Spinal cord injury disrupts the connections between the brain and spinal cord, often resulting in the loss of sensory and motor function below the lesion site. The most important reason for such permanent functional deficits is the failure of injured axons to regenerate after injury. In principle, the functional recovery could be achieved by two forms of axonal regrowth: the regeneration of lesioned axons which will reconnect with their original targets and the sprouting of spared axons that form new circuits and compensate for the lost function. Our recent studies reveal the activity of the mammalian target of rapamycin (mTOR) pathway, a major regulator of new protein synthesis, as a critical determinant of axon regrowth in the adult retinal ganglion neurons[1]. In this review, I summarize current understanding of the cellular and molecular mechanisms that control the intrinsic regenerative ability of mature neurons.

Intrinsic control of axon regeneration

Role of IL-6 in the regulation of neuronal development, survival and function.

Amyotrophic lateral sclerosis overlapping with frontotemporal dementia (ALS/FTD) is a fatal and currently untreatable disease characterized by rapid cognitive decline and paralysis. Elucidating initial cellular pathologies is central to therapeutic target development, but obtaining samples from presymptomatic patients is not feasible. Here, we report the development of a cerebral organoid slice model derived from human induced pluripotent stem cells (iPSCs) that recapitulates mature cortical architecture and displays early molecular pathology of C9ORF72 ALS/FTD. Using a combination of single-cell RNA sequencing and biological assays, we reveal distinct transcriptional, proteostasis and DNA repair disturbances in astroglia and neurons. We show that astroglia display increased levels of the autophagy signaling protein P62 and that deep layer neurons accumulate dipeptide repeat protein poly(GA), DNA damage and undergo nuclear pyknosis that could be pharmacologically rescued by GSK2606414. Thus, patient-specific iPSC-derived cortical organoid slice cultures are a reproducible translational platform to investigate preclinical ALS/FTD mechanisms as well as novel therapeutic approaches.

/pdf/human-als-ftd-brain-organoid-slice-cultures-display-distinct-2mq7rash23.pdf

Human ALS/FTD brain organoid slice cultures display distinct early astrocyte and targetable neuronal pathology

Neurological degeneration after neuroinflammation, such as that resulting from Alzheimer’s disease (AD), stroke, multiple sclerosis (MS), and post-traumatic brain injury (TBI), is typically associated with high mortality and morbidity and with permanent cognitive dysfunction, which places a heavy economic burden on families and society. Diagnosing and curing these diseases in their early stages remains a challenge for clinical investigation and treatment. Recent insight into the onset and progression of these diseases highlights the permeability of the blood–brain barrier (BBB). The primary factor that influences BBB structure and function is inflammation, especially the main cytokines including IL-1β, TNFα, and IL-6, the mechanism on the disruption of which are critical component of the aforementioned diseases. Surprisingly, the main cytokines from systematic inflammation can also induce as much worse as from neurological diseases or injuries do. In this review, we will therefore discuss the physiological structure of BBB, the main cytokines including IL-1β, TNFα, IL-6, and their mechanism on the disruption of BBB and recent research about the main cytokines from systematic inflammation inducing the disruption of BBB and cognitive impairment, and we will eventually discuss the need to prevent the disruption of BBB.

New insight into neurological degeneration: Inflammatory cytokines and blood–brain barrier

Retinitis pigmentosa (RP) is genetically heterogeneous retinopathy caused by photoreceptor cell death and retinal pigment epithelial atrophy that eventually results in blindness in bilateral eyes. Various photoreceptor cell death types and pathological phenotypic changes that have been disclosed in RP demand in-depth research of its pathogenic mechanism that may account for inter-patient heterogeneous responses to mainstream drug treatment. As the primary method for studying the genetic characteristics of RP, molecular biology has been widely used in disease diagnosis and clinical trials. Current technology iterations, such as gene therapy, stem cell therapy, and optogenetics, are advancing towards precise diagnosis and clinical applications. Specifically, technologies, such as effective delivery vectors, CRISPR/Cas9 technology, and iPSC-based cell transplantation, hasten the pace of personalized precision medicine in RP. The combination of conventional therapy and state-of-the-art medication is promising in revolutionizing RP treatment strategies. This article provides an overview of the latest research on the pathogenesis, diagnosis, and treatment of retinitis pigmentosa, aiming for a convenient reference of what has been achieved so far.

https://www.mdpi.com/1422-0067/23/9/4883/pdf?version=1651551235

Retinitis Pigmentosa: Progress in Molecular Pathology and Biotherapeutical Strategies

CNTF-STAT3-IL-6 Axis Mediates Neuroinflammatory Cascade across Schwann Cell-Neuron-Microglia.

Microglial activation occurs in divergent neuropathological conditions. Such microglial event has the key involvement in the progression of CNS diseases. However, the transcriptional mechanism governing microglial activation remains poorly understood. Here, we investigate the microglial response to traumatic injury-induced neurodegeneration by the 3D fluorescence imaging technique. We show that transcription factors IRF8 and PU.1 are both indispensible for microglial activation, as their specific post-developmental deletion in microglia abolishes the process. Mechanistically, we reveal that IRF8 and PU.1 directly target the gene transcription of each other in a positive feedback to sustain their highly enhanced expression during microglial activation. Moreover, IRF8 and PU.1 dictate the microglial response by cooperatively acting through the composite IRF-ETS motifs that are specifically enriched on microglial activation-related genes. This action of cooperative transcription can be further verified biochemically by the synergetic binding of IRF8 and PU.1 proteins to the composite-motif DNA. Our study has therefore elucidated the central transcriptional mechanism of microglial activation in response to neurodegenerative condition.

https://link.springer.com/content/pdf/10.1007/s13238-018-0599-3.pdf

Transcriptional mechanism of IRF8 and PU.1 governs microglial activation in neurodegenerative condition.

Studying the upper critical field (µ0Hc2) and its anisotropy of superconductors is of great importance because it can provide an unusual insight into the pair-breaking mechanism. Since Fe1+yTe1−xSex exhibits the high µ0Hc2 and small anisotropic superconductivity, it has attracted considerable attention. However, some issues related to µ0Hc2 are still unknown, including the effect of excess Fe content on µ0Hc2 behavior and the origin of the crossover of the µ0Hc2c - T and µ0Hc2ab - T curves. In this work, the value of µ0Hc2 of Fe1+yTe0.6Se0.4 single crystals with controlled amounts of excess Fe was obtained by resistivity measurements over a wide range of temperatures down to ∼1.5 K, and magnetic fields up to ∼60 T. The crossover of the µ0Hc2c - T and µ0Hc2ab - T curves was found to be independent of the excess Fe content. The angle dependence of µ0Hc2 was also checked. The µ0Hc2(θ) symmetry at higher temperature near Tc could be fitted by anisotropic G-L model, and novel fourfold symmetry of µ0Hc2 at lower temperature was found. Based on our spin-orientation-locking pairing model, the crossover behavior originates from the anisotropic spin-paramagnetic effect, and the novel four-fold symmetry of µ0Hc2 could be understood by the theoretical analysis. 

Novel Anisotropy of Upper Critical Fields in Fe1+Te0.6Se0.4


 The second magnetization peak (SMP) appears in most superconductors, and is crucial for the understanding of vortex physics as well as the application. Although it is well known that SMP is related to the type and quantity of disorder/defects, the mechanism has not been universally understood. In this work, we selected three stoichiometric superconducting RbCa$_2$Fe$_4$As$_4$F$_2$ single crystals with identical superconducting critical temperature $T_\text{c}$ $\sim$ 31 K and similar self-field critical current density $J_\text{c}$, but with different amounts of disorder/defects, to study the SMP effect. It is found that only the sample S2 with moderate disorder/defects shows significant SMP effect. The evolution of the normalized pinning force density $f_\text{p}$ demonstrates that the dominant pinning mechanism changes from the weak pinning at low temperatures to strong pinning at high temperatures. The microstructure study for sample S2 reveals some expanded Ca$_2$F$_2$ layers and dislocation defects in RbFe$_2$As$_2$ layers. The normalized magnetic relaxation results indicate that SMP is strongly associated with the elastic to plastic (E-P) vortex transition. As temperature increases, the SMP gradually evolves into a step-like shape and then becomes a sharp peak near the irreversibility field similar to what is usually observed in low temperature superconductors. Our findings connect the low field SMP of high temperature superconductors and the high field peak of low temperature superconductors, revealing the possible universal origin related to the E-P phase transition.

Anomalous second magnetization peak in 12442-type RbCa$_2$Fe$_4$As$_4$F$_2$ superconductors

Studying the upper critical field ($\mu_0$$H$$_{\rm{c2}}$) and its anisotropy of superconductors is of great importance because it can provide an unusual insight into the pair-breaking mechanism. Since Fe$_{1+y}$Te$_{1-x}$Se$_x$ exhibits the high $\mu_0$$H$$_{\rm{c2}}$ and small anisotropic superconductivity, it has attracted considerable attention. However, some issues related to $\mu_0$$H$$_{\rm{c2}}$ are still unknown, including the effect of excess Fe content on $\mu_0$$H$$_{\rm{c2}}$ behavior and the origin of the crossover of the $\mu_0H_{\rm{c2}}^c $ -- $ T$ and $\mu_0H_{\rm{c2}}^{ab}$ -- $T$ curves. In this work, the value of $\mu_0$$H$$_{\rm{c2}}$ of Fe$_{1+y}$Te$_{0.6}$Se$_{0.4}$ single crystals with controlled amounts of excess Fe was obtained by resistivity measurements over a wide range of temperatures down to $\sim$ 1.5 K, and magnetic fields up to $\sim$ 60 T. The crossover of the $\mu_0H_{\rm{c2}}^c $ -- $ T$ and $\mu_0H_{\rm{c2}}^{ab}$ -- $T$ curves was found to be independent of the excess Fe content. The angle dependence of $\mu_0H_{\rm{c2}}$ was also checked. The $\mu_0H_{\rm{c2}}(\theta)$ symmetry at higher temperature near $T_c$ could be fitted by anisotropic G-L model, and novel fourfold symmetry of $\mu_0H_{\rm{c2}}$ at lower temperature was found. Based on our spin-locking pairing model, the crossover behavior originates from the anisotropic spin-paramagnetic effect, and the novel fourfold symmetry of $\mu_0H_{\rm{c2}}$ could be understood by our extended anisotropic G-L model.

Novel Anisotropy of Upper Critical Fields in Fe$_{1+y}$Te$_{0.6}$Se$_{0.4}$

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