Improvement of skeletal lesions in mice with mucopolysaccharidosis type VII by neonatal adenoviral gene transfer

C-Type Natriuretic Peptide Restores Growth Impairment Under Enzyme Replacement in Mice With Mucopolysaccharidosis VII

Growth impairment in mucopolysaccharidoses (MPSs) is an unresolved issue as it is resistant to enzyme replacement therapy (ERT) and growth hormone therapy. C-type natriuretic peptide (CNP) is a promising agent that has growth-promoting effects. Here we investigate the effects of CNP on growth impairment of MPSs using Gusbmps-2J mice, a model for MPS type VII, with combination therapy of CNP and ERT by hydrodynamic gene delivery. Although monotherapies were not sufficient to restore short statures of treated mice, combination therapy resulted in successful restoration. The synergistic effects of CNP and ERT were not only observed in skeletal growth but also in growth plates. ERT reduced cell swelling in the resting zone and increased cell number by accelerating proliferation or inhibiting apoptosis. CNP thickened the proliferative and hypertrophic zones. Regarding changes in the bone, ERT restored bone sclerosis through decreased bone formation and increased bone resorption, and CNP did not adversely affect this process. In addition, improvement of joint deformation by ERT was suggested by analyses of joint spaces and articular cartilage. CNP additively provided restoration of the short stature of MPS VII mice in combination with ERT, which improved abnormalities of growth plates and bone metabolism.

Gene therapy for Mucopolysaccharidoses

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders (LSDs) caused by a deficiency of lysosomal enzymes, leading to a wide range of various clinical symptoms depending upon the type of MPS or its severity. Enzyme replacement therapy (ERT), hematopoietic stem cell transplantation (HSCT), substrate reduction therapy (SRT), and various surgical procedures are currently available for patients with MPS. However, there is no curative treatment for this group of disorders. Gene therapy should be a one-time permanent therapy, repairing the cause of enzyme deficiency. Preclinical studies of gene therapy for MPS have been developed over the past three decades. Currently, clinical trials of gene therapy for some types of MPS are ongoing in the United States, some European countries, and Australia. Here, in this review, we summarize the development of gene therapy for MPS in preclinical and clinical trials.

The Cranial Base in Craniofacial Development: a Gene Therapy Study

The etiology of midface retrusion remains largely unclear. We hypothesized that the cranial base synchondroses play a key role in the development of the craniofacial skeleton in the Sandhoff mouse model. We observed that developmental abnormalities of the cranial base synchondroses involving proliferative chondrocytes are important in craniofacial growth and development. Neonatal restitution of β-hexosaminidase in mutant mice by gene therapy successfully ameliorated the attendant skeletal defects and restored craniofacial morphology in vivo, suggesting this as a critical temporal window in craniofacial development. Analysis of our data implicates parathyroid-related peptide (PTHrP) and cyclo-oxygenase-2 (COX-2) as possible factors underlying the development of the aforementioned skeletal defects. Hence, timely restitution of a genetic deficiency or, alternatively, the restoration of PTHrP or cyclo-oxygenase activity by the administration of PTH and/or non-steroidal anti-inflammatory drugs or COX-2 selective inhibitors to affected individuals may prove beneficial in the management of midface retrusion.

Pathogenesis and treatment of spine disease in the mucopolysaccharidoses

The mucopolysaccharidoses (MPS) are a family of lysosomal storage disorders characterized by deficient activity of enzymes that degrade glycosaminoglycans (GAGs). Skeletal disease is common in MPS patients, with the severity varying both within and between subtypes. Within the spectrum of skeletal disease, spinal manifestations are particularly prevalent. Developmental and degenerative abnormalities affecting the substructures of the spine can result in compression of the spinal cord and associated neural elements. Resulting neurological complications, including pain and paralysis, significantly reduce patient quality of life and life expectancy. Systemic therapies for MPS, such as hematopoietic stem cell transplantation and enzyme replacement therapy, have shown limited efficacy for improving spinal manifestations in patients and animal models. Therefore, there is a pressing need for new therapeutic approaches that specifically target this debilitating aspect of the disease. In this review, we examine how pathological abnormalities affecting the key substructures of the spine - the discs, vertebrae, odontoid process and dura - contribute to the progression of spinal deformity and symptomatic compression of neural elements. Specifically, we review current understanding of the underlying pathophysiology of spine disease in MPS, how the tissues of the spine respond to current clinical and experimental treatments, and discuss future strategies for improving the efficacy of these treatments.

Current therapies for Morquio A syndrome and their clinical outcomes

INTRODUCTION

Morquio A syndrome is characterized by a unique skeletal dysplasia, leading to short neck and trunk, pectus carinatum, laxity of joints, kyphoscoliosis, and tracheal obstruction. Cervical spinal cord compression/inability, a restrictive and obstructive airway, and/or bone deformity and imbalance of growth, are life-threatening to Morquio A patients, leading to a high morbidity and mortality. It is critical to review the current therapeutic approaches with respect to their efficacy and limitations.

AREAS COVERED

Patients with progressive skeletal dysplasia often need to undergo orthopedic surgical interventions in the first two decades of life. Recently, we have treated four patients with a new surgery to correct progressive tracheal obstruction. Enzyme replacement therapy (ERT) has been approved clinically. Cell-based therapies such as hematopoietic stem cell therapy (HSCT) and gene therapy are typically one-time, permanent treatments for enzyme deficiencies. We report here on four Morquio A patients treated with HSCT approved in Japan and followed for at least ten years after treatment. Gene therapy is under investigation on mouse models but not yet available as a therapeutic option.

EXPERT OPINION

ERT and HSCT in combination with surgical intervention(s) are a therapeutic option for Morquio A; however, the approach for bone and cartilage lesion remains an unmet challenge.

Neonatal cellular and gene therapies for mucopolysaccharidoses: the earlier the better?

Mucopolysaccharidoses (MPSs) are a group of lysosomal storage disorders (LSDs). The increasing interest in newborn screening procedures for LSDs underlines the need for alternative cellular and gene therapy approaches to be developed during the perinatal period, supporting the treatment of MPS patients before the onset of clinical signs and symptoms. The rationale for considering these early therapies results from the clinical experience in the treatment of MPSs and other genetic disorders. The normal or gene-corrected hematopoiesis transplanted in patients can produce the missing protein at levels sufficient to improve and/or halt the disease-related abnormalities. However, these current therapies are only partially successful, probably due to the limited efficacy of the protein provided through the hematopoiesis. An alternative explanation is that the time at which the cellular or gene therapy procedures are performed could be too late to prevent pre-existing or progressive organ damage. Considering these aspects, in the last several years, novel cellular and gene therapy approaches have been tested in different animal models at birth, a highly early stage, showing that precocious treatment is critical to prevent long-term pathological consequences. This review provides insights into the state-of-art accomplishments made with neonatal cellular and gene-based therapies and the major barriers that need to be overcome before they can be implemented in the medical community.

Delayed hypertrophic differentiation of epiphyseal chondrocytes contributes to failed secondary ossification in mucopolysaccharidosis VII dogs

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.

Skeletal response to lentiviral mediated gene therapy in a mouse model of MPS VII

Mucopolysaccharidosis VII (MPS VII) is an autosomal recessive, lysosomal storage disorder caused by β-glucuronidase (GUSB) deficiency, resulting in the accumulation of glycosaminoglycans (GAGs), in a variety of cell types. Severe, progressive skeletal pathology, termed dysostosis multiplex, is a prominent clinical feature of MPS VII. We have evaluated a gene therapy protocol for its efficacy in preventing the development and progression of bone pathology in MPS VII mice treated with a lentiviral vector at birth or at 7 weeks. Two weeks after injections, high levels of vector expression were observed in liver, spleen and bone marrow and to a lesser extent in kidney, lung and heart. Widespread clearance of GAG storage was observed in somatic tissues of both groups and some clearance of neuronal storage was observed in mice treated from birth. Micro-CT analysis demonstrated a significant decrease in vertebral and femoral bone mineral volume, trabecular number, bone surface density and cortical bone thickness in both treatment groups. Lumbar and femoral bone lengths were significantly decreased in untreated MPS VII mice, while growth plate heights were increased and these parameters did not change upon treatment. Small improvements in performance in the open field and rotarod behaviour tests were noted. Overall, systemic lentiviral-mediated gene therapy results in a measurable improvement in parameters of bone mass and architecture as well as biochemical and enzymatic correction. Conversely, growth plate chondrocytes were not responsive to treatment, as evidenced by the lack of improvement in vertebral and femoral bone length and growth plate height.

Enzyme replacement therapy attenuates disease progression in two Japanese siblings with mucopolysaccharidosis type VI

Mucopolysaccharidosis type VI (MPS VI) is a progressive, multisystem autosomal recessive lysosomal disorder resulting from deficient N-acetylgalactosamine-4-sulphatase (ASB) and the consequent accumulation of glycosaminoglycan (GAG). Preclinical and clinical studies had demonstrated clinical benefits of early initiation of systemic therapies in patients with MPS. In this case report, two siblings with MPS VI started enzyme replacement therapy (ERT) with weekly infusions of recombinant human ASB (Galsulfase) at 1mg/kg. Sibling 1 started ERT 5.6 years of age and Sibling 2 was 6 weeks old. The disease status in these two siblings prior to and for no less than 36 months of ERT was followed up and compared. The treatment was well tolerated by both siblings. During 36 months of ERT, symptoms typical of MPS VI including short stature, progressive dysmorphic facial features, hepatosplenomegaly, hearing impairment, corneal clouding, and dysostosis multiplex were largely absent in the younger sibling. Her cardiac functions and joint mobility were well preserved. On the other hand, her affected brother had typical MPS VI phenotypic features described above before commencing ERT at the equivalent age, of 3 years. There was significant improvement in the shoulder range of motion and hearing loss after 36 months of treatment and cardiac function was largely preserved. His skeletal deformity and short stature remained unchanged. The results showed that early ERT initiated at newborn is safe and effective in preventing or slowing down disease progression of MPS VI including bone deformities. These observations indicate that early diagnosis and treatment of MPS VI before development of an irreversible disease is critical for optimal clinical outcome.

Combination therapies for lysosomal storage disease: is the whole greater than the sum of its parts?

Lysosomal storage diseases (LSDs), as a group, are among the most common inherited diseases affecting children. The primary defect is typically a genetic deficiency of one of the lysosomal enzymes, often causing accumulation of undegraded substrates within the lysosome. This accumulation causes numerous secondary effects that contribute to the disease phenotype. Viral-mediated gene therapy (GT) can supply a persistent source of the deficient enzyme. However, with some notable exceptions, GT has been only modestly successful as a single approach. Recently, various therapies have been combined in order to more effectively target the diverse pathogenic mechanisms at work in LSDs. One strategy that has shown promise involves providing a persistent source of the deficient enzyme (GT, stem cell transplantation) while targeting a secondary consequence of disease with a more transient approach (substrate reduction, anti-inflammatories, pharmacological mimetic, etc.). This general strategy has resulted in both additive and synergistic effects. Interestingly, some therapeutic approaches by themselves provide essentially no clinical benefit but contribute greatly to the overall efficacy when used in combination with other treatments. Unfortunately, no therapeutic combination is universally effective. This adds to the difficulty in predicting and identifying combinations that will be most effective for individual LSDs. A better understanding of both pathogenic and therapeutic mechanisms is necessary in order to identify potentially successful combinations. While a single treatment would be ideal, the complex nature of these diseases may unavoidably limit the efficacy of single therapies. In order to more successfully treat LSDs, a shift in focus towards a combination therapy may be necessary.

Perinatal gene transfer to the liver

The liver acts as a host to many functions hence raising the possibility that any one may be compromised by a single gene defect. Inherited or de novo mutations in these genes may result in relatively mild diseases or be so devastating that death within the first weeks or months of life is inevitable. Some diseases can be managed using conventional medicines whereas others are, as yet, untreatable. In this review we consider the application of early intervention gene therapy in neonatal and fetal preclinical studies. We appraise the tools of this technology, including lentivirus, adenovirus and adeno-associated virus (AAV)-based vectors. We highlight the application of these for a range of diseases including hemophilia, urea cycle disorders such as ornithine transcarbamylase deficiency, organic acidemias, lysosomal storage diseases including mucopolysaccharidoses, glycogen storage diseases and bile metabolism. We conclude by assessing the advantages and disadvantages associated with fetal and neonatal liver gene transfer.

Gene therapy for mucopolysaccharidosis

Mucopolysaccharidoses (MPS) are due to deficiencies in activities of lysosomal enzymes that degrade glycosaminoglycans. Some attempts at gene therapy for MPS in animal models have involved intravenous injection of vectors derived from an adeno-associated virus (AAV), adenovirus, retrovirus or a plasmid, which primarily results in expression in liver and secretion of the relevant enzyme into blood. Most vectors can correct disease in liver and spleen, although correction in other organs including the brain requires high enzyme activity in the blood. Alternative approaches are to transduce hematopoietic stem cells, or to inject a vector locally into difficult-to-reach sites such as the brain. Gene therapy holds great promise for providing a long-lasting therapeutic effect for MPS if safety issues can be resolved.

Bone marrow transplantation for lysosomal storage disorders

Bone marrow transplantation for lysosomal storage disorders has been used for the past 25 years. The early allure of a promising new therapy has given way to more realistic expectations, as it has become clear that bone marrow transplantation is not a cure, but merely ameliorates the clinical phenotype. The results in some disorders are more acceptable than in others. Significant challenges have emerged, particularly the poor mesenchymal and neurological responses. Important recent advances in lysosomal biology, both in health and disease, have helped us to better understand the results of bone marrow transplantation, and to rationalize its role in the treatment of lysosomal storage disorders alongside newer therapies. At the same time, they have helped researchers to explore new therapeutic applications of bone marrow cells, such as gene and stem cell therapy.

Bioluminescent imaging of a marking transgene and correction of Fabry mice by neonatal injection of recombinant lentiviral vectors

Successful therapy for many inherited disorders could be improved if the intervention were initiated early. This is especially true for lysosomal storage disorders. Earlier intervention may allow metabolic correction to occur before lipid buildup has irreversible consequences and/or before the immune system mounts limiting responses. We have been developing gene therapy to treat lysosomal storage disorders, especially Fabry disease. We describe studies directed toward metabolic correction in neonatal animals mediated by recombinant lentiviral vectors. To develop this method, we first injected a marking lentiviral vector that engineers expression of luciferase into the temporal vein of recipient neonatal animals. The use of a cooled charged-coupled device camera allowed us to track transgene expression over time in live animals. We observed intense luciferase expression in many tissues, including the brain, that did not diminish over 24 weeks. Next, we injected neonatal Fabry mice a single time with a therapeutic lentiviral vector engineered to express human alpha-galactosidase A. The injection procedure was well tolerated. We observed increased plasma levels of alpha-galactosidase A activity starting at our first plasma collection point (4 weeks). Levels of alpha-galactosidase A activity were found to be significantly elevated in many tissues even after 28 weeks. No immune response was observed against the corrective transgene product. Increased levels of enzyme activity also led to significant reduction of globotriaosylceramide in the liver, spleen, and heart. This approach provides a method to treat lysosomal storage disorders and other disorders before destructive manifestations occur.