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M H Tuszynski

Publications and source records attributed to M H Tuszynski.

At least 19 recordsLinked to original sources
PubMed2006

Guidelines for the conduct of clinical trials for spinal cord injury as developed by the ICCP panel: spontaneous recovery after spinal cord injury and statistical power needed for therapeutic clinical trials.

The International Campaign for Cures of Spinal Cord Injury Paralysis (ICCP) supported an international panel tasked with reviewing the methodology for clinical trials in spinal cord injury (SCI), and making recommendations on the conduct of future trials. This is the first of four papers. Here, we examine the spontaneous rate of recovery after SCI and resulting consequences for achieving statistically significant results in clinical trials. We have reanalysed data from the Sygen trial to provide some of this information. Almost all people living with SCI show some recovery of motor function below the initial spinal injury level. While the spontaneous recovery of motor function in patients with motor-complete SCI is fairly limited and predictable, recovery in incomplete SCI patients (American spinal injury Association impairment scale (AIS) C and AIS D) is both more substantial and highly variable. With motor complete lesions (AIS A/AIS B) the majority of functional return is within the zone of partial preservation, and may be sufficient to reclassify the injury level to a lower spinal level. The vast majority of recovery occurs in the first 3 months, but a small amount can persist for up to 18 months or longer. Some sensory recovery occurs after SCI, on roughly the same time course as motor recovery. Based on previous data of the magnitude of spontaneous recovery after SCI, as measured by changes in ASIA motor scores, power calculations suggest that the number of subjects required to achieve a significant result from a trial declines considerably as the start of the study is delayed after SCI. Trials of treatments that are most efficacious when given soon after injury will therefore, require larger patient numbers than trials of treatments that are effective at later time points. As AIS B patients show greater spontaneous recovery than AIS A patients, the number of AIS A patients requiring to be enrolled into a trial is lower. This factor will have to be balanced against the possibility that some treatments will be more effective in incomplete patients. Trials involving motor incomplete SCI patients, or trials where an accurate assessment of AIS grade cannot be made before the start of the trial, will require large subject numbers and/or better objective assessment methods.

Clinical Trials as Topic↗
PubMed2006

Guidelines for the conduct of clinical trials for spinal cord injury (SCI) as developed by the ICCP panel: clinical trial outcome measures.

An international panel reviewed the methodology for clinical trials of spinal cord injury (SCI), and provided recommendations for the valid conduct of future trials. This is the second of four papers. It examines clinical trial end points that have been used previously, reviews alternative outcome tools and identifies unmet needs for demonstrating the efficacy of an experimental intervention after SCI. The panel focused on outcome measures that are relevant to clinical trials of experimental cell-based and pharmaceutical drug treatments. Outcome measures are of three main classes: (1) those that provide an anatomical or neurological assessment for the connectivity of the spinal cord, (2) those that categorize a subject's functional ability to engage in activities of daily living, and (3) those that measure an individual's quality of life (QoL). The American Spinal Injury Association impairment scale forms the standard basis for measuring neurologic outcomes. Various electrophysiological measures and imaging tools are in development, which may provide more precise information on functional changes following treatment and/or the therapeutic action of experimental agents. When compared to appropriate controls, an improved functional outcome, in response to an experimental treatment, is the necessary goal of a clinical trial program. Several new functional outcome tools are being developed for measuring an individual's ability to engage in activities of daily living. Such clinical end points will need to be incorporated into Phase 2 and Phase 3 trials. QoL measures often do not correlate tightly with the above outcome tools, but may need to form part of Phase 3 trial measures.

Activities of Daily Living↗
PubMed2006

Guidelines for the conduct of clinical trials for spinal cord injury as developed by the ICCP Panel: clinical trial inclusion/exclusion criteria and ethics.

The International Campaign for Cures of Spinal Cord Injury Paralysis established a panel tasked with reviewing the methodology for clinical trials for spinal cord injury (SCI), and making recommendations on the conduct of future trials. This is the third of four papers. It examines inclusion and exclusion criteria that can influence the design and analysis of clinical trials in SCI, together with confounding variables and ethical considerations. Inclusion and exclusion criteria for clinical trials should consider several factors. Among these are (1) the enrollment of subjects at appropriate stages after SCI, where there is supporting data from animal models or previous human studies; (2) the severity, level, type, or size of the cord injury, which can influence spontaneous recovery rate and likelihood that an experimental treatment will clinically benefit the subject; and (3) the confounding effects of various independent variables such as pre-existing or concomitant medical conditions, other medications, surgical interventions, and rehabilitation regimens. An issue of substantial importance in the design of clinical trials for SCI is the inclusion of blinded assessments and sham surgery controls: every effort should be made to address these major issues prospectively and carefully, if clear and objective information is to be gained from a clinical trial. The highest ethical standards must be respected in the performance of clinical trials, including the adequacy and clarity of informed consent.

Clinical Trials as Topic↗
PubMed2006

Guidelines for the conduct of clinical trials for spinal cord injury as developed by the ICCP panel: clinical trial design.

The International Campaign for Cures of Spinal Cord Injury Paralysis established a panel tasked with reviewing the methodology for clinical trials for spinal cord injury (SCI), and making recommendations on the conduct of future trials. This is the fourth of four papers. Here, we examine the phases of a clinical trial program, the elements, types, and protocols for valid clinical trial design. The most rigorous and valid SCI clinical trial would be a prospective double-blind randomized control trial utilizing appropriate placebo control subjects. However, in specific situations, it is recognized that other trial procedures may have to be considered. We review the strengths and limitations of the various types of clinical trials with specific reference to SCI. It is imperative that the design and conduct of SCI clinical trials should meet appropriate standards of scientific inquiry to insure that meaningful conclusions about efficacy and safety can be achieved and that the interests of trial subjects are protected. We propose these clinical trials guidelines for use by the SCI clinical research community.

Clinical Trials as Topic↗
PubMed2005

BDNF-expressing marrow stromal cells support extensive axonal growth at sites of spinal cord injury.

Bone marrow stromal cells (MSCs) constitute a heterogeneous cell layer in the bone marrow, supporting the growth and differentiation of hematopoietic stem cells. Recently, it has been reported that MSCs harbor pluripotent stem cells capable of neural differentiation and that simple treatment of MSCs with chemical inducing agents leads to their rapid transdifferentiation into neural cells. We examined whether native or neurally induced MSCs would reconstitute an axonal growth-promoting milieu after cervical spinal cord injury (SCI), and whether such cells could act as vehicles of growth factor gene delivery to further augment axonal growth. One month after grafting to cystic sites of SCI, native MSCs supported modest growth of host sensory and motor axons. Cells "neurally" induced in vitro did not sustain a neural phenotype in vivo and supported host axonal growth to a degree equal to native MSCs. Transduction of MSCs to overexpress brain-derived neurotrophic factor (BDNF) resulted in a significant increase in the extent and diversity of host axonal growth, enhancing the growth of host serotonergic, coerulospinal, and dorsal column sensory axons. Measurement of neurotrophin production from implanted cells in the lesion site revealed that the grafts naturally contain nerve growth factor (NGF) and neurotrophin-3 (NT-3), and that transduction with BDNF markedly raises levels of BDNF production. Despite the extensive nature of host axonal penetration into the lesion site, functional recovery was not observed on a tape removal or rope-walking task. Thus, MSCs can support host axonal growth after spinal cord injury and are suitable cell types for ex vivo gene delivery. Combination therapy with other experimental approaches will likely be required to achieve axonal growth beyond the lesion site and functional recovery.

Animals↗
PubMed2004

Anatomical evidence for transsynaptic influences of estrogen on brain-derived neurotrophic factor expression.

Several studies have demonstrated that estrogen modulates brain-derived neurotrophic factor (BDNF) mRNA and protein within the adult hippocampus and cortex. However, mechanisms underlying this regulation are unknown. Although an estrogen response element (ERE)-like sequence has been identified within the BDNF gene, such a classical mechanism of estrogen-induced transcriptional activation requires the colocalized expression of estrogen receptors within cells that produce BDNF. Developmental studies have demonstrated such a relationship, but to date no studies have examined colocalization of estrogen receptors and BDNF within the adult brain. By utilizing double-label immunohistochemistry for BDNF, estrogen receptor-alpha (ER-alpha), and estrogen receptor-beta (ER-beta), we found only sparse colocalization between ER-alpha and BDNF in the hypothalamus, amygdala, prelimbic cortex, and ventral hippocampus. Furthermore, ER-beta and BDNF do not colocalize in any brain region. Given the recent finding that cortical ER-beta is almost exclusively localized to parvalbumin-immunoreactive GABAergic neurons, we performed BDNF/parvalbumin double labeling and discovered that axons from cortical ER-beta-expressing inhibitory neurons terminate on BDNF-immunoreactive pyramidal cells. Collectively, these findings support a potential transsynaptic relationship between estrogen state and cortical BDNF: By directly modulating GABAergic interneurons, estrogen may indirectly influence the activity and expression of BDNF-producing cortical neurons.

Amygdala↗
PubMed2003

Neural stem cells constitutively secrete neurotrophic factors and promote extensive host axonal growth after spinal cord injury.

Neural stem cells (NSCs) offer the potential to replace lost tissue after nervous system injury. This study investigated whether grafts of NSCs (mouse clone C17.2) could also specifically support host axonal regeneration after spinal cord injury and sought to identify mechanisms underlying such growth. In vitro, prior to grafting, C17.2 NSCs were found for the first time to naturally constitutively secrete significant quantities of several neurotrophic factors by specific ELISA, including nerve growth factor, brain-derived neurotrophic factor, and glial cell line-derived neurotrophic factor. When grafted to cystic dorsal column lesions in the cervical spinal cord of adult rats, C17.2 NSCs supported extensive growth of host axons of known sensitivity to these growth factors when examined 2 weeks later. Quantitative real-time RT-PCR confirmed that grafted stem cells expressed neurotrophic factor genes in vivo. In addition, NSCs were genetically modified to produce neurotrophin-3, which significantly expanded NSC effects on host axons. Notably, overexpression of one growth factor had a reciprocal effect on expression of another factor. Thus, stem cells can promote host neural repair in part by secreting growth factors, and their regeneration-promoting activities can be modified by gene delivery.

Animals↗
PubMed2003

Delayed grafting of BDNF and NT-3 producing fibroblasts into the injured spinal cord stimulates sprouting, partially rescues axotomized red nucleus neurons from loss and atrophy, and provides limited regeneration.

Ex vivo gene therapy, utilizing modified fibroblasts that deliver BDNF or NT-3 to the acutely injured spinal cord, has been shown to elicit regeneration and recovery of function in the adult rat. Delayed grafting into the injured spinal cord is of great clinical interest as a model for treatment of chronic injury but may pose additional obstacles that are not present after acute injury, such as the need to remove an established scar, increased retrograde cell loss and/or atrophy, and diminished capacity for regeneration by neurons which may be doubly injured. The purpose of the present study was to determine if delayed grafting of neurotrophin secreting fibroblasts would have anatomical effects similar to those seen in acute grafting models. We grafted a mixture of BDNF and NT-3 producing fibroblasts or control fibroblasts into a complete unilateral cervical hemisection after a 6-week delay. Fourteen weeks after delayed grafting we found that both the neurotrophin secreting fibroblasts and control fibroblasts survived, but that only the neurotrophin secreting grafts provided a permissive environment for host axon growth, as indicated by immunostaining for RT-97, a marker for axonal neurofilaments, GAP-43, a marker for elongating axons, CGRP, a marker for dorsal root axons, and 5-HT, a marker for raphe spinal axons, within the graft. Anterograde tracing of the uninjured vestibulospinal tract showed growth into neurotrophin producing transplants but not into control grafts, while anterograde tracing of the axotomized rubrospinal tract showed a small number of regenerating axons within the genetically modified grafts, but none in control grafts. The neurotrophin expressing grafts, but not the control grafts, significantly reduced retrograde degeneration and atrophy in the injured red nucleus. Grafts of BDNF + NT-3 expressing fibroblasts delayed 6 weeks after injury therefore elicit growth from intact segmental and descending spinal tracts, stimulate modest regenerative growth by rubrospinal axons, and partially rescue axotomized supraspinal neurons and protect them from atrophy. The regeneration of rubrospinal axons into delayed transplants was much less than has been observed when similar transplants were placed acutely into a lateral funiculus or, after a 4-week delay, into a hemisection lesion. This suggests that the regenerative capacity of chronically injured red nucleus neurons was markedly diminished. The increased GAP43 reactivity in the corticospinal tracts ipsilaterally and contralaterally to the combination grafts suggests that these axons remain responsive to the neurotrophins, that the neurotrophins may stimulate both regenerative and sprouting responses, and that the grafted cells continue to secrete the neurotrophins.

Animals↗
PubMed2001

Conservation of neuronal number and size in the entorhinal cortex of behaviorally characterized aged rats.

Despite abundant evidence of behavioral and electrophysiological dysfunction of the rodent hippocampal formation with aging, the structural basis of age-related cognitive decline remains unclear. Recently, unbiased stereological studies of the mammalian hippocampus have found little evidence to support the dogma that cellular loss accompanies hippocampal aging, thereby supporting an alternative hypothesis that aging is marked by widespread conservation of neuronal number. However, to date, the effects of aging have not been reported in another key component of memory systems in the rodent brain, the entorhinal cortex. In the present study, we stereologically estimated total neuronal number and size (cross-sectional area and cell volume) in the subdivisions and cellular layers of the rat entorhinal cortex, using the optical fractionator and nucleator, respectively. Comparisons were made among Fischer 344 rats that were young, aged-impaired, and aged-unimpaired (based on functional analysis in the Morris water maze). No significant differences in cell number or size were observed in any of the entorhinal subdivisions or laminae examined in each group. Thus, aging is associated with widespread conservation of neuronal number, despite varying degrees of cognitive decline, in all memory-related systems examined to date. These data suggest that mechanisms of age-related cognitive decline are to be found in parameters other than neuronal number or size in the cortex of the mammalian brain.

Aging↗
PubMed2001

Chronic intrathecal infusions after spinal cord injury cause scarring and compression.

Intrathecal infusions are used in a number of rodent studies to deliver substances to the injured spinal cord. Whereas this method has been successful in certain paradigms, two potential limitations of this model have not been extensively reported: (1) scar formation at the catheter tip, which can lead to infusion failure, and (2) damage to the spinal cord caused by the catheter itself. Thus, the purpose of the present study was threefold: (1) to determine intrathecal infusion efficiency over 14 days following spinal cord injury; (2) to examine possible secondary damage caused by intrathecal tubing; and (3) to explore whether alternative protocols that avoid such damage are effective. Adult Fischer 344 rats were subjected to spinal cord lesions at T7, followed by placement of an intrathecal catheter attached to an Alzet minipump. Seven or 14 days following injury and catheter placement, tube patency was evaluated by diffusion of Evans Blue dye from the minipump. Results indicate that infusion was efficient 7 days following injury but was markedly reduced after 14 days. Further, histology and immunocytochemistry 14 days after injury demonstrated compression damage to the cord where the tubing rested. Alternative protocols, including intrathecal infusions through metal cannulae, or "drip" infusions directly over the lesion, did not improve delivery. These data suggest that results from rodent studies using infusion from catheters placed adjacent to lesion sites may be attributable to acute or subacute effects of the delivered substance. Future rodent studies using intrathecal infusions should include rigorous evaluation of infusion efficiency and possible secondary tissue damage.

Animals↗
PubMed2001

GDNF gene delivery to injured adult CNS motor neurons promotes axonal growth, expression of the trophic neuropeptide CGRP, and cellular protection.

Glial-cell-line--derived neurotrophic factor (GDNF) has been identified as a potent survival and differentiation factor for several neuronal populations in the central nervous system (CNS), but to date, distinct effects of GDNF on motor axon growth and regeneration in the adult have not been demonstrated. In the present study, ex vivo gene delivery was used to directly examine whether GDNF can influence axonal growth, expression of neuronal regeneration-related genes, and sustain the motor neuronal phenotype after adult CNS injury. Adult Fischer 344 rats underwent unilateral transections of the hypoglossal nerve, followed by intramedullary grafts of fibroblasts genetically modified to secrete GDNF. Control animals received lesions and grafts of cells expressing a reporter gene. Two weeks later, GDNF gene delivery (1) robustly promoted the growth of lesioned hypoglossal motor axons, (2) altered the expression and intracellular trafficking of the growth-related protein calcitonin gene-related peptide (CGRP), and (3) significantly sustained the cholinergic phenotype in 84 +/- 6% of hypoglossal neurons compared with 39 +/- 6% in control animals (P < 0.001). This is the first neurotrophic factor identified to increase the in vivo expression of the trophic peptide CGRP and the first report that GDNF promotes motor axonal growth in vivo in the adult CNS. Taken together with previous in vitro studies, these findings serve as the foundation for a model wherein GDNF and CGRP interact in a paracrine manner to regulate neuromuscular development and regeneration.

Animals↗
PubMed2001

Neurotrophism without neurotropism: BDNF promotes survival but not growth of lesioned corticospinal neurons.

Neurotrophic factors exert many effects on the intact and lesioned adult central nervous system (CNS). Among these effects are prevention of neuronal death (neurotrophism) and promotion of axonal growth (neurotropism) after injury. To date, however, it has not been established whether survival and axonal growth functions of neurotrophins can be independently modulated in injured adult neurons in vivo. To address this question, the ability of brain-derived neurotrophic factor (BDNF) to influence corticospinal motor neuronal survival and axonal growth was examined in two injury paradigms. In the first paradigm, a survival assay, adult Fischer 344 rats underwent subcortical lesions followed by grafts to the lesion cavity of syngenic fibroblasts genetically modified to secrete high amounts BDNF or, in control subjects, the reporter gene green fluorescent protein. In control subjects, only 36.2 +/- 7.0% of the retrogradely labeled corticospinal neurons survived the lesion, whereas 89.8 +/- 5.9% (P < 0.001) of the corticospinal neurons survived in animals that received BDNF-secreting grafts. However, in an axonal growth assay, BDNF-secreting cell grafts that were placed into either subcortical lesion sites or sites of thoracic spinal cord injury failed to elicit corticospinal axonal growth. Despite this lack of a neurotropic effect on lesioned corticospinal axons, BDNF-secreting cell grafts placed in the injured spinal cord significantly augmented the growth of other types of axons, including local motor, sensory, and coerulospinal axons. Immunolabeling for tyrosine kinase B (trkB) demonstrated that BDNF receptors were present on corticospinal neuronal somata and apical dendrites but were not detected on their projecting axons. Thus, single classes of neurons in the adult CNS appear to exhibit disparate survival and growth sensitivity to neurotrophic factors, potentially attributable at least in part to differential trafficking of neurotrophin receptors. The possibility of tropic/trophic divergence must be considered when designing strategies to promote CNS recovery from injury.

Animals↗
PubMed2001

Neurotrophic factors, cellular bridges and gene therapy for spinal cord injury.

Injury to the adult mammalian spinal cord results in extensive axonal degeneration, variable amounts of neuronal loss, and often severe functional deficits. Restoration of controlled function depends on regeneration of these axons through an injury site and the formation of functional synaptic connections. One strategy that has emerged for promoting axonal regeneration after spinal cord injury is the implantation of autologous Schwann cells into sites of spinal cord injury to support and guide axonal growth. Further, more recent experiments have shown that neurotrophic factors can also promote axonal growth, and, when combined with Schwann cell grafts, can further amplify axonal extension after injury. Continued preclinical development of these approaches to neural repair may ultimately generate strategies that could be tested in human injury.

Animals↗
PubMed2001

Reactive astrocytes express estrogen receptors in the injured primate brain.

Previous studies have suggested that estrogen may regulate the expression of genes related to the inflammatory response within the nervous system, particularly within glia. In the present study, we examined whether injury induces estrogen sensitivity in reactive glia in the primate brain. Three adult Macaca fascicularis (cynomolgous) monkeys received unilateral fimbria fornix transections followed by chronic intracranial cannula implants through which a vehicle solution was infused intracerebroventricularly for a 4-week period. Astrocytes adjacent to areas of parenchymal disruption caused either by the lesion or by the instrumentation procedure became reactive, as evidenced by cellular hypertrophy and up-regulation of glial fibrillary acidic protein (GFAP) immunolabeling. Of note, specific estrogen receptor-alpha immunolabeling also was induced adjacent to injured regions, and this labeling strictly colocalized with GFAP immunoreactivity upon double fluorescent confocal immunolabeling. Induction of estrogen receptor immunoreactivity in reactive astrocytes occurred in all monkeys examined, whereas nonreactive glia distant from disrupted regions did not exhibit estrogen receptor labeling. Thus, expression of estrogen receptors is up-regulated in reactive astrocytes of the primate brain, potentially allowing estrogen to modulate aspects of the central nervous system's inflammatory response to injury.

Alzheimer Disease↗