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The effect of neonatal gene therapy on skeletal manifestations in mucopolysaccharidosis VII dogs after a decade.

ABSTRACT: Mucopolysaccharidosis (MPS) VII is a lysosomal storage disease due to deficient activity of ?-glucuronidase (GUSB), and results in glycosaminoglycan accumulation. Skeletal manifestations include bone dysplasia, degenerative joint disease, and growth retardation. One gene therapy approach for MPS VII involves neonatal intravenous injection of a gamma retroviral vector expressing GUSB, which results in stable expression in liver and secretion of enzyme into blood at levels predicted to be similar or higher to enzyme replacement therapy. The goal of this study was to evaluate the long-term effect of neonatal gene therapy on skeletal manifestations in MPS VII dogs. Treated MPS VII dogs could walk throughout their lives, while untreated MPS VII dogs could not stand beyond 6 months and were dead by 2 years. Luxation of the coxofemoral joint and the patella, dysplasia of the acetabulum and supracondylar ridge, deep erosions of the distal femur, and synovial hyperplasia were reduced, and the quality of articular bone was improved in treated dogs at 6 to 11 years of age compared with untreated MPS VII dogs at 2 years or less. However, treated dogs continued to have osteophyte formation, cartilage abnormalities, and an abnormal gait. Enzyme activity was found near synovial blood vessels, and there was 2% as much GUSB activity in synovial fluid as in serum. We conclude that neonatal gene therapy reduces skeletal abnormalities in MPS VII dogs, but clinically-relevant abnormalities remain. Enzyme replacement therapy will probably have similar limitations long-term.

SUBMITTER: Xing EM

PROVIDER: S-EPMC3690974 | biostudies-literature | 2013 Jun

REPOSITORIES: biostudies-literature

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The effect of neonatal gene therapy on skeletal manifestations in mucopolysaccharidosis VII dogs after a decade.

Xing Elizabeth M EM Knox Van W VW O'Donnell Patricia A PA Sikura Tracey T Liu Yuli Y Wu Susan S Casal Margret L ML Haskins Mark E ME Ponder Katherine P KP

Molecular genetics and metabolism 20130406 2

Mucopolysaccharidosis (MPS) VII is a lysosomal storage disease due to deficient activity of β-glucuronidase (GUSB), and results in glycosaminoglycan accumulation. Skeletal manifestations include bone dysplasia, degenerative joint disease, and growth retardation. One gene therapy approach for MPS VII involves neonatal intravenous injection of a gamma retroviral vector expressing GUSB, which results in stable expression in liver and secretion of enzyme into blood at levels predicted to be similar ...[more]

PMID: 23628461

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Project description:Mucopolysaccharidosis I (MPS I) is a lysosomal storage disease characterized by deficient ?-L-iduronidase activity, leading to the accumulation of poorly degraded glycosaminoglycans (GAGs). Children with MPS I exhibit high incidence of spine disease, including accelerated disc degeneration and vertebral dysplasia, which in turn lead to spinal cord compression and kyphoscoliosis. In this study we investigated the efficacy of neonatal enzyme replacement therapy (ERT), alone or in combination with oral simvastatin (ERT?+?SIM) for attenuating cervical spine disease progression in MPS I, using a canine model. Four groups were studied: normal controls; MPS I untreated; MPS I ERT-treated; and MPS I ERT?+?SIM-treated. Animals were euthanized at age 1 year. Intervertebral disc condition and spinal cord compression were evaluated from magnetic resonance imaging (MRI) images and plain radiographs, vertebral bone condition and odontoid hypoplasia were evaluated using micro-computed tomography (µCT), and epiphyseal cartilage to bone conversion was evaluated histologically. Untreated MPS I animals exhibited more advanced disc degeneration and more severe spinal cord compression than normal animals. Both treatment groups resulted in partial preservation of disc condition and cord compression, with ERT?+?SIM not significantly better than ERT alone. Untreated MPS I animals had significantly lower vertebral trabecular bone volume and mineral density, whereas ERT treatment resulted in partial preservation of these properties. ERT?+?SIM treatment demonstrated similar, but not greater, efficacy. Both treatment groups partially normalized endochondral ossification in the vertebral epiphyses (as indicated by absence of persistent growth plate cartilage), and odontoid process size and morphology. These results indicate that ERT begun from a very early age attenuates the severity of cervical spine disease in MPS I, particularly for the vertebral bone and odontoid process, and that additional treatment with simvastatin does not provide a significant additional benefit over ERT alone.

Project description:Mucopolysaccharidosis (MPS) VII is a lysosomal storage disorder characterized by deficient β-glucuronidase activity, which leads to the accumulation of incompletely degraded glycosaminoglycans (GAGs). MPS VII patients present with severe skeletal abnormalities, which are particularly prevalent in the spine. Incomplete cartilage-to-bone conversion in MPS VII vertebrae during postnatal development is associated with progressive spinal deformity and spinal cord compression. The objectives of this study were to determine the earliest postnatal developmental stage at which vertebral bone disease manifests in MPS VII and to identify the underlying cellular basis of impaired cartilage-to-bone conversion, using the naturally-occurring canine model. Control and MPS VII dogs were euthanized at 9 and 14 days-of-age, and vertebral secondary ossification centers analyzed using micro-computed tomography, histology, qPCR, and protein immunoblotting. Imaging studies and mRNA analysis of bone formation markers established that secondary ossification commences between 9 and 14 days in control animals, but not in MPS VII animals. mRNA analysis of differentiation markers revealed that MPS VII epiphyseal chondrocytes are unable to successfully transition from proliferation to hypertrophy during this critical developmental window. Immunoblotting demonstrated abnormal persistence of Sox9 protein in MPS VII cells between 9 and 14 days-of-age, and biochemical assays revealed abnormally high intra and extracellular GAG content in MPS VII epiphyseal cartilage at as early as 9 days-of-age. In contrast, assessment of vertebral growth plates and primary ossification centers revealed no significant abnormalities at either age. The results of this study establish that failed vertebral bone formation in MPS VII can be traced to the failure of epiphyseal chondrocytes to undergo hypertrophic differentiation at the appropriate developmental stage, and suggest that aberrant processing of Sox9 protein may contribute to this cellular dysfunction. These results also highlight the importance of early diagnosis and therapeutic intervention to prevent the progression of debilitating skeletal disease in MPS patients.

Dataset Information

The effect of neonatal gene therapy on skeletal manifestations in mucopolysaccharidosis VII dogs after a decade.

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The effect of neonatal gene therapy on skeletal manifestations in mucopolysaccharidosis VII dogs after a decade.

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