Masahiro Nonaka

Accumulation of Amyloid β and Tau and the Formation of Neurofilament Inclusions Following Diffuse Brain Injury in the Pig

Brain trauma in humans increases the risk for developing Alzheimer disease (AD) and may induce the acute formation of AD-like plaques containing amyloid beta (A beta). To further explore the potential link between brain trauma and neurodegeneration, we conducted neuropathological studies using a pig model of diffuse brain injury. Brain injury was induced in anesthetized animals via nonimpact head rotational acceleration of 110 degrees over 20 ms in the coronal plane (n = 15 injured, n = 3 noninjured). At 1, 3, 7, and 10 days post-trauma, control and injured animals were euthanized and immunohistochemical analysis was performed on brain sections using antibodies specific for A beta, beta-amyloid precursor protein (betaPP), tau, and neurofilament (NF) proteins. In addition to diffuse axonal pathology, we detected accumulation of A beta and tau that colocalized with immunoreactive betaPP and NF in damaged axons throughout the white matter in all injured animals at 3-10 days post-trauma. In a subset of brain injured animals, diffuse A beta-containing plaque-like profiles were found in both the gray and white matter, and accumulations of tau and NF rich inclusions were observed in neuronal perikarya. These results show that this pig model of diffuse brain injury is characterized by accumulations of proteins that also form pathological aggregates in AD and related neurodegenerative diseases.

FINITE ELEMENT MODELING APPROACHES FOR PREDICTING INJURY IN AN EXPERIMENTAL MODEL OF SEVERE DIFFUSE AXONAL INJURY

Traumatic brain injury (TBI) finite element (FE) analyses have evolved from crude geometric representations of the skull and brain system into sophisticated models which take into account distinct anatomical features. Two distinct FE modeling approaches have evolved to account for the relative motion that occurs between the skull and cerebral cortex during TBI. The first approach assumes that the relative motion can be estimated by representing the cerebrospinal fluid inside the subarachnoid space as a low shear modulus, virtually incompressible solid. The second approach assumes that the relative motion can be approximated by defining a frictional interface between the cerebral cortex and dura mater. This study presents data from an experimental model of TBI coupled with FE analyses to evaluate the modeling approachs ability to predict specific forms of TBI. Axial plane rotational accelerations produced prolonged traumatic coma in the miniature pig, axonal injury throughout regions of the white matter, and macroscopic hemorrhagic cortical contusions. Results from 2-dimensional FE analyses of the miniature pig showed that the manner in which the modeling approach accounts for the relative motions occurring between the skull and cerebral cortex can dramatically influence the outcome of an analysis. This study clearly demonstrated that the modeling approach which represented the relative motion between the skull and cerebral cortex as a frictional interface best predicted the resulting injury pattern in a 5th axial plane animal experiment.

Neurogenesis and glial proliferation persist for at least one year in the subventricular zone following brain trauma in rats.

In several models of traumatic brain injury in rodents, remarkably progressive tissue loss and neuron death has been observed accompanied by expanding ventricles. Here, we explored potential cell proliferation in the subventricular zone (SVZ) in response to this progressive posttraumatic neurodegeneration. Four-month-old rats (n = 57) were subjected to parasagittal fluid-percussion brain injury or sham treatment (no injury), and their brains were harvested at 2 weeks, 2 months, 6 months, and 1 year (n = 6-8/group) after injury or sham treatment. Brain sections (6 microm) were stained with markers of cell proliferation, Ki-67, and proliferative cell nuclear antigen (PCNA) to detect mitotically active cells. In sham animals, we found a typical age-dependent decrease in Ki-67- and PCNA-labelled cells in the SVZ over the course of 1 year. However, in brain-injured animals, this decrease was reversed culminating in a sixfold increase in the number of cells staining with Ki-67 and a threefold increase in cells staining with PCNA by 1 year following injury compared to age-matched controls. Using double labeling, we also determined that many of the cells staining with Ki-67 or PCNA expressed markers selective for neurons (neurofilament protein) and glia (GFAP). These data suggest that there is a persistent proliferation of neurons and glia in the SVZ following brain trauma that does not diminish during aging as found in non-injured animals.

Evolution of Neurofilament Subtype Accumulation in Axons Following Diffuse Brain Injury in the Pig

Although accumulation of neurofilament (NF) proteins in axons has been recognized as a prominent feature of brain trauma, the temporal course of the accumulation of specific NF subtypes has not been well established. In the present study, 17 miniature swine were subjected to nonimpact inertial brain injury. At 3 hours (h), 6 h, 24 h, 3 days, 7 days, and 10 days post-trauma, immunohistochemical analysis was performed to determine axonal accumulation of NF-light (NF-L), the rod and sidearm domains and sidearm phosphorylation states of NF-medium (NF-M), and heavy (NF-H). We found that NF-L accumulation was easily identified in damaged axons by 6 h post-trauma, but NF-M and H accumulation was not clearly visualized until 3 days following injury. In addition, the axonal accumulation of NF-M and H appeared to be primarily comprised of the sidearm domains. While the accumulating NF was found to be predominantly dephosphorylated, we also detected accumulation of phosphorylated NF. Finally, we found that developing axonal pathology may proceed either towards axotomy with discrete terminal bulb formation or towards the development of varicose swellings encompassing long portions of axons. These findings suggest that there is a differential temporal course in NF subtype disassembly, dephosphorylation, and accumulation in axons following initial brain trauma and that these processes occur in morphologically distinct phenotypes of maturing axonal pathology.

A combination of TERT promoter mutation and MGMT methylation status predicts clinically relevant subgroups of newly diagnosed glioblastomas

The prognostic impact of TERT mutations has been controversial in IDH-wild tumors, particularly in glioblastomas (GBM). The controversy may be attributable to presence of potential confounding factors such as MGMT methylation status or patients’ treatment. This study aimed to evaluate the impact of TERT status on patient outcome in association with various factors in a large series of adult diffuse gliomas. We analyzed a total of 951 adult diffuse gliomas from two cohorts (Cohort 1, n = 758; Cohort 2, n = 193) for IDH1/2, 1p/19q, and TERT promoter status. The combined IDH/TERT classification divided Cohort 1 into four molecular groups with distinct outcomes. The overall survival (OS) was the shortest in IDH wild-type/TERT mutated groups, which mostly consisted of GBMs (P < 0.0001). To investigate the association between TERT mutations and MGMT methylation on survival of patients with GBM, samples from a combined cohort of 453 IDH-wild-type GBM cases treated with radiation and temozolomide were analyzed. A multivariate Cox regression model revealed that the interaction between TERT and MGMT was significant for OS (P = 0.0064). Compared with TERT mutant-MGMT unmethylated GBMs, the hazard ratio (HR) for OS incorporating the interaction was the lowest in the TERT mutant-MGMT methylated GBM (HR, 0.266), followed by the TERT wild-type-MGMT methylated (HR, 0.317) and the TERT wild-type-MGMT unmethylated GBMs (HR, 0.542). Thus, patients with TERT mutant-MGMT unmethylated GBM have the poorest prognosis. Our findings suggest that a combination of IDH, TERT, and MGMT refines the classification of grade II-IV diffuse gliomas.

Diagnosis, treatment, and long-term outcomes of fetal hydrocephalus

This study analyzed 156 cases of fetal hydrocephalus treated at Osaka National Hospital from 1992 to 2011 to review current methods for diagnosing and treating fetal hydrocephalus, and for estimating its clinical outcome. This was a retrospective study of a single institute (Osaka National Hospital). Of 156 cases in total, 37% were diagnosed as isolated ventriculomegaly, 50% as another type of malformation (36 cases of myelomeningocele, six of holoprosencephaly, three of Dandy-Walker syndrome, one case of Joubert syndrome, 12 of arachnoid cyst, nine of encephalocele, three of atresia of Monro and eight of corpus callosum agenesis, and 13% as secondary hydrocephalus. Diagnoses were made between 13 and 40 weeks of gestation (average 27 weeks). Diagnosis was made before 21 weeks of gestation in 24% of cases, from the first day of 22 weeks to the sixth day of 27 weeks in 27%, and after the first day of 28 weeks in 49%. With the exclusion of 17 aborted cases and 40 cases in which the patients were too young to evaluate or lost during follow-up, the final outcome was analyzed for 90 cases. Of these, 17% of the patients died, 21% showed severe retardation, 13% moderate retardation, 26% mild retardation, and 23% showed a good outcome. The long-term outcome was mostly influenced by the basic disease and accompanying anomaly. The time of diagnosis showed no correlation with outcome. Hydrocephalus associated with arachnoid cyst, atresia of Monro, and corpus callosum agenesis, and hydrocephalus due to fetal intracranial hemorrhage, resulted in good outcomes. By contrast, holoprosencephaly, hydrocephalus associated with encephalocele, syndromic hydrocephalus, and hydrocephalus due to fetal virus infection led to poor outcomes. For accurate diagnosis and proper counseling, established protocols are important for the diagnosis and treatment of fetal hydrocephalus, including not only fetal sonography, fetal magnetic resonance imaging, and TORCH (toxoplasma, rubella, cytomegalovirus, herpes simplex) screening test, but also chromosomal and gene testing.

Diagnostic and Prognostic Value of 11C-Methionine PET for Nonenhancing Gliomas

BACKGROUND AND PURPOSE: Noninvasive radiologic evaluation of glioma can facilitate correct diagnosis and detection of malignant transformation. Although positron-emission tomography is considered valuable in the care of patients with gliomas, 18F-fluorodeoxyglucose and 11C-methionine have reportedly shown ambiguous results in terms of grading and prognostication. The present study compared the diagnostic and prognostic capabilities of diffusion tensor imaging, FDG, and 11C-methionine PET in nonenhancing gliomas. MATERIALS AND METHODS: Thirty-five consecutive newly diagnosed, histologically confirmed nonenhancing gliomas that underwent both FDG and 11C-methionine PET were retrospectively investigated (23 grade II and 12 grade III gliomas). Apparent diffusion coefficient, fractional anisotropy, and tumor-to-normal tissue ratios of both FDG and 11C-methionine PET were compared between grade II and III gliomas. Prognostic values of these parameters were also tested by using progression-free survival. RESULTS: Grade III gliomas showed significantly higher average tumor-to-normal tissue and maximum tumor2-to-normal tissue than grade II gliomas in 11C-methionine (P = .013, P = .0017, respectively), but not in FDG-PET imaging. There was no significant difference in average ADC, minimum ADC, average fractional anisotropy, and maximum fractional anisotropy. 11C-methionine PET maximum tumor-to-normal tissue ratio of 2.0 was most suitable for detecting grade III gliomas among nonenhancing gliomas (sensitivity, 83.3%; specificity, 73.9%). Among patients not receiving any adjuvant therapy, median progression-free survival was 64.2 ± 7.2 months in patients with maximum tumor-to-normal tissue ratio of <2.0 for 11C-methionine PET and 18.6 ± 6.9 months in patients with maximum tumor-to-normal tissue ratio of >2.0 (P = .0044). CONCLUSIONS: 11C-methionine PET holds promise for World Health Organization grading and could offer a prognostic imaging biomarker for nonenhancing gliomas.

Genome-wide methylation profiles in primary intracranial germ cell tumors indicate a primordial germ cell origin for germinomas

Intracranial germ cell tumors (iGCTs) are the second most common brain tumors among children under 14 in Japan. The World Health Organization classification recognizes several subtypes of iGCTs, which are conventionally subclassified into pure germinoma or non-germinomatous GCTs. Recent exhaustive genomic studies showed that mutations of the genes involved in the MAPK and/or PI3K pathways are common in iGCTs; however, the mechanisms of how different subtypes develop, often as a mixed-GCT, are unknown. To elucidate the pathogenesis of iGCTs, we investigated 61 GCTs of various subtypes by genome-wide DNA methylation profiling. We showed that pure germinomas are characterized by global low DNA methylation, a unique epigenetic feature making them distinct from all other iGCTs subtypes. The patterns of methylation strongly resemble that of primordial germ cells (PGC) at the migration phase, possibly indicating the cell of origin for these tumors. Unlike PGC, however, hypomethylation extends to long interspersed nuclear element retrotransposons. Histologically and epigenetically distinct microdissected components of mixed-GCTs shared identical somatic mutations in the MAPK or PI3K pathways, indicating that they developed from a common ancestral cell.

Differentiation, polarization, and migration of human induced pluripotent stem cell-derived neural progenitor cells co-cultured with a human glial cell line with radial glial-like characteristics

Here we established a unique human glial cell line, GDC90, derived from a human glioma and demonstrated its utility as a glial scaffold for the polarization and differentiation of human induced pluripotent stem cell-derived neural progenitor cells (iPSC-NPCs). When co-cultured with GDC90 cells, iPSC-NPCs underwent rapid polarization and neurite extension along the radially spreading processes of the GDC90 cells, and showed migratory behavior. This method is potentially useful for detailed examination of neurites or for controlling neurites behavior for regenerative medicine.

Prenatal molecular diagnosis of a severe type of L1 syndrome (X-linked hydrocephalus).

OBJECT The aim of this study was to evaluate the feasibility of prenatal L1CAM gene testing for X-linked hydrocephalus (XLH). METHODS In a nationwide study conducted in Japan between 1999 and 2009, the authors identified 51 different L1CAM gene mutations in 56 families with XLH. Of these 56 families, 9 obligate carriers requested prenatal gene mutation analysis for the fetal L1CAM gene in 14 pregnancies. RESULTS In 2004, new clinical guidelines for genetic testing were established by 10 Japanese genetic medicine-related societies. These guidelines stated that the genetic testing of carriers should be done only with their consent and with genetic counseling. Therefore, because females are carriers, since 2004, L1CAM gene analysis has not been performed for female fetuses. The authors report on 7 fetal genetic analyses that were performed at the request of families carrying L1CAM mutations, involving 3 female (prior to 2004) and 4 male fetuses. Of the 7 fetuses, 3 (1 male and 2 female) carried L1CAM mutations. Of these 3, 1 pregnancy (the male fetus) was terminated; in the other cases, the pregnancies continued, and 3 female and 3 male babies without the XLH phenotype were born. CONCLUSIONS Prenatal L1CAM gene testing combined with genetic counseling was beneficial for families carrying L1CAM mutations.