Teiji Tominaga

Mechanisms of Primary Blast-Induced Traumatic Brain Injury: Insights from Shock-Wave Research

Traumatic brain injury caused by explosive or blast events is traditionally divided into four phases: primary, secondary, tertiary, and quaternary blast injury. These phases of blast-induced traumatic brain injury (bTBI) are biomechanically distinct and can be modeled in both in vivo and in vitro systems. The primary bTBI injury phase represents the response of brain tissue to the initial blast wave. Among the four phases of bTBI, there is a remarkable paucity of information about the cause of primary bTBI. On the other hand, 30 years of research on the medical application of shockwaves (SW) has given us insight into the mechanisms of tissue and cellular damage in bTBI, including both air-mediated and underwater SW sources. From a basic physics perspective, the typical blast wave consists of a lead SW followed by supersonic flow. The resultant tissue injury includes several features observed in bTBI, such as hemorrhage, edema, pseudoaneurysm formation, vasoconstriction, and induction of apoptosis. These are well-described pathological findings within the SW literature. Acoustic impedance mismatch, penetration of tissue by shock/bubble interaction, geometry of the skull, shear stress, tensile stress, and subsequent cavitation formation, are all important factors in determining the extent of SW-induced tissue and cellular injury. Herein we describe the requirements for the adequate experimental set-up when investigating blast-induced tissue and cellular injury; review SW physics, research, and the importance of engineering validation (visualization/pressure measurement/numerical simulation); and, based upon our findings of SW-induced injury, discuss the potential underlying mechanisms of primary bTBI.

Analysis of IDH1 and IDH2 mutations in Japanese glioma patients

A recent study reported on mutations in the active site of the isocitrate dehydrogenase 1 (IDH1) gene in several types of gliomas. All mutations detected resulted in an amino acid exchange at position 132. We analyzed the genomic region spanning wild‐type R132 of IDH1 by direct sequencing in 125 glial tumors. A total of 39 IDH1 mutations were observed. Mutations of the IDH2 gene, homologous to IDH1, were often detected in gliomas without IDH1 mutations. In the present study, R172 mutation of the IDH2 gene was detected in one anaplastic astrocytoma. IDH1 or IDH2 mutations were frequently in oligodendrogliomas (67%), anaplastic astrocytomas (62%), anaplastic oligoastrocytomas (75%), anaplastic oligodendrogliomas (50%), secondary glioblastomas (67%), gangliogliomas (38%), and anaplastic gangliogliomas (60%). Primary glioblastomas were characterized by a low frequency of mutations (5%) at amino acid position 132 of IDH1. Mutations of the IDH1 or IDH2 genes were significantly associated with improved outcome in patients with anaplastic astrocytomas. Our data suggest that IDH1 or IDH2 mutation plays a role in early tumor progression of several types of glioma and might arise from a common glial precursor. The infrequency of IDH1 mutation in primary glioblastomas revealed that these subtypes are genetically distinct entities from other glial tumors. (Cancer Sci 2009; 100: 1996–1998)

Neuroprotective effect of an antioxidant in ischemic brain injury: involvement of neuronal apoptosis.

The production of reactive oxygen species (ROS) has been implicated in reperfusion injury after cerebral ischemia, and antioxidant enzymes are believed to be among the major mechanisms by which the cells counteract the deleterious effect of ROS after cerebral ischemia. ROS also mediate the mitochondrial signaling pathway that may lead to apoptosis following cerebral ischemia. The recent development and availability of transgenic and knockout mutant rodents that either overexpress or are deficient in antioxidant genes have provided powerful tools for dissecting the molecular and cellular mechanisms of signaling pathways, direct oxidative damage, or both that are involved in ischemic brain injury. This article focuses on the contribution of ROS or an antioxidant system to the molecular pathway of postischemic apoptosis following transient focal cerebral ischemia by using transgenic mice that overexpress the cytosolic antioxidant copper/zinc superoxide dismutase.

Genetics and Biomarkers of Moyamoya Disease: Significance of RNF213 as a Susceptibility Gene

Moyamoya disease is characterized by a progressive stenosis at the terminal portion of the internal carotid artery and an abnormal vascular network at the base of the brain. Although its etiology is still unknown, recent genome-wide and locus-specific association studies identified RNF213 as an important susceptibility gene of moyamoya disease among East Asian population. A polymorphism in c.14576G>A in RNF213 was identified in 95% of familial patients with moyamoya disease and 79% of sporadic cases, and patients having this polymorphism were found to have significantly earlier disease onset and a more severe form of moyamoya disease, such as the presentation of cerebral infarction and posterior cerebral artery stenosis. The exact mechanism by which the RNF213 abnormality relates to moyamoya disease remains unknown, while recent reports using genetically engineered mice lacking RNF213 by homologous recombination provide new insight for the pathogenesis of this rare entity. Regarding biomarkers of moyamoya disease, moyamoya disease is characterized by an increased expression of angiogenic factors and pro-inflammatory molecules such as vascular endothelial growth factors and matrix metalloproteinase-9, which may partly explain its clinical manifestations of the pathologic angiogenesis, spontaneous hemorrhage, and higher incidence of cerebral hyperperfusion after revascularization surgery. More recently, blockade of these pro-inflammatory molecules during perioperative period is attempted to reduce the potential risk of surgical complication including cerebral hyperperfusion syndrome. In this review article, we focus on the genetics and biomarkers of moyamoya disease, and sought to discuss their clinical implication.

Mutations in genes encoding the glycine cleavage system predispose to neural tube defects in mice and humans

Neural tube defects (NTDs), including spina bifida and anencephaly, are common birth defects of the central nervous system. The complex multigenic causation of human NTDs, together with the large number of possible candidate genes, has hampered efforts to delineate their molecular basis. Function of folate one-carbon metabolism (FOCM) has been implicated as a key determinant of susceptibility to NTDs. The glycine cleavage system (GCS) is a multi-enzyme component of mitochondrial folate metabolism, and GCS-encoding genes therefore represent candidates for involvement in NTDs. To investigate this possibility, we sequenced the coding regions of the GCS genes: AMT, GCSH and GLDC in NTD patients and controls. Two unique non-synonymous changes were identified in the AMT gene that were absent from controls. We also identified a splice acceptor site mutation and five different non-synonymous variants in GLDC, which were found to significantly impair enzymatic activity and represent putative causative mutations. In order to functionally test the requirement for GCS activity in neural tube closure, we generated mice that lack GCS activity, through mutation of AMT. Homozygous Amt−/− mice developed NTDs at high frequency. Although these NTDs were not preventable by supplemental folic acid, there was a partial rescue by methionine. Overall, our findings suggest that loss-of-function mutations in GCS genes predispose to NTDs in mice and humans. These data highlight the importance of adequate function of mitochondrial folate metabolism in neural tube closure.

Efficacy of prophylactic blood pressure lowering according to a standardized postoperative management protocol to prevent symptomatic cerebral hyperperfusion after direct revascularization surgery for moyamoya disease.

Background: Cerebral hyperperfusion is a potential complication of superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis for moyamoya disease, but the optimal postoperative management has not been determined. Aggressive blood pressure lowering is controversial because of the risk of ischemic complications. Objective: To establish the optimal postoperative management protocol to prevent symptomatic cerebral hyperperfusion in moyamoya disease. Methods: N-isopropyl-p-[123I]-iodoamphetamine single-photon emission computed tomography was performed 1 and 7 days after STA-MCA anastomosis on 152 hemispheres from 108 consecutive patients with moyamoya disease (2–69, mean 33.3 years). Between 2004 and 2007 (period 1), 65 patients were maintained under normotensive conditions after 93 operations, and only patients with cerebral hyperperfusion underwent blood pressure lowering. Between 2008 and 2010 (period 2), all 43 patients were prospectively subjected to intensive blood pressure lowering (<130 mm Hg of systolic blood pressure) immediately after 59 operations. Then the incidence of symptomatic cerebral hyperperfusion was compared between the two groups. Results: Systolic blood pressure the day after surgery was significantly lower in period 2 (mean, 120.9 mm Hg) than in period 1 (133.9 mm Hg) (p < 0.0001). Symptomatic cerebral hyperperfusion was seen in 22 patients during period 1 (23 hemispheres, 24.7%), but only in 4 patients during period 2 (6.7%, p = 0.0047). Multivariate analysis revealed that prophylactic blood pressure lowering was significantly associated with the prevention of symptomatic cerebral hyperperfusion (p = 0.015). Symptomatic cerebral hyperperfusion was relieved in all patients without developing a permanent neurological deficit due to cerebral hyperperfusion. Conclusion: Prophylactic blood pressure lowering prevents symptomatic cerebral hyperperfusion after STA-MCA anastomosis in patients with moyamoya disease. Accurate diagnosis of cerebral hyperperfusion and blood pressure lowering, and considering the severity of hemodynamic compromise in the contralateral and/or remote areas are essential for postoperative management of moyamoya disease.

Temporal profile of the vascular anatomy evaluated by 9.4-T magnetic resonance angiography and histopathological analysis in mice lacking RNF213: A susceptibility gene for moyamoya disease

Moyamoya disease (MMD) is a chronic occlusive cerebrovascular disease with unknown etiology. Recent genome-wide and locus-specific association studies identified RNF213 as an important MMD susceptibility gene. However, the exact mechanism by which an abnormality in RNF213 leads to MMD is unknown. To evaluate the role of RNF213 in the etiology of MMD, we generated RNF213-deficient mice (RNF213-/-) by deleting exon 32 of RNF213 by the Cre-lox system, and investigated whether they developed MMD. The temporal profile of cervical/intracranial arteries was evaluated by 9.4-T magnetic resonance angiography (MRA). The anatomy of the circle of Willis was analyzed by a trans-cardiac injection of carbon black dye. The common carotid arteries (CCA) were sectioned and the arterial wall thickness/thinness was evaluated by Elastica-Masson staining before and after CCA ligation, which selectively induced vascular hyperplasia. As a result, RNF213-/- grew normally, and no significant difference was observed in MRA findings, the anatomy of the circle of Willis, or vascular wall thickness/thinness between RNF-/- and wild-type littermates (Wt.) under normal conditions until 64 weeks of age. However, Elastica-Masson staining demonstrated that both the intima and medial layer were significantly thinner after CCA ligation in RNF213-/- than in Wt. after 14 days (P<0.01). In conclusion, mice lacking the RNF213 gene did not spontaneously develop MMD, indicating that a functional loss of RNF213 did not sufficiently induce MMD. Suppression of vascular remodeling in RNF213-/- requires further examination to clarify the role of RNF213.

Therapeutic efficacy of a polymeric micellar doxorubicin infused by convection-enhanced delivery against intracranial 9L brain tumor models

Convection-enhanced delivery (CED) with various drug carrier systems has recently emerged as a novel chemotherapeutic method to overcome the problems of current chemotherapies against brain tumors. Polymeric micelle systems have exhibited dramatically higher in vivo antitumor activity in systemic administration. This study investigated the effectiveness of CED with polymeric micellar doxorubicin (DOX) in a 9L syngeneic rat model. Distribution, toxicity, and efficacy of free, liposomal, and micellar DOX infused by CED were evaluated. Micellar DOX achieved much wider distribution in brain tumor tissue and surrounding normal brain tissue than free DOX. Tissue toxicity increased at higher doses, but rats treated with micellar DOX showed no abnormal neurological symptoms at any dose tested (0.1-1.0 mg/ml). Micellar DOX infused by CED resulted in prolonged median survival (36 days) compared with free DOX (19.6 days; p = 0.0173) and liposomal DOX (16.6 days; p = 0.0007) at the same dose (0.2 mg/ml). This study indicates the potential of CED with the polymeric micelle drug carrier system for the treatment of brain tumors.

Minocycline Prevents Focal Neurological Deterioration Due to Cerebral Hyperperfusion After Extracranial-Intracranial Bypass for Moyamoya Disease

BACKGROUND Cerebral hyperperfusion (CHP) is a potential complication of superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis for moyamoya disease (MMD), and optimal postoperative management has not yet been established. Minocycline, a neuroprotective antibiotic agent, plays a role in blocking matrix metalloproteinase 9 (MMP-9), which contributes to edema formation and hemorrhagic conversion after cerebral ischemia-reperfusion. Patients with MMD have been shown to have increased serum MMP-9 levels. OBJECTIVE To examine the effect of minocycline on the prevention of postoperative CHP after STA-MCA anastomosis for MMD. METHODS N-isopropyl-p-[I]iodoamphetamine single-photon emission computed tomography was performed 1 and 7 days after STA-MCA anastomosis on 109 hemispheres in 86 consecutive patients with MMD (ages, 9-69 years; mean, 37.2 years). Postoperative systolic blood pressure was strictly maintained at lower than 130 mm Hg in all 109 surgeries. The most 60 recent hemispheres were managed by the intraoperative and postoperative intravenous administration of minocycline hydrochloride (200 mg/d). The incidence of focal neurological deterioration (FND) due to CHP was then compared with that in 36 patients undergoing 49 surgeries managed without minocycline. RESULTS FND due to CHP was observed in 4 operated hemispheres in patients treated without minocycline (4/49, 8.16%), and in none in the minocycline-treated group (0/60) (P = .0241). Multivariate analysis revealed that minocycline administration (P < .001), surgery on the left hemisphere (P = .031), and a smaller recipient artery diameter (P < .001) significantly correlated with FND due to CHP. CONCLUSION The administration of minocycline with strict blood pressure control may represent secure and effective postoperative management to prevent symptomatic CHP after STA-MCA anastomosis for MMD.

Enhanced post-ischemic angiogenesis in mice lacking RNF213; a susceptibility gene for moyamoya disease.

Moyamoya disease (MMD) is a chronic occlusive cerebrovascular disease with unknown etiology that is characterized by the development of abnormal vascular networks at the base of the brain. Recent genome-wide studies identified RNF213 as an important MMD susceptibility gene. However, the exact mechanism by which the RNF213 abnormality leads to MMD remains unknown. Thus, we sought to clarify the role of RNF213 in angiogenesis under ischemic conditions using conventional RNF213 knockout mice. We assessed the infarction volume, cerebral edema, and vascular density in the ischemic brain after transient middle cerebral artery occlusion (tMCAO). To further evaluate systemic angiogenesis following chronic ischemia, we investigated blood flow recovery using laser speckle flowmetry, the severity of ambulatory impairments, and vascular density in the hind-limb after permanent femoral artery ligation. Results were compared between homozygous RNF213 knockout mice (RNF213 -/-) and wild-type littermates (Wt). No significant differences were observed in infarction volume or the formation of edema following tMCAO, or in vascular density 28 days after tMCAO between RNF213 -/- and Wt. Blood flow recovery was significantly improved in RNF213 -/- from 3 to 28 days after femoral artery ligation, and angiogenesis as shown by vascular density in the hind-limb was significantly enhanced in RNF213 -/- at 28 days. The amelioration of ambulatory impairments was also evident in RNF213 -/-. Angiogenesis was enhanced in mice lacking RNF213 after chronic hind-limb ischemia, which suggested the potential role of the RNF213 abnormality in the development of pathological vascular networks in chronic ischemia.