脇田 英明

Vascular dementia is a heterogeneous syndrome, and includes subcortical ischemic vascular dementia. For translational research, subcortical ischemic vascular dementia is an appropriate target since this is the most prevalent subtype and exhibits relatively uniform clinical and neuropathological changes. These changes consist of hypertensive arteriolar changes, lacunar infarctions, hypertensive hemorrhage and white matter lesions. Among various species, rodents are most frequently used, but their small volume of white matter may impede analysis of white matter lesions. Primate models have a larger volume, but the degree of white matter lesions is inconsistent. Animal models should accommodate the effect of aging and comorbidities, and in the case of primate models, low accessibility should be overcome by repeated and quantitative examinations using modern neuroimaging techniques and functional measures, especially for memory and motor function. There is no model that replicates all features of subcortical ischemic vascular dementia and, therefore, rodent and primate models should be selected appropriately for translational research. © 2014 Future Medicine Ltd.

Regenerative therapy using stem cells is a promising approach for the treatment of stroke. Recently, we reported that dental pulp stem cells (DPSC) ameliorated ischemic tissue injury in the rat brain and accelerated functional recovery after middle cerebral artery occlusion (MCAO). In this study, we investigated the effects of stem cells from human exfoliated deciduous tooth (SHED)-derived conditioned medium (SHED-CM) on permanent MCAO (pMCAO). Adult male Sprague-Dawley rats were subjected to pMCAO. SHED-CM were then administered intranasally, and the motor function and infarct volume were evaluated. Neurogenesis and vasculogenesis were determined using immunochemical markers. The SHED-CM group had more positive signals than the Dulbecco's modified Eagle's medium group, with doublecortin (DCX), neurofilament H, neuronal nuclei, and rat endothelial cell antigen observed in the peri-infarct area. Migration of neuronal progenitor cells (NPC) with DCX from the subventricular zone to the peri-infarct area was observed on days 6 and 16, with migration on day 6 being the most prominent. In conclusion, SHED-CM promoted the migration and differentiation of endogenous NPC, induced vasculogenesis, and ameliorated ischemic brain injury after pMCAO as well as transplantation of DPSC.

It has long been debated whether watershed infarcts are caused by hemodynamic or embolic mechanisms. In the present study, we investigated microembolic roles in the pathogenesis of watershed infarcts by examining MRI in a macaque monkey model of multiple microinfarcts. 50 mu m microbeads were injected into each internal carotid artery twice with a month interval. Monkeys (n = 4) injected with 2250-2800 microbeads per unilateral side showed both cortical and internal watershed infarcts in the acute phase and atrophic changes with microbleeds in the chronic phase. These results suggest embolic pathogenesis can contribute to the genesis of both cortical and internal watershed infarcts in primates. (C) 2011 Elsevier Ireland Ltd. All rights reserved.

Regenerative therapy using stem cells is a promising approach for the treatment of stroke. Recently, we reported that CD31(-)/CD146(-) side population (SP) cells from porcine dental pulp exhibit highly vasculogenic potential in hindlimb ischemia. In this study, we investigated the influence of CD31(-)/CD146(-) SP cells after transient middle cerebral artery occlusion (TMCAO). Adult male Sprague-Dawley rats were subjected to 2 h of TMCAO. Twenty-four hours after TMCAO, CD31(-)/CD146(-) SP cells were transplanted into the brain. Motor function and infarct volume were evaluated. Neurogenesis and vasculogenesis were determined with immunochemical markers, and the levels of neurotrophic factors were assayed with real-time reverse transcription-polymerase chain reaction. In the cell transplantation group, the number of doublecortin-positive cells increased twofold, and the number of NeuN-positive cells increased eightfold, as compared with the control phosphate-buffered saline group. The vascular endothelial growth factor level in the ischemic brain with transplanted cells was 28 times higher than that in the normal brain. In conclusion, CD31(-)/CD146(-) SP cells promoted migration and differentiation of the endogenous neuronal progenitor cells and induced vasculogenesis, and ameliorated ischemic brain injury after TMCAO.

Apolipoprotein E (apoE) epsilon 4 and hyperhomocysteinemia are risk factors for Alzheimer disease (AD). The dimerization of apoE3 by disulfide bonds between cysteine residues enhances apoE3 function to generate HDL. Because homocysteine (Hcy) harbors a thiol group, we examined whether Hcy interferes with the dimerization of apoE3 and thereby impairs apoE3 function. We found that Hcy inhibits the dimerization of apoE3 and reduces apoE3-mediated HDL generation to a level similar to that by apoE4, whereas Hcy does not affect apoE4 function. Western blot analysis of cerebrospinal fluid showed that the ratio of apoE3 dimers was significantly lower in the samples from the patients with hyperhomocysteinemia than in those that from control subjects. Hyperhomocysteinemia induced by subcutaneous injection of Hcy to apoE3 knock-in mice decreased the level of the apoE3 dimer in the brain homogenate. Because apoE-HDL plays a role in amyloid beta-protein clearance, these results suggest that two different risk factors, apoE4 and hyperhomocysteinemia, may share a common mechanism that accelerates the pathogenesis of AD in terms of reduced HDL generation.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is caused by mutations in human NOTCH3. We have recently reported that mutant Notch3 shows a greater propensity to form aggregates, and these aggregates resist degradation, leading to accumulation in the endoplasmic reticulum (ER). In this study, we searched for low-molecular compounds that decrease the amount of mutant Notch3 aggregates. Using a cell-based system, we found that degradation of preformed mutant aggregates was enhanced by treatment with either 4,5-dianilinophthalimide (DAPH) or staurosporine aglycone (SA), both of which inhibit amyloid beta (A beta) fibrillization. Regarding other low-molecular compounds interacting with A beta fibrils, thioflavin T (ThT) also enhanced the clearance of mutant Notch3. These findings suggest that DAPH. SA, and ThT are potent reagents to dissociate the preformed aggregates of mutant Notch3 by disruption of intermolecular contacts of misfolded proteins. Our study may provide the basis for the development of a pharmacological therapy for CADASIL. (C) 2010 Elsevier Inc. All rights reserved.

Generally angiogenic factors induce the expression of E-selectin in vascular endothelial cells in the tumors. In this study, we employed an anti-E-selectin monoclonal antibody to target tumors in vivo and evaluated an optical imaging reagent to visualize tumor regions. The anti-E-selectin antibody was conjugated on the surface of liposomes, which encapsulated the near-infrared fluorescent substances Cy3 or Cy5.5. The liposomes efficiently recognized human umbilical vein endothelial cells only when E-selectin was induced by angiogenic factors such as TNF-alpha in vitro. Cy5.5 encapsulated into liposomes that were conjugated with an anti-E-selectin antibody successfully visualized Ehrlich ascites tumor cells when transplanted into mice. Thus, E-selectin targeting with liposomes containing a near-infrared fluorescent dye was found effective in visualizing tumors in vivo. This strategy should be extremely useful as a method to identify sentinel lymphatic nodes and angiogenic tumors as well as use for drug delivery to tumor cells. Copyright (C) 2010 John Wiley & Sons, Ltd.