2005 Second Cycle Individual Research Grant Recipients
Total awarded: $1,841,889
Fouad, Karim, Ph.D., University of Alberta, Alberta, Canada
$150,000, 2-year Grant
Cyclic AMP and rehabilitative training to promote regeneration and functional recovery after spinal cord injury
Research Category: Promotion of Axon Growth and Remyelination
An imbalance between "stop" and "go" growth signals within neurons may keep them from regenerating their axons after a spinal cord injury. One of the strongest "go" messages is a signaling molecule called cyclic AMP. Scientists at the Miami Project to Cure Paralysis recently proved that raising the concentration of cyclic AMP following an injury to the thoracic spinal cord promoted regeneration and the recovery of some walking ability in rat models. In this study, Dr. Fouad will try to explain precisely how elevated levels of cAMP lead to recovery in rat models of a partial injury in the cervical spinal cord. He will assess how the ability of the animals to perform specific tasks, such as grasping, correlates with the integrity of the two major nerve fiber systems from the brain and brainstem that control the forelimbs. In addition, Dr. Fouad and his colleagues will test whether certain forms of rehabilitation training enhance the effects of cAMP.
One month after the injury, Dr. Fouad will test three dosages of cAMP, infusing each directly into the spinal cord lesion. He and his team then will use a battery of behavioral and electrophysiological measures to analyze changes in the damaged nerve networks. A subgroup of the treated animals also will undergo six weeks of training in grasping and negotiating a horizontal ladder. Dr. Fouad expects that coordinating the training routine with the administration of cAMP will lead to strong new connections between regenerating nerve cells. If this dual approach improves the recovery of function in the test animals, then these results could pave the way to clinical trials.
Freeman, Marc R., Ph.D., University of Massachusetts Medical School, Worcester, MA
$150,000, 2-year Grant
A Drosophila model for acute nerve injury
Research Category: Neuroprotection
Scientists still do not know precisely what molecular events launch and sustain the second wave of cell death after a spinal cord injury. Dr. Freeman will address this issue by studying nerve injuries in the fruit fly Drosophila, whose well-defined nerves are very similar to those in humans. The nerves of the fly can be injured, and then post-injury events can be studied easily at the single-cell level. This young scientist already has shown that the cellular and molecular changes that follow nerve injury in Drosophila are strikingly similar to those observed in mammals with injured spinal cords. Moreover, because the Drosophila's genome has been decoded, the organism lends itself to an unparalleled array of powerful molecular and genetic analyses, which enable researchers to assess gene activity quickly and accurately and to track how that activity changes over time and space.
In this study, Dr. Freeman will explore how, after an injury, glial cells, which normally support and nourish neurons, become agents of destruction promoting inflammation and the death of more neurons. He will focus on two specific molecules, Draper and Shark, that he suspects influence how glial cells switch roles. Draper is present on the surface of these cells and seems to be involved in identifying injured neurons and driving their elimination. Shark is a molecule that binds to the portion of Draper that lies within the cell and probably enables Draper to transmit the, "I've-found-an- injured-neuron" signal. Under this grant, Dr Freeman will describe the way these two molecules dispatch glial cells on their missions. He also plans to use sophisticated genetic tools to deactivate each of the 15,000 or so of Drosohpila's genes to identify which ones control two different parts of the post-injury scenario. First he will explore a newly-identified event during which an injured axon destroys itself. This self-destruction is akin to apoptosis, or programmed cell death, but it is distinct molecularly and completely unexplored. Second, he will search for the genes that cause glia to respond to and dispose of injured neurons. This research could yield exciting new information on the genes that control how cells react to a spinal cord injury and other neural traumas.
Gan, Wen-Biao, Ph.D., New York University School of Medicine, New York, NY
$150,000, 2-year Grant
The role of purinergic receptors in microglial response, scar formation and axon regeneration following spinal cord injury
Research Category: Axon Guidance, Synapse Formation and Neurotransmission
The scar that forms at the site of a spinal cord injury blocks axon regeneration. Microglia, the immune cells in the brain and spinal cord, are among the first responders that flock to the site of a spinal cord injury. They appear to be involved in scar formation, but their precise role remains unclear. Dr. Gan's laboratory has developed a novel way to watch microglia in action. Using the latest imaging techniques of cell biology, he has pioneered a technique to take real-time shots of microglial cells in the injured spinal cord of live mice. The animals have been bred with microglia that emit a green fluorescence, making it easy to spot them. This approach gives researchers ring-side seats as microglial cells in a live animal model react immediately and over time to an injury. The method also can be used to record how injured axons respond to the trauma. Using this new imaging, Dr. Gan will determine whether the rapid response of microglial cells after a spinal cord injury leads to scar formation and prevents axons from regrowing. He also will test whether drugs that block the influx of glial cells prevent scarring and enable axons to regenerate. These studies could offer important insights into the sequence of events following spinal cord injury and point to new treatment strategies to repair the damage.
Glover, Joel Clinton, Ph.D., University of Oslo, Oslo, Norway
$149,600, 2-year Grant
Imaging descending inputs to mammalian spinal interneurons
Research Category: Rehabilitation
Researchers can prod injured axons to regrow but still cannot gauge whether the nerve fibers that do regenerate make appropriate, working connections that could reactivate damaged nerve circuits. In fact, researchers know little about how fibers from the brain latch onto their target nerve cells in the spinal cord in the first place. This lack of information is particularly true for interneurons, the nerve cells that comprise most of the functional circuitry in the spinal cord and brain. Mapping the connections to spinal interneurons has been very difficult because the techniques for identifying and characterizing those connections have been tedious at best. Fortunately, Dr. Glover and his team have perfected a far more efficient approach. They now can quickly pinpoint the connections from the brain onto large numbers of spinal interneurons. The new technique uses an optical recording technique that involves labeling spinal interneurons with a dye that lights up when a nerve cell is activated by the nerve fibers that connect to it. In this project, Dr. Glover will use brain and spinal cords preparations from fetal mice to study spinal interneurons. He will label the different types of spinal interneurons one at a time and then electrically stimulate fibers that descend from the brain. Within minutes, he and his colleagues will see precisely which brain fibers connect to which types of spinal interneurons. The researchers then can test the relevant spinal interneurons with more conventional tools to assess their performance. This study is likely to yield valuable new data on precisely how the spinal cord is wired and provide a new way to evaluate new neuron-to-neuron connections that form after a spinal cord injury.
Hochman, Shawn, Ph.D., Emory University, Atlanta, GA
$150,000, 2-year Grant
Plasticity of GABAergic interneurons after chronic spinal cord injury
Research Category: Concomitant Function
Spasticity, pain, and other troubling sensations frequently plague people with spinal cord injuries. These problems occur in part because a spinal cord injury can damage connections between the spinal cord and the brain systems that otherwise would temper the strength of messages from the sensory system. The loss leaves the spinal cord in an over-excited state. After an injury, the control of spinal cord excitability is left to a network of inhibitory spinal interneurons that release GABA, the most abundant inhibitory neurotransmitter in the spinal cord. Baclofen, a drug that reduces spasticity, amplifies this inhibitory mechanism, but scientists still know very little about how the mechanism works. Recent studies have shown that certain forms of physical training after a spinal cord injury, such as step and stand training, can reshape inhibitory circuitry in the spinal cord in beneficial ways. In this study, Dr. Hochman, an experienced spinal cord researcher, will undertake the first electrical recordings from these inhibitory cells. From the recordings, he will characterize both the fundamental properties of the cells, before and after spinal cord injury, and their ability to adapt to the injury. He then will examine the extent to which drugs that mimic the chemical messages from the brain can facilitate function of these inhibitory interneurons to limit hyperexcitability. Results from this study could enable scientists to design better ways to exploit this inhibitory system to ameliorate some of the troubling conditions that affect the quality of life of the spinal cord injured.
Hooper, Douglas Craig, Ph.D., Thomas Jefferson University, Philadelphia, PA
$75,000.00, 1-year Grant
Intervention against secondary neuronal injury in SCI by the inactivation of peroxynitrite-dependent radicals
Research Category: Neuroprotection
Inflammation is part of the body's natural response to an injury. It occurs when damaged cells release signals that attract immune cells to the site to remove debris, fight infection, and promote repair. In soft tissue, swelling has few harmful consequences; but in the closed confines of the spinal cord, swelling considerably worsens the outcome by killing cells that survived the initial injury. Any treatment that calms inflammation following spinal cord injury may protect uninjured cells but also risks limiting the beneficial effects of the immune response. Dr. Hooper, a veteran immunology researcher, is interested in the chemicals produced by inflammatory cells. These chemicals permit the immune cells to cross the blood-brain barrier but also are toxic to neurons. Dr. Hooper and his team have been trying to deactivate these chemicals in animal models of spinal cord injuries to see if the intervention enables the animals to recover from paralysis. He and his colleagues found that uric acid, which occurs naturally in the human blood stream, deactivates dangerous, unstable molecules called peroxynitrite-dependent radicals. When mouse models received uric acid before they underwent experimental spinal cord injuries, they regained significant use of their hind limbs; untreated mice did not. Furthermore, the uric acid did not appear to interfere with repair mechanisms. In this study, Dr. Hooper will test whether administering uric acid after a spinal cord injury will provide the same benefits and determine the optimal time to administer it. Raising uric acid levels has already been shown to be safe in clinical trials that are testing uric acid as a treatment for multiple sclerosis. Dr. Hooper has been collaborating with the doctors at the University of Pennsylvania who are running the study, which is using an over-the-counter product containing inosine, a substance that quickly raises the level of uric acid level in the body. The results of Dr. Hooper's experiments with mice could lead to trials of uric acid, or a related therapy, as a first-line treatment for spinal cord injury.
Jessell, Thomas M., Ph.D., Columbia University, New York, NY
$75,000, 1-year Grant
Axonal Receptors and the Control of Motor Axon Guidance
Research Category: Axon Guidance, Synapse Formation and Neurotransmission
This is a continuation grant. Please see write-up from the 2004 Second Cycle.
Lichtman, Jeff, M.D., Ph.D., Harvard University, Cambridge, MA
$149,217, 2-year Grant
Growth of native spinal axons in an unperturbed CNS milieu
Research Category: Growth Inhibition and New Tools and Models for Spinal Cord Research
Peripheral axons can regenerate, but axons in the central nervous system (CNS) cannot. What accounts for the difference? In the peripheral nervous system, the degree of nerve damage is a key variable. When damage to nerves is light, regeneration succeeds. After severe damage, even peripheral axons struggle to find their original targets because the glial cells are also lost. Those supporting cells ensheath and protect axons and would guide them back to their targets after minor lesion. Whether glial loss also curtails regeneration of axons in the injured spinal cord is unclear. Perhaps the environment of the brain and spinal cord is simply too hostile to permit axons to regrow. Evidence supports both points of view. On the one hand, when neurons are transplanted into the unlesioned spinal cord using techniques that avoid glial damage, their axons achieve impressive long-distance growth. On the other hand, many components of the normal brain and spinal cord prevent axons from growing. The dilemma has been compounded by the difficulty of transecting CNS axons in animal models without damaging the surrounding tissues. Until recently, single axons could not be visualized in the living spinal cord, so scientists could not confirm that experimental transections were complete. They could not distinguish easily which axons regrew and which simply escaped transection. To avoid sparing axons, all fibers in a given tract had to be cut blindly, causing severe collateral damage.
In this project, Drs. Lichtman and Misgeld will utilize a new method of imaging single axons that Dr. Misgeld developed under an earlier CRF grant. They also will use another sophisticated technique called two-photon excitation that enables them to destroy individual axons. Thus they can precisely control and observe axon damage while leaving glial cells unscathed. The researchers will stain the lesioned axon so they also can watch what guides or what hampers its attempts to regrow. Their experiments are designed to answer these major questions: Do central axons regrow under the best of circumstances, when the surrounding tissue is not damaged? If they regrow, do they follow their original path? If so, which structures do they grow along? If they deviate from their original trajectory, where do they change paths? If they stall, where so they stop? Understanding how transected axons behave normally could help scientists determine whether to focus on promoting the growth of nerve cells, preventing glial damage, or providing artificial conduits or scaffolding to support regenerating axons ¾ or some combination of these strategies.
Lu, Yan, Ph.D., University of North Carolina at Chapel Hill, Chapel Hill, NC
$150,000, 2-year Grant
Role of cation - Cl- cotransporters in central neuropathic pain after spinal cord injury
Research Category: Concomitant Function
Dr. Lu hopes to learn how chemical changes in the injured spinal cord may over-excite the neurons that process signals from the sensory nerves. This hyperactive state may cause the intractable pain that often develops after spinal cord trauma. The healthy central nervous system has neurotransmitters for exciting and inhibiting the electrical activity of neurons. GABA, the most abundant inhibitory neurotransmitter in the spinal cord, acts by binding to a protein on the cell membrane called the GABAA receptor. Interestingly, the GABAA receptor, which normally inhibits electrical activity, can have the opposite effect if the concentration of chloride ion is high. In mature spinal tissue, this concentration normally is low, permitting the inhibitory effect; in developing neural tissue, the concentration is high, so GABAA has an excitatory effect. The amount of chloride ion in the tissue is regulated by proteins that act like gates, controlling the passage of ions through the cell membrane. Two of these proteins, NKCC1 and a KCC2, have opposite effects. NKCC1 promotes concentrations of chloride ion and is prevalent in early development; KCC2 lowers levels of chloride ion and is scarcer in early development. Thus, the balance between NKCC1 and KCC2 determines the effect of GABAA on the neuron. During development, the switch from excitatory to inhibitory GABAA responses results as KCC2 increases and NKCC1 decreases.
Pathological conditions like spinal cord injuries can lower KCC2 and raise NKCC1, changing the GABAA receptor to excitatory. Peripheral nerve injury also has this effect. In this study, Dr. Lu will use rat models to evaluate how an injury disrupts the relative concentrations of KCC2 and NKCC1 as well as the function of GABAA receptors in the neurons that receive sensory messages. His results could provide a new explanation for why people with spinal cord injuries suffer from pain and might suggest better ways to treat it.
Luo, Zhigang David, M.D., Ph.D., University of California, Irvine, Irvine, CA
$149,600, 2-year Grant
A Novel Pathway of Spinal Cord Injury Pain
Research Category: Concomitant Function
Dr. Luo is an expert in the mechanisms of chronic pain. He recently has been studying a signaling pathway related to a protein that may play a role in initiating or maintaining ¾ or both ¾ the intractable pain that often develops after a spinal cord injury. The protein, alpha-2-delta-1, anchors calcium channels to the cell membrane. These channels permit calcium to pass through the membrane to trigger intracellular actions, including the release of neurotransmitters, when the cells are stimulated by sensory or other input. Dr. Luo has discovered that nerve injuries raise the amount of alpha-2-delta-1 in tissues that are important in the processing of pain and the change correlates with the onset and duration of chronic pain in experimental animals. By blocking the increase, Dr. Luo and his colleagues have decreased the abnormal sensations in the animals. Additional evidence that implicates alpha-2delta-1 in spinal cord pain comes from the use of the anti-convulsive drug gabapentin. It has an analgesic effect in people with spinal cord injuries, and gabapentin binds to alpha-2-delta-1. In this study, Dr. Luo will delve further into how a spinal cord injury boosts the levels of this protein. He also will test two approaches that might prevent pain from occurring and relieve established pain. Using animal models, he first will disrupt the chain of cellular signals that are set off by a spinal cord injury and lead to more alpha-2-delta-1. Second, he will directly block the production of this protein. He will test both interventions, before and after the onset of pain. Dr. Luo predicts that these experiments will yield not only a novel explanation for why some people with spinal cord injuries suffer chronic pain but also new targets for more specific drugs to prevent or alleviate it.
Temple, Sally, Ph.D., Albany Medical College, Albany, NY
$150,000, 2-year Grant
Targeting IGF/IGFBPL1 to stimulate CNS neuron survival and regrowth
Research Category: Other
A spinal cord injury kills or maims the two major types of neurons in the spinal cord: motor neurons and interneurons. Motor neurons reside in the front part of the spinal cord, and send their axons to the internal organs and muscle, enabling movement. Interneurons comprise the majority of the neurons in the spinal cord, and they conduct sensory stimuli to motor neurons and connect to neurons at different levels of the spinal cord. An approach to repairing the injured spinal cord is to recreate the environment in which newborn neurons developed, one that was rich in substances called neurotrophins, substances that act like nerve fertilizer. One neurotrophin, insulin-related growth factor 1, (IGF1) appears to supports the survival of injured neurons and promote their regrowth. Clinical trials are underway to see if it can prevent the death of spinal motor neurons in people with amyotrophic lateral sclerosis (Lou Gehrig's disease). However the effect of IGF1 on the critical corticospinal neurons has not been established.
Although relatively little is known about how IGF1 functions in the nervous system, its effects on cells depend on receptors called IGF binding proteins (IGFBPs). Dr. Temple, a neurobiologist and stem cell expert, has discovered a new member of the IGFBP family called IGFBPL1. This receptor is active during development, when neurons are the most responsive to the growth factors that help them flourish. This newly-identified IGF binding protein disappears once cells are completely mature. Dr. Temple hypothesizes that by reintroducing IGFBP into adult neurons, she can trick neurons into behaving like their youthful selves and reacting to the added IGF. Under this grant, she and her colleagues will try to learn more about the mechanisms of Insulin-related growth factor 1. She will first determine in cell cultures whether the interaction between and IGF1and the IGFBPL1 receptor is critical to neuronal growth and survival. She then will add IGFBPL1 to mature corticospinal and motor neurons and assess how well they survive and regrow their axons in a tissue culture. She also will test IGFBPL1 in a mouse model. Finally, to gain a better understanding of how IGF1 signaling affects the central nervous system, Dr. Temple will monitor what happens in the absence of IGFBPL1 to the proliferation, differentiation, and axon growth of developing neurons. If Dr. Temple proves her hypothesis, then IGFBPL1 might one day be used protect neurons that survive a spinal cord injury and prime injured neurons to regenerate their axons.
Tom, Veronica J., Ph.D., Drexel University College of Medicine, Philadelphia, PA
$119,900, 2-year Grant
Combining modification of the glial scar with stimulation of axonal growth to promote functional axonal regeneration
Research Category: Axon Guidance, Synapse Formation and Neurotransmission
Dr. Tom, a postdoctoral fellow in neurobiology, will test a combination of therapies in an attempt to overcome two obstacles to spinal cord repair: the limited ability of mature neurons to replace their damaged axons and the scarring at the site of an injury that poses a physical and chemical barrier to any new axons that might be coaxed to grow. Using mouse models, she will graft one end of a peripheral nerve into the spinal cord following injury to the cervical spine at C4. The grafted nerve will serve as a hospitable "highway" over which axons can travel as they regenerate. The injury site then will be treated with one of three chemicals that have shown promise in preventing or degrading scar tissue. Dr. Tom will compare the efficacy of each these treatments alone in promoting axonal regeneration and functional recovery. Three weeks later, once new axons have grown into the peripheral nerve graft, she will create a second lesion at C6 and place the unattached end of the nerve into it. This maneuver decreases the distance the regenerating axons have to travel to reach their target neurons, eliminating some of the variables in this experiment; it is not intended to be a treatment strategy. At the time she attaches the free end of the nerve graft, Dr. Tom also will administer a combination of the most effective of the three anti-scarring agents together with substances that stimulate injured axons to grow. After six weeks, she will assess whether the treated animals show more axonal outgrowth from the nerve graft and more, if any, improvements in function compared to untreated control animals. Dr. Tom's dual approach, using a peripheral nerve graft along with a treatment to reduce scar tissue, promises to help spinal cord researchers devise the ideal combination of therapies and the best time to administer them.
Tomlinson, Stephen, Ph.D., Medical University of South Carolina, Charleston, SC
$148,706, 2-year Grant
Novel complement inhibitors and therapy of spinal cord injury
Research Category: Neuroprotection
Trying to suppress the harmful inflammation that follows a spinal cord injuries is tricky business, in part because inflammation is part of an immune response that fights infection and helps create an environment where healing can occur. Any systemic suppression of the immune response can make people with spinal cord injuries, who already are at risk for serious infections, even more vulnerable.
Dr. Tomlinson is a microbiologist who focuses on the immune system, especially on an important part of the inflammatory response known as the complement system. More than thirty blood proteins comprise this system, which is activated by injured cells and tissues. The complement system amplifies the inflammatory response and produces molecules that either are toxic or recruit and activate other immune cells to produce toxins. Inhibiting the complement system has been shown to be an effective therapy for inflammatory disease in various animal models, and some complement inhibitors are in human clinical trials for a variety of conditions, including complications following cardiac surgery. Dr. Tomlinson and his colleagues have shown that mice bred without a complement system and normal mice treated with a complement inhibitor are protected from neuronal loss in the aftermath of a spinal cord injury. Both types of mice had significantly improved function when compared to control animals. However, not all of the mechanisms that contribute to the secondary injury following SCI are understood, and safety concerns have been raised about existing drugs that are systemic inhibitors of the complement system and may compromise its beneficial actions.
The Tomlinson laboratory is perfecting a more precise "switch" to turn off the harmful parts of the complement system only at the injury site, leaving the rest of the response intact. In preliminary tests, this targeted approach has been highly effective in experiments in vitro and in mouse models of spinal cord injuries and some inflammatory diseases. In this study, Dr. Tomlinson and his colleagues will continue to explore the mechanisms that activate the complement system and damage tissue and to test various forms of their new therapy. These studies will help to establish the guidelines that are needed to move this promising approach to clinical trials.
Yoon, Sung Ok, Ph.D., The Ohio State University, Columbus, OH
$150,000, 2-year Grant
Promoting oligodendrocyte survival by disrupting proNGF-p75 interaction in vivo
Research Category: Promotion of Axon Growth and Remyelination
This project is the next step in Dr. Yoon's quest to develop treatments that will protect the spinal cord cells that survive an injury only to succumb later to a self-destructive mechanism called apoptosis. Currently, methylprednisolone, a powerful steroid that combats inflammation, is the only approved treatment for acute spinal cord injuries. It must be infused intravenously within hours of an injury to confer any protection. This researcher and her colleagues have developed a novel synthetic compound that may be a valuable addition to the current treatment protocols. Dr. Yoon has previously reported that apoptosis of one group of cells, oligodendrocytes, was due in part to a dramatic increase in the production of proNGF, an apoptotic signalling molecule, and its receptor, p75. Oligodendrocytes normally provide the myelin sheaths that enwrap axons that emanate from neurons. If an injury or its aftermath destroys oligodendrocytes, then axons shed myelin. Naked axons can no longer transmit electrical impulses, and their neurons eventually die off. The compound developed in the Yoon laboratory has disrupted the interaction between proNGF and p75 in cultured oligodendrocytes. In this project, Dr. Yoon and her colleagues will test whether the compound can preserve oligodendrocytes in mouse models after a spinal cord injury.
Because the binding between p75 and proNGF begins hours after the injury and persists for several days, this treatment could potentially allow a wider therapeutic window for treatment than does methylprednisolone. In addition, this compound easily crosses the blood-brain barrier, so it can be given orally or by injection without invasive surgeries or special devices. Increased survival of oligodendrocytes should translate into more myelin and greater functional recovery for the injured. Dr. Yoon is hopeful these experiments on mice will determine the best timing and dosages of the new therapy. If Dr. Yoon's compound works well on mice, she predicts that tests on primates could begin in four to five years.
|
