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In JoVE (1)
Other Publications (6)
Articles by Karen-Amanda Irvine in JoVE
JoVE Neuroscience
A Novel Method for Assessing Proximal and Distal Forelimb Function in the Rat: the Irvine, Beatties and Bresnahan (IBB) Forelimb Scale
Department of Neurological Surgery, University of California, San Francisco
Here we will describe a rodent behavioral assay that can detect recovery of both proximal and distal forelimb function including digit movements during a naturally occurring behavior that does not require extensive training or deprivation to enhance motivation.
Other articles by Karen-Amanda Irvine on PubMed
A Different Regional Response by Mouse Oligodendrocyte Progenitor Cells (OPCs) to High-dose X-irradiation Has Consequences for Repopulating OPC-depleted Normal Tissue
This study was designed to investigate whether the residual, dysfunctional oligodendrocyte progenitor cells (OPCs) observed following X-irradiation of the mouse spinal cord [D. M. Chari et al. (2003) Exp. Neurol., 198, 145-153], the presence of which prevented the endogenous repopulation of these areas from normal tissue, reflects a general response of OPCs in the mouse central nervous system (CNS) to X-irradiation. The brains of adult mice were exposed to 40 Gy of X-irradiation and the effect of X-irradiation on the OPCs was assessed up to 4 weeks post-irradiation using anti-NG2 antibodies. X-irradiation resulted in almost complete depletion of OPCs within the telencephalon (cortex, corpus callosum and hippocampus) by 7 days post-irradiation, which was followed by progressive repopulation of OPCs from non-irradiated areas of the cortex. By contrast, within the lower brain centres (the diencephalon and mesencephalon) OPC loss occurred much more slowly so that 26% of the OPCs still remained 4 weeks after X-irradiation. The consequence of this heterogeneous response to X-irradiation was that whereas transplanted and endogenous OPCs rapidly established themselves in the OPC-depleted telencephalon this did not occur in the areas where there was incomplete depletion of endogenous OPCs. Our findings confirm not only the requirement for almost complete OPC depletion in order to establish transplanted OPCs in normal tissue but also highlight a heterogeneity of progenitor populations in different areas of the mouse CNS.
Environmental Signals Regulate Lineage Choice and Temporal Maturation of Neural Stem Cells from Human Embryonic Stem Cells
Human embryonic stem cells (hESCs) are a potential source of defined tissue for cell-based therapies in regenerative neurology. In order for this potential to be realized, there is a need for the evaluation of the behaviour of human embryonic stem cell-derived neural stem cells (hES-NSCs) both in the normal and the injured CNS. Using normal tissue and two experimental models, we examined the response of clinically compatible hES-NSCs to physiological and pathological signals. We demonstrate that the phenotypic potential of a multipotent population of hES-NSCs is influenced by these cues both in vitro and in vivo. hES-NSCs display a temporal profile of neurogenic and gliogenic differentiation, with the generation of mature neurons and glia over 4 weeks in vitro, and 20 weeks in the uninjured rodent brain. However, transplantation into the pathological CNS accelerates maturation and polarizes hES-NSC differentiation potential. This study highlights the role of environmental signals in determining both lineage commitment and temporal maturation of human neural stem cells. Controlled manipulation of environmental signals appropriate to the pathological specificity of the targeted disease will be necessary in the design of therapeutic stem cell-based strategies.
An Experimental Model of Secondary Progressive Multiple Sclerosis That Shows Regional Variation in Gliosis, Remyelination, Axonal and Neuronal Loss
Multiple sclerosis (MS) represents a considerable challenge to experimentally model due to its twin pathologies of inflammatory demyelination and neurodegeneration along with its multifocal and multiphasic nature. Experimental autoimmune encephalomyelitis (EAE) in Biozzi ABH mice has previously been shown to reproduce many clinical features also found in secondary progressive MS. In this study we sought to characterise the pathology of chronic EAE in ABH mice. In addition to marked gliosis, we report substantial demyelination, remyelination and axonal and neuronal loss. Together with the clinical pattern, our findings identify chronic EAE as an excellent model of secondary progressive multiple sclerosis.
Transplanted Oligodendrocyte Precursor Cells Reduce Neurodegeneration in a Model of Glaucoma
Glaucoma is a common neurodegenerative disease for which current therapies are often insufficient; thus, new neuroprotective strategies are an important goal. Stem cells are attracting increasing attention as mediators of neuroprotection, often conferred via the trophic support of injured neurons. The purpose of our investigation was to determine whether oligodendrocyte precursor cells (OPCs), a type of neural stem cell, can protect retinal ganglion cells (RGCs) from glaucomatous damage in vivo.
Dysregulation of the Wnt Pathway Inhibits Timely Myelination and Remyelination in the Mammalian CNS
The progressive loss of CNS myelin in patients with multiple sclerosis (MS) has been proposed to result from the combined effects of damage to oligodendrocytes and failure of remyelination. A common feature of demyelinated lesions is the presence of oligodendrocyte precursors (OLPs) blocked at a premyelinating stage. However, the mechanistic basis for inhibition of myelin repair is incompletely understood. To identify novel regulators of OLP differentiation, potentially dysregulated during repair, we performed a genome-wide screen of 1040 transcription factor-encoding genes expressed in remyelinating rodent lesions. We report that approximately 50 transcription factor-encoding genes show dynamic expression during repair and that expression of the Wnt pathway mediator Tcf4 (aka Tcf7l2) within OLPs is specific to lesioned-but not normal-adult white matter. We report that beta-catenin signaling is active during oligodendrocyte development and remyelination in vivo. Moreover, we observed similar regulation of Tcf4 in the developing human CNS and lesions of MS. Data mining revealed elevated levels of Wnt pathway mRNA transcripts and proteins within MS lesions, indicating activation of the pathway in this pathological context. We show that dysregulation of Wnt-beta-catenin signaling in OLPs results in profound delay of both developmental myelination and remyelination, based on (1) conditional activation of beta-catenin in the oligodendrocyte lineage in vivo and (2) findings from APC(Min) mice, which lack one functional copy of the endogenous Wnt pathway inhibitor APC. Together, our findings indicate that dysregulated Wnt-beta-catenin signaling inhibits myelination/remyelination in the mammalian CNS. Evidence of Wnt pathway activity in human MS lesions suggests that its dysregulation might contribute to inefficient myelin repair in human neurological disorders.
Forelimb Locomotor Assessment Scale (FLAS): Novel Assessment of Forelimb Dysfunction After Cervical Spinal Cord Injury
We describe here a novel forelimb locomotor assessment scale (FLAS) that assesses forelimb use during locomotion in rats injured at the cervical level. A quantitative scale was developed that measures movements of shoulder, elbow, and wrist joints, forepaw position and digit placement, forelimb-hindlimb coordination, compensatory behaviors adopted while walking, and balance. Female Sprague-Dawley rats received graded cervical contusions ranging from 200 to 230 ("mild," n=11) and 250-290 kdyn ("moderate," n=13) between C5 and C8. Rats were videotaped post-injury as they walked along an alley to determine deficits and recovery of forelimb function. Recovery of shoulder and elbow joint movement occurred rapidly (within 1-7 days post-injury), whereas recovery of wrist joint movement was slower and more variable. Most rats in all groups displayed persistent deficits in forepaw and digit movement, but developed compensatory behaviors to allow functional forward locomotion within 1-2 weeks post-injury. Recovery of forelimb function as measured by the FLAS reached a plateau by 3 weeks post-injury in all groups. Rats with mild contusions displayed greater locomotor recovery than rats with moderate contusions, but exhibited persistent deficits compared to sham controls. Reliability was tested by having seven raters (three internal, four external) from different laboratories, independently and blindly score videos of all rats. The multivariate correlation between all raters, all animals, and all time points ranged from r(2)=0.88-0.96 (p<0.0001), indicating a high inter-rater reliability. Thus, the FLAS is a simple, inexpensive, sensitive, and reliable measure of forelimb function during locomotion following cervical SCI.
