Isolation of living neurons from human elderly brains using the immunomagnetic sorting DNA-linker system

Comparing stem cells, transdifferentiation and brain organoids as tools for psychiatric research

The inaccessibility of neurons coming directly from patients has hindered our understanding of mental illnesses at the cellular level. To overcome this obstacle, six different cellular approaches that carry the genetic vulnerability to psychiatric disorders are currently available: Olfactory Neuroepithelial Cells, Mesenchymal Stem Cells, Pluripotent Monocytes, Induced Pluripotent Stem Cells, Induced Neuronal cells and more recently Brain Organoids. Here we contrast advantages and disadvantages of each of these six cell-based methodologies. Neuronal-like cells derived from pluripotent monocytes are presented in more detail as this technique was recently used in psychiatry for the first time. Among the parameters used for comparison are; accessibility, need for reprograming, time to deliver differentiated cells, differentiation efficiency, reproducibility of results and cost. We provide a timeline on the discovery of these cell-based methodologies, but, our main goal is to assist researchers selecting which cellular approach is best suited for any given project. This manuscript also aims to help readers better interpret results from the published literature. With this goal in mind, we end our work with a discussion about the differences and similarities between cell-based techniques and postmortem research, the only currently available tools that allow the study of mental illness in neurons or neuronal-like cells coming directly from patients.

Cryopreservation of Animals and Cryonics: Current Technical Progress, Difficulties and Possible Research Directions

The basis of cryonics or medical cryopreservation is to safely store a legally dead subject until a time in the future when technology and medicine will permit reanimation after eliminating the disease or cause of death. Death has been debunked as an event occurring after cardiac arrest to a process where interjecting its progression can allow for reversal when feasible. Cryonics technology artificially halts further damages and injury by restoring respiration and blood circulation, and rapidly reducing temperature. The body can then be preserved at this extremely low temperature until the need for reanimation. Presently, the area has attracted numerous scientific contributions and advancement but the practice is still flooded with challenges. This paper presents the current progression in cryonics research. We also discuss obstacles to success in the field, and identify the possible solutions and future research directions.

Hydrogen Peroxide Scavenging Restores N-Type Calcium Channels in Cardiac Vagal Postganglionic Neurons and Mitigates Myocardial Infarction-Evoked Ventricular Arrhythmias in Type 2 Diabetes Mellitus

Objective

Withdrawal of cardiac vagal activity is associated with ventricular arrhythmia-related high mortality in patients with type 2 diabetes mellitus (T2DM). Our recent study found that reduced cell excitability of cardiac vagal postganglionic (CVP) neurons is involved in cardiac vagal dysfunction and further exacerbates myocardial infarction (MI)-evoked ventricular arrhythmias and mortality in T2DM. However, the mechanisms responsible for T2DM-impaired cell excitability of CVP neurons remain unclear. This study tested if and how elevation of hydrogen peroxide (H2O2) inactivates CVP neurons and contributes to cardiac vagal dysfunction and ventricular arrhythmogenesis in T2DM.

Methods and Results

Rat T2DM was induced by a high-fat diet plus streptozotocin injection. Local in vivo transfection of adenoviral catalase gene (Ad.CAT) successfully induced overexpression of catalase and subsequently reduced cytosolic H2O2 levels in CVP neurons in T2DM rats. Ad.CAT restored protein expression and ion currents of N-type Ca2+ channels and increased cell excitability of CVP neurons in T2DM. Ad.CAT normalized T2DM-impaired cardiac vagal activation, vagal control of ventricular function, and heterogeneity of ventricular electrical activity. Additionally, Ad.CAT not only reduced the susceptibility to ventricular arrhythmias, but also suppressed MI-evoked lethal ventricular arrhythmias such as VT/VF in T2DM.

Conclusions

We concluded that endogenous H2O2 elevation inhibited protein expression and activation of N-type Ca2+ channels and reduced cell excitability of CVP neurons, which further contributed to the withdrawal of cardiac vagal activity and ventricular arrhythmogenesis in T2DM. Our current study suggests that the H2O2-N-type Ca2+ channel signaling axis might be an effective therapeutic target to suppress ventricular arrhythmias in T2DM patients with MI.

Brain vulnerability and viability after ischaemia

The susceptibility of the brain to ischaemic injury dramatically limits its viability following interruptions in blood flow. However, data from studies of dissociated cells, tissue specimens, isolated organs and whole bodies have brought into question the temporal limits within which the brain is capable of tolerating prolonged circulatory arrest. This Review assesses cell type-specific mechanisms of global cerebral ischaemia, and examines the circumstances in which the brain exhibits heightened resilience to injury. We suggest strategies for expanding such discoveries to fuel translational research into novel cytoprotective therapies, and describe emerging technologies and experimental concepts. By doing so, we propose a new multimodal framework to investigate brain resuscitation following extended periods of circulatory arrest.

Human in vitro systems for examining synaptic function and plasticity in the brain

The human brain shows remarkable complexity in its cellular makeup and function, which are distinct from nonhuman species, signifying the need for human-based research platforms for the study of human cellular neurophysiology and neuropathology. However, the use of adult human brain tissue for research purposes is hampered by technical, methodological, and accessibility challenges. One of the major problems is the limited number of in vitro systems that, in contrast, are readily available from rodent brain tissue. With recent advances in the optimization of protocols for adult human brain preparations, there is a significant opportunity for neuroscientists to validate their findings in human-based systems. This review addresses the methodological aspects, advantages, and disadvantages of human neuron in vitro systems, focusing on the unique properties of human neurons and synapses in neocortical microcircuits. These in vitro models provide the incomparable advantage of being a direct representation of the neurons that have formed part of the human brain until the point of recording, which cannot be replicated by animal models nor human stem-cell systems. Important distinct cellular mechanisms are observed in human neurons that may underlie the higher order cognitive abilities of the human brain. The use of human brain tissue in neuroscience research also raises important ethical, diversity, and control tissue limitations that need to be considered. Undoubtedly however, these human neuron systems provide critical information to increase the potential of translation of treatments from the laboratory to the clinic in a way animal models are failing to provide.

Human Brain Slice Culture: A Useful Tool to Study Brain Disorders and Potential Therapeutic Compounds

Investigating the pathophysiological mechanisms underlying brain disorders is a priority if novel therapeutic strategies are to be developed. In vivo studies of animal models and in vitro studies of cell lines/primary cell cultures may provide useful tools to study certain aspects of brain disorders. However, discrepancies among these studies or unsuccessful translation from animal/cell studies to human/clinical studies often occur, because these models generally represent only some symptoms of a neuropsychiatric disorder rather than the complete disorder. Human brain slice cultures from postmortem tissue or resected tissue from operations have shown that, in vitro, neurons and glia can stay alive for long periods of time, while their morphological and physiological characteristics, and their ability to respond to experimental manipulations are maintained. Human brain slices can thus provide a close representation of neuronal networks in vivo, be a valuable tool for investigation of the basis of neuropsychiatric disorders, and provide a platform for the evaluation of novel pharmacological treatments of human brain diseases. A brain bank needs to provide the necessary infrastructure to bring together donors, hospitals, and researchers who want to investigate human brain slices in cultures of clinically and neuropathologically well-documented material.

Purification of cells from fresh human brain tissue: primary human glial cells

In order to translate the findings obtained from postmortem brain tissue samples to functional biologic mechanisms of central nervous system disease, it will be necessary to understand how these findings affect the different cell populations in the brain. The acute isolation and analysis of pure glial cell populations are common practice in animal models for neurologic diseases, but are not yet regularly applied to human postmortem brain material. The development of novel cell isolation techniques and methods for transcriptomic and proteomic analysis have made it possible to isolate and phenotype primary human cell populations from the central nervous system. The psychiatric program of the Netherlands Brain Bank has considerable experience with the purification of glial cells. This chapter will review the rapid isolation and phenotyping procedures for two major glia cell populations in the human brain, microglia and astrocytes, and will also discuss the potential for biobanking these cells, as well as the possible alternatives to cell isolations. The acute isolation of glial cells without culture-based adherence steps allows the analysis of glial alterations that underlie, or are the result of, disease neuropathology of the donor.

Deficiency of GDNF Receptor GFRα1 in Alzheimer's Neurons Results in Neuronal Death

We have recently developed aged cortical neuron cultures from autopsied human brains with Alzheimer's disease (AD). During the culturing process, we found that glutamatergic cortical neurons from the AD brain lacked a response to glial cell line-derived neurotrophic factor (GDNF), including no axonal regrowth, and were starting to undergo apoptosis. Here we showed that, in cortical neurons from age- and gender-matched cognitively normal control (NC) subjects (NC neurons), GDNF enhanced the expression of GDNF family receptor subtype α1 (GFRα1), but not the other three subtypes (GFRα2, GFRα3, and GFRα4), whereas GDNF failed to induce GFRα1 expression in cortical neurons from the AD brain (AD neurons). The exogenous introduction of GFRα1, but not of its binding partner α1-neural cell adhesion molecule, or RET into AD neurons restored the effect of GDNF on neuronal survival. Moreover, between NC and AD neurons, the AMPA receptor blocker CNQX and the NMDA receptor blocker AP-5 had opposite effects on the GFRα1 expression induced by GDNF. In NC neurons, the presence of glutamate receptors was necessary for GDNF-linked GFRα1 expression, while in AD neurons the absence of glutamate receptors was required for GFRα1 expression by GDNF stimulation. These results suggest that, in AD neurons, specific impairments of GFRα1, which may be linked to glutamatergic neurotransmission, shed light on developing potential therapeutic strategies for AD by upregulation of GFRα1 expression.

Evaluation of cell damage in organotypic hippocampal slice culture from adult mouse: a potential model system to study neuroprotection

The use of organotypic hippocampal slice culture (OHSC) has become a powerful tool for studying cell damage in different neuropathological states, since it reproduces the basic morphological and functional properties of hippocampal neuronal network. However, the conventional OHSCs are established from postnatal animals rather than adult. Here we reevaluated the features of cell death in adult OHSC in detail and found potential utility for the study of neuroprotection. Organotypic culture of hippocampal slices from adult mice under conventional conditions led to a time-dependent and reproducible cell death. Around 6days in vitro (DIV), slices lost 50% of the cells, based on LDH release assessment. The cell death was greater than 90% after DIV 15. The cell loss was linearly correlated (r=0.944, P<0.01) with the time in culture. The electrophysiological responses to the stimulus in the cultured adult slices were accordingly reduced. The cell degeneration during adult OHSC might be utilized as a tool for studying neuroprotective effects in drug development. To illustrate this potential use, adult OHSCs were challenged with brain-derived neurotrophic factor (BDNF). We found that the continuous supplementation of 300ng/ml BDNF promoted cell survival of adult OHSC. Using immunohistochemistry and Western blot analyses of neuronal markers, we also demonstrated the pro-survival effects of BDNF on neurons in the adult OHSC system. It is suggested that OHSCs from adult mice might provide an alternative model system for neuronal degeneration, suitable for studying physiological factors and pharmacological compounds contributing to neuronal survival.

Synthesis and functionalization of superparamagnetic poly-ε-caprolactone microparticles for the selective isolation of subpopulations of human adipose-derived stem cells

There has been a growing interest in using biofunctionalized magnetic particles for cell isolation. This paper describes the synthesis and characterization of magnetite-polymer (Fe(3)O(4)-poly-ε-caprolactone, magnetite-PCL) microparticles surface functionalized with amino and epoxy groups allowing easy covalent attachment of specific antibodies and subsequent ability to bind target cells. Particles with different sizes (4-135 µm), spherical shape and superparamagnetic behaviour (magnetite content of about 13 wt%) were obtained. The functionalized microparticles presented high protein-binding capacity (coupling efficiency of 47% for epoxy- and 71% for amino-functionalized particles) with a low level of non-specific binding. We have further investigated the influence of initial protein concentration, pH, ionic strength, temperature and incubation time on the capacity of amino-functionalized particles to bind protein molecules. The results showed that maximum protein coupling is rapidly achieved (≤5 h) at pH 5.5 and low ionic strength (0.05 M NaCl). Furthermore, when cultured in direct contact with osteoblast-like cells (Saos-2) or human-derived adipose stem cells (ASCs), the amino-functionalized particles did not affect the proliferation and morphology of the cells. As a proof of principle for the application of magnetic microparticles for cell isolation, CD105 (endoglin) antibody was coupled to the magnetic particle surface to bind subpopulations of human ASCs expressing the CD105 antigen. The isolation of CD105+ ASCs from a heterogeneous cell population was confirmed by flow cytometry analysis. Given the demonstrated potential of functionalized magnetite-PCL microparticles for selective cell isolation, we expect that these particles may be further applied in immuno-magnetic cell separation owing to their versatility and ease of surface modification.

New insights on culture and calcium signalling in neurons and astrocytes from epileptic patients

Primary brain cell cultures are a useful tool for understanding the physiopathology of epilepsy and for searching new potential antiepileptic drugs. These cell types are usually prepared from murine species and few human models have been described. The main goal of this study is the establishment of experimental conditions to isolate and culture neurons and astrocytes from human brain and to test its functionality. The tissues came from antiepileptic drug-resistant epileptic patients undergoing surgery. Human neurons and astrocytes were isolated following an enzymatic and mechanical dissociation protocol. Cultures were viable for 3-6 weeks. Cytological characterization was performed by immunocytochemistry using specific antibodies against both neuron (anti-NeuN) and astrocyte (anti-GFAP) protein markers. In order to test their viability and functionality, cells were loaded with the fluorescent calcium probe fura-2 and variations in cytosolic calcium concentrations ([Ca2+]c) were measured by cell imaging. [Ca2+]c increases were evoked upon cell stimulation with high K+ (KCl 75 mM), glutamate (500 μM) or bicuculline (100 μM). Interestingly, spontaneous [Ca2+]c transients were also observed in some neuron-like cells. A novel unreported finding in this study has been the incorporation of human serum that was critical for cell functionality. The setting of these human cultures open the opportunity to new insights on culture and calcium signalling studies on the mechanism(s) of cell resistance to antiepileptic drugs, as well as to studies on plasticity, maturation and possible neurite emission for graft studies.

Telomere attrition occurs during ex vivo expansion of human dental pulp stem cells

We provide a detailed characteristic of stem cells isolated and expanded from the human dental pulp. Dental pulp stem cells express mesenchymal cell markers STRO-1, vimentin, CD29, CD44, CD73, CD90, CD166, and stem cell markers Sox2, nestin, and nucleostemin. They are multipotent as shown by their osteogenic and chondrogenic potential. We measured relative telomere length in 11 dental pulp stem cell lines at different passages by quantitative real-time PCR. Despite their large proliferative capacity, stable viability, phenotype, and genotype over prolonged cultivation, human dental pulp stem cells suffer from progressive telomere shortening over time they replicate in vitro. Relative telomere length (T/S) was inversely correlated with cumulative doubling time. Our findings indicate that excessive ex vivo expansion of adult stem cells should be reduced at minimum to avoid detrimental effects on telomere maintenance and measurement of telomere length should become a standard when certificating the status and replicative age of stem cells prior therapeutic applications.

Differential activation of tumor necrosis factor receptors distinguishes between brains from Alzheimer's disease and non-demented patients

We reported that tumor necrosis factor receptor I (TNFRI) is required for neuronal death induced by amyloid-beta protein in the Alzheimer's disease (AD) brain. However, whether TNF receptor subtypes are expressed and activated differentially in AD brains compared to non-demented brains remains unclear. Our studies on Western blot and ELISA measurements demonstrated that TNFRI levels are increased whereas TNFRII levels are decreased in AD brains compared to non-demented brains (p <0.05). Immunohistochemical results demonstrated that both TNFRI and TNFRII are expressed in neurons in AD and non-demented brains. However, in situ hybridization studies showed little change in the mRNA levels of either type of TNF receptor in the neurons of AD brains compared to non-demented brains. To examine whether different levels of TNF receptors in AD brains are correlated with the alteration of functional binding of TNF receptors, by using 125I-TNF-alpha binding technique, we found that, in AD brains, 125I-TNF-alpha binding affinity to TNFRI is increased, whereas binding affinity to TNFRII is decreased (p < 0.01). These studies reveal a novel observation of abnormal TNF receptor activation in AD brains. Differential TNF receptor protein levels and binding affinities suggest distinct pathogenic mechanisms of neurodegeneration in the AD brain.

Interruption of beta-catenin signaling reduces neurogenesis in Alzheimer's disease

The neuronal loss associated with Alzheimer's disease (AD) affects areas of the brain that are vital to cognition. Although recent studies have shown that new neurons can be generated from progenitor cells in the neocortices of healthy adults, the neurogenic potential of the stem/progenitor cells of AD patients is not known. To answer this question, we compared the properties of glial progenitor cells (GPCs) from the cortices of healthy control (HC) and AD subjects. The GPCs from AD brain samples displayed reduced renewal capability and reduced neurogenesis compared with GPCs from HC brains. To investigate the mechanisms underlying this difference, we compared beta-catenin signaling proteins in GPCs from AD versus HC subjects and studied the effect of amyloid beta peptide (Abeta, a hallmark of AD pathology) on GPCs. Interestingly, GPCs from AD patients exhibited elevated levels of glycogen synthase kinase 3beta (GSK-3beta, an enzyme known to phosphorylate beta-catenin), accompanied by an increase in phosphorylated beta-catenin and a decrease in nonphosphorylated beta-catenin compared with HC counterparts. Furthermore. we found that Abeta treatment impaired the ability of GPCs from HC subjects to generate new neurons and caused changes in beta-catenin signaling proteins similar to those observed in GPCs from AD patients. Similar results were observed in GPCs isolated from AD transgenic mice. These results suggest that Abeta-induced interruption of beta-catenin signaling may contribute to the impairment of neurogenesis in AD progenitor cells.

Dissembled DJ-1 high molecular weight complex in cortex mitochondria from Parkinson's disease patients

The PARK7 gene encodes a protein, DJ-1, with several functions such as protection of cells from oxidative stress, sperm maturation and fertilization, and chaperone activity. Mutations in the PARK7 gene are associated with autosomal recessive early-onset Parkinson's disease (PD). DJ-1 has been reported to be expressed in multiple cells in the central nerve system. Here, by using both native and denatured Western blots, we examined levels of total DJ-1 and high molecular weight complexes of DJ-1 (HMW) in both the substantia nigra and cortex from rapidly autopsied 18 PD and 9 non-pathological control (NPC) brains. We have discovered that the level of total DJ-1 protein is significantly reduced in the substantia nigra in brains of sporadic PD patients. Moreover, in the PD cortex mitochondria fraction, the HMW DJ-1 complex is significantly lower than in the NPC. These results suggest abnormal DJ-1 expression levels and DJ-1 complex changes may contribute to PD pathogenesis.

The adult human brain in preclinical drug development

Neurodegenerative disorders are caused by the death and dysfunction of brain cells, but despite a huge worldwide effort, no neuroprotective treatments that slow cell death currently exist. The failure of translation from animal models to humans in the clinic is due to many factors including species differences, human brain complexity, age, patient variability and disease-specific phenotypes. Additional methods are therefore required to overcome these obstacles in neuroprotective drug development. Incorporating target validation using human brain-tissue microarray screening and direct human brain-cell testing at an early preclinical stage to isolate molecules that protect the human brain may be an effective strategy.

Scientific justification of cryonics practice

Very low temperatures create conditions that can preserve tissue for centuries, possibly including the neurological basis of the human mind. Through a process called vitrification, brain tissue can be cooled to cryogenic temperatures without ice formation. Damage associated with this process is theoretically reversible in the same sense that rejuvenation is theoretically possible by specific foreseeable technology. Injury to the brain due to stopped blood flow is now known to result from a complex series of processes that take much longer to run to completion than the 6 min limit of ordinary resuscitation technology. Reperfusion beyond the 6 min limit primarily damages blood vessels rather than brain tissue. Apoptosis of neurons takes many hours. This creates a window of opportunity between legal death and irretrievable loss of life for human and animal subjects for cryopreservation with possibility of future resuscitation. Under ideal conditions, the time interval between onset of clinical death and beginning of cryonics procedures can be reduced to less than 1 min, but much longer delays could also be compatible with ultimate survival. Although the evidence that cryonics may work is indirect, the application of indirect evidence is essential in many areas of science. If complex changes due to aging are reversible at some future date, then similarly complex changes due to stopped blood flow and cryopreservation may also be reversible, with life-saving results for anyone with medical needs that exceed current capabilities.

Immunomagnetic separation of adult human olfactory neural progenitors

Olfactory neuroepithelium (ONe) has lifelong regenerative capacity owing to the presence of mitotically active progenitors. The accessibility of ONe makes it a unique source of progenitors for cell replacement strategies in the CNS. We have established lines of neurosphere forming cells (NSFCs) from adult postmortem ONe and patients undergoing nasal sinus surgery by endoscopic biopsy. These heterogeneous lines are composed primarily of an immature neuronally restricted and a small glial restricted subpopulation. More homogeneous subpopulations of the NSFCs are essential for detailed study of factors influencing their lineage restriction. Immunomagnetic bead separation using an antibody against tyrosine kinase (Trk) receptors (Trk-pan, which recognizes Trk-A, B, C) resulted in viable, enriched positive and negative subpopulations that could be analyzed immunocytochemically. The positive cells remained positive for the first week after which the number of Trk-pan expressing cells decreased. The negative subpopulation began to express Trk-pan immunoreactivity after five days in vitro. Both subpopulations reverted to the heterogeneous composition after two weeks. Furthermore, most NSFCs were positive for Trk-B, a few for Trk-A, while no reactivity was observed for Trk-C. Because NSFCs produce brain derived neurotrophic factor (BDNF) and express Trk B, the specific receptor for BDNF, it is likely that population dynamics are under a paracrine and/or autocrine regulatory mechanism. Lineage restriction analysis demonstrated that the isolated subpopulation had a restriction potential equivalent to the original heterogeneous population. These studies characterize further the NSFCs and support the future potential therapeutic use of ONe-derived progenitors for CNS injury and neurodegenerative disorders.

Pro/con ethics debate: when is dead really dead?

Contemporary intensive care unit (ICU) medicine has complicated the issue of what constitutes death in a life support environment. Not only is the distinction between sapient life and prolongation of vital signs blurred but the concept of death itself has been made more complex. The demand for organs to facilitate transplantation promotes a strong incentive to define clinical death in a manner that most effectively supplies that demand. We consider the problem of defining death in the ICU as a function of viable organ availability for transplantation

Development of a rapid autopsy program for studies of brain immunity

Human glia are essential cellular models used for studies of neurodegenerative diseases. Fetal neuroglia are commonly used, as they can be recovered in large quantities and sustained for long periods in culture. However, fetal neuroglia may have limitations in reflecting adult diseases and additionally can pose ethical issues in translating products of abortion for research use. To address these concerns, we developed a rapid autopsy program to procure age- and disease-specific neuroglia from adult brain tissues within hours of death. The challenges in developing this initiative, reflecting experiences from 69 autopsies over 4 years, are presented.

Differential utilization of upstream AUGs in the beta-secretase mRNA suggests that a shunting mechanism regulates translation

beta-Secretase [also known as the beta-site amyloid precursor protein-cleaving enzyme 1 (BACE1)] is an enzyme involved in the production of A beta-amyloid plaques in the brains of patients with Alzheimer's disease. The enhanced production of this enzyme occurs without corresponding changes in BACE1 mRNA levels. The complex 5' leader of BACE1 mRNA contains three upstream ORFs (uORFs) preceding the BACE1 initiation codon. In this study, we investigated how this 5' leader affects translation efficiency as a first step in understanding the enhanced production of the enzyme in the disease. Using reporter constructs in transfected mammalian cell lines and cell-free lysates, we showed that the translation mediated by the BACE1 5' leader is cap-dependent and inhibited by cis-acting segments contained within the 5' leader. Disruption of the uORFs had no effect on translation in B104 cells, which was surprising because the first two AUGs reside in contexts able to function as initiation codons. Possible mechanisms to explain how ribosomes bypass the uORFs, including reinitiation, leaky scanning, and internal initiation of translation were found to be inconsistent with the data. The data are most consistent with a model in which ribosomes shunt uORF-containing segments of the 5' leader as the ribosomes move from the 5' end of the mRNA to the initiation codon. In PC12 cells, however, the second uORF appears to be translated. We hypothesize that the translation efficiency of the BACE1 initiation codon may be increased in patients with Alzheimer's disease by molecular mechanisms that enhance shunting or increase the relative accessibility the BACE1 initiation codon.

Amyloid beta peptide load is correlated with increased beta-secretase activity in sporadic Alzheimer's disease patients

Whether elevated beta-secretase (BACE) activity is related to plaque formation or amyloid beta peptide (Abeta) production in Alzheimer's disease (AD) brains remains inconclusive. Here, we report that we used sandwich enzyme-linked immunoabsorbent assay to quantitate various Abeta species in the frontal cortex of AD brains homogenized in 70% formic acid. We found that most of the Abeta species detected in rapidly autopsied brains (<3 h) with sporadic AD were Abeta(1-x) and Abeta(1-42), as well as Abeta(x-42). To establish a linkage between Abeta levels and BACE, we examined BACE protein, mRNA expression and enzymatic activity in the same brain region of AD brains. We found that both BACE mRNA and protein expression is elevated in vivo in the frontal cortex. The elevation of BACE enzymatic activity in AD is correlated with brain Abeta(1-x) and Abeta(1-42) production. To examine whether BACE elevation was due to mutations in the BACE-coding region, we sequenced the entire ORF region of the BACE gene in these same AD and nondemented patients and performed allelic association analysis. We found no mutations in the ORF of the BACE gene. Moreover, we found few changes of BACE protein and mRNA levels in Swedish mutated amyloid precursor protein-transfected cells. These findings demonstrate correlation between Abeta loads and BACE elevation and also suggest that as a consequence, BACE elevation may lead to increased Abeta production and enhanced deposition of amyloid plaques in sporadic AD patients.