Knockdown of cortical transthyretin expression around implanted neural prosthetic devices using intraventricular siRNA injection in the brain.

Neural prosthetic devices are showing increasing clinical use for the treatment of a variety of neurological disorders. However the functions on these devices are often limited due to an inability to effectively and chronically interface with neural tissue. The insertion of devices has been shown to result in significant cellular and vascular trauma surrounding the insertion site.

Optical monitoring of neural networks evoked by focal electrical stimulation on microelectrode arrays using FM dyes.

Patch-clamping or microelectrode arrays (MEA) are conventional methods to monitor the electrical activity in biological neural networks in vitro. Despite the effectiveness of these techniques, there are disadvantages including the limited number of electrodes and the predetermined location of electrodes in MEAs. In particular, these drawbacks raise a difficulty in monitoring a number of neurons outnumbering the electrodes.

Effects of glial cells on electrode impedance recorded from neuralprosthetic devices in vitro.

Neural prosthetic devices hold the potential to be used in the treatment of a variety of neurological disorders. However, their long-term clinical success is currently limited by the ability to achieve stable interfaces between devices and the CNS. Immunohistochemical analysis has shown that cellular responses occur in tissue surrounding implanted devices.

Biomedical Technologies for in vitro Screening and Controlled Delivery of Neuroactive Compounds.

Cell culture models can provide information pertaining to the effective dose, toxiciology, and kinetics, for a variety of neuroactive compounds. However, many in vitro models fail to adequately predict how such compounds will perform in a living organism. At the systems level, interactions between organs can dramatically affect the properties of a compound by alteration of its biological activity or by elimination of it from the body.

Release of nerve growth factor from HEMA hydrogel-coated substrates and its effect on the differentiation of neural cells.

Local pharmacological intervention may be needed to ensure the long-term performance of neural prosthetic devices because of insertion-related neuron loss and reactive cell responses that form compact sheaths, leading to decreased device performance. We propose that local delivery of neurotrophins would enhance neuron survival and promote neuron sprouting toward device electrodes, thus providing improved electrode-neuron communication and device performance for recording and stimulating CNS activity. In this study, three different types of poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogels were developed and assessed for storage capacity and release rates of the neurotrophin, nerve growth factor (NGF).

Cryopreservation of transfected primary dorsal root ganglia neurons.

Primary dorsal root ganglia (DRG) neurons are often used to investigate the relative strength of various guidance cues to promote re-growth in vitro. Current methods of neuron isolation are laborious and disposal of excess dissected cells is inefficient. Traditional immunostaining techniques are inadequate to visualize real-time neurite outgrowth in co-culture.

Modulation of cultured neural networks using neurotrophin release from hydrogel-coated microelectrode arrays.

Polyacrylamide and poly(ethylene glycol) diacrylate hydrogels were synthesized and characterized for use as drug release and substrates for neuron cell culture. Protein release kinetics was determined by incorporating bovine serum albumin (BSA) into hydrogels during polymerization. To determine if hydrogel incorporation and release affect bioactivity, alkaline phosphatase was incorporated into hydrogels and a released enzyme activity determined using the fluorescence-based ELF-97 assay.

Applications of hydrogels for neural cell engineering.

Hydrogels, three-dimensional networks of hydrophilic polymers, are currently being investigated for use in a variety of tissue-engineering applications. Hydrogel materials generally exhibit a number of properties including permeability to oxygen and nutrients, which make these materials attractive for use in biological applications. However, in order for such polymers to be successfully integrated into biological systems, these constructs must be engineered so as to mimic native biological interfaces.

Electrical stimulation-induced cell clustering in cultured neural networks.

Planar microelectrode arrays (MEAs) are widely used to record electrical activity from neural networks. However, only a small number of functional recording sites frequently show electrical activity. One contributing factor may be that neurons in vitro receive insufficient synaptic input to develop into fully functional networks.

Directed cell growth on protein-functionalized hydrogel surfaces.

Biochemical surface modification has been used to direct cell attachment and growth on a biocompatible gel surface. Acrylamide-based hydrogels were photo-polymerized in the presence of an acroyl-streptavidin monomer to create planar, functionalized surfaces capable of binding biotin-labelled proteins. Soft protein lithography (microcontact printing) of proteins was used to transfer the biotinylated extracellular matrix proteins, fibronectin and laminin, and the laminin peptide biotin-IKVAV, onto modified surfaces.

Functionalized hydrogel surfaces for the patterning of multiple biomolecules.

Patterning of multiple proteins and enzymes onto biocompatible surfaces can provide multiple signals to control cell attachment and growth. Acrylamide-based hydrogels were photo-polymerized in the presence of streptavidin-acrylamide, resulting in planar gel surfaces functionalized with the streptavidin protein. This surface was capable of binding biotin-labeled biomolecules.

Low-density neuronal networks cultured using patterned poly-l-lysine on microelectrode arrays.

Synaptic activity recorded from low-density networks of cultured rat hippocampal neurons was monitored using microelectrode arrays (MEAs). Neuronal networks were patterned with poly-l-lysine (PLL) using microcontact printing (microCP). Polydimethysiloxane (PDMS) stamps were fabricated with relief structures resulting in patterns of 2 microm-wide lines for directing process growth and 20 microm-diameter circles for cell soma attachment.

Differential expression of N-methyl-D-aspartate receptor NR2 isoforms in Alzheimer's disease.

We have previously shown that the expression of NMDA receptor NR1 subunit mRNA splice variants in Alzheimer's disease (AD) brain varies according to regional susceptibility to pathological damage. Here we investigated the expression of the modulatory NR2 subunits of the NMDA receptor using quantitative RT-PCR to assay all NR2 isoforms. Significantly lower expression of NR2A and NR2B transcripts was found in susceptible regions of AD brain, whereas expression of NR2C and NR2D transcripts did not differ from that in controls.

Glutamate-mediated excitotoxicity and neurodegeneration in Alzheimer's disease.

Alzheimer's disease (AD) is the most common form of dementia, accounting for 60-70% of cases in subjects over 65 years of age. Several postulates have been put forward that relate AD neuropathology to intellectual and functional impairment. These range from free-radical-induced damage, through cholinergic dysfunction, to beta-amyloid-induced toxicity.

Selective loss of NMDA receptor NR1 subunit isoforms in Alzheimer's disease.

Previous work had shown that the ratio of NMDA receptor NR1 subunit mRNA transcripts containing an N-terminal splice cassette to those that do not is markedly lower in regions of the Alzheimer's disease (AD) brain that are susceptible to pathological damage, compared with spared regions in the same cases or homotropic regions in controls. To elucidate the origins of this difference in proportionate expression, we measured the absolute levels of each of the eight NR1 transcripts by quantitative internally standardized RT-PCR assay. Expression of transcripts with the cassette was strongly attenuated in susceptible regions of Alzheimer's brain, whereas expression of non-cassette transcripts differed little from that in controls.

Quantitation of NMDA receptor NR2 mRNA transcripts in human brain by competitive RT-PCR.

The NMDA-selective ionotropic receptor constitutes one of the three principal classes of L-glutamate receptors within the mammalian brain. It plays key roles in neuronal differentiation and synapse consolidation, activity-dependent forms of synaptic plasticity, and excitatory amino acid-mediated neuronal toxicity [Lab. Invest.

Quantitation of alternatively spliced NMDA receptor NR1 isoform mRNA transcripts in human brain by competitive RT-PCR.

The N-methyl-D-aspartate (NMDA)-selective subtype of ionotropic glutamate receptor is of importance in neuronal differentiation and synapse consolidation, activity-dependent forms of synaptic plasticity, and excitatory amino acid-mediated neuronal toxicity [Neurosci. Res. Program Bull.

Biochemical and molecular studies using human autopsy brain tissue.

The use of human brain tissue obtained at autopsy for neurochemical, pharmacological and physiological analyses is reviewed. RNA and protein samples have been found suitable for expression profiling by techniques that include RT-PCR, cDNA microarrays, western blotting, immunohistochemistry and proteomics. The rapid development of molecular biological techniques has increased the impetus for this work to be applied to studies of brain disease.