MAPK/ERK1/2-Synapsin I signaling pathway

Advances of the MAPK pathway in the treatment of spinal cord injury

Spinal cord injury (SCI) represents a complex pathology within the central nervous system (CNS), leading to severe sensory and motor impairments. It activates various signaling pathways, notably the mitogen-activated protein kinase (MAPK) pathway. Present treatment approaches primarily focus on symptomatic relief, lacking efficacy in addressing the underlying pathophysiological mechanisms. Emerging research underscores the significance of the MAPK pathway in neuronal differentiation, growth, survival, axonal regeneration, and inflammatory responses post-SCI. Modulating this pathway post-injury has shown promise in attenuating inflammation, minimizing apoptosis, alleviating neuropathic pain, and fostering neural regeneration. Given its pivotal role, the MAPK pathway emerges as a potential therapeutic target in SCI management. This review synthesizes current knowledge on SCI pathology, delineates the MAPK pathway's characteristics, and explores its dual roles in SCI pathology and therapeutic interventions. Furthermore, it addresses the existing challenges in MAPK research in the context of SCI, proposing solutions to overcome these hurdles. Our aim is to offer a comprehensive reference for future research on the MAPK pathway and SCI, laying the groundwork for targeted therapeutic strategies.

Identification and Validation of Synapse-related Hub Genes after Spinal Cord Injury by Bioinformatics Analysis

BACKGROUND

Spinal cord injury (SCI) is a neurological disease with high morbidity and mortality. Previous studies have shown that abnormally expressed synapse-related genes are closely related to the occurrence and development of SCI. However, little is known about the interaction of these aberrantly expressed genes and the molecular mechanisms that play a role in the injury response. Therefore, deeply exploring the correlation between synapse-related genes and functional recovery after spinal cord injury and the molecular regulation mechanism is of great significance.

METHODS

First, we selected the function GSE45006 dataset to construct three clinically meaningful gene modules by hierarchical clustering analysis in 4 normal samples and 20 SCI samples. Subsequently, we performed functional and pathway enrichment analyses of key modules.

RESULTS

The results showed that related module genes were significantly enriched in synaptic structures and functions, such as the regulation of synaptic membranes and membrane potential. A protein-protein interaction network (PPI) was constructed to identify 10 hub genes of SCI, and the results showed that Snap25, Cplx1, Stxbp1, Syt1, Rims1, Rab3a, Syn2, Syn1, Cask, Lin7b were most associated with SCI. Finally, these hub genes were further verified by quantitative real-time fluorescence polymerase chain reaction (qRT-PCR) in the spinal cord tissues of the blank group and SCI rats, and it was found that the expression of these hub genes was significantly decreased in the spinal cord injury compared with the blank group (P ≤ 0.05).

CONCLUSION

These results suggest that the structure and function of synapses play an important role after spinal cord injury. Our study helps to understand the underlying pathogenesis of SCI patients further and identify new targets for SCI treatment.

PACAP/PAC1-R activation contributes to hyperalgesia in 6-OHDA-induced Parkinson's disease model rats via promoting excitatory synaptic transmission of spinal dorsal horn neurons

Pain is a common annoying non-motor symptom in Parkinson's disease (PD) that causes distress to patients. Treatment for PD pain remains a big challenge, as its underlying mechanisms are elusive. Pituitary adenylate cyclase-activating polypeptide (PACAP) and its receptor PAC1-R play important roles in regulating a variety of pathophysiological processes. In this study, we investigated whether PACAP/PAC1-R signaling was involved in the mechanisms of PD pain. 6-hydroxydopamine (6-OHDA)-induced PD model was established in rats. Behavioral tests, electrophysiological and Western blotting analysis were conducted 3 weeks later. We found that 6-OHDA rats had significantly lower mechanical paw withdrawal 50% threshold in von Frey filament test and shorter tail flick latency, while mRNA levels of Pacap and Adcyap1r1 (gene encoding PAC1-R) in the spinal dorsal horn were significantly upregulated. Whole-cell recordings from coronal spinal cord slices at L4-L6 revealed that the frequency of spontaneous excitatory postsynaptic currents (sEPSCs) in dorsal horn neurons was significantly increased, which was reversed by application of a PAC1-R antagonist PACAP 6-38 (250 nM). Furthermore, we demonstrated that intrathecal microinjection of PACAP 6-38 (0.125, 0.5, 2 μg) dose-dependently ameliorated the mechanical and thermal hyperalgesia in 6-OHDA rats. Inhibition of PACAP/PAC1-R signaling significantly suppressed the activation of Ca2+/calmodulin-dependent protein kinase II and extracellular signal-regulated kinase (ERK) in spinal dorsal horn of 6-OHDA rats. Microinjection of pAAV-Adcyap1r1 into L4-L6 spinal dorsal horn alleviated hyperalgesia in 6-OHDA rats. Intrathecal microinjection of ERK antagonist PD98059 (10 μg) significantly alleviated hyperalgesia in 6-OHDA rats associated with the inhibition of sEPSCs in dorsal horn neurons. In addition, we found that serum PACAP-38 concentration was significantly increased in PD patients with pain, and positively correlated with numerical rating scale score. In conclusion, activation of PACAP/PAC1-R induces the development of PD pain and targeting PACAP/PAC1-R is an alternative strategy for treating PD pain.

Localisation of oestrogen receptors in stem cells and in stem cell-derived neurons of the mouse

Oestrogen receptors (ER) transduce the effects of the endogenous ligand, 17β-estradiol in cells to regulate a number of important processes such as reproduction, neuroprotection, learning and memory and anxiety. The ERα or ERβ are classical intracellular nuclear hormone receptors while some of their variants or novel proteins such as the G-protein coupled receptor (GPCR), GPER1/GPR30 are reported to localise in intracellular as well as plasma membrane locations. Although the brain is an important target for oestrogen with oestrogen receptors expressed differentially in various nuclei, subcellular organisation and crosstalk between these receptors is under-explored. Using an adapted protocol that is rapid, we first generated neurons from mouse embryonic stem cells. Our immunocytochemistry approach shows that the full length ERα (ERα-66) and for the first time, that an ERα variant, ERα-36, as well as GPER1 is present in embryonic stem cells. In addition, these receptors typically decrease their nuclear localisation as neuronal maturation proceeds. Finally, although these ERs are present in many subcellular compartments such as the nucleus and plasma membrane, we show that they are specifically not colocalised with each other, suggesting that they initiate distinct signalling pathways.

Regulatory Effects of Gradient Microtopographies on Synapse Formation and Neurite Growth in Hippocampal Neurons

Among approaches aiming toward functional nervous system restoration, those implementing microfabrication techniques allow the manufacture of platforms with distinct geometry where neurons can develop and be guided to form patterned connections in vitro. The interplay between neuronal development and the microenvironment, shaped by the physical limitations, remains largely unknown. Therefore, it is crucial to have an efficient way to quantify neuronal morphological changes induced by physical or contact guidance of the microenvironment. In this study, we first devise and assess a method to prepare anisotropic, gradient poly(dimethylsiloxane) micro-ridge/groove arrays featuring variable local pattern width. We then demonstrate the ability of this single substrate to simultaneously profile the morphologcial and synaptic connectivity changes of primary cultured hippocampal neurons reacting to variable physical conditons, throughout neurodevelopment, in vitro. The gradient microtopography enhanced adhesion within microgrooves, increasing soma density with decreasing pattern width. Decreasing pattern width also reduced dendritic arborization and increased preferential axon growth. Finally, decreasing pattern geometry inhibited presynaptic puncta architecture. Collectively, a method to examine structural development and connectivity in response to physical stimuli is established, and potentially provides insight into microfabricated geometries which promote neural regeneration and repair.

Biomaterials in Neurodegenerative Disorders: A Promising Therapeutic Approach

Neurodegenerative disorders (i.e., Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and spinal cord injury) represent a great problem worldwide and are becoming prevalent because of the increasing average age of the population. Despite many studies having focused on their etiopathology, the exact cause of these diseases is still unknown and until now, there are only symptomatic treatments. Biomaterials have become important not only for the study of disease pathogenesis, but also for their application in regenerative medicine. The great advantages provided by biomaterials are their ability to mimic the environment of the extracellular matrix and to allow the growth of different types of cells. Biomaterials can be used as supporting material for cell proliferation to be transplanted and as vectors to deliver many active molecules for the treatments of neurodegenerative disorders. In this review, we aim to report the potentiality of biomaterials (i.e., hydrogels, nanoparticles, self-assembling peptides, nanofibers and carbon-based nanomaterials) by analyzing their use in the regeneration of neural and glial cells their role in axon outgrowth. Although further studies are needed for their use in humans, the promising results obtained by several groups leads us to suppose that biomaterials represent a potential therapeutic approach for the treatments of neurodegenerative disorders.

Biomimetic Polymer-Based Engineered Scaffolds for Improved Stem Cell Function

Scaffolds are considered promising materials for tissue engineering applications due to their unique physiochemical properties. The high porosity and adequate mechanical properties of the scaffolds facilitate greater cell adhesion, proliferation, and differentiation. Stem cells are frequently applied in tissue engineering applications due to their excellent potential. It has been noted that cell functions are profoundly affected by the nature of the extracellular matrix (ECM). Naturally derived ECM contains the bioactive motif that also influences the immune response of the organism. The properties of polymer scaffolds mean they can resemble the native ECM and can regulate cellular responses. Various techniques such as electrospinning and 3D printing, among others, are frequently used to fabricate polymer scaffolds, and their cellular responses are different with each technique. Furthermore, enhanced cell viability, as well as the differentiation ability of stem cells on the surface of scaffolds, opens a fascinating approach to the formation of ECM-like environments for tissue engineering applications.

iTRAQ-Based Proteomics Analysis Reveals the Effect of Rhubarb in Rats with Ischemic Stroke

Background. Rhubarb, a traditional Chinese medicine, promotes viscera and remove blood stasis. Rhubarb is skilled in smoothening meridians, improving blood circulation which exhibits better efficacy on cerebral ischemic stroke. In this study, we aimed to analyze the underlying mechanisms of rhubarb which treated rats of middle cerebral artery occlusion (MCAO) model according to an iTRAQ-based proteomics and bioinformatics analysis. 30 rats were randomly allocated into three groups including sham group (SG), model group (MG), and rhubarb group (RG). Rhubarb group was given a gavage of rhubarb decoction at dose of 3 g/kg and the remaining groups were prepared with normal saline by gavage. Rats from MG and RG were induced into MCAO model. The effects of rhubarb were estimated by Modified Neurological Severity Score (mNSS) and cerebral infarct volume. The brain tissues were measured via the quantitative proteomic approach of iTRAQ coupled to liquid chromatography-tandem mass spectrometry (LC-MS/MS). Furthermore, the bioinformatics analysis of overlapping differentially expression proteins (DEPs) was conducted by DAVID, KEGG, and Cytoscape. Specific selective DEPs were validated by Western blotting. Rats treated with rhubarb after MCAO showed a significant reduction on mNSS and cerebral infarct volume compared with MG. In MG versus SG and RG versus MG, we identified a total of 4578 proteins, of which 287 were DEPs. There were 76 overlapping DEPs between MG versus SG and RG versus MG. Through bioinformatics analysis, 14 associated pathways were searched including cGMP-PKG signaling pathway, tuberculosis, synaptic vesicle cycle, amyotrophic lateral sclerosis, long-term potentiation, and so on. 76 overlapping DEPs mainly involved synaptic vesicle cycling biological processes based on GO annotation. Further, the selective overlapping DEPs were verified at the protein level by using Western blotting. Our present study reveals that rhubarb highlights promising neuroprotective effect. Rhubarb exerts novel therapeutic action via modulating multiple proteins, targets, and pathways.

Nanofibrous scaffolds for the guidance of stem cell-derived neurons for auditory nerve regeneration

Impairment of spiral ganglion neurons (SGNs) of the auditory nerve is a major cause for hearing loss occurring independently or in addition to sensory hair cell damage. Unfortunately, mammalian SGNs lack the potential for autonomous regeneration. Stem cell based therapy is a promising approach for auditory nerve regeneration, but proper integration of exogenous cells into the auditory circuit remains a fundamental challenge. Here, we present novel nanofibrous scaffolds designed to guide the integration of human stem cell-derived neurons in the internal auditory meatus (IAM), the foramen allowing passage of the spiral ganglion to the auditory brainstem. Human embryonic stem cells (hESC) were differentiated into neural precursor cells (NPCs) and seeded onto aligned nanofiber mats. The NPCs terminally differentiated into glutamatergic neurons with high efficiency, and neurite projections aligned with nanofibers in vitro. Scaffolds were assembled by seeding GFP-labeled NPCs on nanofibers integrated in a polymer sheath. Biocompatibility and functionality of the NPC-seeded scaffolds were evaluated in vivo in deafened guinea pigs (Cavia porcellus). To this end, we established an ouabain-based deafening procedure that depleted an average 72% of SGNs from apex to base of the cochleae and caused profound hearing loss. Further, we developed a surgical procedure to implant seeded scaffolds directly into the guinea pig IAM. No evidence of an inflammatory response was observed, but post-surgery tissue repair appeared to be facilitated by infiltrating Schwann cells. While NPC survival was found to be poor, both subjects implanted with NPC-seeded and cell-free control scaffolds showed partial recovery of electrically-evoked auditory brainstem thresholds. Thus, while future studies must address cell survival, nanofibrous scaffolds pose a promising strategy for auditory nerve regeneration.

Wnt3a is critical for endothelial progenitor cell-mediated neural stem cell proliferation and differentiation

The present study aimed to determine whether co-culture with bone marrow‑derived endothelial progenitor cells (EPCs) affects the proliferation and differentiation of spinal cord-derived neural stem cells (NSCs), and to investigate the underlying mechanism. The proliferation and differentiation of the NSCs were evaluated by an MTT cell proliferation and cytotoxicity assay, and immunofluorescence, respectively. The number of neurospheres and the number of β‑tubulin III‑positive cells were detected by microscopy. The wingless‑type MMTV integration site family, member 3a (Wnt3a)/β-catenin signaling pathway was analyzed by western blot analysis and reverse transcription‑quantitative polymerase chain reaction to elucidate the possible mechanisms of EPC‑mediated NSC proliferation and differentiation. The results revealed that co‑culture with EPCs significantly induced NSC proliferation and differentiation. In addition, co‑culture with EPCs markedly induced the expression levels of Wnt3a and β‑catenin and inhibited the phosphorylation of glycogen synthase kinase 3β (GSK‑3β). By contrast, Wnt3a knockdown using a short hairpin RNA plasmid in the EPCs reduced EPC‑mediated NSC proliferation and differentiation, accompanied by inhibition of the EPC‑mediated expression of β‑catenin, and its phosphorylation and activation of GSK‑3β. Taken together, the findings of the present study demonstrated that Wnt3a was critical for EPC‑mediated NSC proliferation and differentiation.

Differences in Cognitive Function of Rats with Traumatic Brain Injuries Following Hyperbaric Oxygen Therapy

Background

Hyperbaric oxygen (HBO) is a historical therapeutic option in the treatment of various types of brain damage. At present, clinical treatment of hypoxic-ischemic injury is giving priority to cognitive training. The effects of HBO on cognitive dysfunction were observed in a controlled cortical impact (CCI) rat model.

Material/Methods

Seventy male SD rats were randomly divided into control (n=10) and intervention (n=60) groups. All rats underwent baseline water maze testing 1 day before modeling, and were retested 8 weeks after modeling. The percentage of residence time during escape latency in the target quadrant and the total time were recorded. Data were analyzed by SPSS 16.0 software. P<0.05 was considered statistically significant.

Results

After 8 weeks, no statistical difference (P>0.05) existed in spatial learning ability in the 3-day and 5-day groups when compared with baseline. The other groups were statistically different by auto-comparison (P<0.05). No statistical difference (P>0.05) in spatial memory existed in the 5-day and 1-week groups when compared with baseline, while a significant difference was noted in the other groups by self-comparison (P<0.05). No statistical difference (P>0.05) was noted in the level of expression of growth-associated protein-43 (GAP-43) and synaptophysin (Syn) in the 1-day group compared with the control group. The remaining groups and the control group were statistically different (P<0.05), while the level of expression of GAP-43 and Syn in the 5-day, 1-week, and 2-week groups was significantly different compared with that in the control group (P<0.01).

Conclusions

If HBO therapy was provided 5–7 days after craniocerebral trauma, there was apparent improvement in cognitive function and neuroplasticity.

Tetrahydroxystilbene glucoside ameliorates memory and movement functions, protects synapses and inhibits α-synuclein aggregation in hippocampus and striatum in aged mice

PURPOSE

To investigate the effects of 2,3,5,4'-tetrahydroxystilbene-2-O-β-D-glucoside (TSG) on the memory and movement functions and its mechanisms related to synapses and α-synuclein in aged mice.

METHODS

The memory ability of mice was detected by step-through passive avoidance task. The movement function was measured by the pole test and rotarod test. Transmission electron microscopy was used to observe the synaptic ultrastructure. Western blotting was applied to measure the expression of synapse-related proteins and α-synuclein.

RESULTS

Intragastrical administration of TSG for 3 months significantly improved the memory and movement functions in aged mice. TSG treatment obviously protected the synaptic ultrastructure and increased the number of synaptic connections in the hippocampal CA1 region and striatum; enhanced the expression of synaptophysin, phosphorylated synapsin I and postsynaptic density protein 95 (PSD95), elevated phosphorylated calcium/calmodulin-dependent protein kinase II (p-CaMKII) expression, and inhibited the overexpression and aggregation of α-synuclein in the hippocampus, striatum and cerebral cortex of aged mice.

CONCLUSION

TSG improved the memory and movement functions in aged mice through protecting synapses and inhibiting α-synuclein overexpression and aggregation in multiple brain regions. The results suggest that TSG may be beneficial to the treatment of ageing-related neurodegenerative diseases.

Biomimetic collagen I and IV double layer Langmuir-Schaefer films as microenvironment for human pluripotent stem cell derived retinal pigment epithelial cells

The environmental cues received by the cells from synthetic substrates in vitro are very different from those they receive in vivo. In this study, we applied the Langmuir-Schaefer (LS) deposition, a variant of Langmuir-Blodgett technique, to fabricate a biomimetic microenvironment mimicking the structure and organization of native Bruch's membrane for the production of the functional human embryonic stem cell derived retinal pigment epithelial (hESC-RPE) cells. Surface pressure-area isotherms were measured simultaneously with Brewster angle microscopy to investigate the self-assembly of human collagens type I and IV on air-subphase interface. Furthermore, the structure of the prepared collagen LS films was characterized with scanning electron microscopy, atomic force microscopy, surface plasmon resonance measurements and immunofluorescent staining. The integrity of hESC-RPE on double layer LS films was investigated by measuring transepithelial resistance and permeability of small molecular weight substance. Maturation and functionality of hESC-RPE cells on double layer collagen LS films was further assessed by RPE-specific gene and protein expression, growth factor secretion, and phagocytic activity. Here, we demonstrated that the prepared collagen LS films have layered structure with oriented fibers corresponding to architecture of the uppermost layers of Bruch's membrane and result in increased barrier properties and functionality of hESC-RPE cells as compared to the commonly used dip-coated controls.

Upregulation of D site of albumin promoter binding protein in the brain of patients with intractable epilepsy

The mechanisms that underlie the pathogenesis of intractable epilepsy (IE) remain to be elucidated. The present study aimed to investigate the expression of D site of albumin promoter binding protein (DBP) and mitogen‑activated protein kinases (MAPKs) in the temporal lobes of patients with IE, in order to examine the possible roles of DBP in the pathogenesis of IE. The expression of DBP and MAPK was detected by immunohistochemistry and double‑label immunofluorescence staining against DBP/MAPK in 35 patients with IE, and the data were compared with those of the 15 controls. The results demonstrated that DBP expression in IE group (0.31±0.03) was significantly higher compared with that in the controls (0.18±0.02; P<0.05) and MAPK expression in the IE group (0.19±0.03) was also higher compared with that in the controls (0.12±0.02; P<0.05). DBP and MAPK were mainly expressed in the cytoplasm of neurons and the double‑label immunofluorescence staining demonstrated that DBP and MAPK expression occurred in the same neurons. Therefore, the expression of DBP and MAPK in epilepsy patients was upregulated, suggesting a possible pathogenetic role in IE.