Brain Pathology最新文献

Demyelination of corticospinal tract neurons contributes to long-term disability after cortical stroke. Nonetheless, poststroke myelin loss has not been addressed as a therapeutic target, so far. We hypothesized that an antibody-mediated inhibition of the Nogo receptor-interacting protein (LINGO-1, leucine-rich repeat and immunoglobulin domain-containing Nogo receptor-interacting protein) may counteract myelin loss, enhance remyelination and axonal growth, and thus promote functional recovery following stroke. To verify this hypothesis, mice were subjected to photothrombotic stroke and received either an antibody against LINGO-1 (n = 19) or a control treatment (n = 18). Behavioral tests were performed to assess the effects of anti-LINGO-1 treatment on the functional recovery. Seven weeks after stroke, immunohistochemical analyses were performed to analyze the effect of anti-LINGO-1 treatment on myelination and axonal loss of corticospinal tract neurons, proliferation of oligodendrocytes and neurogenesis. Anti-LINGO-1 treatment resulted in significantly improved functional recovery (p < 0.0001, repeated measures analysis of variance), and increased neurogenesis in the hippocampus and subventricular zone of the ipsilateral hemisphere (p = 0.0094 and p = 0.032, t-test). Notably, we observed a significant increase in myelin (p = 0.0295, t-test), platelet-derived growth factor receptor α-positive oligodendrocyte precursor cells (p = 0.0356, t-test) and myelinating adenomatous polyposis coli-positive cells within the ipsilateral internal capsule of anti-LINGO-1-treated mice (p = 0.0021, t-test). In conclusion, we identified anti-LINGO-1 as the first neuroregenerative treatment that counteracts poststroke demyelination of corticospinal tract neurons, presumably by increased proliferation of myelin precursor cells, and thereby improves functional recovery. Most importantly, our study presents myelin loss as a novel therapeutic target following stroke.

The prognosis for many pediatric brain tumors, including cerebellar medulloblastoma (MB), remains dismal but there is promise in new therapies. We have previously generated a mouse model developing spontaneous MB at high frequency, Ptch1^+/−/Tis21^−/−. In this model, reproducing human tumorigenesis, we identified the decline of the Cxcl3 chemokine in cerebellar granule cell precursors (GCPs) as responsible for a migration defect, which causes GCPs to stay longer in the proliferative area rather than differentiate and migrate internally, making them targets of transforming insults. We demonstrated that 4-week Cxcl3 infusion in cerebella of 1-month-old mice, at the initial stage of MB formation, forces preneoplastic GCPs (pGCPs) to leave lesions and differentiate, with a complete suppression of MB development. In this study, we sought to verify the effect of 4-week Cxcl3 treatment in 3-month-old Ptch1^+/−/Tis21^−/− mice, when MB lesions are at an advanced, irreversible stage. We found that Cxcl3 treatment reduces tumor volumes by sevenfold and stimulates the migration and differentiation of pGCPs from the lesion to the internal cerebellar layers. We also tested whether the pro-migratory action of Cxcl3 favors metastases formation, by xenografting DAOY human MB cells in the cerebellum of immunosuppressed mice. We showed that DAOY cells express the Cxcl3 receptor, Cxcr2, and that Cxcl3 triggers their migration. However, Cxcl3 did not significantly affect the frequency of metastases or the growth of DAOY-generated MBs. Finally, we mapped the expression of the Cxcr2 receptor in human MBs, by evaluating a well-characterized series of 52 human MBs belonging to different MB molecular subgroups. We found that Cxcr2 was variably expressed in all MB subgroups, suggesting that Cxcl3 could be used for therapy of different MBs.

Although the concept that the blood–brain barrier (BBB) plays an important role in the etiology and pathogenesis of Alzheimer's disease (AD) has become increasingly accepted, little is known yet about how it actually contributes. We and others have recently identified a novel functionally distinct subset of BBB pericytes (PCs). In the present study, we sought to determine whether these PC subsets differentially contribute to AD-associated pathologies by immunohistochemistry and amyloid beta (Aβ) peptidomics. We demonstrated that a disease-associated PC subset (PC2) expanded in AD patients compared to age-matched, cognitively unimpaired controls. Surprisingly, we found that this increase in the percentage of PC2 (%PC2) was correlated negatively with BBB breakdown in AD patients, unlike in natural aging or other reported disease conditions. The higher %PC2 in AD patients was also correlated with a lower Aβ42 plaque load and a lower Aβ42:Aβ40 ratio in the brain as determined by immunohistochemistry. Colocalization analysis of multicolor confocal immunofluorescence microscopy images suggests that AD patient with low %PC2 have higher BBB breakdown due to internalization of Aβ42 by the physiologically normal PC subset (PC1) and their concomitant cell death leading to more vessels without PCs and increased plaque load. On the contrary, it appears that PC2 can secrete cathepsin D to cleave and degrade Aβ built up outside of PC2 into more soluble forms, ultimately contributing to less BBB breakdown and reducing Aβ plaque load. Collectively our data shows functionally distinct mechanisms for PC1 and PC2 in high Aβ conditions, demonstrating the importance of correctly identifying these populations when investigating the contribution of neurovascular dysfunction to AD pathogenesis.

Early diagnosis of late-onset Alzheimer's disease (AD) by peripheral biomarkers remains a challenge; many have been proposed, but none have been evaluated in a prospective manner. CLUSTERIN (CLU), a chaperone protein expressed in the brain and found in relatively high concentrations in plasma, is a promising candidate. CLU contributes to the elimination of β-amyloid (Aβ), which is associated to neurofibrillary tangles and to the genetic risk for AD. We performed a longitudinal measurement of CLU in the brain and the plasma in 3xTgAD mice. Assessment of CLU was also conducted in 12-month-old TgF344-AD rats. In humans, brain CLU was measured in non-demented and in AD subjects. The plasma CLU was longitudinally measured in four cohorts defined as healthy controls that remained stable, healthy controls that presented a cognitive decline between the two measures, mild cognitive impairment (MCI) that presented a cognitive decline between the two measures and AD. A validation cohort composed of 19 MCI was used and plasma CLU was measured before and after conversion in AD. Increases in CLU were measured in the hippocampus of 3xTgAD and TgF344-AD animals in the absence of plasmatic changes. CLU is heterogeneously expressed in the hippocampus in non-demented individuals and increased in AD. In the plasma, two CLU levels were measured: low in controls and MCI, and high in AD. To validate that the elevation in CLU is associated with conversion to AD, a replication study showed, in a second group MCI patients converting to AD in the follow-up that CLU levels increased in 16/19 individuals. The increase in brain CLU occurs in AD models as in humans, and seems to precede plasma variations, which could make it an AD therapeutic target. Plasma CLU seems to be a promising marker of cognitive decline, and its association with AD may be a useful complementary diagnostic tool.

Voltage-gated Ca_V2.1 (P/Q-type) Ca²⁺ channels play a crucial role in regulating neurotransmitter release, thus contributing to synaptic plasticity and to processes such as learning and memory. Despite their recognized importance in neural function, there is limited information on their potential involvement in neurodegenerative conditions such as Alzheimer's disease (AD). Here, we aimed to explore the impact of AD pathology on the density and nanoscale compartmentalization of Ca_V2.1 channels in the hippocampus in association with GABA_B receptors. Histoblotting experiments showed that the density of Ca_V2.1 channel was significantly reduced in the hippocampus of APP/PS1 mice in a laminar-dependent manner. Ca_V2.1 channel was enriched in the active zone of the axon terminals and was present at a very low density over the surface of dendritic tree of the CA1 pyramidal cells, as shown by quantitative SDS-digested freeze-fracture replica labelling (SDS-FRL). In APP/PS1 mice, the density of Ca_V2.1 channel in the active zone was significantly reduced in the strata radiatum and lacunosum-moleculare, while it remained unaltered in the stratum oriens. The decline in Cav2.1 channel density was found to be associated with a corresponding impairment in the GABAergic synaptic function, as evidenced by electrophysiological experiments carried out in the hippocampus of APP/PS1 mice. Remarkably, double SDS-FRL showed a co-clustering of Ca_V2.1 channel and GABA_B1 receptor in nanodomains (~40–50 nm) in wild type mice, while in APP/PS1 mice this nanoarchitecture was absent. Together, these findings suggest that the AD pathology-induced reduction in Ca_V2.1 channel density and Ca_V2.1-GABA_B1 de-clustering may play a role in the synaptic transmission alterations shown in the AD hippocampus. Therefore, uncovering these layer-dependent changes in P/Q calcium currents associated with AD pathology can benefit the development of future strategies for AD management.

Growing evidence indicates that non-neuronal oligodendrocyte plays an important role in Amyotrophic lateral sclerosis (ALS) and other neurodegenerative diseases. In patient's brain, the impaired myelin structure is a pathological feature with the observation of TDP-43 in cytoplasm of oligodendrocyte. However, the mechanism underlying the gain of function by TDP-43 in oligodendrocytes, which are vital for the axonal integrity, remains unclear. Recently, we found that the primate-specific cleavage of truncated TDP-43 fragments occurred in cytoplasm of monkey neural cells. This finding opened up the avenue to investigate the myelin integrity affected by pathogenic TDP-43 in oligodendrocytes. In current study, we demonstrated that the truncated TDP-35 in oligodendrocytes specifically, could lead to the dysfunctional demyelination in corpus callosum of monkey. As a consequence of the interaction of myelin regulatory factor with the accumulated TDP-35 in cytoplasm, the downstream myelin-associated genes expression was downregulated at the transcriptional level. Our study aims to investigate the potential effect on myelin structure injury, affected by the truncated TDP-43 in oligodendrocyte, which provided the additional clues on the gain of function during the progressive pathogenesis and symptoms in TDP-43 related diseases.

Decreased microvascular levels of claudin-5 in the occipital and temporal lobe of patients with cerebral amyloid angiopathy are associated with intracerebral haemorrhage.

Glycosylation is the most common form of post-translational modification in the brain. Aberrant glycosylation has been observed in cerebrospinal fluid and brain tissue of Alzheimer's disease (AD) cases, including dysregulation of terminal sialic acid (SA) modifications. While alterations in sialylation have been identified in AD, the localization of SA modifications on cellular or aggregate-associated glycans is largely unknown because of limited spatial resolution of commonly utilized methods. The present study aims to overcome these limitations with novel combinations of histologic techniques to characterize the sialylation landscape of O- and N-linked glycans in autopsy-confirmed AD post-mortem brain tissue. Sialylated glycans facilitate important cellular functions including cell-to-cell interaction, cell migration, cell adhesion, immune regulation, and membrane excitability. Previous studies have not investigated both N- and O-linked sialylated glycans in neurodegeneration. In this study, the location and distribution of sialylated glycans were evaluated in three brain regions (frontal cortex, hippocampus, and cerebellum) from 10 AD cases using quantitative digital pathology techniques. Notably, we found significantly greater N-sialylation of the Aβ plaque microenvironment compared with O-sialylation. Plaque-associated microglia displayed the most intense N-sialylation proximal to plaque pathology. Further analyses revealed distinct differences in the levels of N- and O-sialylation between cored and diffuse Aβ plaque morphologies. Interestingly, phosphorylated tau pathology led to a slight increase in N-sialylation and no influence of O-sialylation in these AD brains. Confirming our previous observations in mice with novel histologic approach, these findings support microglia sialylation appears to have a relationship with AD protein aggregates while providing potential targets for therapeutic strategies.