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Aim: Glucose‐dependent insulinotropic polypeptide (GIP) is a ligand of glucose‐dependent insulinotropic polypeptide receptor (GIPR) that plays an important role in the digestive system. In recent years, GIP has been regarded as a hormone‐like peptide to regulate the local metabolic environment. In this study, we investigated the antioxidant role of GIP on the neuron and explored the possible mechanism. Methods: Cell counting Kit‐8 (CCK‐8) was used to measure cell survival. TdT‐mediated dUTP Nick‐End Labeling (TUNEL) was used to detect apoptosis in vitro and in vivo. Reactive oxygen species (ROS) levels were probed with 2', 7'‐Dichloro dihydrofluorescein diacetate (DCFH‐DA), and glucose intake was detected with 2‐NBDG. Immunofluorescence staining and western blot were used to evaluate the protein level in cells and tissues. Hematoxylin‐eosin (HE) staining, immunofluorescence staining and tract‐tracing were used to observe the morphology of the injured spinal cord. Basso‐Beattie‐Bresnahan (BBB) assay was used to evaluate functional recovery after spinal cord injury. Results: GIP reduced the ROS level and protected cells from apoptosis in cultured neurons and injured spinal cord. GIP facilitated wound healing and functional recovery of the injured spinal cord. GIP significantly improved the glucose uptake of cultured neurons. Meanwhile, inhibition of glucose uptake significantly attenuated the antioxidant effect of GIP. GIP increased glucose transporter 3 (GLUT3) expression via up‐regulating the level of hypoxia‐inducible factor 1α (HIF‐1α) in an Akt‐dependent manner. Conclusion: GIP increases GLUT3 expression and promotes glucose intake in neurons, which exerts an antioxidant effect and protects neuronal cells from oxidative stress both in vitro and in vivo. [ABSTRACT FROM AUTHOR]

Spinal cord injury (SCI) has a high disability rate and poor treatment efficacy and severely affects the health and daily life of patients. Improving the local microenvironment after SCI is crucial for restoring the normal physiological function of the spinal cord. In this study, the injectable near-infrared (NIR) photothermal responsive drug-loaded multiwalled carbon nanotubes (DMWCNTs) containing hydrogel microspheres were prepared by microfluidic technology for SCI treatment. Specifically, paclitaxel (PTX) and vascular endothelial growth factor (VEGF) were loaded into dopamine-modified DMWCNTs, which were then further compounded into gellan gum (GG) by using microfluidic technology to obtain [PTX/VEGF]@DMWCNTs/GG microspheres. The physicochemical properties of the microspheres were characterized using various methods, including transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, optical microscopy, and scanning electron microscopy (SEM). Results showed that microspheres with good injectability and controllable drug release were successfully prepared by using microfluidic technology. The presence of MWCNTs endowed the microspheres with photothermal responsiveness, which led to more drug release under NIR irradiation. The cytotoxicity test results showed that the microspheres had no obvious cytotoxicity and the drug-loaded MWCNTs containing hydrogel microspheres could promote the differentiation of neural stem cells (NSCs). Immunofluorescence results in rats with hemisectioned SCI showed that the microspheres promoted the differentiation of NSCs and the growth of neurons and inhibited the formation of astrocytes and glial scars at the lesion site. In conclusion, the injectable near-infrared photothermal responsive drug-loaded multiwalled carbon nanotube hydrogel microspheres prepared in this study exhibit a promoting effect on SCI repair and provide a strategy for developing transplantation materials for SCI treatment. [ABSTRACT FROM AUTHOR]

Due to the complex spatial‐temporal pathophysiology of spinal cord injury (SCI), effective modulation of SCI‐specific inflammatory pathogenesis to achieve desirable therapeutic effects on functional recovery still remains challenging. Herein, cell‐enhanced photocrosslinked silk fibroin hydrogels with extracellular matrix‐mimicking cues of mechanical properties and RGD (Arg‐Gly‐Asp) signals are gelled in situ to fill the lesion site to modulate injury‐induced neuroinflammation and promote neurite regrowth after SCI. The bionic hydrogel system provides biomimetic mechanical cues to promote neuronal differentiation of neural stem/progenitor cells (NPCs) and neurite growth by activating YAP nuclear expression. Importantly, favored by the strong capacity of silk fibroin hydrogels on macrophage/microglia recruitment, NPCs encapsulated hydrogel (NPCs@SFRGD0.1) effectively promotes recruited macrophages/microglia to M2 polarization in the lesion site by releasing S100A4 and thereby remodels the inflammatory microenvironment after SCI. Moreover, NPCs@SFRGD0.1 successfully reduces glial scar formation and accelerates corticospinal tract axon regrowth to improve locomotor recovery. Overall, this work contributes to illustrating the therapeutic mechanism of NPCs development based biomaterial therapies on modulating inflammatory microenvironment and this NPCs enhanced silk fibroin hydrogel provides a promising therapeutic strategy for SCI. [ABSTRACT FROM AUTHOR]

Aims: This study aimed to evaluate the effects of the depletion of SAM and SH3 domain‐containing protein 1 (SASH1) on functional recovery after spinal cord injury (SCI) and to investigate the possible mechanism of SASH1 knockdown in astrocytes facilitating axonal growth. Methods: SCI model was established in adult rats. SASH1 small interfering RNA (siSASH1) was used to investigate its function. Hindlimb motor function was evaluated by the Basso‐Bresnahan‐Beattie (BBB) assay. The gene expressions were evaluated by the methods of qRT‐PCR, Western‐blotting, ELISA, and immunohistochemistry. Results: SASH1 knockdown improved the BBB scores after SCI and significantly reduced GFAP expression. In cultured spinal astrocytes, siSASH1 treatment decreased interferon‐γ release and increased brain‐derived neurotrophic factor (BDNF) release. When cocultured with SASH1‐knockdown astrocytes, axonal growth increased. The neuronal tropomyosin receptor kinase B (BDNF receptor) expression increased, especially in the axonal tips. SASH1 expression increased while NSCs differentiated into glial cells, instead of neurons. After SASH1 depletion, differentiated NSCs maintained a higher level of Nestin protein and an increase in BDNF release. Conclusions: These results indicate that SASH1 acts as an astrocytic differentiation‐maintaining protein, and SASH1 downregulation limits glial activation and contributes toward functional recovery after SCI. [ABSTRACT FROM AUTHOR]

Spinal cord injury (SCI), one of the most severe types of neurological damage, results in persistent motor and sensory dysfunction and involves complex gene alterations. Circular RNAs (circRNAs) are a recently discovered class of regulatory molecules, and their roles in SCI still need to be addressed. This study comprehensively investigated circRNA alterations in rats across a set time course (days 0, 1, 3, 7, 14, 21, and 28) after hemisection SCI at the right T9 site. A total of 360 differentially expressed circRNAs were identified using RNA sequencing. From these, the functions of the exonic circRNA_01477 were further explored in cultured spinal cord astrocytes. Knockdown of circRNA_01477 significantly inhibited astrocyte proliferation and migration. The circRNA_01477/microRNAs (miRNA)/messenger RNA (mRNA) interaction network was visualized following microarray assay. Among the downregulated differentially expressed mRNAs, four of the seven validated genes were controlled by miRNA-423-5p. We then demonstrated that miRNA-423-5p is significantly upregulated after circRNA_01477 depletion. In summary, this study provides, for the first time, a systematic evaluation of circRNA alterations following SCI and an insight into the transcriptional regulation of the genes involved. It further reveals that circRNA_01477/miR-423-5p could be a key regulator involved in regulating the changeable regeneration environment that occurs during recovery from SCI. [ABSTRACT FROM AUTHOR]

Spinal cord injury (SCI) is a challenging clinical problem worldwide. The cellular state and molecular expression in spinal cord tissue after injury are extremely complex and closely related to functional recovery. However, the spatial and temporal changes of gene expression and regulation in various cell types after SCI are still unclear. Here, we collected the rostral and caudal regions to the lesion at 11 time points over a period of 28 days after rat hemisection SCI. Combining whole-transcriptome sequencing and bioinformatic analysis, we identified differentially expressed genes (DEGs) between spinal cord tissue from injured and sham-operated animals. Significantly altered biological processes were enriched from DEGs in astrocytes, microglia, oligodendrocytes, immune cells, and vascular systems after SCI. We then identified dynamic trends in these processes using the average expression profiles of DEGs. Gene expression and regulatory networks for selected biological processes were also constructed to illustrate the complicate difference between rostral and caudal tissues. Finally, we validated the expressions of some key genes from these networks, including α-synuclein, heme oxygenase 1, bone morphogenetic protein 2, activating transcription factor 3, and leukemia inhibitory factor. Collectively, we provided a comprehensive network of gene expression and regulation to shed light on the molecular characteristics of critical biological processes that occur after SCI, which will broaden the understanding of SCI and facilitate clinical therapeutics for SCI. [ABSTRACT FROM AUTHOR]

Neurons require a constant increase in protein synthesis during axonal growth and regeneration. AKT-mTOR is a central pathway for mammalian cell survival and regeneration. Fidgetin (Fign) is an ATP-dependent microtubule (MT)-severing enzyme whose functions are associated with neurite outgrowth, axon regeneration and cell migration. Although most previous studies have indicated that depletion of Fign is involved in those biological activities by increasing labile MT mass, it remains unknown whether mTOR activation contributes to this process. Here, we showed that depletion of Fign enhanced p-mTOR/p-S6K activation, and the mTOR inhibitor Rapamycin inhibited axon outgrowth and p-rpS6 activation. We then investigated the effects of neuronal-specific Fign deletion in a rat spinal cord hemisection model by injecting syn -GFP Fign shRNA virus. BBB values revealed an improvement in functional recovery. The p-mTOR was activated along with neuronal Fign depletion. The syn-mCherry virus showed more sprouting neurites entering the injury region, which was confirmed by immunostaining GAP43 protein. Further, we showed that Fign siRNA treatment promoted axon outgrowth and branching, whose underlying mechanism was firstly attributed to local activation of the mTOR pathway, and increased MT dynamicity. Finally, considering L-leucine, promotes axonal growth and neuronal survival, we applied L-leucine with Fign depletion after spinal cord injury or in chondroitin sulfate proteoglycan inhibitory molecules. The phenomenon of synergistically augmented axon regeneration was observed. In summary, our results indicated a novel local mTOR pathway for fidgetin to impact axon growth and provided a combined strategy in SCI. • Depletion of fidgetin, increased axonal length and branching via local mTOR activation, and together with L-leu augmented axon regeneration. [ABSTRACT FROM AUTHOR]