Prolonged expression of a lysosomal enzyme in mouse liver after Sleeping Beauty transposon-mediated gene delivery: implications for non-viral gene therapy of mucopolysaccharidoses

BACKGROUND: The Sleeping Beauty (SB) transposon system is a non-viral vector system that can integrate precise sequences into chromosomes. We evaluated the SB transposon system as a tool for gene therapy of mucopolysaccharidosis (MPS) types I and VII. METHODS: We constructed SB transposon plasmids for high-level expression of human beta-glucuronidase (hGUSB) or alpha-L-iduronidase (hIDUA). Plasmids were delivered with and without SB transposase to mouse liver by rapid, high-volume tail-vein injection. We studied the duration of expressed therapeutic enzyme activity, transgene presence by PCR, lysosomal pathology by toluidine blue staining and cell-mediated immune response histologically and by immunohistochemical staining. RESULTS: Transgene frequency, distribution of transgene and enzyme expression in liver and the level of transgenic enzyme required for amelioration of lysosomal pathology were estimated in MPS I and VII mice. Without immunomodulation, initial GUSB and IDUA activities in plasma reached > 100-fold of wild-type (WT) levels but fell to background within 4 weeks post-injection. In immunomodulated transposon-treated MPS I mice plasma IDUA persisted for over 3 months at up to 100-fold WT activity in one-third of MPS I mice, which was sufficient to reverse lysosomal pathology in the liver and, partially, in distant organs. Histological and immunohistochemical examination of liver sections in IDUA transposon-treated WT mice revealed inflammation 10 days post-injection consisting predominantly of mononuclear cells, some of which were CD4- or CD8-positive. CONCLUSIONS: Our results demonstrate the feasibility of achieving prolonged expression of lysosomal enzymes in the liver and reversing MPS disease in adult mice with a single dose of therapeutic SB transposons.     

Glycosaminoglycan Storage in Cultured Neonatal Murine Mucopolysaccharidosis Type VII Neuroglial Cells and Correction by β-Glucuronidase Gene Transfer

Abstract: The inherited deficiency of β-glucuronidase activity causes the lysosomal storage disorder mucopolysaccharidosis (MPS) type VII (Sly disease). The sequential catabolism of glycosaminoglycans in lysosomes is blocked, and undegraded substrates accumulate in cells of many tissues, including neurons and glia in the brain. To evaluate the deficient metabolic pathway, primary cultures of mixed brain cells were established from newborn MPS VII mice. β-Glucuronidase levels and glycosaminoglycan accumulation were studied in normal, carrier, and MPS VII cells. Retroviral vector-mediated transfer of a normal β-glucuronidase cDNA corrected the enzymatic deficiency in MPS VII cells and restored glycosaminoglycan catabolism to normal. High levels of β-glucuronidase expression were sustained in vector-corrected nondividing glial cell cultures for >2 months. These studies provide an in vitro model for evaluating somatic gene transfer in neural cells affected in mucopolysaccharidoses.     

Characterization of the defective beta-glucuronidase activity in canine mucopolysaccharidosis type VII

Canine mucopolysaccharidosis type VII results from deficient activity of lysosomal beta-glucuronidase. Residual enzymatic activity (0.2-1.7% of normal) was detected in tissue homogenates from affected dogs. In contrast, serum and urine from affected animals had up to 15% residual activity. To further characterize the nature of the defective enzyme, hepatic beta-glucuronidase was partially purified from normal and MPS VII dogs for determination of their physical and kinetic properties. About 65% of the total beta-glucuronidase in normal canine liver required detergent for solubilization (i.e., membrane-associated), whereas only 22% of the residual activity in canine MPS VII liver was membrane-associated. Compared to the normal hepatic enzyme, the Km towards 4-methylumbelliferyl-beta-glucuronide was markedly increased in MPS VII dogs (i.e., 0.48 versus greater than 2.5 mmol/l). In contrast, the thermo-, cryo-, and pH stability properties, as well as the pH optimum (approximately 4.6), were essentially unaffected. In addition, the canine MPS VII hepatic residual activity was unresponsive to sulfhydryl reducing reagents and divalent cations, despite the fact that incubation of normal canine beta-glucuronidase with dithiothreitol and magnesium and/or calcium enhanced the activity more than 15-fold.     

Mutational analysis in longest known survivor of mucopolysaccharidosis type VII

Mucopolysaccharidosis VII (MPS VII) is an autosomal recessive disorder caused by the deficiency of beta-glucuronidase leading to the intralysosomal storage of heparan, dermatan, and chondroitin sulfate. Here, we report the identification of two novel missense mutations K350N and R577L in a 37-year-old patient with beta-glucuronidase deficiency and a relatively mild MPS VII phenotype. Expression of the K350N mutation in baby hamster kidney cells has revealed residual enzymatic activity and normal transport of the enzyme to the lysosome. However, expression of the R577L or the double mutant K350N/R577L results in rapid degradation of the enzyme in early biosynthetic compartments and a total loss of enzymatic activity. We attribute the mild phenotype to the residual catalytic activity provided by the K350N mutant. At the time of her death at the age of 37 years, this patient was the longest known survivor with MPS VII.     

Adipose deficiency and aberrant autophagy in a Drosophila model of MPS VII is corrected by pharmacological stimulators of mTOR

Mucopolysaccharidosis type VII (MPS VII) is a recessively inherited lysosomal storage disorder caused due to β-glucuronidase (β-GUS) enzyme deficiency. Prominent clinical symptoms include hydrops fetalis, musculoskeletal deformities, neurodegeneration and hepatosplenomegaly leading to premature death in most cases. Apart from these, MPS VII is also characterized as adipose storage deficiency disorder although the underlying mechanism of this lean phenotype in the patients or β-GUS-deficient mice still remains a mystery. We addressed this issue using our recently developed Drosophila model of MPS VII (the CG2135^-/- fly), which also exhibited a significant loss of body fat. We report here that the lean phenotype of the CG2135^?/? larvae is due to fewer number of adipocytes, smaller lipid droplets and reduced adipogenesis. Our data further revealed that there is an abnormal accumulation of autophagosomes in the CG2135^?/? larvae due to autophagosome-lysosome fusion defect. Decreased lysosome-mediated turnover also led to attenuated mTOR activity in the CG2135^?/? larvae. Interestingly, treatment of the CG2135^?/? larvae with mTOR stimulators, 3BDO or glucose, led to the restoration of mTOR activity with simultaneous correction of the autophagy defect and adipose storage deficiency. Our finding thus established a hitherto unknown mechanistic link between autophagy dysfunction, mTOR downregulation and reduced adiposity in MPS VII.     

Gene therapy for acute hepatitis using CrmA gene transduction

Fas-Fas ligand interactions between adenovirus-infected hepatocytes and cytotoxic T lymphocytes (CTLs) play a major role in killing of vector-transduced hepatocytes. Cytokine response modifier A (CrmA) is known to protect lymphoid cells from Fas-mediated apoptosis by inhibiting caspase 8. In this study, we generated an E1-deleted adenovirus expressing CrmA, and investigated the effect of exogenous CrmA expression on the inhibition of Fas-mediated apoptosis in murine hepatocytes in vitro and on the prolongation of the transgene expression in adenovirus-transduced hepatocytes in vivo. Agonistic anti-Fas antibody induced massive apoptosis into hepatocytes, however, most of the cells expressing CrmA were escaped from apoptosis and survived. This result showed that anti-apoptic function was obtained in murine hepatocytes by expressing CrmA. The prolongation of the transgene expression was studied using mice with congenital deficiency of lysosomal beta-glucuronidase (GUSB). The serum GUSB activity from the mice injected only an adenovirus expressing human beta-glucuronidase disappeared within 70 days, however, significant GUSB activity was observed for more than 130 days in the mice co-transduced with adenoviruses expressing both GUSB and CrmA. Moreover, histochemical analysis showed GUSB expressions in the liver even at 130 days after the viral administration. These observations demonstrate that the prolongation of the transgene expression can be achieved in rodent liver by CrmA co-expression using adenoviral gene transfer.     

Rapid prenatal testing for human beta-glucuronidase deficiency (MPS VII)

Prenatal diagnosis for the lysosomal storage disorders is typically achieved by enzymatic analysis of the relevant lysosomal enzyme in cultured amniocytes or chorionic villi. While prenatal diagnosis of some genetic diseases can be done by analysis of pertinent metabolites in amniotic fluid, there are few data regarding prenatal diagnosis of lysosomal disorders by enzyme analysis of amniotic fluid. Prenatal diagnosis by enzyme analysis of amniotic fluid has the potential advantage of providing a more rapid prenatal test result. In this study we describe an assay for the prenatal diagnosis of the mucopolysaccharidosis beta-glucuronidase deficiency (MPS VII; MIM #253220) using amniotic fluid and we confirm its reliability in detecting an affected fetus in an at-risk pregnancy by enzyme analysis of cultured amniocytes and fetal fibroblasts. Because MPS VII is rare and few instances of prenatal diagnosis for this and nearly all other lysosomal disorders have been accomplished by enzyme analysis of amniotic fluid, confirmation of results obtained from enzyme analysis of amniotic fluid should be carried out by enzyme or mutation analysis using cultured amniocytes or chorionic villus specimens.     

Biodistribution, kinetics, and efficacy of highly phosphorylated and non-phosphorylated beta-glucuronidase in the murine model of mucopolysaccharidosis VII

Enzyme replacement therapy (ERT) has been shown to be effective at reducing the accumulation of undegraded substrates in lysosomal storage diseases. Most ERT studies have been performed with recombinant proteins that are mixtures of phosphorylated and non-phosphorylated enzyme. Because different cell types use different receptors to take up phosphorylated or non-phosphorylated enzyme, it is difficult to determine which form of enzyme contributed to the clinical response. Here we compare the uptake, distribution, and efficacy of highly phosphorylated and non-phosphorylated beta-glucuronidase (GUSB) in the MPS VII mouse. Highly phosphorylated murine GUSB was efficiently taken up by a wide range of tissues. In contrast, non-phosphorylated murine GUSB was taken up primarily by tissues of the reticuloendothelial (RE) system. Although the tissue distribution was different, the half-lives of both enzymes in any particular tissue were similar. Both preparations of enzyme were capable of preventing the accumulation of lysosomal storage in cell types they targeted. An important difference in clinical efficacy emerged in that phosphorylated GUSB was more efficient than non-phosphorylated enzyme at preventing the hearing loss associated with this disease. These data suggest that both forms of enzyme contribute to the clinical responses of ERT in MPS VII mice but that enzyme preparations containing phosphorylated GUSB are more broadly effective than non-phosphorylated enzyme.     

Gastrointestinal pathology in a mouse model of mucopolysaccharidosis type IIIA

Mucopolysaccharidosis type IIIA (MPS IIIA) is a lysosomal storage disorder caused by a deficiency in sulphamidase (NS), a lysosomal enzyme required for the degradation of heparan sulphate glycosaminoglycans (gags). The MPS IIIA mouse is a naturally occurring model that accurately reflects the human pathology and disease course. It displays primarily central nervous system pathology accompanied by widespread accumulation of gag in somatic tissues. MPS IIIA mice exhibit greater bodyweight gain than normal littermates and attain a higher mature bodyweight. In this study, gastrointestinal morphology and function was characterised in the IIIA mouse. Stomach and duodenum weight increased in MPS IIIA mice and duodenum length also increased. An increased submucosal thickness was observed in MPS IIIA intestine compared to normal mice and lysosomal storage of gag was observed in this region. Storage was also observed in the lamina propria of the villus tip. All other morphometric measurements including villus height and crypt depth fell within the normal range. The gastric emptying half‐life of solid and liquid meals decreased with age in normal mice whereas the T_½ of solid meals did not alter with age in MPS IIA mice such that they were elevated above normal by 38 weeks of age. Sucrase activity was higher than normal in MPS IIIA at all ages tested. These abnormalities in GI structure and function observed in MPS IIIA may contribute to weight gain in this disorder. J. Cell. Physiol. 219: 259–264, 2009. © 2009 Wiley‐Liss, Inc.     

β-Glucuronidase P408S,P415L mutations: evidence that both mutations combine to produce an MPS VII allele in certain Mexican patients

Mucopolysaccharidosis type VII (MPS VII, Sly syndrome) is an autosomal recessively inherited lysosomal storage disease caused by a deficiency in β-glucuronidase. We identified and studied a novel allele containing two C-to-T transitions resulting in P408S and P415L alterations, which is present in homozygous state in one Mexican patient and in heterozygous state in another. None of the previous reports describing mutations in the MPS VII gene include Mexican patients. Expression of either of the mutations individually showed only modest effects on the properties of the enzyme. However, expression of the doubly mutant allele resulted in markedly reduced activity and rapid degradation in an early biosynthetic compartment. Received: 13 December 1995 / Revised: 3 April 1996     

Use of nonviral promoters in adenovirus-mediated gene therapy: reduction of lysosomal storage in the aspartylglucosaminuria mouse

BACKGROUND: Aspartylglucosaminuria (AGU) is a lysosomal storage disease with severe neurodegenerative clinical features resulting from the deficiency of lysosomal aspartylglucosaminidase (AGA). The AGU knockout mouse is a good model to test different therapy strategies, as it mimics well the human pathogenesis of the disease exhibiting storage vacuoles in all tissues. In this study we investigated the efficiency of nonviral promoters in adenovirus-mediated gene therapy. METHODS: The deficient corrective enzyme, AGA, was expressed using two tissue-specific promoters, neuron-specific enolase (NSE), astrocyte-specific (GFAP) and the endogenous AGA promoter. An intrastriatal injection site was chosen due to its wide connections in the central nervous system (CNS). The expression of AGA was analyzed 1 week, 2 weeks, 4 weeks, 2 months and 4 months after the virus injection by lysosomal AGA-specific immunostaining. A correction of the lysosomal storage in the brain of treated mice was also studied using toluidine blue stained thin sections. RESULTS: The overexpressed AGA enzyme was detected in addition to the injection site, also in the ipsilateral parietal cortex indicating migration of AGA in the brain tissue. Duration of AGA expression was markedly longer with all the viruses used compared to the green fluorescent protein (GFP) expression driven by the viral cytomegalovirus (CMV) promoter. In most animals the storage was decreased by at least 50% as compared to untreated AGU mouse brains. Remarkably, >90% correction of storage at the ipsilateral cortex was found with the NSE promoter at 4 weeks and 2 months after injection. Additionally, partial clearance of storage was demonstrated also in the contralateral side of the brain. CONCLUSIONS: These data implicate that tissue-specific promoters are especially useful in virus-mediated gene therapy aiming at long-term gene expression.     

Helper-dependent canine adenovirus vector-mediated transgene expression in a neurodegenerative lysosomal storage disorder

Mucopolysaccharidosis type IIIA (MPS-IIIA) is a severe neurodegenerative lysosomal storage disorder caused by a deficiency of N-sulfoglucosamine sulfohydrolase (SGSH) activity with subsequent accumulation of partially-degraded heparan sulfate and other glycolipids. In this study, we have evaluated a gene therapy approach using a helper-dependent canine adenovirus vector that expresses human SGSH as a means of delivering sustained transgene expression to the brain. Initial testing in a mixed neural cell culture model demonstrated that the vector could significantly increase SGSH activity in transduced cells, resulting in near-normalization of heparan sulfate-derived fragments. While administration of vector by direct injection into the brain of adult MPS-IIIA mice enabled transgene expression for at least 8.5 months post-treatment, it was only in discrete areas of brain. Heparan sulfate storage was reduced in some regions following treatment, however there was no improvement in secondary neuropathological changes. These data demonstrate that helper-dependent canine adenovirus vectors are capable of neural transduction and mediate long-term transgene expression, but increased SGSH expression throughout the brain is likely to be required in order to effectively treat all aspects of the MPS-IIIA phenotype.     

Lysosomal dysfunction results in altered energy balance

The mucopolysaccharidosis (MPS) type VII mouse was originally described as the adipose storage deficiency mouse because of its extreme lean phenotype of unknown etiology. Here, we show that adipose storage deficiency and lower leptin levels are common to five different lysosomal storage diseases (LSDs): MPSI, MPSIIIB, MPSVII, Niemann-Pick type A/B, and infantile neuronal ceroid lipofuscinosis. Elevated circulating pro-inflammatory proteins (VCAM1 and MCP1) were found in multiple LSDs. Multiple anti-inflammatory strategies (dexamethasone, MCP1 deficiency, M3 expression) failed to alter adiposity in LSD animals. All of the models had normal or greater caloric intake and lower to normal metabolic rate, fasting plasma glucose, non-esterified fatty acids, cholesterol, and triglycerides. Triglycerides were lower in the livers of MPSI mice, and the trend was lower in the muscle. Lipid absorption and processing in MPSI mice were indistinguishable from those in normal mice following oral gavage of olive oil. The increased lean mass of MPSI and MPSIIIB mice suggests a shift in adipose triglycerides to lysosomal storage. In agreement, MPSI livers had a similar total caloric content but reduced caloric density, indicating a shift in energy from lipids to proteins/carbohydrates (lysosomal storage). Enzyme replacement therapy normalized the caloric density within 48 h without reducing total caloric content. This was due to an increase in lipids. Recycling of stored material is likely reduced or nonexistent. Therefore, to maintain homeostasis, energy is likely diverted to synthesis at the expense of typical energy storage depots. Thus, these diseases will serve as important tools in studying the role of lysosome function in metabolism and obesity.     

Effect of high dose,repeated intra‐cerebrospinal fluid injection of sulphamidase on neuropathology in mucopolysaccharidosis type IIIA mice

Mucopolysaccharidosis type IIIA (MPS IIIA) is an inherited neurodegenerative lysosomal storage disorder characterized by progressive loss of learned skills, sleep disturbance and behavioural problems. Reduced activity of sulphamidase (N‐sulphoglucosamine sulphohydrolase; SGSH; EC 3.10.1.1) results in intracellular accumulation of heparan sulphate (HS), with the brain as the primary site of pathology. We have used a naturally occurring MPS IIIA mouse model to determine the effectiveness of SGSH replacement through the cerebrospinal fluid (CSF) to decrease neuropathology. This is a potential therapeutic option for patients with this disorder. Mice received intra‐CSF injections of recombinant human SGSH (30, 50 or 70 μg) fortnightly from 6 to 18 weeks of age, and the cumulative effect on neuropathology was examined and quantified. Anti‐SGSH antibodies detected in plasma at euthanasia did not appear to impact upon the health of the mice or the experimental outcome, with significant but region‐dependent and dose‐dependent reductions in an HS‐derived oligosaccharide observed in the brain and spinal cord using tandem mass spectrometry. SGSH infusion reduced the number of storage inclusions observed in the brain when visualized using electron microscopy, and this correlated with a significant decrease in the immunohistochemical staining of a lysosomal membrane marker. Reduced numbers of activated isolectin B4‐positive microglia and glial fibrillary acidic protein‐positive astrocytes were seen in many, but not all, brain regions. Significant reductions in the number of ubiquitin‐positive intracellular inclusions were also observed. These outcomes show the effectiveness of this method of enzyme delivery in reducing the spectrum of neuropathological changes in murine MPS IIIA brain.     

Phenotypic rescue after adeno-associated virus-mediated delivery of 4-sulfatase to the retinal pigment epithelium of feline mucopolysaccharidosis VI

Background

Mucopolysaccharidosis VI (MPS VI), due to recessively inherited 4‐sulfatase (4S) deficiency, results in lysosomal storage of dermatan sulfate in numerous tissues. Retinal involvement is limited to the retinal pigment epithelium (RPE). This study aimed to determine whether recombinant adeno‐associated virus (AAV)‐mediated delivery of 4S would reverse the RPE pathology seen in MPS VI cats.

Methods

AAV.f4S, containing the feline 4S cDNA, was delivered unilaterally to eyes of affected cats by subretinal or intravitreal injection. Contralateral eyes received AAV with the green fluorescent protein (GFP) reporter gene as control. At 2–11 months post‐injection, the cats were sacrificed and the treatment effects were evaluated histologically.

Results

By ophthalmoscopy and histological analyses, GFP was evident as early as 4 weeks and persisted through the latest time point (11 months). Untreated and AAV.GFP‐treated diseased retinas contained massively hypertrophied RPE cells secondary to accumulation of dilated lysosomal inclusions containing dermatan sulfate. MPS VI eyes treated subretinally with AAV.f4S had minimal RPE cell inclusions and, consequently, were not hypertrophied.

Conclusions

AAV‐mediated subretinal delivery of f4S provided correction of the disease phenotype in RPE cells of feline MPS VI, supporting the utility of AAV as a vector for the treatment of RPE‐specific as well as lysosomal storage diseases. Copyright © 2002 John Wiley & Sons, Ltd.

     

Feline immunodeficiency virus vectors. Gene transfer to mouse retina following intravitreal injection

Background

Transduction of the murine retinal pigmented epithelium (RPE) with adenovirus vectors requires technically difficult and invasive subretinal injections. This study tested the hypothesis that recombinant vectors based on feline immunodeficiency virus (FIV) could access the retina following intravitreal injection.

Methods

FIV vectors expressing E. coli β‐galactosidase (FIVβgal) were injected alone, or in combination with adenovirus vectors expressing eGFP, into the vitreous of normal mice and eyes evaluated for transgene expression. In further studies, the utility of FIV‐mediated gene transfer to correct lysosomal storage defects in the anterior and posterior chambers of eyes was tested using recombinant FIV vectors expressing β‐glucuronidase. FIVβgluc vectors were injected into β‐glucuronidase‐deficient mice, an animal model of mucopolysacharridoses type VII.

Results

The results of this study show that similar to adenovirus, both corneal endothelium and cells of the iris could be transduced following intravitreal injection of FIVβgal. However, in contrast to adenovirus, intravitreal injection of FIVβgal also resulted in transduction of the RPE. Immunohistochemistry following an intravitreal injection of an AdeGFP (adenovirus expressing green fluorescent protein) and FIVβgal mixture confirmed that both viruses mediated transduction of corneal endothelium and cells of the iris, while only FIVβgal transduced cells in the retina. Using the β‐glucuronidase‐deficient mouse, the therapeutic efficacy of intravitreal injection of FIVβgluc (FIV expressing β‐glucuronidase) was tested. Intravitreal injection of FIVβgluc to the eyes of β‐glucuronidase‐deficient mice resulted in rapid reduction (within 2 weeks) of the lysosomal storage defect within the RPE, corneal endothelium, and the non‐pigmented epithelium of the ciliary process. Transgene expression and correction of the lysosomal storage defect remained for at least 12 weeks, the latest time point tested.

Conclusion

These studies demonstrate that intravitreal injection of FIV‐based vectors can mediate efficient and lasting transduction of cells in the cornea, iris, and retina. Copyright © 2002 John Wiley & Sons, Ltd.

     

The HIV Tat protein transduction domain improves the biodistribution of beta-glucuronidase expressed from recombinant viral vectors.

Treatment of inherited genetic diseases of the brain remains an intractable problem. Methods to improve the distribution of enzymes that are injected or expressed from transduced cells will be required for many human brain therapies. Recent studies showed that a peptide, the protein transduction domain (PTD) from HIV Tat, could improve the distribution of cytoplasmic reporter proteins when administered systemically as fusion proteins or cross-linked chimeras. The utility of this motif for noncytoplasmic proteins has not been determined. Here, we tested how the Tat motif affected uptake and biodistribution of the lysosomal enzyme beta-glucuronidase, the protein deficient in the disease mucopolysaccharidosis VII, when expressed from viral vectors. The Tat motif allowed for mannose-6-phosphate (M6P) independent uptake in vitro and significantly increased the distribution of beta-glucuronidase secreted from transduced cells after intravenous or direct brain injection in mice of recombinant vectors. Thus, enzymes modified to contain protein transduction motifs may represent a general strategy for improving the distribution of secreted proteins following in vivo gene transfer.