TDP-43 and Alzheimer's Disease Pathology in the Brain of a Harbor Porpoise Exposed to the Cyanobacterial Toxin BMAA.

Cetaceans are well-regarded as sentinels for toxin exposure. Emerging studies suggest that cetaceans can also develop neuropathological changes associated with neurodegenerative disease. The occurrence of neuropathology makes cetaceans an ideal species for examining the impact of marine toxins on the brain across the lifespan. Here, we describe TAR DNA-binding protein 43 (TDP-43) proteinopathy and Alzheimer's disease (AD) neuropathological changes in a beached harbor porpoise (Phocoena phocoena) that was exposed to a toxin produced by cyanobacteria called ß-N-methylamino-L-alanine (BMAA). We found pathogenic TDP-43 cytoplasmic inclusions in neurons throughout the cerebral cortex, midbrain and brainstem. P62/sequestosome-1, responsible for the autophagy of misfolded proteins, was observed in the amygdala, hippocampus and frontal cortex. Genes implicated in AD and TDP-43 neuropathology such as APP and TARDBP were expressed in the brain. AD neuropathological changes such as amyloid-ß plaques, neurofibrillary tangles, granulovacuolar degeneration and Hirano bodies were present in the hippocampus. These findings further support the development of progressive neurodegenerative disease in cetaceans and a potential causative link to cyanobacterial toxins. Climate change, nutrient pollution and industrial waste are increasing the frequency of harmful cyanobacterial blooms. Cyanotoxins like BMAA that are associated with neurodegenerative disease pose an increasing public health risk.

Fatal iatrogenic cerebral ß-amyloid-related arteritis in a woman treated with lecanemab for Alzheimer's disease.

We report the case of a 79-year-old woman with Alzheimer's disease who participated in a Phase III randomized controlled trial called CLARITY-AD testing the experimental drug lecanemab. She was randomized to the placebo group and subsequently enrolled in an open-label extension which guaranteed she received the active drug. After the third biweekly infusion, she suffered a seizure characterized by speech arrest and a generalized convulsion. Magnetic resonance imaging revealed she had multifocal swelling and a marked increase in the number of cerebral microhemorrhages. She was treated with an antiepileptic regimen and high-dose intravenous corticosteroids but continued to worsen and died after 5 days. Post-mortem MRI confirmed extensive microhemorrhages in the temporal, parietal and occipital lobes. The autopsy confirmed the presence of two copies of APOE4, a gene associated with a higher risk of Alzheimer's disease, and neuropathological features of moderate severity Alzheimer's disease and severe cerebral amyloid angiopathy with perivascular lymphocytic infiltrates, reactive macrophages and fibrinoid degeneration of vessel walls. There were deposits of ß-amyloid in meningeal vessels and penetrating arterioles with numerous microaneurysms. We conclude that the patient likely died as a result of severe cerebral amyloid-related inflammation.

BMAA, Methylmercury, and Mechanisms of Neurodegeneration in Dolphins: A Natural Model of Toxin Exposure.

Dolphins are well-regarded sentinels for toxin exposure and can bioaccumulate a cyanotoxin called ß-N-methylamino-l-alanine (BMAA) that has been linked to human neurodegenerative disease. The same dolphins also possessed hallmarks of Alzheimer's disease (AD), suggesting a possible association between toxin exposure and neuropathology. However, the mechanisms of neurodegeneration in dolphins and the impact cyanotoxins have on these processes are unknown. Here, we evaluate BMAA exposure by investigating transcription signatures using PCR for dolphin genes homologous to those implicated in AD and related dementias: APP, PSEN1, PSEN2, MAPT, GRN, TARDBP, and C9orf72. Immunohistochemistry and Sevier Münger silver staining were used to validate neuropathology. Methylmercury (MeHg), a synergistic neurotoxicant with BMAA, was also measured using PT-GC-AFS. We report that dolphins have up to a three-fold increase in gene transcription related to Aß+ plaques, neurofibrillary tangles, neuritic plaques, and TDP-43+ intracytoplasmic inclusions. The upregulation of gene transcription in our dolphin cohort paralleled increasing BMAA concentration. In addition, dolphins with BMAA exposures equivalent to those reported in AD patients displayed up to a 14-fold increase in AD-type neuropathology. MeHg was detected (0.16-0.41 µg/g) and toxicity associated with exposure was also observed in the brain. These results demonstrate that dolphins develop neuropathology associated with AD and exposure to BMAA and MeHg may augment these processes.

Cyanobacterial neurotoxin BMAA and brain pathology in stranded dolphins.

Dolphin stranding events occur frequently in Florida and Massachusetts. Dolphins are an excellent sentinel species for toxin exposures in the marine environment. In this report we examine whether cyanobacterial neurotoxin, ß-methylamino-L-alanine (BMAA), is present in stranded dolphins. BMAA has been shown to bioaccumulate in the marine food web, including in the muscles and fins of sharks. Dietary exposure to BMAA is associated with the occurrence of neurofibrillary tangles and ß-amyloid plaques in nonhuman primates. The findings of protein-bound BMAA in brain tissues from patients with Alzheimer's disease has advanced the hypothesis that BMAA may be linked to dementia. Since dolphins are apex predators and consume prey containing high amounts of BMAA, we examined necropsy specimens to determine if dietary and environmental exposures may result in the accumulation of BMAA in the brains of dolphins. To test this hypothesis, we measured BMAA in a series of brains collected from dolphins stranded in Florida and Massachusetts using two orthogonal analytical methods: 1) high performance liquid chromatography, and 2) ultra-performance liquid chromatography with tandem mass spectrometry. We detected high levels of BMAA (20-748 µg/g) in the brains of 13 of 14 dolphins. To correlate neuropathological changes with toxin exposure, gross and microscopic examinations were performed on cortical brain regions responsible for acoustico-motor navigation. We observed increased numbers of ß-amyloid+ plaques and dystrophic neurites in the auditory cortex compared to the visual cortex and brainstem. The presence of BMAA and neuropathological changes in the stranded dolphin brain may help to further our understanding of cyanotoxin exposure and its potential impact on human health.

Intramedullary spinal sarcoidosis masquerading as cervical stenosis.

OBJECTIVE: Intramedullary spinal sarcoidosis is a difficult diagnosis to make because of its nonspecific clinical and imaging features and its imitation of other common spine disorders. We present a patient with intramedullary spinal sarcoidosis that mimicked spinal cord injury from a cervical disk herniation. METHODS: Relevant information was extracted from the patient's medical and imaging records. A thorough literature review subsequently was performed. RESULTS: A 59-year-old woman presented to our institution with several months of intermittent parathesias, pain, and subjective weakness in her right upper and lower extremities. Magnetic resonance imaging of the cervical spine demonstrated a large osteophyte-disk complex at C4-5 adjacent to a small area of intramedullary spinal cord enhancement. The patient underwent C4-5 anterior cervical diskectomy and fusion for the osteophyte-disk complex. She initially improved postoperatively but subsequently worsened after a few months. Because of more prominent spinal cord enhancement, a posterior laminectomy and biopsy of the enhancing lesion was performed. Intramedullary spinal sarcoidosis was diagnosed, and she was treated medically with steroids and immunosuppressive agents. CONCLUSION: Spinal sarcoidosis can mimic more common disease processes, such as cervical spondylosis. It is an important consideration in the diagnosis of intramedullary or intradural lesions of the spinal cord because early medical treatment may improve the course of the disease process. Surgery should be limited to biopsy for diagnostic purposes.

Hybrid peripheral nerve sheath tumor.

In recent literature, there have been case reports of an extremely rare entity characterized by hybrid peripheral nerve tumors consisting of elements of neurofibroma, schwannoma, and/or perineurioma. The authors present a unique case of a patient with multiple painful hybrid tumors with negative genetic testing for neurofibromatosis Type 1 and no clinical evidence of neurofibromatosis Type 2 or schwannomatosis. A 28-year-old woman presented with tentatively diagnosed schwannomatosis. She had painful bilateral retromastoid scalp tumors as well as multiple other painful tumors in the distribution of the saphenous, femoral, and sciatic nerves. Her family history was significant for a paternal grandfather with a solitary schwannoma. The patient underwent multiple surgical procedures for tumor resection, including tumors in the regions of the retromastoid scalp, bilateral sciatic nerves, left femoral nerve, and left axilla. These tumors were examined and evaluated histologically. Within the tumors, components of both neurofibromas and schwannomas were found, even though these 2 peripheral nerve sheath tumors have been long considered to be distinct entities. This case report suggests a distinct syndrome that has not previously been appreciated.

IgG4-related inflammatory pseudotumor of the central nervous system responsive to mycophenolate mofetil.

Orbital apex and skull base masses often present with neuro-ophthalmic signs and symptoms. Though the localization of these syndromes and visualization of the responsible lesion on imaging is typically straightforward, definitive diagnosis usually relies on biopsy. Immunohistochemistry is important for categorization and treatment planning. IgG4-related disease is emerging as a pathologically defined inflammatory process that can occur in multiple organ systems. We present two patients with extensive inflammatory mass lesions of the central nervous system with immunohistochemistry positive for IgG4 and negative for ALK-1 as examples of meningeal based IgG4-related inflammatory pseudotumors. In both patients, there was treatment response to mycophenolate mofetil.

Isolation, characterization, and differentiation of stem cells derived from the rat amniotic membrane.

Stem-cell-based therapies may offer treatments for a variety of intractable diseases. A fundamental goal in stem-cell biology concerns the characterization of diverse populations that exhibit different potentials, growth capabilities, and therapeutic utilities. We report the characterization of a stem-cell population isolated from tissue explants of rat amniotic membrane. Similar to mesenchymal stem cells, these amnion-derived stem cells (ADSCs) express the surface markers CD29 and CD90, but were negative for the lymphohematopoietic markers CD45 and CD11b. ADSCs exist in culture in a multidifferentiated state, expressing neuroectodermal (neurofilament-M), mesodermal (fibronectin), and endodermal (alpha-1-antitrypsin) genes. To assess plasticity, ADSCs were subjected to a number of culture conditions intended to encourage differentiation into neuroectodermal, mesodermal, and endodermal cell types. ADSCs cultured in a defined neural induction media assumed neuronal morphologies and up-regulated neural-specific genes. Under different conditions, ADSCs were capable of differentiating into presumptive bone and fat cells, indicated by the deposition of mineralized matrix and accumulated lipid droplets, respectively. Moreover, ADSCs cultured in media that promotes liver cell differentiation up-regulated liver-specific genes (albumin) and internalized low-density lipoprotein (LDL), consistent with a hepatocyte phenotype. To determine whether this observed plasticity reflects the presence of true stem cells within the population, we have derived individual clones from single cells. Clonal lines recapitulate the expression pattern of parental ADSC cultures and are multipotent. ADSCs have been cultured for 20 passages without losing their plasticity, suggesting long-term self-renewal. In sum, our data suggest that ADSCs and derived clonal lines are capable of long-term self-renewal and multidifferentiation, fulfilling all the criteria of a stem-cell population.

Disparate host response and donor survival after the transplantation of mesenchymal or neuroectodermal cells to the intact rodent brain.

BACKGROUND: To circumvent ethical and legal complications associated with embryonic cell sources, investigators have proposed the use of nonneural donor sources for use in neural transplantation strategies. Leading candidate sources include autologous marrow stromal cells (MSCs) and fibroblasts, which are mesodermal derivatives. However, we recently reported that MSCs transplanted to the adult brain are rapidly rejected by an inflammatory response. Whether extrinsic variables or intrinsic mesenchymal traits stimulated inflammation and rejection is unknown. To determine the future utility of these cells in neural transplantation, we have now performed a systematic analysis of MSC transplantation to the brain. METHODS: To examine the effects of extrinsic variables on transplantation, green fluorescent protein (GFP)-expressing rat MSCs, cultured under distinct conditions, were transplanted stereotactically to the normal adult rat striatum, and donor survival and the host response was compared. To examine whether intrinsic donor traits promoted rejection, 50,000 GFP-expressing rat MSCs, fibroblasts, or astrocytes were transplanted stereotactically to the adult rat striatum and graft survival and the host response was compared. RESULTS: Irrespective of preoperative culture conditions, MSCs elicited an inflammatory response and were rejected by 14 days, indicating acute rejection was not mediated by culture conditions. Comparison of MSC, fibroblast, or astrocyte grafts revealed that mesenchymal derivatives, MSCs and fibroblasts, elicited an inflammatory response and were rapidly rejected, whereas neuroectodermal astrocytes demonstrated robust survival in the absence of inflammation. CONCLUSIONS: Our findings suggest that intrinsic characteristics of mesenchymal cells may stimulate host inflammation, and thus may not represent an ideal donor source for transplantation to the adult brain.

Marrow stromal cells transplanted to the adult brain are rejected by an inflammatory response and transfer donor labels to host neurons and glia.

Abstract The remarkable plasticity of marrow stromal cells (MSCs) after transplantation to models of neurological disease and injury has been described. In this report, we investigated the plasticity and long-term survival of MSCs transplanted into the normal brain. MSCs were isolated from green fluorescent protein (GFP) transgenic rats and double-labeled with 5-bromo-2-deoxyuridine (BrdU) and bis benzamide (BBZ) prior to transplantation into the adult hippocampus or striatum. Surgery elicited an immediate inflammatory response. MSC grafts were massively infiltrated by ED1-positive microglia/macrophages and surrounded by a marked astrogliosis. By 14 days, graft volume had retracted and GFP immunoreactivity was absent, indicating complete donor rejection. Consequently, MSCs did not exhibit plasticity formerly identified in other studies. However, BrdU- and BBZ-labeled cells were detected up to 12 weeks. Control transplants of nonviable MSCs demonstrated the transfer of donor labels to host cells. Unexpectedly, BrdU labeling was colocalized to host phagocytes, astrocytes, and neurons in both regions. Our results indicate that MSCs transplanted to the intact adult brain are rejected by an inflammatory response. Moreover, use of the traditional cell labels BrdU and BBZ may provide a misleading index of donor survival and differentiation after transplantation.

Adult bone marrow stromal cells in the embryonic brain: engraftment, migration, differentiation, and long-term survival.

We recently differentiated adult rat and human bone marrow stromal cells (MSCs) into presumptive neurons in cell culture. To determine whether the MSCs assume neuronal functions in vivo, we now characterize for the first time engraftment, migration, phenotypic expression, and long-term survival after infusion into embryonic day 15.5 (E15.5) rat ventricles in utero. By E17.5, donor cells formed discrete spheres in periventricular germinal zones, suggesting preferential sites of engraftment. The cells expressed progenitor vimentin and nestin but not mature neuronal markers. By E19.5, a subset assumed elongated migratory morphologies apposed to radial nestin-positive fibers running through the cortical white matter and plate, suggesting migration along radial glial processes. Cells remaining in germinal zones extended long, vimentin-positive fibers into the parenchyma, suggesting that the MSCs generated both migratory neurons and guiding radial glia. Consistent with this suggestion, >50% of cultured mouse MSCs expressed the neuroprecursor/radial glial protein RC2. From E19.5 to postnatal day 3, MSCs populated distant areas, including the neocortices, hippocampi, rostral migratory stream, and olfactory bulbs. Whereas donor cells confined to the subventricular zone continued to express nestin, cells in the neocortex and midbrain expressed mature neuronal markers. The donor cells survived for at least 2 months postnatally, the longest time examined. Confocal analysis revealed survival of thousands of cells per cubic millimeter in the frontal cortex and olfactory bulb at 1 month. In the cortex and bulb, 98.6 and 77.3% were NeuN (neuronal-specific nuclear protein) positive, respectively. Our observations suggest that transplanted adult MSCs differentiate in a regionally and temporally specific manner.