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In Vivo Zinc Finger Nuclease-Mediated Targeted Integration of a Glucose-6-Phosphatase Transgene Promotes Survival in Mice with Glycogen Storage Disease Type IA. - Molecular therapy : the journal of the American Society of Gene Therapy
Glycogen storage disease type Ia (GSD Ia) is caused by glucose-6-phosphatase (G6Pase) deficiency in association with severe, life-threatening hypoglycemia that necessitates lifelong dietary therapy. Here we show that use of a zinc-finger nuclease (ZFN) targeted to the ROSA26 safe harbor locus and a ROSA26-targeting vector containing a G6PC donor transgene, both delivered with adeno-associated virus (AAV) vectors, markedly improved survival of G6Pase knockout (G6Pase-KO) mice compared with mice receiving the donor vector alone (p<0.04). Furthermore transgene integration has been confirmed by sequencing in the majority of the mice treated with both vectors. Targeted alleles were 4.6-fold more common in livers of mice with GSD Ia, as compared with normal littermates, at 8 months following vector administration (p<0.02). This suggests a selective advantage for vector-transduced hepatocytes following ZFN-mediated integration of the G6Pase vector. A short-term experiment also showed that 3-month-old mice receiving the ZFN had significantly-improved biochemical correction, in comparison with mice that received the donor vector alone. These data suggest that the use of ZFNs to drive integration of G6Pase at a safe harbor locus might improve vector persistence and efficacy, and lower mortality in GSD Ia.Molecular Therapy (2016); doi:10.1038/mt.2016.35.
Induction of autophagy improves hepatic lipid metabolism in glucose-6-phosphatase deficiency. - Journal of hepatology
Glucose-6-phosphatase (G6Pase Î±, G6PC) deficiency, also known as von Gierke's disease or GSDIa, is the most common glycogen storage disorder. It is characterized by a decreased ability of the liver to convert glucose-6-phosphate (G6P) to glucose leading to glycogen and lipid over-accumulation progressing to liver failure and/or hepatomas and carcinomas. Autophagy of intracellular lipid stores (lipophagy) has been shown to stimulate fatty acid Î²-oxidation in hepatic cells. Thus, we examined autophagy and its effects on reducing hepatic lipid over-accumulation in several cell culture and animal models of GSDIa.Autophagy in G6PC-deficient hepatic cell lines, mice, and dogs was measured by Western blotting for key autophagy markers. Pro-autophagic Unc51-like kinase 1 (ULK1/ATG1) was overexpressed in G6PC-deficient hepatic cells, and lipid clearance and oxidative phosphorylation measured. G6PC(-/-) mice and GSDIa dogs were treated with rapamycin and assessed for liver function.Autophagy was impaired in the cell culture, mouse, and canine models of GSDIa. Stimulation of the anti-autophagic mTOR, and inhibition of the pro-autophagic AMPK pathways occurred both in vitro and in vivo. Induction of autophagy by ULK1/ATG1 overexpression decreased lipid accumulation and increased oxidative phosphorylation in G6PC-deficient hepatic cells. Rapamycin treatment induced autophagy and decreased hepatic triglyceride and glycogen content in G6PC(-/-) mice, as well as reduced liver size and improved circulating markers of liver damage in GSDIa dogs.Autophagy is impaired in GSDIa. Pharmacological induction of autophagy corrects hepatic lipid over-accumulation and may represent a new therapeutic strategy for GSDIa.Copyright Â© 2015 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.
A beta-blocker, propranolol, decreases the efficacy from enzyme replacement therapy in Pompe disease. - Molecular genetics and metabolism
Enzyme replacement therapy (ERT) with recombinant human acid Î±-glucosidase (rhGAA) fails to completely reverse muscle weakness in Pompe disease. Î²2-agonists enhanced ERT by increasing receptor-mediated uptake of rhGAA in skeletal muscles.To test the hypothesis that a Î²-blocker might reduce the efficacy of ERT, because the action of Î²-blockers opposes those of Î²2-agonists.Mice with Pompe disease were treated with propranolol (a Î²-blocker) or clenbuterol in combination with ERT, or with ERT alone.Propranolol-treated mice had decreased weight gain (p<0.01), in comparison with clenbuterol-treated mice. Left ventricular mass was decreased (and comparable to wild-type) in ERT only and clenbuterol-treated groups of mice, and unchanged in propranolol-treated mice. GAA activity increased following either clenbuterol or propranolol in skeletal muscles. However, muscle glycogen was reduced only in clenbuterol-treated mice, not in propranolol-treated mice. Cell-based experiments confirmed that propranolol reduces uptake of rhGAA into Pompe fibroblasts and also demonstrated that the drug induces intracellular accumulation of glycoproteins at higher doses.Propranolol, a commonly prescribed Î²-blocker, reduced weight, increased left ventricular mass and decreased glycogen clearance in skeletal muscle following ERT. Î²-Blockers might therefore decrease the efficacy from ERT in patients with Pompe disease.Copyright Â© 2015 Elsevier Inc. All rights reserved.
Synergistic Efficacy from Gene Therapy with Coreceptor Blockade and a Î²2-Agonist in Murine Pompe Disease. - Human gene therapy
Pompe disease (glycogen storage disease type II; acid maltase deficiency) is a devastating myopathy resulting from acid Î±-glucosidase (GAA) deficiency in striated and smooth muscle. Despite the availability of enzyme replacement therapy (ERT) with recombinant human GAA (rhGAA), the limitations of ERT have prompted the preclinical development of gene therapy. Gene therapy has the advantage of continuously producing GAA, in contrast to ERT, which requires frequent injections of rhGAA. An adeno-associated viral (AAV) vector containing a muscle-specific promoter, AAV-MHCK7hGAApA, achieved high GAA expression in heart and skeletal muscle in mice with Pompe disease. However, elevated GAA activity was not sufficient to completely clear accumulated glycogen in skeletal muscle. The process of glycogen clearance from lysosomes might require improved trafficking of GAA to the lysosomes in skeletal muscle, previously achieved with the Î²(2)-agonist clenbuterol that enhanced glycogen clearance in skeletal muscle without increasing GAA activity. Glycogen clearance was clearly enhanced by treatment with a nondepleting anti-CD4 monoclonal antibody (anti-CD4â€‰mAb) along with muscle-specific GAA expression in cardiac muscle, but that treatment was not effective in skeletal muscle. Furthermore, anti-CD4â€‰mAb treatment along with clenbuterol achieved synergistic therapeutic efficacy in both cardiac and skeletal muscle. This triple therapy increased both muscle strength and weight gain. Overall, triple therapy to enhance GAA trafficking and to suppress immune responses significantly improved the efficacy of muscle-targeted gene therapy in murine Pompe disease.
Preclinical Development of New Therapy for Glycogen Storage Diseases. - Current gene therapy
Glycogen storage disease (GSD) consists of more than 10 discrete conditions for which the biochemical and genetic bases have been determined, and new therapies have been under development for several of these conditions. Gene therapy research has generated proof-of-concept for GSD types I (von Gierke disease) and II (Pompe disease). Key features of these gene therapy strategies include the choice of vector and regulatory cassette, and recently adeno-associated virus (AAV) vectors containing tissue-specific promoters have achieved a high degree of efficacy. Efficacy of gene therapy for Pompe disease depend upon the induction of immune tolerance to the therapeutic enzyme. Efficacy of von Gierke disease is transient, waning gradually over the months following vector administration. Small molecule therapies have been evaluated with the goal of improving standard of care therapy or ameliorating the cellular abnormalities associated with specific GSDs. The receptor-mediated uptake of the therapeutic enzyme in Pompe disease was enhanced by administration of Î²2 agonists. Rapamycin reduced the liver fibrosis observed in GSD III. Further development of gene therapy could provide curative therapy for patients with GSD, if efficacy from preclinical research is observed in future clinical trials and these treatments become clinically available.
Vision of correction for classic homocystinuria. - The Journal of clinical investigation
Inherited metabolic disorders are often characterized by the lack of an essential enzyme and are currently treated by dietary restriction and other strategies to replace the substrates or products of the missing enzyme. Patients with homocystinuria lack the enzyme cystathionine Î²-synthase (CBS), and many of these individuals do not respond to current treatment protocols. In this issue of the JCI, Bublil and colleagues demonstrate that enzyme replacement therapy (ERT) provides long-term amelioration of homocystinuria-associated phenotypes in CBS-deficient murine models. A PEGylated form of CBS provided long-term stability and, when used in conjunction with the methylation agent betaine, dramatically increased survival in mice fed a normal diet. The results of this study provide one of the first examples of ERT for a metabolic disorder and suggest that PEGylated CBS should be further explored for use in patients.
Salmeterol enhances the cardiac response to gene therapy in Pompe disease. - Molecular genetics and metabolism
Enzyme replacement therapy (ERT) with recombinant human (rh) acid Î±-glucosidase (GAA) has prolonged the survival of patients. However, the paucity of cation-independent mannose-6-phosphate receptor (CI-MPR) in skeletal muscle, where it is needed to take up rhGAA, correlated with a poor response to ERT by muscle in Pompe disease. Clenbuterol, a selective Î²2 receptor agonist, enhanced the CI-MPR expression in striated muscle through Igf-1 mediated muscle hypertrophy, which correlated with increased CI-MPR (also the Igf-2 receptor) expression. In this study we have evaluated 4 new drugs in GAA knockout (KO) mice in combination with an adeno-associated virus (AAV) vector encoding human GAA, 3 alternative Î²2 agonists and dehydroepiandrosterone (DHEA). Mice were injected with AAV2/9-CBhGAA (1E+11 vector particles) at a dose that was not effective at clearing glycogen storage from the heart. Heart GAA activity was significantly increased by either salmeterol (p<0.01) or DHEA (p<0.05), in comparison with untreated mice. Furthermore, glycogen content was reduced in the heart by treatment with DHEA (p<0.001), salmeterol (p<0.05), formoterol (p<0.01), or clenbuterol (p<0.01) in combination with the AAV vector, in comparison with untreated GAA-KO mice. Wirehang testing revealed that salmeterol and the AAV vector significantly increased performance, in comparison with the AAV vector alone (p<0.001). Similarly, salmeterol with the vector increased performance significantly more than any of the other drugs. The most effective individual drugs had no significant effect in absence of vector, in comparison with untreated mice. Thus, salmeterol should be further developed as adjunctive therapy in combination with either ERT or gene therapy for Pompe disease.Copyright Â© 2016 Elsevier Inc. All rights reserved.
Complex III deficiency due to an in-frame MT-CYB deletion presenting as ketotic hypoglycemia and lactic acidosis. - Molecular genetics and metabolism reports
Complex III deficiency due to a MT-CYB mutation has been reported in patients with myopathy. Here, we describe a 15-year-old boy who presented with metabolic acidosis, ketotic hypoglycemia and carnitine deficiency. Electron transport chain analysis and mitochondrial DNA sequencing on muscle tissue lead to the eventual diagnosis of complex III deficiency. This case demonstrates the critical role of muscle biopsies in a myopathy work-up, and the clinical efficacy of supplement therapy.
Corrigendum to "Assessment of toxicity and biodistribution of recombinant AAV8 vector-mediated immunomodulatory gene therapy in mice with Pompe disease". - Molecular therapy. Methods & clinical development
[This corrects the article DOI: 10.1038/mtm.2014.18.].
A natural choice for hemophilia B. - Blood
In this issue of Blood, Crudele et al describe a novel study of adeno-associated virus (AAV) vector-mediated gene therapy that induced immune tolerance to factor IX (FIX) in a hemophilia B (HB) dog with previously formed anti-FIX inhibitor antibodies (IAs).
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