Upregulated expression of Nogo-A and NgR in an experimental model of focal microgyria regulates the migration, proliferation and self-renewal of subventricular zone neural progenitors

Trillium tschonoskii rhizome saponin improves spatial learning and memory by enhancing neurovascular restorative in ischemic rats

BACKGROUND

Trillium tschonoskii rhizome saponins (TSTT) has been significantly effective in treating traumatic injury, neurasthenia, cancer and inflammatory diseases as a folk medicine. However, the mechanism regarding to TSTT induced the neurovascular restorative after ischemia is without fully elucidated.

PURPOSE

This research was constructed to study the value of TSTT in promoting endogenous repair of neurovascular and augmenting the ability of spatial study and memory retention in ischaemic rats.

STUDY DESIGN

The improvement of TSTT on cerebral infraction and perfusion was observed by magnetic resonance imaging (MRI) experiments and the molecular mechanisms were further explored.

METHODS

First, rats were ligated the middle cerebral artery to construct a permanent ischaemia model, subsequently intragastric injection administrated with TSTT (120, 60, 30 mg kg-1) at 6 h after operation, then once a day during next 30 days. Morris water maze was applied to observe the neurobehavioral changes. Multimodal MRI sequences were performed to monitoring brain injuries as well as cerebral blood flow. Histopathological staining was employed to evaluate the morphological changes of neurons. Transmission electron microscopy (TEM) was employed to detect the neurons, vascular structure, and synapse. Immunofluorescent staining was utilized to evaluate the endogenous repair progress. The axonal growth-inhibitors and axonal guidance cues were analyzed using western blotting.

RESULTS

Contrast to the model group, TSTT declined the infarction and elevated the parenchymal volume. Notably, treated with TSTT significantly decreased the ADC (ipsilateral/contralateral). In histopathologic examination, TSTT prominently boosted amounts of cortical and striatal nerve cells and protected ultrastructure of neurovascular unit. According with results of nuclear magnetic imaging, TSTT enhanced endogenous repair progress. Especially, TSTT treatments obviously inhibited protein levels of NogoA/NgR/RhoA/ROCK2, accompanied by increased expression of Netrin/DCC and Slit2/Robo1.

CONCLUSION

To sum up, our data illustrated that TSTT promoted cerebral reestablishment. The above result was in line with improving cerebral blood flow, elevated integrity of neurovascular structure, accelerating endogenous restoration and impairing the axonal growth inhibitors NogoA/NgR/RhoA/ROCK2 signaling, thereby improving poststroke learning and memory.

Identification and verification of key molecules in the epileptogenic process of focal cortical dysplasia

Focal cortical dysplasia (FCD) represents a common developmental malformation associated with drug-resistant epilepsy (DRE) among children. However, the exact molecular mechanisms behind this condition are still unclear. In our study, FCD-associated microarray data from the Gene Expression Omnibus (GEO) database were analyzed. A comprehensive series of bioinformatics analyses were conducted, including screening for differentially expressed genes (DEGs), functional enrichment analysis, weighted gene co-expression network analysis (WGCNA), and protein-protein interaction (PPI) analysis. Subsequently, a freezing lesion (FL) rat model was developed to validate expression levels of hub genes along with the molecular pathways behind FCD epileptogenicity. 320 DEGs were identified, and functional enrichment analysis revealed significant enrichment of these DEGs in "Neuroinflammatory response", "Cytokine production involved in immune response", and "Macrophage activation". Ultimately, 5 potential hub genes (CYBB, ITGAM, FCG3A, LY86, and CD86) were pinpointed. Notably, 4 hub genes (CYBB, ITGAM, FCG3A, and CD86) were validated in in vivo experiments, suggesting possible associations with neuroinflammation triggered by microglia. This underscores the tight relationship between microglia-induced neuroinflammation and the pathological progression of epileptic seizures in FCD. ITGAM, FCG3A, CD86, CYBB, and LY86 may emerge as promising candidate biomarkers, influencing diagnostic and therapeutic strategies.

Neurite Outgrowth Inhibitor (NogoA) Is Upregulated in White Matter Lesions of Complex Cortical Malformations

Complex cortical malformations (CCMs), such as hemimegalencephaly and polymicrogyria, are associated with drug-resistant epilepsy and developmental impairment. They share certain neuropathological characteristics including mammalian target of rapamycin (mTOR) activation and an atypical number of white matter neurons. To get a better understanding of the pathobiology of the lesion architecture, we investigated the role of neurite outgrowth inhibitor A (NogoA), a known regulator of neuronal migration. Epilepsy surgery specimens from 16 CCM patients were analyzed and compared with sections of focal cortical dysplasia IIB (FCD IIB, n = 22), tuberous sclerosis complex (TSC, n = 8) as well as healthy controls (n = 15). Immunohistochemistry was used to characterize NogoA, myelination, and mTOR signaling. Digital slides were evaluated automatically with ImageJ. NogoA staining showed a significantly higher expression within the white matter of CCM and FCD IIB, whereas cortical tubers presented levels similar to controls. Further analysis of possible associations of NogoA with other factors revealed a positive correlation with mTOR and seizure frequency. To identify the main expressing NogoA cell type, double staining revealed dysmorphic neuronal white matter cells. Increased NogoA expression is associated with profound inhibition of neuritic sprouting and therefore contributes to a decrease in neuronal network complexity in CCM patients.

Dynamic Changes in the Neurogenic Potential in the Ventricular-Subventricular Zone of Common Marmoset during Postnatal Brain Development

Even after birth, neuronal production continues in the ventricular-subventricular zone (V-SVZ) and hippocampus in many mammals. The immature new neurons ("neuroblasts") migrate and then mature at their final destination. In humans, neuroblast production and migration toward the neocortex and the olfactory bulb (OB) occur actively only for a few months after birth and then sharply decline with age. However, the precise spatiotemporal profiles and fates of postnatally born neurons remain unclear due to methodological limitations. We previously found that common marmosets, small nonhuman primates, share many features of V-SVZ organization with humans. Here, using marmosets injected with thymidine analogue(s) during various postnatal periods, we demonstrated spatiotemporal changes in neurogenesis during development. V-SVZ progenitor proliferation and neuroblast migration toward the OB and neocortex sharply decreased by 4 months, most strikingly in a V-SVZ subregion from which neuroblasts migrated toward the neocortex. Postnatally born neurons matured within a few months in the OB and hippocampus but remained immature until 6 months in the neocortex. While neurogenic activity was sustained for a month after birth, the distribution and/or differentiation diversity was more restricted in 1-month-born cells than in the neonatal-born population. These findings shed light on distinctive features of postnatal neurogenesis in primates.

The Nogo receptor inhibits proliferation, migration and axonal extension by transcriptionally regulating WNK1 in PC12 cells

Neuronal regeneration and axonal regrowth mechanisms in the injured mammalian central nervous system are largely unknown. As part of a major pathway for inhibiting axonal regeneration, activated neuronal glycosylphosphatidylinositol-anchored Nogo receptor (NgR) interacts with LINGO-1 and p75NTR to form a complex at the cell surface. However, it was found in our previous report that upregulation of NgR stimulated by injury plays a key role in neuronal regeneration in the neonatal cortex freeze-lesion model, but its downstream signalling remains elusive. In the present study, the novel regulatory role of NgR in a serine-threonine kinase WNK1 was identified. NgR's transcriptional regulation of WNK1 was identified by RT-qPCR and semiquantitative western blot after the overexpression or knockdown of NgR, and the regulation is specific to WNK1, which is not the same for its family members, WNK2, WNK3 and WNK4. Furthermore, NgR inhibition by NEP fails to affect WNK1, which indicates that WNK1 functions outside of the Nogo-A/NgR pathway. By performing a proliferation, migration and axonal extension assay, we also identified that overexpressed NgR critically regulated these processes and impairment by overexpressing NgR was rescued with coexpression of WNK1, indicating the partial role of WNK1 in NgR-mediated morphological regulation. Our study identifies a separation of functions for the NgR-regulated WNK1 in mediating proliferation, migration and axonal extension in PC12 cells as well as a specific regulatory role between NgR and WNK1 that is important for recovery from central nervous system injury.