Faculty Bibliography

Regenerative procedures using barrier membrane technology are presently well established in periodontal/endodontic surgery. The objective of this study was to compare the subsequent effects of the released platelet-derived growth factor (PDGF) and growth/differentiation factor 5 (GDF-5) from collagen membranes (CMs) on bone regeneration in vitro and in vivo. In vitro studies were conducted using MC3T3-E1 mouse preosteoblasts cultured with or without factors. Cell viability, cell proliferation, alkaline phosphatase (ALP) activity and bone marker gene expression were then measured. In vivo studies were conducted by placing CMs with low or high dose PDGF or GDF-5 in rat mandibular defects. At 4 weeks after surgery new bone formation was measured using muCT and histological analysis. The results of in vitro studies showed that CM/GDF-5 significantly increased ALP and cell proliferation activities without cytotoxicity in MC3T3-E1 cells when compared to CM/PDGF or CM alone. Gene expression analysis revealed that Runx2 and Osteocalcin were significantly increased in CM/GDF-5 compared to CM/PDGF or control. Quantitative and qualitative muCT and histological analysis for new bone formation revealed that although CM/PDGF significantly enhanced bone regeneration compared to CM alone or control, CM/GDF-5 significantly accelerated bone regeneration to an even greater extent than CM/PDGF. The results also showed that GDF-5 induced new bone formation in a dose-dependent manner. These results suggest that this strategy, using a CM carrying GDF-5, might lead to an improvement in the current clinical treatment of bone defects for periodontal and implant therapy.

Disappointing findings from recent phase III trials on amyloid-beta (Abeta) immunotherapy for Alzheimer's disease (AD) have shifted the focus of such treatments to the tau protein. As tau pathology correlates better with the degree of dementia than Abeta plaque burden, it is a more attractive target once cognitive impairments are evident, while Abeta therapies may be better suited for the presymptomatic phase of the disease. Over 12 years ago, we initiated a tau immunotherapy program, seeking to alleviate the functional impairments associated with tau lesions in tauopathies. We have reported that various active and passive tau immunizations diminish tau pathology and improve function, including cognition, in different mouse models. Both extra- and intracellular pathways are likely involved. The antibodies may block the spread of tau pathology via microglial phagocytosis of the antibody-tau complex and facilitate lysosomal tau clearance in neurons after endosomal uptake. We have observed such antibody internalization following intracarotid injection in mice and in various culture models. These include brain slices and primary neurons from tangle mice as well as human neuroblastoma cell lines. Antibody targeting of different intracellular protein aggregates, including alpha-synuclein, Abeta and superoxide dismutase has been reported by others. Now, several laboratories have confirmed and extended our findings using various active and passive tau immunizations in different models, thereby clearly establishing the feasibility of this approach for clinical trials. We are also working on imaging approaches to monitor tau pathology, its consequences and the efficacy of treatments. Dire need exists for such diagnostic methods for tauopathies. Overall, therapies and diagnostic tools targeting tau pathology have a great potential for AD and other tauopathies. (c) 2013 S. Karger AG, Basel.

Multiple system atrophy (MSA) is a neurodegenerative disease with two motor phenotypes: parkinsonian (MSA-P) and cerebellar (MSA-C). To elucidate whether in addition to the motor abnormalities there are other significant differences between these phenotypes, we performed a retrospective review of 100 patients (61 males, 39 females) with a diagnosis of possible (12 %), or probable (88 %) MSA. Four patients eventually had post-mortem confirmation (i.e., definite MSA). Sixty percent were classified as having MSA-P and 40 % as MSA-C. MSA-C and MSA-P patients had similar male prevalence (60 %), age of onset (56 +/- 9 years), and frequency of OH (69 %). Brain MRI abnormalities were more frequent in MSA-C patients (p < 0.001). Mean survival was 8 +/- 3 years for MSA-C and 9 +/- 4 years for MSA-P patients (p = 0.22). Disease onset before 55 years predicted longer survival in both phenotypes. Initial autonomic involvement did not influence survival. We conclude that patients with both motor phenotypes have mostly similar survivals and demographic distributions. The differences here identified could help counseling of patients with MSA.

Automatic identification of action potentials from one or more extracellular electrode recordings is generally achieved by clustering similar segments of the measured voltage trace, a method that fails (or requires substantial human intervention) for spikes whose waveforms overlap. We formulate the problem in terms of a simple probabilistic model, and develop a unified method to identify spike waveforms along with continuous-valued estimates of their arrival times, even in the presence of overlap. Specifically, we make use of a recent algorithm known as Continuous Basis Pursuit for solving linear inverse problems in which the component occurrences are sparse and are at arbitrary continuous-valued times. We demonstrate significant performance improvements over current state-of-the-art clustering methods for four simulated and two real data sets with ground truth, each of which has previously been used as a benchmark for spike sorting. In addition, performance of our method on each of these data sets surpasses that of the best possible clustering method (i.e., one that is specifically optimized to minimize errors on each data set). Finally, the algorithm is almost completely automated, with a computational cost that scales well for multi-electrode arrays.

ATP-sensitive potassium (KATP) channels have the unique ability to adjust membrane excitability and functions in accordance with the metabolic status of the cell. Skeletal muscles are primary sites of activity-related energy consumption and have KATP channels expressed in very high density. Previously, we demonstrated that transgenic mice with skeletal muscle-specific disruption of KATP channel function consume more energy than wild-type littermates. However, how KATP channel activation modulates skeletal muscle resting and action potentials under physiological conditions, particularly low-intensity workloads, and how this can be translated to muscle energy expenditure are yet to be determined. Here, we developed a technique that allows evaluation of skeletal muscle excitability in situ, with minimal disruption of the physiological environment. Isometric twitching of the tibialis anterior muscle at 1 Hz was used as a model of low-intensity physical activity in mice with normal and genetically disrupted KATP channel function. This workload was sufficient to induce KATP channel opening, resulting in membrane hyperpolarization as well as reduction in action potential overshoot and duration. Loss of KATP channel function resulted in increased calcium release and aggravated activity-induced heat production. Thus, this study identifies low-intensity workload as a trigger for opening skeletal muscle KATP channels and establishes that this coupling is important for regulation of myocyte function and thermogenesis. These mechanisms may provide a foundation for novel strategies to combat metabolic derangements when energy conservation or dissipation is required.

Magnetic resonance imaging (MRI) of autism populations is confounded by the inherent heterogeneity in the individuals' genetics and environment, two factors difficult to control for. Imaging genetic animal models that recapitulate a mutation associated with autism quantify the impact of genetics on brain morphology and mitigate the confounding factors in human studies. Here, we used MRI to image three genetic mouse models with single mutations implicated in autism: Neuroligin-3 R451C knock-in, Methyl-CpG binding protein-2 (MECP2) 308-truncation and integrin beta3 homozygous knockout. This study identified the morphological differences specific to the cerebellum, a structure repeatedly linked to autism in human neuroimaging and postmortem studies. To accomplish a comparative analysis, a segmented cerebellum template was created and used to segment each study image. This template delineated 39 different cerebellar structures. For Neuroligin-3 R451C male mutants, the gray (effect size (ES) = 1.94, FDR q = 0.03) and white (ES = 1.84, q = 0.037) matter of crus II lobule and the gray matter of the paraflocculus (ES = 1.45, q = 0.045) were larger in volume. The MECP2 mutant mice had cerebellar volume changes that increased in scope depending on the genotype: hemizygous males to homozygous females. The integrin beta3 mutant mouse had a drastically smaller cerebellum than controls with 28 out of 39 cerebellar structures smaller. These imaging results are discussed in relation to repetitive behaviors, sociability, and learning in the context of autism. This work further illuminates the cerebellum's role in autism. Autism Res 2013, : -. (c) 2013 International Society for Autism Research, Wiley Periodicals, Inc.

Many studies have described potent effects of BDNF, 17beta-estradiol or androgen on hippocampal synapses and their plasticity. Far less information is available about the interactions between 17beta-estradiol and BDNF in hippocampus, or interactions between androgen and BDNF in hippocampus. Here we review the regulation of BDNF in the mossy fiber pathway, a critical part of hippocampal circuitry. We discuss the emerging view that 17beta-estradiol upregulates mossy fiber BDNF synthesis in the adult female rat, while testosterone exerts a tonic suppression of mossy fiber BDNF levels in the adult male rat. The consequences are interesting to consider: in females, increased excitability associated with high levels of BDNF in mossy fibers could improve normal functions of area CA3, such as the ability to perform pattern completion. However, memory retrieval may lead to anxiety if stressful events are recalled. Therefore, the actions of 17beta-estradiol on the mossy fiber pathway in females may provide a potential explanation for the greater incidence of anxiety-related disorders and post-traumatic stress syndrome (PTSD) in women relative to men. In males, suppression of BDNF-dependent plasticity in the mossy fibers may be protective, but at the 'price' of reduced synaptic plasticity in CA3. This article is part of the Special Issue entitled 'BDNF Regulation of Synaptic Structure, Function, and Plasticity'.

Recent advances in understanding the molecular mechanisms underlying various paths toward the pathogenesis of Alzheimer's disease (AD) has begun to provide new insight for interventions to modify disease progression. The evolving knowledge gained from multidisciplinary basic research has begun to identify new concepts for treatments and distinct classes of therapeutic targets; as well as putative disease-modifying compounds that are now being tested in clinical trials. There is a mounting consensus that such disease modifying compounds and/or interventions are more likely to be effectively administered as early as possible in the cascade of pathogenic processes preceding and underlying the clinical expression of AD. The budding sentiment is that "treatments" need to be applied before various molecular mechanisms converge into an irreversible pathway leading to morphological, metabolic and functional alterations that characterize the pathophysiology of AD. In light of this, biological indicators of pathophysiological mechanisms are desired to chart and detect AD throughout the asymptomatic early molecular stages into the prodromal and early dementia phase. A major conceptual development in the clinical AD research field was the recent proposal of new diagnostic criteria, which specifically incorporate the use of biomarkers as defining criteria for preclinical stages of AD. This paradigm shift in AD definition, conceptualization, operationalization, detection and diagnosis represents novel fundamental opportunities for the modification of interventional trial designs. This perspective summarizes not only present knowledge regarding biological markers but also unresolved questions on the status of surrogate indicators for detection of the disease in asymptomatic people and diagnosis of AD.

Polyethylenimine (PEI), a cationic polymer, has been widely studied and shown great promise as an efficient gene delivery vehicle. Likewise, the HIV-1 Tat peptide, a cell-permeable peptide, has been successfully used for intracellular gene delivery. To improve the favorable properties of these two vectors, we combine PEI with the modified Tat peptide sequence bearing histidine and cysteine residues (mTat). In vitro mTat/PEI-mediated transfection was evaluated by luciferase expression plasmid in two cell types. mTat/PEI produced significant improvement ( approximately 5-fold) in transfection efficiency of both cell lines with little cytotoxicity when compared to mTat alone, PEI alone, or four commercial reagents. The particle size of mTat/PEI/DNA complex was significantly smaller than mTat or PEI alone, and it was correlated with higher transfection efficiency. Filipin III, an inhibitor of caveolae-mediated endocytosis, significantly inhibited mTat/PEI transfection. In contrast, chlorpromazine, an inhibitor of clathrin-mediated endocytosis, did not. This suggested caveolae-mediated endocytosis as the transfection mechanism. Furthermore, the results of in vivo studies showed that animals administered mTat/PEI/DNA intramuscularly had significantly higher and longer luciferase expression ( approximately 7 months) than those with mTat/DNA, PEI/DNA, or DNA alone, without any associated toxicity. The combination of mTat with PEI could significantly improve transfection efficiency, expanding the potential use as a non-viral gene vector both in vitro and in vivo.