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Neurodegenerative diseases pose some of modern medicine’s most difficult challenges. Not only does our aging population face epidemic proportions of those ailments. The diseases also invade the most inaccessible reaches of the brain, making it extremely difficult to track the illnesses and determine the mechanisms behind them — the essential starting points for designing direct treatments or cures. Compounding that difficulty is the fact that the human nervous system consists of more than one trillion nerve cells.

The path to cures is plainly a long one. Nevertheless, researchers have given themselves a head start by applying such tools as agonists and antagonists, antibodies and other cell labeling reagents, microscopy, and imaging analysis systems to gain insights into the ways in which the nervous system functions — and malfunctions. “The road ahead is really exciting,” declares Weiping Jiang, assistant director of R&D Systems. Understanding neurological diseases “is clearly the Holy Grail within science at the moment,” adds Keith Watling, director of cell signaling and neuroscience for Sigma-Aldrich.

Two Prominent Diseases
Among the large number of neurological disorders, two have emerged as the most prominent in terms of both public knowledge and research focus. “Alzheimer’s disease is the fourth largest cause of death among adults,” says Chandra Mohan, senior director of technical service and senior technical writer at EMD Biosciences (an affiliate of German company Merck KGaA). “The major cause is believed to be deposits of amyloid peptides in the brain, which leads to the loss of neuronal cell function and the axonal flow.” While Alzheimer’s is a disease of aging, Mohan continues, “Parkinson’s disease can happen at any age, mainly due to the loss of neurons that produce dopamine.”

Current treatments of the two diseases represent hardly more than holding actions. To develop more reliable remedies, life scientists must gain a deeper understanding of their basic causes. “The two main challenges are understanding how the brain is structurally and anatomically differentiated on a cellular level,” explains Bob Fasulka, director of applied optical microscopy at Leica Microsystems. That presents problems, though. “What scares me most about therapeutic development in neurobiology is the want of relevant in vitro models,” says John Dunne, associate scientific director at BD Biosciences — Immunocytometry Systems. Stephanie Nickles, senior product manager at Cambrex Bio Science, points to another difficulty. “The availability of human neuronal cell types is very limited,” she says. “Rodents are models, but they are not the real thing.”

Nevertheless, the research community has begun to probe more deeply into normal and diseased brains, helped by emerging tools and technologies. “We help develop tools to help scientists assay how genes function in a cell,” says Rick Ayer, product development manager at Sutter Instruments. “People are looking for genetic markers to identify some of the genes involved; it hasn’t been a very clear picture so far,” echoes Monika Trzcinska, neuroscience business development tech transfer manager at Sigma-Aldrich. “There is a need for media, culturing surfaces, and better definition of the materials in neuroscience,” says Phil Vanek, BD Bioscience’s director of global marketing for bioimaging. “We work with people who have a need for unique cultures and surfaces. We also have a confocal microscopy technology that’s being used in the neurosciences.”

Cultures, Cells, and Extracts
Every study of living cells starts with a choice of cell culture media and reagents. To ensure that cells stay alive and well during in vitro experiments, researchers and manufacturers have developed several types of growth media, some of which contain undefined biological components while others are completely defined. To study the response of nerve and other cells to changing environments, scientists can supplement these “defined” and “serum-free” media with growth factors. Companies such as ATCC, Cambrex, and Invitrogen offer those products for researchers.

Several companies also supply cells and tissue for use in the lab. Asterand, for example, provides human tissue samples for neurological and cancer research, while Cambrex offers a wide variety of products. “We have an extensive offering of human and animal primary cells and media kits for growth and differentiation,” Nickles says. “For neural cells, we offer primary human astrocyte and neural progenitor cell systems. We also offer rat and mouse neurons and astrocytes from various regions of the brain. We guarantee our cell systems with recommended protocols for use, so the risk of failure for the customer is eliminated.”

Most traditional assays require a purified cell extract. This can take several hours to prepare. It also demands great care to avoid altering the intracellular contents of living cells through mechanical forces or enzymatic degradation of proteins and nucleic acids via native DNase, RNase and protease molecules. Several vendors have responded to those difficulties by creating systems that allow scientists to use cell based assays to examine intact living cells. BD Biosciences, Guava Technologies, and PerkinElmer Life and Analytical Sciences, among other firms, have designed systems that can process large numbers of living cells under relatively natural conditions to examine molecular interactions within the cells. These systems expose cells to a compound of interest to check for any interaction with the living cells. They often use fluorescent tags to allow scientists to detect the interactions.

From Reagents to Antibodies
For several years, companies such as Alexis Biochemicals, Biomol, and Tocris Cookson have produced reagents for cell signaling and neuroscience. Other vendors, including Invitrogen, R&D Systems, and Sigma-Aldrich, offer a wide range of kits and reagents for biochemical assays and neuroscience research. “We see a lot of interest in the secretases, enzymes responsible for carving up beta amyloid,” Watling says. “We have certainly got some of the inhibitors of those enzymes. We also have a beta amyloid cleaving enzyme for chopping up amyloid precursors; our kit allows customers to measure the amount of precursors.”

Neuroscience research also targets several of the drugs currently used to treat neurological disorders. Indeed, some of the drug candidates that fail to survive clinical trials turn out to be valuable reagents in basic research, allowing scientists to alter cellular functions in very specific ways and to target particular receptors or biomolecules. Providers of these pharmacologicals include Alexis Biochemicals, BD Biosciences, and EMD Biosciences. “We have introduced a variety of secreatase inhibitors and compounds to reduce the phosophorylation of proteins in animal studies,” EMD’s Mohan says. “And for research on Parkinson’s disease we have various factors relevant to stem cell research.”

Antibodies also play key roles in the neuroscience research lab. Tagged with labels such as fluorescein, which allow scientists to visualize them, antibodies help to identify and locate specific proteins in or on a cell. They also find use in histochemical applications, in which a cell is fixed in paraffin and sections of it stained with antibodies against a specific molecule. Researchers can identify the tagged cells using microscopy, fluorescent readers, or flow cytometers.

Companies that provide antibodies tagged with markers to eliminate the need for conjugating the antibody with a label include Chemicon, R&D Systems, and Upstate. “We have different types of antibodies — monoclonal and labeled,” says R&D Systems’ Jiang. “We have some that can be used in flow cytometry to follow cells and others for histochemistry under the microscope. We also have an antibody for ELISA [enzyme-linked immunosorbent assay] kits to detect how many nanograms or picograms of a compound exist.”

Micromanipulation and Microscopy
Monitoring events in brain cells presents challenges more complex than those in other segments of cell biology. Sutter Instrument’s Ayer gives an example. “The ability to make electrical recordings from cells in mammalian brains requires micromanipulators able to move carefully along several microns and put a pipette into or on the cell to make the recording,” he explains. Other vendors of such manipulators include Applied Scientific Instrumentation and Narishige.

In addition, Sutter offers a manipulator controlled by a joystick that gives users the ability to move pipettes in three dimensions with a single control. “It has the same feel and motion as the classic manipulators, but works in an electric stepper format,” Ayer explains. “It seems like a product that will gather a fairly significant part of the microinjection manipulation market over the next year or two.”

Sutter also focuses on products for visual monitoring of gene function. “We have supported microscopy in a number of ways — via a powerful xenon lamp, for example, and by developing filter wheels for fluorescence microscopes,” Ayer says.

Microscopy of all varieties plays a critical part in research on brain cells. “Confocal microscopy has made large advances, with its implications of high-accuracy imaging,” Leica’s Fasulka points out. “Scientists use fixed stage microscopy primarily to understand the very weak electrical signals and signaling pathways taking place in neural tissue. And people are using upright and inverted microscopes for multidimensional microscopy, which takes place over time or via many different wavelength probes.”

Leica offers microscopes of all types, in user-friendly forms. “A novice microscope user can sit down and concentrate on the science,” Fasulka says. A recent Leica advance in laser microscopy permits scientists to capture dissected materials directly into the centrifuge tube. In addition to Leica, companies such as Molecular Machines & Industries offer laser microdissection systems.

Other major producers of microscopes include Carl Zeiss, Nikon Instruments, and Olympus. Like Leica, they have not only refined the microscope but also developed digital camera systems and analytical software for data analysis.

Scientists who use microscopes to study cells face one inherent problem: Cells are colorless and translucent, and hence almost invisible under the lens of a standard light microscope. To counter the problem, companies such as Fisher Scientific, Sigma-Aldrich, and Wako Chemicals offer biological stains and dyes that allow researchers to visualize cellular structures based on their chemical characteristics. “We’ve introduced probes for visualizing the beta amyloids,” Sigma’s Watling says.

Going with the Flow
In addition to seeing cells, neuroscientists want to characterize them according to their inherent properties. For that, they use flow cytometers. Over the past three decades, BD Biosciences — Immuno-cytometry Systems and Beckman Coulter have introduced leading edge instruments.

BD aims its recent products, such as the BD FACSAria cell sorter, at scientists new to the use of cytometry. “Lots more people are sorting than ever used to in the old days,” Dunne says. Another new introduction, the FACSCanto system, combines a patented optical design for enhanced signal collection on six fluorescent and two scatter parameters, digital electronics for processing up to 10,000 events per second, and a novel sample injection tube supporting carryover of less than 0.1 percent. “It is part of a family of cytometers with unusual internal controls designed to make very high end flow technology available to routine practice,” Dunne explains. “The most immediate relevance of this class of cytometer is in biomarker discovery and a clinical laboratory environment.”

In another recent advance, Sigma-Aldrich has introduced fibrillogenesis inhibitors — small organic molecules that can perturb large, misfolded proteins. “This represents a new approach to studying neurodegenerative diseases,” Trzcinska says.

Scientists still have plenty to learn about the central nervous system and the complex disorders that affect this intricate system of highly specialized cells. But new tools and technologies have accelerated their advance toward that understanding and its application to finding treatments for neurological disorders.

Peter Gwynne (pgwynne767{at}aol.com) is a freelance science writer based on Cape Cod, Massachusetts, U.S.A. Gary Heebner (gheebner{at}cell-associates.com) is a marketing consultant with Cell Associates in St. Louis, Missouri, U.S.A.