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The effect of Tlr4 and/or C3 deficiency and of neonatal gene therapy on skeletal disease in mucopolysaccharidosis VII mice.

ABSTRACT: Mucopolysaccharidosis (MPS) VII is a lysosomal storage disorder caused by the deficiency of the enzyme ?-glucuronidase (Gusb(-/-)) and results in glycosaminoglycan (GAG) accumulation. Skeletal abnormalities include stunted long bones and bone degeneration. GAGs have been hypothesized to activate toll-like receptor 4 (Tlr4) signaling and the complement pathway, resulting in upregulation of inflammatory cytokines that suppress growth and cause degeneration of the bone. Gusb(-/-) mice were bred with Tlr4- and complement component 3 (C3)-deficient mice, and the skeletal manifestations of the doubly- and triply-deficient mice were compared to those of purebred Gusb(-/-) mice. Radiographs showed that purebred Gusb(-/-) mice had shorter tibias and femurs, and wider femurs, compared to normal mice. No improvement was seen in Tlr4, C3, or Tlr4/C3-deficient Gusb(-/-) mice. The glenoid cavity and humerus were scored on a scale from 0 (normal) to +3 (severely abnormal) for dysplasia and bone irregularities, and the joint space was measured. No improvement was seen in Tlr4, C3, or Tlr4/C3-deficient Gusb(-/-) mice, and their joint space remained abnormally wide. Gusb(-/-) mice treated neonatally with an intravenous retroviral vector (RV) had thinner femurs, longer legs, and a narrowed joint space compared with untreated purebred Gusb(-/-) mice, but no improvement in glenohumeral degeneration. We conclude that Tlr4- and/or C3-deficiency fail to ameliorate skeletal abnormalities, and other pathways may be involved. RV treatment improves some but not all aspects of bone disease. Radiographs may be an efficient method for future evaluation, as they readily show glenohumeral joint abnormalities.

SUBMITTER: Xing EM

PROVIDER: S-EPMC4381425 | biostudies-literature | 2015 Feb

REPOSITORIES: biostudies-literature

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The effect of Tlr4 and/or C3 deficiency and of neonatal gene therapy on skeletal disease in mucopolysaccharidosis VII mice.

Xing Elizabeth M EM Wu Susan S Ponder Katherine P KP

Molecular genetics and metabolism 20141219 2

Mucopolysaccharidosis (MPS) VII is a lysosomal storage disorder caused by the deficiency of the enzyme β-glucuronidase (Gusb(-/-)) and results in glycosaminoglycan (GAG) accumulation. Skeletal abnormalities include stunted long bones and bone degeneration. GAGs have been hypothesized to activate toll-like receptor 4 (Tlr4) signaling and the complement pathway, resulting in upregulation of inflammatory cytokines that suppress growth and cause degeneration of the bone. Gusb(-/-) mice were bred wit ...[more]

PMID: 25559179

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Project description:Mucopolysaccharidosis (MPS) VII is a lysosomal storage disorder characterized by deficient activity of β-glucuronidase, leading to progressive accumulation of incompletely degraded heparan, dermatan and chondroitin sulfate glycosaminoglycans (GAGs). Patients with MPS VII exhibit progressive skeletal deformity including kyphoscoliosis and joint dysplasia, which decrease quality of life and increase mortality. Previously, using the naturally-occurring canine model, we demonstrated that one of the earliest skeletal abnormalities to manifest in MPS VII is failed initiation of secondary ossification in vertebrae and long bones at the requisite postnatal developmental stage. The objective of this study was to obtain global insights into the molecular mechanisms underlying this failed initiation of secondary ossification using whole transcriptome sequencing (RNA-Seq). Epiphyseal tissue was isolated from the vertebrae of control and MPS VII affected dogs at 9 and 14 days-of-age (n=5 for each group). Differences in global gene expression across this developmental window for both cohorts were established using RNA-Seq. A targeted analysis focused on signaling pathways important in the regulation of endochondral ossification, and a subset of gene expression changes were validated using qPCR. Principal Component Analysis revealed clustering of samples from each group, indicating clear effects of both age and disease state. At 9 days-of-age, 1375 genes were significantly differentially expression between MPS VII and control, and by 14 days-of-age, this increased to 4719 genes. Osteoactivin (GPNMB) was the top upregulated gene in MPS VII at both ages. Targeted analysis revealed temporal changes in gene expression from 9 to 14 days-of-age in control samples consistent with chondrocyte maturation, cartilage resorption, and osteogenesis. In MPS VII samples, however, elements of key osteogenic pathways such as Wnt/β-catenin and BMP signaling were dysregulated. In conclusion, this study represents the first step towards identifying druggable therapeutic targets and putative biomarkers for bone disease in MPS VII patients during postnatal growth.

Dataset Information

The effect of Tlr4 and/or C3 deficiency and of neonatal gene therapy on skeletal disease in mucopolysaccharidosis VII mice.

Publications

The effect of Tlr4 and/or C3 deficiency and of neonatal gene therapy on skeletal disease in mucopolysaccharidosis VII mice.

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