The effects of intracisternal enzyme replacement versus sham treatment on central neuropathology in preclinical canine fucosidosis.

BACKGROUND: Fucosidosis results from lack of α-L-fucosidase activity, with accumulation of fucose-linked substrates in the nervous system and viscera leading to progressive motor and mental deterioration, and death. The naturally occurring dog model of fucosidosis was used to evaluate the neuropathological responses to partial enzyme replacement, and substrate reduction in early disease following treatment with recombinant canine α-L-fucosidase delivered through cerebrospinal fluid. METHODS: Neuropathology in both treated (n = 3) and untreated fucosidosis-affected (n = 3) animals was evaluated with immunohistochemistry, image analysis, manual quantification and gene expression analysis and compared with unaffected age-matched controls (n = 3) in an extension of our previous biochemical report on the same cohort. Data were analyzed by ANOVA. RESULTS: Quantification demonstrated a consistent trend to reduction in vacuolation, pyramidal neuron loss, astrocytosis, microgliosis, perivascular storage, apoptosis, oligodendrocyte loss, and hypomyelination throughout the central nervous system of enzyme treated animals compared to placebo-treated, age-matched affected controls. Key lesions including lysosomal expansion in neurons of deep cortex, astrocytosis in cerebral cortex and medulla, and increased lysosomal membrane associated protein-1 (LAMP-1) gene expression were ameliorated in treated animals. There was no change in spheroid formation and loss of Purkinje cells, but Purkinje cell vulnerability to apoptosis was reduced with treatment. CONCLUSIONS: Despite reduced severity of fucosidosis neuropathology with partial enzyme replacement, more complete and sustained biochemical correction is required to halt neuropathological processes in this large animal model of lysosomal storage disease.

Canine fucosidosis: a neuroprogressive disorder.

The lysosomal storage disease, canine fucosidosis, is caused by the absence of the lysosomal enzyme canine α-L-fucosidase with storage of undegraded fucose-rich material in different organs. Canine fucosidosis is a severe, progressive, fatal neurological disease which results in death or euthanasia and is the only available animal model for this human disease. We analysed the progressive neuropathology from birth to severe clinical disease and related this to the clinical signs. At birth no vacuolation was observed in fucosidosis brain; however, a complex storage presence with vacuolation was well established by 4 months of age, before the clinical signs of motor dysfunction which occurred at 10-12 months of age. Purkinje cell loss, neuronal loss, gliosis, perivascular storage and demyelination accompanied disease progression. Increased vacuolation (15.3-fold increase compared to controls) coincided with advanced motor and mental deterioration in late-stage disease. Significant loss of myelin commenced early, with greatest impact in the cerebellum, and was severe in late disease (1.6- to 1.9-fold decrease) compared to controls (p < 0.05) contributing to clinical signs of motor and mental dysfunction. This detailed description and quantification of the CNS pathology in canine fucosidosis will inform monitoring of the onset, progression and response of this disease to therapy.