Murine Model Of Globoid Cell Leukodystrophy Research Articles

Clinical, electrophysiological, and biochemical markers of peripheral and central nervous system disease in canine globoid cell leukodystrophy (Krabbe'sdisease).

Globoid cell leukodystrophy (GLD), or Krabbe's disease, is a debilitating and always fatal pediatric neurodegenerative disease caused by a mutation in the gene encoding the hydrolytic enzyme galactosylceramidase (GALC). In the absence of GALC, progressive loss of myelin and accumulation of a neurotoxic substrate lead to incapacitating loss of motor and cognitive function and death, typically by 2 years of age. Currently, there is no cure. Recent convincing evidence of the therapeutic potential of combining gene and cell therapies in the murine model of GLD has accelerated the requirement for validated markers of disease to evaluate therapeutic efficacy. Here we demonstrate clinically relevant and quantifiable measures of central (CNS) and peripheral (PNS) nervous system disease progression in the naturally occurring canine model of GLD. As measured by brainstem auditory-evoked response testing, GLD dogs demonstrated a significant increase in I-V interpeak latency and hearing threshold at all time points. Motor nerve conduction velocities (NCVs) in GLD dogs were significantly lower than normal by 12-16 weeks of age, and sensory NCV was significantly lower than normal by 8-12 weeks of age, serving as a sensitive indicator of peripheral nerve dysfunction. Post-mortem histological evaluations confirmed neuroimaging and electrodiagnostic assessments and detailed loss of myelin and accumulation of storage product in the CNS and the PNS. Additionally, cerebrospinal fluid psychosine concentrations were significantly elevated in GLD dogs, demonstrating potential as a biochemical marker of disease. These data demonstrate that CNS and PNS disease progression can be quantified over time in the canine model of GLD with tools identical to those used to assess human patients. © 2016 Wiley Periodicals, Inc.

Mitigation of cerebellar neuropathy in globoid cell leukodystrophy mice by AAV-mediated gene therapy

Globoid cell leukodystrophy (GLD) is an autosomal recessive, lysosomal storage disease caused by deficiency of the enzyme galactocerebrosidase (GALC). The absence of GALC activity leads to the accumulation of the toxic substance psychosine and the preferential loss of myelinating cells in the central and peripheral nervous systems. Profound demyelination, astrogliosis and axonopathy are the hallmarks of the pathogenesis of GLD, and cerebellar ataxia is one of the dominant manifestations in adolescents and adults affected with GLD. To date, studies regarding cerebellar degeneration in GLD are limited. In this study, the efficacy of cerebellum-targeted gene therapy on the cerebellar neuropathology in twitcher mice (a murine model of GLD) has been validated. We observed degeneration of Purkinje cells, Bergmann glia, and granule cells in addition to astrocytosis and demyelination in the cerebellum of the twitcher mice. Ultrastructural analysis revealed dark cell degeneration and disintegration of the cellular composition of Purkinje cells in untreated twitcher mice. In addition, the expressions of neurotrophic factors CNTF, GDNF and IGF-I were up-regulated and the expression of BDNF was down-regulated. Intracerebellar-mediated gene therapy efficiently corrected enzymatic deficiency by direct transduction to Purkinje cells and cross-correction in other cell types in the cerebellum, leading to the amelioration of both neuroinflammation and demyelination. The population, dendritic territory, and axonal processes of Purkinje cells remained normal in the cerebellum of treated twitcher mice, where radial fibers of Bergmann glia spanned the molecular layer and collateral branches ensheathed the dendritic processes of Purkinje cells. Moreover, the aberrant expressions of neurotrophic factors were mitigated in the cerebellum of treated twitcher mice, indicating the preservation of cellular function in addition to maintaining the neuronal architecture. The life span of the treated twitcher mice was significantly prolonged and their neurobehavioral performance was improved. Taken together, our findings underscore the complexity of cerebellar neurodegeneration in GLD and highlight the potential effectiveness of gene therapy in mitigating neuropathological deficits in GLD and other neurodegenerative disorders in which Purkinje cells are involved.

Bone Marrow Transplantation Augments the Effect of Brain- and Spinal Cord-Directed Adeno-Associated Virus 2/5 Gene Therapy by Altering Inflammation in the Murine Model of Globoid-Cell Leukodystrophy

Globoid-cell leukodystrophy (GLD) is an inherited demyelinating disease caused by the deficiency of the lysosomal enzyme galactosylceramidase (GALC). A previous study in the murine model of GLD (twitcher) demonstrated a dramatic synergy between CNS-directed adeno-associated virus 2/5 (AAV2/5) gene therapy and myeloreductive bone marrow transplantation (BMT). However, the mechanism by which these two disparate therapeutic approaches synergize is not clear. In addition, the therapeutic efficacy may have been limited since the CNS-directed gene therapy was restricted to the forebrain and thalamus. In the current study, intrathecal and intracerebellar injections were added to the therapeutic regimen and the mechanism of synergy between BMT and gene therapy was determined. Although AAV2/5 alone provided supraphysiological levels of GALC activity and reduced psychosine levels in both the brain and spinal cord, it significantly increased CNS inflammation. Bone marrow transplantation alone provided essentially no GALC activity to the CNS and did not reduce psychosine levels. When AAV2/5 is combined with BMT, there are sustained improvements in motor function and the median life span is increased to 123 d (range, 92-282 d) compared with 41 d in the untreated twitcher mice. Interestingly, addition of BMT virtually eliminates both the disease and AAV2/5-associated inflammatory response. These data suggest that the efficacy of AAV2/5-mediated gene therapy is limited by the associated inflammatory response and BMT synergizes with AAV2/5 by modulating inflammation.

Adeno-associated Virus Type 5 Reduces Learning Deficits and Restores Glutamate Receptor Subunit Levels in MPS VII Mice CNS

A major challenge in treating lysosomal storage diseases with enzyme therapy is correcting symptoms in the central nervous system (CNS). This study used a murine model of mucopolysaccharidosis type VII (MPS VII) to test whether pathological and functional CNS defects could be corrected by expressing beta-glucuronidase via bilateral intrastriatal injection of adeno-associated virus type 5 (AAV5betagluc) vectors. After injecting AAV5betagluc, different brain regions expressed active beta-glucuronidase, which corrected lysosomal storage defects. Compared to age-matched littermates, adult MPS VII mice were impaired in spatial learning and memory, as measured by the repeated acquisition and performance chamber (RAPC) assay. AAV5betagluc-treated MPS VII mice improved significantly in the RAPC assay, relative to saline-injected littermates. Moreover, our studies reveal that cognitive changes in MPS VII mice correlate with decreased N-methyl-d-aspartate and alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid receptor expression. Importantly, AAV5betagluc delivery restored glutamate receptor levels. Together, these data demonstrate that AAV5 vectors deliver a therapeutically effective beta-glucuronidase gene to the CNS and further suggest a possible mechanism underlying spatial learning defects in MPS VII mice.

Central Nervous System-directed AAV2/5-Mediated Gene Therapy Synergizes with Bone Marrow Transplantation in the Murine Model of Globoid-cell Leukodystrophy

Globoid-cell leukodystrophy (GLD) is a rapidly progressing inherited neurodegenerative disorder caused by a deficiency in galactosylceramidase activity. Previous studies in the murine model of GLD (Twitcher mouse) have shown that both bone marrow transplantation (BMT) and central nervous system (CNS)-directed gene therapy can be moderately effective at ameliorating certain aspects of GLD. As BMT and CNS-directed gene therapy target fundamentally different tissues, we tested the hypothesis that combining these disparate therapies would be more efficacious than either therapy alone. Mice receiving myeloreductive conditioning at birth followed by syngeneic BMT had approximately 25-35% donor chimerism. Untreated Twitcher mice, Twitcher mice treated with BMT alone, AAV2/5 alone, or a combination of BMT and AAV2/5 had mean lifespans of 39, 44, 49, and 104 days, respectively. Twitcher mice treated with a combination of BMT and AAV2/5 also had significantly improved performance in several behavioral tests and greater reduction in demyelination, astrocytosis, and macrophage infiltration compared to untreated Twitcher mice or mice that received either therapy alone. These data suggest that CNS-directed gene therapy synergizes with BMT. The combination of these disparate therapeutic approaches may form the basis for more effective treatment of this inherited neurodegenerative disorder.

AAV2/5 vector expressing galactocerebrosidase ameliorates CNS disease in the murine model of globoid-cell leukodystrophy more efficiently than AAV2

Globoid-cell leukodystrophy (GLD) is an autosomal recessive lysosomal storage disorder caused by mutations in the galactosylceramidase (GALC) gene. Infantile GLD has a lethal course with severe cerebral demyelination that progresses to death by 2 years of age. In the current study twitcher mice, an authentic murine model of infantile GLD, were given intracranial injections of either recombinant adeno-associated virus serotype 2 encoding the murine Galc cDNA (AAV2-GALC) or the same genome pseudotyped with AAV5 capsid proteins (AAV2/5-GALC) on day 3 of age. The group injected intracranially with AAV2/5-GALC had approximately 25-fold greater than normal Galc levels in the brain, while AAV2-GALC-injected animals had 28% normal levels. The average life expectancy of twitcher mice ( approximately 38 days) was significantly (P < 0.0001) increased to 48 and 52 days for the AAV2-GALC- and AAV2/5-GALC-treated groups, respectively. The AAV2/5-GALC group performed significantly better in a battery of behavioral tests compared to untreated, AAV2-GFP-treated, or AAV2-treated twitcher animals. This longitudinal study demonstrated that AAV2/5-GALC-mediated gene therapy resulted in higher levels of Galc expression and slowed the neurologic deterioration more completely than AAV2-GALC in the murine model of globoid-cell leukodystrophy. However, the clinical improvements, as assessed by behavioral tests and life span, were only modest.

424. Intracranial AAV5 Synergizes with Non-Myeloablative Bone Marrow Transplantation in the Murine Model of Globoid-Cell Leukodystrophy

Top of pageAbstract Globoid-cell leukodystrophy (GLD or Krabbe disease) is a neurodegenerative lysosomal storage disease caused by an inherited deficiency in galactosylceramidase (GALC) activity. A murine model of GLD (Twitcher mouse) exists that mimics many of the biochemical and clinical aspects of the human disease. It has been shown previously that bone marrow transplantation (BMT) following myeloablative radiation (800-900 rads) performed in 8-9 day old Twitcher mice significantly increased the average life span (increased from |[sim]|40 to |[sim]|80 days) and reduced the levels of pro-inflammatory cytokines in the brain. Due to the severe developmental damage caused by high dose radiation, we treated newborn Twitcher mice (2 days old) with BMT following myeloreductive (400 rads) rather than myeloablative radiation. The animals had 20-40% normal donor chimerism, low level GALC activity in the brain, and a minor, but significant increase in the average life span (|[sim]|45 days). Unfortunately, the lower radiation dose combined with earlier treatment was less effective than the previous BMT regimen, although there was a minor but global decrease in CD11b(+) cells in the brain. It has been shown that intracranial injections of AAV vectors can improve the anatomical and functional deficits in animal models of other lysosmal storage diseases. We showed previously that injection of AAV2 or AAV5 vectors encoding murine GALC directly into the brains of newborn Twitcher mice resulted in GALC levels of 28% and 2,500% of normal, respectively, and a local reduction in both GFAP(+) and CD11b(+) cells in the brain. Surprisingly, there was only a moderate, albeit significant improvement in average life span (untreated |[sim]|38d, AAV2 |[sim]|45d, AAV5 |[sim]|53d). The AAV data suggest that simply supplying high levels of enzyme to targeted areas is not sufficient to fully correct this disease. Because AAV and myeloreductive BMT target different aspects of the disease to varying degrees (ie. GFAP(+) and CD11b(+) cells; local vs. global reductions), we hypothesized that combining the two therapies would synergize and be more efficacious than either approach alone. We injected newborn Twitcher mice intracranially with AAV5 and then intravenously with 106 GALC(+) bone marrow cells from a normal donor following 400 rads of conditioning radiation (AAV5/BMT-treated). High level GALC activity was measured in the brains of Twitcher mice that received combination AAV5/BMT treatment. The animals receiving the combination AAV5/BMT treatment had a more complete and widespread reduction of both GFAP(+) and CD11b(+) cells than either the AAV5-treated or BMT-treated animals. Interestingly, the average life span of the AAV5/BMT-treated Twitcher mice was 103 days (range = 38-153 days), which is considerably longer than any previous therapeutic approach. Our results suggest that a combination of approaches will likely be required for effective treatment of GLD.

Immunohistological study of globoid cell leukodystrophy

We examined three autopsy cases of globoid cell leukodystrophy (GLD) with different survival, using immunohistochemistry and in situ nick end labeling (ISEL). The white matter lesion was pronounced in the corona radiata, corpus callosum and cerebellar peduncles in three cases, where a spongy state developed, in addition to the neuronal loss in the thalamus, cerebellum and inferior olivary nucleus. Ramified microglia, being immunoreactive for ferritin and HLA-DR alpha, were scattered in the white matter, and some of them also had immunoreactivity for TNF-alpha. Both the small-sized and large-sized globoid cells showed immunoreactivity for ferritin KP-1 and NCAM, while some of the small-sized globoid cells were also immunoreactive for HLA-DR alpha and TNF-alpha. As the survival became longer, the occurrence of the globoid cells decreased, however, they were commonly observed in the corpus callosum and cerebellar peduncle in three cases. T lymphocytes immunoreactive for LCA, UCHL-1 and CD3 were increased around the vessels in the white matter. ISEL stained nuclei of mononuclear cells in the white matter in two cases with short survival, although the cell origin was not verified. ISEL also visualized a few nuclei of the small-sized globoid cells in one case. On the other hand, immunostainings against cell death proteins such as bcl-2 family members and p53 failed to identify any significant changes. These data suggest that the immunological step and to a lesser extent the apoptotic process may partly be involved in the myelin breakdown and glial pathology in GLD, as reported in the twitcher mouse, a murine model of GLD.

Globoid cell leukodystrophy: specialized contact of globoid cell with astrocyte in the brain of twitcher mouse.

Subplasmalemmal linear densities (Yajima et al. 1977 a) were the membrane specializations observed in globoid cells in globoid cell leukodystrophy (GLD) and in the cells of the mononuclear phagocytic system (Kawanami et al. 1980). In the spinal cord of the twitcher mouse, an authentic murine model of GLD, somewhat similar membrane specializations were noted in astrocytes, and on some occasions, a spot desmosome-like cellular contact was observed between globoid cells, which were likely to be mesodermal in origin, and astrocytes, which are of ectodermal origin. Possible significance of such apparent cellular contact is discussed briefly.