Massive astrocyte destruction in neuromyelitis optica despite natalizumab therapy.

Auto-antibody mediated astrocyte injury is implicated as a primary event in neuromyelitis optica (NMO) by biomarker, post-mortem and experimental studies that differentiate the condition from multiple sclerosis. We describe the clinical, radiological and neuropathological features of a severe cerebral attack in a natalizumab-treated patient with relapsing myelitis and serum aquaporin-4 antibodies. Our findings support autopsy evidence that abrupt astrocyte destruction precedes demyelination in NMO, and emphasize the importance of serological testing in patients with limited disease. Adherence to current NMO diagnostic criteria may delay treatment, or lead to inappropriate therapy with beta-interferon or natalizumab.

Extracellular Vesicles Released by Glioblastoma Cells Stimulate Normal Astrocytes to Acquire a Tumor-Supportive Phenotype Via p53 and MYC Signaling Pathways.

The role of astrocytes is becoming increasingly important to understanding how glioblastoma (GBM) tumor cells diffusely invade the brain. Yet, little is known of the contribution of extracellular vesicle (EV) signaling in GBM/astrocyte interactions. We modeled GBM-EV signaling to normal astrocytes in vitro to assess whether this mode of intercellular communication could support GBM progression. EVs were isolated and characterized from three patient-derived GBM stem cells (NES+/CD133+) and their differentiated (diff) progeny cells (NES-/CD133-). Uptake of GBM-EVs by normal primary astrocytes was confirmed by fluorescence microscopy, and changes in astrocyte podosome formation and gelatin degradation were measured. Quantitative mass spectrometry-based proteomics was performed on GBM-EV stimulated astrocytes. Interaction networks were generated from common, differentially abundant proteins using Ingenuity® (Qiagen Bioinformatics) and predicted upstream regulators were tested by qPCR assays. Podosome formation and Cy3-gelatin degradation were induced in astrocytes following 24-h exposure to GBM-stem and -diff EVs, with EVs released by GBM-stem cells eliciting a greater effect. More than 1700 proteins were quantified, and bioinformatics predicted activations of MYC, NFE2L2, FN1, and TGFß1 and inhibition of TP53 in GBM-EV stimulated astrocytes that were then confirmed by qPCR. Further qPCR studies identified significantly decreased Δ133p53 and increased p53ß in astrocytes exposed to GBM-EVs that might indicate the acquisition of a pro-inflammatory, tumor-promoting senescence-associated secretory phenotype (SASP). Inhibition of TP53 and activation of MYC signaling pathways in normal astrocytes exposed to GBM-EVs may be a mechanism by which GBM manipulates astrocytes to acquire a phenotype that promotes tumor progression.

Alterations in expression of the neurotrophic factors glial cell line-derived neurotrophic factor, ciliary neurotrophic factor and brain-derived neurotrophic factor, in the target-deprived olfactory neuroepithelium.

Neuronal growth factors play an important role in the development and maintenance of the nervous system. In the olfactory system, neurogenesis and synapse formation occur not only during development but throughout life and it would be expected that growth factors play a significant role in these ongoing processes. We have examined the expression of three neurotrophic factors, glial cell line-derived neurotrophic factor, ciliary neurotrophic factor and brain-derived neurotrophic factor in the normal rat olfactory system and following synaptic target ablation (olfactory bulbectomy). We found that brain-derived neurotrophic factor immunoreactivity was confined to the horizontal basal cells of the olfactory neuroepithelium and was unaltered by bulbectomy. Glial cell line-derived neurotrophic factor immunoreactivity was present in the mature olfactory neurons and also their synaptic target cells in the olfactory bulb. Following bulbectomy, glial cell line-derived neurotrophic factor immunoreactivity was abolished from the neuroepithelium. Ciliary neurotrophic factor was present throughout the olfactory neuronal lineage with strongest immunoreactivity in the horizontal basal cells and mature olfactory neurons as well as several cell types in the olfactory bulb. Postbulbectomy, there was loss of strong ciliary neurotrophic factor immunoreactivity in olfactory neurons, however, low levels persisted in the remaining neuronal population. Horizontal basal cell immunoreactivity persisted over three months. Our results would be consistent with glial cell line-derived neurotrophic factor expression in mature olfactory neurons being dependent upon functional synaptic contact with the olfactory bulb. Alternatively, this factor may be acting as target-derived growth factor for olfactory neurons, a role in keeping with its function in spinal motoneurons and in the nigrostriatal system. Brain-derived neurotrophic factor is implicated in the trophic support of immature neurons. Ciliary neurotrophic factor is clearly important in this unique neuronal system but elucidation of its role awaits further investigation.

Alterations in the neurotrophic factors BDNF, GDNF and CNTF in the regenerating olfactory system.

Neurogenesis, axonal outgrowth and synapse formation are usually restricted to specific stages during central nervous system development, but the mature olfactory system maintains these capacities. The cycle of neuronal turnover can be experimentally induced by surgical ablation of the olfactory bulb (OB). We are interested in the growth factor regulation of these processes and the trophic role played by the target tissue, the OB. We studied the immunohistochemical expression of three neurotrophic factors, brain derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF) and ciliary neurotrophic factor (CNTF) in the rat olfactory neuroepithelium (ON) and OB and in target-deprived ON at 1, 3 and 12 weeks post unilateral bulbectomy. We found BDNF immunoreactivity (IR) was restricted to the basal cells and did not alter postbulbectomy. GDNF-IR was expressed by mature olfactory receptor neurons (ORNs), their axons and target cells in the OB in controls, but was absent from the ON postbulbectomy. Hence, the expression of GDNF by ORNs was found to be target-dependent. CNTF-IR was present in ORNs and their target cells in the OB, in basal cells and in some immature ORNs. Postbulbectomy, CNTF-IR was unaltered in the basal cells, and very low levels were detectable in maturing ORNs in the ON. Our results indicate that these three factors may contribute to the trophic regulation of this neuronal pathway in a coordinated fashion. Previous work has shown that BDNF promotes survival of ORNs in vitro, and TrkB expression has been found in both immature and mature ORNs. Hence, BDNF produced by basal cells may be acting locally on neurons expressing TrkB. Expression of CNTF by both the basal cells and the ORNs suggests that it may play an integral role in this neuronal differentiation pathway. Finally, the expression of GDNF exclusively by mature ORNs in the ON, its presence in the target cells in the OB and abolition of expression by bulbectomy, suggests that it may be target-derived. This provides a major mechanism by which the bulb could exert trophic influences on ORNs.

Spinal chloroma presenting with triplegia in an aleukaemic patient.

Malignant myeloid blast cells may occasionally form a solid mass in tissues outside the haemopoietic system. These tumours are known as chloromas or granulocytic sarcomas. Chloromas occur most commonly in the context of acute myelogenous leukaemia but, rarely, they occur in the absence of other haematological disease, and may be misdiagnosed as lymphoma. A case of a previously well 35-year-old woman presenting with rapidly progressive triplegia caused by a paraspinal and extradural cervical chloroma with no evidence of bone marrow or other haematological involvement is described. Few cases of spinal cord compression caused by chloroma in otherwise healthy patients have been reported. Morphological features of myeloid differentiation, histochemistry and immunohistochemistry, may all aid in rapid diagnosis and allow early and appropriate therapy.

Isocitrate dehydrogenase mutations in diffuse gliomas: clinical and aetiological implications.

The discovery of isocitrate dehydrogenase (IDH) mutations in gliomas is one example of the large impact that next-generation sequencing is having on the understanding of tumour biology and human disease in general. IDH mutations are early and common events in the development of astrocytomas, oligodendrogliomas and oligoastrocytomas. IDH mutations are also found in some myeloid malignancies and soft tissue tumours, but are rare in other malignancies. IDH mutation detection can be incorporated into routine pathology practice via immunohistochemistry and/or standard sequencing techniques and has great diagnostic value. An emerging theme is that IDH mutation status in gliomas is of great prognostic relevance, and there are proposals to include IDH mutation status in the next iteration of the WHO classification of gliomas. The mechanisms of action(s) of mutant IDH are not fully understood, but the understanding is progressing rapidly, and may provide a mechanism to link diverse proneoplastic processes such as oxidative damage and epigenetic dysregulation. There are exciting prospects of novel therapies for glioma patients emerging from the elucidation of these mechanisms. Given the diagnostic and prognostic implications of IDH mutation, and the potential for new therapies, all gliomas should be assessed for IDH mutation status in the future.