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Makris G, Veit L, Rüfenacht V, Klassa S, Zürcher N, Matsumoto S, Poms M, Häberle J. Expression and function of the urea cycle in widely-used hepatic cellular models. J Inherit Metab Dis 2024. [PMID: 38192032 DOI: 10.1002/jimd.12701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 11/30/2023] [Accepted: 12/04/2023] [Indexed: 01/10/2024]
Abstract
The group of rare metabolic defects termed urea cycle disorders (UCDs) occur within the ammonia elimination pathway and lead to significant neurocognitive sequelae for patients surviving decompensation episodes. Besides orthotopic liver transplantation, curative options are lacking for UCDs, with dietary management being the gold clinical standard. Novel therapeutic approaches are essential for UCDs; however, such effort presupposes preclinical testing in cellular models that effectively capture disease manifestation. Several cellular and animal models exist and aim to recapitulate the broad phenotypic spectrum of UCDs; however, the majority of those lack extensive molecular and biochemical characterization. The development of cellular models is emerging since animal models are extremely time and cost consuming, and subject to ethical considerations, including the 3R principle that endorses animal welfare over unchecked preclinical testing. The aim of this study was to compare the extent of expression and functionality of the urea cycle in two commercial hepatoma-derived cell lines, induced pluripotent stem cell hepatocytes (iPSC-Heps), primary human hepatocytes (PHHs) and human liver cell preparations. Using immunoblotting, immunocytochemistry, and stable isotope tracing of the urea cycle metabolites, we identified that the hepatoma-derived, 2-week differentiated HepaRG cells are urea cycle proficient and behave as cellular alternatives to PHHs. Furthermore, HepaRG cells were superior to iPSC-Heps, which are known to exhibit batch-to-batch variabilities in terms of hepatic maturity and enzyme expression. Finally, HepG2 cells lack the urea cycle enzymes ornithine transcarbamylase and arginase 1, the transporter ORNT1, which limits their suitability as model for the study of UCDs.
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Affiliation(s)
- Georgios Makris
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, Zurich, Switzerland
- Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Lara Veit
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, Zurich, Switzerland
| | - Véronique Rüfenacht
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, Zurich, Switzerland
| | - Sven Klassa
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, Zurich, Switzerland
| | - Nadia Zürcher
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, Zurich, Switzerland
| | - Shirou Matsumoto
- Department of Pediatrics, Graduate School of Medical Sciences, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Martin Poms
- Division of Clinical Chemistry and Biochemistry, University Children's Hospital Zurich, Zurich, Switzerland
| | - Johannes Häberle
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, Zurich, Switzerland
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2
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Siri B, Olivieri G, Lepri FR, Poms M, Goffredo BM, Commone A, Novelli A, Häberle J, Dionisi-Vici C. Father-to-daughter transmission in late-onset OTC deficiency: an underestimated mechanism of inheritance of an X-linked disease. Orphanet J Rare Dis 2024; 19:3. [PMID: 38167094 PMCID: PMC10763478 DOI: 10.1186/s13023-023-02997-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Accepted: 12/13/2023] [Indexed: 01/05/2024] Open
Abstract
BACKGROUND Ornithine Transcarbamylase Deficiency (OTCD) is an X-linked urea cycle disorder characterized by acute hyperammonemic episodes. Hemizygous males are usually affected by a severe/fatal neonatal-onset form or, less frequently, by a late-onset form with milder disease course, depending on the residual enzymatic activity. Hyperammonemia can occur any time during life and patients could remain non- or mis-diagnosed due to unspecific symptoms. In heterozygous females, clinical presentation varies based on the extent of X chromosome inactivation. Maternal transmission in X-linked disease is the rule, but in late-onset OTCD, due to the milder phenotype of affected males, paternal transmission to the females is possible. So far, father-to-daughter transmission of OTCD has been reported only in 4 Japanese families. RESULTS We identified in 2 Caucasian families, paternal transmission of late-onset OTCD with severe/fatal outcome in affected males and 1 heterozygous female. Furthermore, we have reassessed the pedigrees of other published reports in 7 additional families with evidence of father-to-daughter inheritance of OTCD, identifying and listing the family members for which this transmission occurred. CONCLUSIONS Our study highlights how the diagnosis and pedigree analysis of late-onset OTCD may represent a real challenge for clinicians. Therefore, the occurrence of paternal transmission in OTCD should not be underestimated, due to the relevant implications for disease inheritance and risk of recurrence.
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Affiliation(s)
- Barbara Siri
- Division of Metabolic Diseases and Hepatology, Bambino Gesù Children's Hospital, IRCCS, Piazza S. Onofrio 4, 00165, Rome, Italy.
- Department of Paediatrics, Città della Salute e della Scienza, OIRM, University of Turin, Turin, Italy.
| | - Giorgia Olivieri
- Division of Metabolic Diseases and Hepatology, Bambino Gesù Children's Hospital, IRCCS, Piazza S. Onofrio 4, 00165, Rome, Italy
| | - Francesca Romana Lepri
- Translational Cytogenomics Research Unit, Laboratory of Medical Genetics, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Martin Poms
- Division of Clinical Chemistry and Biochemistry and Children's Research Center, University Children's Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Bianca Maria Goffredo
- Division of Metabolism and Metabolic Diseases Research Unit, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Anna Commone
- Division of Metabolic Diseases and Hepatology, Bambino Gesù Children's Hospital, IRCCS, Piazza S. Onofrio 4, 00165, Rome, Italy
| | - Antonio Novelli
- Translational Cytogenomics Research Unit, Laboratory of Medical Genetics, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Johannes Häberle
- Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Carlo Dionisi-Vici
- Division of Metabolic Diseases and Hepatology, Bambino Gesù Children's Hospital, IRCCS, Piazza S. Onofrio 4, 00165, Rome, Italy
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Deplazes S, Schlegel A, Song Z, Allegri G, Rimann N, Scherer T, Willimann M, Opitz L, Cunningham SC, Alexander IE, Kipar A, Häberle J, Thöny B, Grisch-chan HM. Intrabiliary infusion of naked DNA vectors targets periportal hepatocytes in mice. Molecular Therapy - Methods & Clinical Development 2022; 27:352-367. [DOI: 10.1016/j.omtm.2022.10.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 10/07/2022] [Indexed: 11/06/2022]
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4
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Bazo A, Lantero A, Mauleón I, Neri L, Poms M, Häberle J, Ricobaraza A, Bénichou B, Combal JP, Gonzalez-Aseguinolaza G, Aldabe R. Gene Therapy in Combination with Nitrogen Scavenger Pretreatment Corrects Biochemical and Behavioral Abnormalities of Infant Citrullinemia Type 1 Mice. Int J Mol Sci 2022; 23:14940. [PMID: 36499263 PMCID: PMC9736988 DOI: 10.3390/ijms232314940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 11/22/2022] [Accepted: 11/23/2022] [Indexed: 12/02/2022] Open
Abstract
Citrullinemia type I (CTLN1) is a rare autosomal recessive disorder caused by mutations in the gene encoding argininosuccinate synthetase 1 (ASS1) that catalyzes the third step of the urea cycle. CTLN1 patients suffer from impaired elimination of nitrogen, which leads to neurotoxic levels of circulating ammonia and urea cycle byproducts that may cause severe metabolic encephalopathy, death or irreversible brain damage. Standard of care (SOC) of CTLN1 consists of daily nitrogen-scavenger administration, but patients remain at risk of life-threatening decompensations. We evaluated the therapeutic efficacy of a recombinant adeno-associated viral vector carrying the ASS1 gene under the control of a liver-specific promoter (VTX-804). When administered to three-week-old CTLN1 mice, all the animals receiving VTX-804 in combination with SOC gained body weight normally, presented with a normalization of ammonia and reduction of citrulline levels in circulation, and 100% survived for 7 months. Similar to what has been observed in CTLN1 patients, CTLN1 mice showed several behavioral abnormalities such as anxiety, reduced welfare and impairment of innate behavior. Importantly, all clinical alterations were notably improved after treatment with VTX-804. This study demonstrates the potential of VTX-804 gene therapy for future clinical translation to CTLN1 patients.
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Affiliation(s)
- Andrea Bazo
- Division of Gene Therapy and Regulation of Gene Expression, CIMA, University of Navarra, 31008 Pamplona, Spain
| | | | - Itsaso Mauleón
- Division of Gene Therapy and Regulation of Gene Expression, CIMA, University of Navarra, 31008 Pamplona, Spain
| | - Leire Neri
- Vivet Therapeutics, S.L., 31008 Pamplona, Spain
| | - Martin Poms
- Department of Clinical Chemistry and Biochemistry, University Children’s Hospital Zurich, University of Zurich, 8091 Zurich, Switzerland
| | - Johannes Häberle
- Division of Metabolism, Children’s Research Centre (CRC), University Children’s Hospital Zurich, 8091 Zurich, Switzerland
| | - Ana Ricobaraza
- Division of Gene Therapy and Regulation of Gene Expression, CIMA, University of Navarra, 31008 Pamplona, Spain
| | | | | | - Gloria Gonzalez-Aseguinolaza
- Division of Gene Therapy and Regulation of Gene Expression, CIMA, University of Navarra, 31008 Pamplona, Spain
- Vivet Therapeutics, S.L., 31008 Pamplona, Spain
| | - Rafael Aldabe
- Division of Gene Therapy and Regulation of Gene Expression, CIMA, University of Navarra, 31008 Pamplona, Spain
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Soria LR, Makris G, D'Alessio AM, De Angelis A, Boffa I, Pravata VM, Rüfenacht V, Attanasio S, Nusco E, Arena P, Ferenbach AT, Paris D, Cuomo P, Motta A, Nitzahn M, Lipshutz GS, Martínez-Pizarro A, Richard E, Desviat LR, Häberle J, van Aalten DMF, Brunetti-Pierri N. O-GlcNAcylation enhances CPS1 catalytic efficiency for ammonia and promotes ureagenesis. Nat Commun 2022; 13:5212. [PMID: 36064721 PMCID: PMC9445089 DOI: 10.1038/s41467-022-32904-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 08/24/2022] [Indexed: 11/09/2022] Open
Abstract
Life-threatening hyperammonemia occurs in both inherited and acquired liver diseases affecting ureagenesis, the main pathway for detoxification of neurotoxic ammonia in mammals. Protein O-GlcNAcylation is a reversible and nutrient-sensitive post-translational modification using as substrate UDP-GlcNAc, the end-product of hexosamine biosynthesis pathway. Here we show that increased liver UDP-GlcNAc during hyperammonemia increases protein O-GlcNAcylation and enhances ureagenesis. Mechanistically, O-GlcNAcylation on specific threonine residues increased the catalytic efficiency for ammonia of carbamoyl phosphate synthetase 1 (CPS1), the rate-limiting enzyme in ureagenesis. Pharmacological inhibition of O-GlcNAcase, the enzyme removing O-GlcNAc from proteins, resulted in clinically relevant reductions of systemic ammonia in both genetic (hypomorphic mouse model of propionic acidemia) and acquired (thioacetamide-induced acute liver failure) mouse models of liver diseases. In conclusion, by fine-tuned control of ammonia entry into ureagenesis, hepatic O-GlcNAcylation of CPS1 increases ammonia detoxification and is a novel target for therapy of hyperammonemia in both genetic and acquired diseases.
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Affiliation(s)
- Leandro R Soria
- Telethon Institute of Genetics and Medicine, Pozzuoli, Italy.
| | - Georgios Makris
- Division of Metabolism and Children's Research Center, University Children's Hospital, Zurich, Switzerland
| | | | | | - Iolanda Boffa
- Telethon Institute of Genetics and Medicine, Pozzuoli, Italy
| | | | - Véronique Rüfenacht
- Division of Metabolism and Children's Research Center, University Children's Hospital, Zurich, Switzerland
| | | | - Edoardo Nusco
- Telethon Institute of Genetics and Medicine, Pozzuoli, Italy
| | - Paola Arena
- Telethon Institute of Genetics and Medicine, Pozzuoli, Italy
| | | | - Debora Paris
- Institute of Biomolecular Chemistry, National Research Council, Pozzuoli, Italy
| | - Paola Cuomo
- Institute of Biomolecular Chemistry, National Research Council, Pozzuoli, Italy
| | - Andrea Motta
- Institute of Biomolecular Chemistry, National Research Council, Pozzuoli, Italy
| | - Matthew Nitzahn
- Molecular Biology Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Gerald S Lipshutz
- Molecular Biology Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
- Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Ainhoa Martínez-Pizarro
- Centro de Biología Molecular Severo Ochoa UAM-CSIC, CIBERER, IdiPaz, Universidad Autónoma, Madrid, Spain
| | - Eva Richard
- Centro de Biología Molecular Severo Ochoa UAM-CSIC, CIBERER, IdiPaz, Universidad Autónoma, Madrid, Spain
| | - Lourdes R Desviat
- Centro de Biología Molecular Severo Ochoa UAM-CSIC, CIBERER, IdiPaz, Universidad Autónoma, Madrid, Spain
| | - Johannes Häberle
- Division of Metabolism and Children's Research Center, University Children's Hospital, Zurich, Switzerland
| | | | - Nicola Brunetti-Pierri
- Telethon Institute of Genetics and Medicine, Pozzuoli, Italy.
- Department of Translational Medicine, Federico II University, Naples, Italy.
- Scuola Superiore Meridionale (SSM, School of Advanced Studies), Genomics and Experimental Medicine Program, University of Naples Federico II, Naples, Italy.
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6
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Laemmle A, Poms M, Hsu B, Borsuk M, Rüfenacht V, Robinson J, Sadowski MC, Nuoffer J, Häberle J, Willenbring H. Aquaporin 9 induction in human iPSC-derived hepatocytes facilitates modeling of ornithine transcarbamylase deficiency. Hepatology 2022; 76:646-659. [PMID: 34786702 PMCID: PMC9295321 DOI: 10.1002/hep.32247] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Revised: 10/30/2021] [Accepted: 11/14/2021] [Indexed: 12/16/2022]
Abstract
BACKGROUND AND AIMS Patient-derived human-induced pluripotent stem cells (hiPSCs) differentiated into hepatocytes (hiPSC-Heps) have facilitated the study of rare genetic liver diseases. Here, we aimed to establish an in vitro liver disease model of the urea cycle disorder ornithine transcarbamylase deficiency (OTCD) using patient-derived hiPSC-Heps. APPROACH AND RESULTS Before modeling OTCD, we addressed the question of why hiPSC-Heps generally secrete less urea than adult primary human hepatocytes (PHHs). Because hiPSC-Heps are not completely differentiated and maintain some characteristics of fetal PHHs, we compared gene-expression levels in human fetal and adult liver tissue to identify genes responsible for reduced urea secretion in hiPSC-Heps. We found lack of aquaporin 9 (AQP9) expression in fetal liver tissue as well as in hiPSC-Heps, and showed that forced expression of AQP9 in hiPSC-Heps restores urea secretion and normalizes the response to ammonia challenge by increasing ureagenesis. Furthermore, we proved functional ureagenesis by challenging AQP9-expressing hiPSC-Heps with ammonium chloride labeled with the stable isotope [15 N] (15 NH4 Cl) and by assessing enrichment of [15 N]-labeled urea. Finally, using hiPSC-Heps derived from patients with OTCD, we generated a liver disease model that recapitulates the hepatic manifestation of the human disease. Restoring OTC expression-together with AQP9-was effective in fully correcting OTC activity and normalizing ureagenesis as assessed by 15 NH4 Cl stable-isotope challenge. CONCLUSION Our results identify a critical role for AQP9 in functional urea metabolism and establish the feasibility of in vitro modeling of OTCD with hiPSC-Heps. By facilitating studies of OTCD genotype/phenotype correlation and drug screens, our model has potential for improving the therapy of OTCD.
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Affiliation(s)
- Alexander Laemmle
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell ResearchUniversity of California San FranciscoSan FranciscoCaliforniaUSA,Department of PediatricsUniversity Children's HospitalBernSwitzerland,University Institute of Clinical ChemistryUniversity of BernBernSwitzerland
| | - Martin Poms
- Division of Clinical Chemistry and BiochemistryUniversity Children’s Hospital ZurichZurichSwitzerland
| | - Bernadette Hsu
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell ResearchUniversity of California San FranciscoSan FranciscoCaliforniaUSA
| | - Mariia Borsuk
- University Institute of Clinical ChemistryUniversity of BernBernSwitzerland
| | - Véronique Rüfenacht
- Division of Metabolism and Children`s Research CenterUniversity Children’s HospitalZurichSwitzerland
| | - Joshua Robinson
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell ResearchUniversity of California San FranciscoSan FranciscoCaliforniaUSA,Center for Reproductive SciencesUniversity of California San FranciscoSan FranciscoCaliforniaUSA,Department of Obstetrics, Gynecology, and Reproductive SciencesUniversity of California San FranciscoSan FranciscoCaliforniaUSA,Department of PediatricsMedical GeneticsUniversity of California San FranciscoSan FranciscoCaliforniaUSA
| | | | - Jean‐Marc Nuoffer
- Department of PediatricsUniversity Children's HospitalBernSwitzerland,University Institute of Clinical ChemistryUniversity of BernBernSwitzerland
| | - Johannes Häberle
- Division of Metabolism and Children`s Research CenterUniversity Children’s HospitalZurichSwitzerland,Zurich Center for Integrative Human PhysiologyUniversity of ZurichZurichSwitzerland
| | - Holger Willenbring
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell ResearchUniversity of California San FranciscoSan FranciscoCaliforniaUSA,Department of SurgeryDivision of Transplant SurgeryUniversity of California San FranciscoSan FranciscoCaliforniaUSA,Liver CenterUniversity of California San FranciscoSan FranciscoCaliforniaUSA
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7
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Zabulica M, Jakobsson T, Ravaioli F, Vosough M, Gramignoli R, Ellis E, Rooyackers O, Strom SC. Gene Editing Correction of a Urea Cycle Defect in Organoid Stem Cell Derived Hepatocyte-like Cells. Int J Mol Sci 2021; 22:1217. [PMID: 33530582 DOI: 10.3390/ijms22031217] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 01/18/2021] [Accepted: 01/20/2021] [Indexed: 12/17/2022] Open
Abstract
Urea cycle disorders are enzymopathies resulting from inherited deficiencies in any genes of the cycle. In severe cases, currently available therapies are marginally effective, with liver transplantation being the only definitive treatment. Donor liver availability can limit even this therapy. Identification of novel therapeutics for genetic-based liver diseases requires models that provide measurable hepatic functions and phenotypes. Advances in stem cell and genome editing technologies could provide models for the investigation of cell-based genetic diseases, as well as the platforms for drug discovery. This report demonstrates a practical, and widely applicable, approach that includes the successful reprogramming of somatic cells from a patient with a urea cycle defect, their genetic correction and differentiation into hepatic organoids, and the subsequent demonstration of genetic and phenotypic change in the edited cells consistent with the correction of the defect. While individually rare, there is a large number of other genetic-based liver diseases. The approach described here could be applied to a broad range and a large number of patients with these hepatic diseases where it could serve as an in vitro model, as well as identify successful strategies for corrective cell-based therapy.
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8
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Zabulica M, Srinivasan RC, Akcakaya P, Allegri G, Bestas B, Firth M, Hammarstedt C, Jakobsson T, Jakobsson T, Ellis E, Jorns C, Makris G, Scherer T, Rimann N, van Zuydam NR, Gramignoli R, Forslöw A, Engberg S, Maresca M, Rooyackers O, Thöny B, Häberle J, Rosen B, Strom SC. Correction of a urea cycle defect after ex vivo gene editing of human hepatocytes. Mol Ther 2021; 29:1903-1917. [PMID: 33484963 PMCID: PMC8116578 DOI: 10.1016/j.ymthe.2021.01.024] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2020] [Revised: 11/17/2020] [Accepted: 01/12/2021] [Indexed: 12/25/2022] Open
Abstract
Ornithine transcarbamylase deficiency (OTCD) is a monogenic disease of ammonia metabolism in hepatocytes. Severe disease is frequently treated by orthotopic liver transplantation. An attractive approach is the correction of a patient’s own cells to regenerate the liver with gene-repaired hepatocytes. This study investigates the efficacy and safety of ex vivo correction of primary human hepatocytes. Hepatocytes isolated from an OTCD patient were genetically corrected ex vivo, through the deletion of a mutant intronic splicing site achieving editing efficiencies >60% and the restoration of the urea cycle in vitro. The corrected hepatocytes were transplanted into the liver of FRGN mice and repopulated to high levels (>80%). Animals transplanted and liver repopulated with genetically edited patient hepatocytes displayed normal ammonia, enhanced clearance of an ammonia challenge and OTC enzyme activity, as well as lower urinary orotic acid when compared to mice repopulated with unedited patient hepatocytes. Gene expression was shown to be similar between mice transplanted with unedited or edited patient hepatocytes. Finally, a genome-wide screening by performing CIRCLE-seq and deep sequencing of >70 potential off-targets revealed no unspecific editing. Overall analysis of disease phenotype, gene expression, and possible off-target editing indicated that the gene editing of a severe genetic liver disease was safe and effective.
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Affiliation(s)
- Mihaela Zabulica
- Department of Laboratory Medicine, Karolinska Institutet, 141 52 Huddinge, Sweden
| | | | - Pinar Akcakaya
- Discovery Sciences, BioPharmaceuticals R&D Unit, AstraZeneca, Gothenburg, Sweden
| | - Gabriella Allegri
- Division of Metabolism and Children's Research Center, University Children's Hospital, Zürich, Switzerland
| | - Burcu Bestas
- Discovery Sciences, BioPharmaceuticals R&D Unit, AstraZeneca, Gothenburg, Sweden
| | - Mike Firth
- Discovery Sciences, BioPharmaceuticals R&D Unit, AstraZeneca, Cambridge, UK
| | | | - Tomas Jakobsson
- Department of Laboratory Medicine, Karolinska Institutet, 141 52 Huddinge, Sweden
| | - Towe Jakobsson
- Department of Clinical Sciences Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
| | - Ewa Ellis
- Department of Clinical Sciences Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
| | - Carl Jorns
- Department of Clinical Sciences Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
| | - Georgios Makris
- Division of Metabolism and Children's Research Center, University Children's Hospital, Zürich, Switzerland
| | - Tanja Scherer
- Division of Metabolism and Children's Research Center, University Children's Hospital, Zürich, Switzerland
| | - Nicole Rimann
- Division of Metabolism and Children's Research Center, University Children's Hospital, Zürich, Switzerland
| | - Natalie R van Zuydam
- Department of Quantitative Biology, Discovery Sciences, R&D BioPharmaceuticals, AstraZeneca, Gothenburg, Sweden
| | - Roberto Gramignoli
- Department of Laboratory Medicine, Karolinska Institutet, 141 52 Huddinge, Sweden
| | - Anna Forslöw
- Discovery Sciences, BioPharmaceuticals R&D Unit, AstraZeneca, Gothenburg, Sweden
| | - Susanna Engberg
- Discovery Sciences, BioPharmaceuticals R&D Unit, AstraZeneca, Gothenburg, Sweden
| | - Marcello Maresca
- Discovery Sciences, BioPharmaceuticals R&D Unit, AstraZeneca, Gothenburg, Sweden
| | - Olav Rooyackers
- Department of Clinical Sciences Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
| | - Beat Thöny
- Division of Metabolism and Children's Research Center, University Children's Hospital, Zürich, Switzerland
| | - Johannes Häberle
- Division of Metabolism and Children's Research Center, University Children's Hospital, Zürich, Switzerland
| | - Barry Rosen
- Discovery Sciences, BioPharmaceuticals R&D Unit, AstraZeneca, Cambridge, UK
| | - Stephen C Strom
- Department of Laboratory Medicine, Karolinska Institutet, 141 52 Huddinge, Sweden.
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9
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Nitzahn M, Allegri G, Khoja S, Truong B, Makris G, Häberle J, Lipshutz GS. Split AAV-Mediated Gene Therapy Restores Ureagenesis in a Murine Model of Carbamoyl Phosphate Synthetase 1 Deficiency. Mol Ther 2020; 28:1717-1730. [PMID: 32359471 DOI: 10.1016/j.ymthe.2020.04.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 02/25/2020] [Accepted: 04/09/2020] [Indexed: 02/07/2023] Open
Abstract
The urea cycle enzyme carbamoyl phosphate synthetase 1 (CPS1) catalyzes the initial step of the urea cycle; bi-allelic mutations typically present with hyperammonemia, vomiting, ataxia, lethargy progressing into coma, and death due to brain edema if ineffectively treated. The enzyme deficiency is particularly difficult to treat; early recognition is essential to minimize injury to the brain. Even under optimal conditions, therapeutic interventions are of limited scope and efficacy, with most patients developing long-term neurologic sequelae. One significant encumberment to gene therapeutic development is the size of the CPS1 cDNA, which, at 4.5 kb, nears the packaging capacity of adeno-associated virus (AAV). Herein we developed a split AAV (sAAV)-based approach, packaging the large transgene and its regulatory cassette into two separate vectors, thereby delivering therapeutic CPS1 by a dual vector system with testing in a murine model of the disorder. Cps1-deficient mice treated with sAAVs survive long-term with markedly improved ammonia levels, diminished dysregulation of circulating amino acids, and increased hepatic CPS1 expression and activity. In response to acute ammonia challenging, sAAV-treated female mice rapidly incorporated nitrogen into urea. This study demonstrates the first proof-of-principle that sAAV-mediated therapy is a viable, potentially clinically translatable approach to CPS1 deficiency, a devastating urea cycle disorder.
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Affiliation(s)
- Matthew Nitzahn
- Molecular Biology Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Gabriella Allegri
- Division of Metabolism and Children's Research Center, University Children's Hospital, Zurich, Switzerland
| | - Suhail Khoja
- Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Brian Truong
- Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Georgios Makris
- Division of Metabolism and Children's Research Center, University Children's Hospital, Zurich, Switzerland
| | - Johannes Häberle
- Division of Metabolism and Children's Research Center, University Children's Hospital, Zurich, Switzerland
| | - Gerald S Lipshutz
- Molecular Biology Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Department of Psychiatry, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Intellectual and Developmental Disabilities Research Center, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Semel Institute for Neuroscience, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
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10
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Allegri G, Deplazes S, Rimann N, Causton B, Scherer T, Leff JW, Diez-Fernandez C, Klimovskaia A, Fingerhut R, Krijt J, Kožich V, Nuoffer JM, Grisch-Chan HM, Thöny B, Häberle J. Comprehensive characterization of ureagenesis in the spf ash mouse, a model of human ornithine transcarbamylase deficiency, reveals age-dependency of ammonia detoxification. J Inherit Metab Dis 2019; 42:1064-1076. [PMID: 30714172 DOI: 10.1002/jimd.12068] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 01/30/2019] [Indexed: 12/24/2022]
Abstract
The most common ureagenesis defect is X-linked ornithine transcarbamylase (OTC) deficiency which is a main target for novel therapeutic interventions. The spf ash mouse model carries a variant (c.386G>A, p.Arg129His) that is also found in patients. Male spf ash mice have a mild biochemical phenotype with low OTC activity (5%-10% of wild-type), resulting in elevated urinary orotic acid but no hyperammonemia. We recently established a dried blood spot method for in vivo quantification of ureagenesis by Gas chromatography-mass spectrometry (GC-MS) using stable isotopes. Here, we applied this assay to wild-type and spf ash mice to assess ureagenesis at different ages. Unexpectedly, we found an age-dependency with a higher capacity for ammonia detoxification in young mice after weaning. A parallel pattern was observed for carbamoylphosphate synthetase 1 and OTC enzyme expression and activities, which may act as pacemaker of this ammonia detoxification pathway. Moreover, high ureagenesis in younger mice was accompanied by elevated periportal expression of hepatic glutamine synthetase, another main enzyme required for ammonia detoxification. These observations led us to perform a more extensive analysis of the spf ash mouse in comparison to the wild-type, including characterization of the corresponding metabolites, enzyme activities in the liver and plasma and the gut microbiota. In conclusion, the comprehensive enzymatic and metabolic analysis of ureagenesis performed in the presented depth was only possible in animals. Our findings suggest such analyses being essential when using the mouse as a model and revealed age-dependent activity of ammonia detoxification.
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Affiliation(s)
- Gabriella Allegri
- Division of Metabolism and Children's Research Center (CRC), University Children's Hospital Zurich, Zurich, Switzerland
| | - Sereina Deplazes
- Division of Metabolism and Children's Research Center (CRC), University Children's Hospital Zurich, Zurich, Switzerland
| | - Nicole Rimann
- Division of Metabolism and Children's Research Center (CRC), University Children's Hospital Zurich, Zurich, Switzerland
| | | | - Tanja Scherer
- Division of Metabolism and Children's Research Center (CRC), University Children's Hospital Zurich, Zurich, Switzerland
| | | | - Carmen Diez-Fernandez
- Division of Metabolism and Children's Research Center (CRC), University Children's Hospital Zurich, Zurich, Switzerland
| | - Anna Klimovskaia
- Institute for Molecular Systems Biology, ETH Zurich, Zurich, Switzerland
| | - Ralph Fingerhut
- Swiss Newborn Screening Laboratory, University Children's Hospital, Zurich, Switzerland
| | - Jakub Krijt
- Department of Pediatrics and Adolescent Medicine, Charles University-First Faculty of Medicine and General University Hospital in Prague, Prague, Czech Republic
| | - Viktor Kožich
- Department of Pediatrics and Adolescent Medicine, Charles University-First Faculty of Medicine and General University Hospital in Prague, Prague, Czech Republic
| | - Jean-Marc Nuoffer
- Department of Clinical Chemistry, Inselspital Bern, Bern, Switzerland
| | - Hiu M Grisch-Chan
- Division of Metabolism and Children's Research Center (CRC), University Children's Hospital Zurich, Zurich, Switzerland
| | - Beat Thöny
- Division of Metabolism and Children's Research Center (CRC), University Children's Hospital Zurich, Zurich, Switzerland
| | - Johannes Häberle
- Division of Metabolism and Children's Research Center (CRC), University Children's Hospital Zurich, Zurich, Switzerland
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11
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Häberle J, Burlina A, Chakrapani A, Dixon M, Karall D, Lindner M, Mandel H, Martinelli D, Pintos-Morell G, Santer R, Skouma A, Servais A, Tal G, Rubio V, Huemer M, Dionisi-Vici C. Suggested guidelines for the diagnosis and management of urea cycle disorders: First revision. J Inherit Metab Dis 2019; 42:1192-1230. [PMID: 30982989 DOI: 10.1002/jimd.12100] [Citation(s) in RCA: 229] [Impact Index Per Article: 45.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 04/04/2019] [Accepted: 04/08/2019] [Indexed: 02/06/2023]
Abstract
In 2012, we published guidelines summarizing and evaluating late 2011 evidence for diagnosis and therapy of urea cycle disorders (UCDs). With 1:35 000 estimated incidence, UCDs cause hyperammonemia of neonatal (~50%) or late onset that can lead to intellectual disability or death, even while effective therapies do exist. In the 7 years that have elapsed since the first guideline was published, abundant novel information has accumulated, experience on newborn screening for some UCDs has widened, a novel hyperammonemia-causing genetic disorder has been reported, glycerol phenylbutyrate has been introduced as a treatment, and novel promising therapeutic avenues (including gene therapy) have been opened. Several factors including the impact of the first edition of these guidelines (frequently read and quoted) may have increased awareness among health professionals and patient families. However, under-recognition and delayed diagnosis of UCDs still appear widespread. It was therefore necessary to revise the original guidelines to ensure an up-to-date frame of reference for professionals and patients as well as for awareness campaigns. This was accomplished by keeping the original spirit of providing a trans-European consensus based on robust evidence (scored with GRADE methodology), involving professionals on UCDs from nine countries in preparing this consensus. We believe this revised guideline, which has been reviewed by several societies that are involved in the management of UCDs, will have a positive impact on the outcomes of patients by establishing common standards, and spreading and harmonizing good practices. It may also promote the identification of knowledge voids to be filled by future research.
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Affiliation(s)
- Johannes Häberle
- University Children's Hospital Zurich and Children's Research Centre, Zurich, Switzerland
| | - Alberto Burlina
- Division of Inborn Metabolic Disease, Department of Pediatrics, University Hospital Padua, Padova, Italy
| | - Anupam Chakrapani
- Department of Metabolic Medicine, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Marjorie Dixon
- Dietetics, Great Ormond Street Hospital for Children, NHS Trust, London, UK
| | - Daniela Karall
- Clinic for Pediatrics, Division of Inherited Metabolic Disorders, Medical University of Innsbruck, Innsbruck, Austria
| | - Martin Lindner
- University Children's Hospital, Frankfurt am Main, Germany
| | - Hanna Mandel
- Institute of Human Genetics and metabolic disorders, Western Galilee Medical Center, Nahariya, Israel
| | - Diego Martinelli
- Division of Metabolism, Bambino Gesù Children's Hospital, Rome, Italy
| | - Guillem Pintos-Morell
- Centre for Rare Diseases, University Hospital Vall d'Hebron, Barcelona, Spain
- CIBERER_GCV08, Research Institute IGTP, Barcelona, Spain
- Universitat Autònoma de Barcelona, Barcelona, Spain
| | - René Santer
- Department of Pediatrics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Anastasia Skouma
- Institute of Child Health, Agia Sofia Children's Hospital, Athens, Greece
| | - Aude Servais
- Service de Néphrologie et maladies métaboliques adulte Hôpital Necker 149, Paris, France
| | - Galit Tal
- The Ruth Rappaport Children's Hospital, Rambam Medical Center, Haifa, Israel
| | - Vicente Rubio
- Instituto de Biomedicina de Valencia (IBV-CSIC), Centro de Investigación Biomédica en Red para Enfermedades Raras (CIBERER), Valencia, Spain
| | - Martina Huemer
- University Children's Hospital Zurich and Children's Research Centre, Zurich, Switzerland
- Department of Paediatrics, Landeskrankenhaus Bregenz, Bregenz, Austria
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12
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Srinivasan RC, Zabulica M, Hammarstedt C, Wu T, Gramignoli R, Kannisto K, Ellis E, Karadagi A, Fingerhut R, Allegri G, Rüfenacht V, Thöny B, Häberle J, Nuoffer JM, Strom SC. A liver-humanized mouse model of carbamoyl phosphate synthetase 1-deficiency. J Inherit Metab Dis 2019; 42:1054-1063. [PMID: 30843237 DOI: 10.1002/jimd.12067] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 01/25/2019] [Indexed: 12/31/2022]
Abstract
A liver-humanized mouse model for CPS1-deficiency was generated by the high-level repopulation of the mouse liver with CPS1-deficient human hepatocytes. When compared with mice that are highly repopulated with CPS1-proficient human hepatocytes, mice that are repopulated with CPS1-deficient human hepatocytes exhibited characteristic symptoms of human CPS1 deficiency including an 80% reduction in CPS1 metabolic activity, delayed clearance of an ammonium chloride infusion, elevated glutamine and glutamate levels, and impaired metabolism of [15 N]ammonium chloride into urea, with no other obvious phenotypic differences. Because most metabolic liver diseases result from mutations that alter critical pathways in hepatocytes, a model that incorporates actual disease-affected, mutant human hepatocytes is useful for the investigation of the molecular, biochemical, and phenotypic differences induced by that mutation. The model is also expected to be useful for investigations of modified RNA, gene, and cellular and small molecule therapies for CPS1-deficiency. Liver-humanized models for this and other monogenic liver diseases afford the ability to assess the therapy on actual disease-affected human hepatocytes, in vivo, for long periods of time and will provide data that are highly relevant for investigations of the safety and efficacy of gene-editing technologies directed to human hepatocytes and the translation of gene-editing technology to the clinic.
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Affiliation(s)
- Raghuraman C Srinivasan
- Department of Laboratory Medicine, Division of Pathology, Karolinska Institutet, Stockholm, Sweden
| | - Mihaela Zabulica
- Department of Laboratory Medicine, Division of Pathology, Karolinska Institutet, Stockholm, Sweden
| | - Christina Hammarstedt
- Department of Laboratory Medicine, Division of Pathology, Karolinska Institutet, Stockholm, Sweden
| | - Tingting Wu
- Department of Laboratory Medicine, Division of Pathology, Karolinska Institutet, Stockholm, Sweden
| | - Roberto Gramignoli
- Department of Laboratory Medicine, Division of Pathology, Karolinska Institutet, Stockholm, Sweden
| | - Kristina Kannisto
- Department of Laboratory Medicine, Clinical Research Center, Karolinska Institutet, Stockholm, Sweden
| | - Ewa Ellis
- Department of Clinical Science, Intervention and Technology (CLINTEC), Karolinska Institutet, Stockholm, Sweden
| | - Ahmad Karadagi
- Department of Clinical Science, Intervention and Technology (CLINTEC), Karolinska Institutet, Stockholm, Sweden
| | - Ralph Fingerhut
- Division of Metabolism and Children's Research Centre (CRC), University Children's Hospital Zurich, Zurich, Switzerland
- Swiss Newborn Screening Laboratory, University Children's Hospital Zurich, Zurich, Switzerland
| | - Gabriella Allegri
- Division of Metabolism and Children's Research Centre (CRC), University Children's Hospital Zurich, Zurich, Switzerland
| | - Véronique Rüfenacht
- Division of Metabolism and Children's Research Centre (CRC), University Children's Hospital Zurich, Zurich, Switzerland
| | - Beat Thöny
- Division of Metabolism and Children's Research Centre (CRC), University Children's Hospital Zurich, Zurich, Switzerland
- Swiss Newborn Screening Laboratory, University Children's Hospital Zurich, Zurich, Switzerland
| | - Johannes Häberle
- Division of Metabolism and Children's Research Centre (CRC), University Children's Hospital Zurich, Zurich, Switzerland
- Zurich Centre for Integrative Human Physiology (ZIHP) and, Neuroscience Centre Zurich (ZNZ), Zurich, Switzerland
| | - Jean-Marc Nuoffer
- Institute for Clinical Chemistry and University Children's Hospital, Bern, Switzerland
| | - Stephen C Strom
- Department of Laboratory Medicine, Division of Pathology, Karolinska Institutet, Stockholm, Sweden
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Truong B, Allegri G, Liu XB, Burke KE, Zhu X, Cederbaum SD, Häberle J, Martini PGV, Lipshutz GS. Lipid nanoparticle-targeted mRNA therapy as a treatment for the inherited metabolic liver disorder arginase deficiency. Proc Natl Acad Sci U S A 2019; 116:21150-9. [PMID: 31501335 DOI: 10.1073/pnas.1906182116] [Citation(s) in RCA: 80] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Arginase deficiency is caused by biallelic mutations in arginase 1 (ARG1), the final step of the urea cycle, and results biochemically in hyperargininemia and the presence of guanidino compounds, while it is clinically notable for developmental delays, spastic diplegia, psychomotor function loss, and (uncommonly) death. There is currently no completely effective medical treatment available. While preclinical strategies have been demonstrated, disadvantages with viral-based episomal-expressing gene therapy vectors include the risk of insertional mutagenesis and limited efficacy due to hepatocellular division. Recent advances in messenger RNA (mRNA) codon optimization, synthesis, and encapsulation within biodegradable liver-targeted lipid nanoparticles (LNPs) have potentially enabled a new generation of safer, albeit temporary, treatments to restore liver metabolic function in patients with urea cycle disorders, including ARG1 deficiency. In this study, we applied such technologies to successfully treat an ARG1-deficient murine model. Mice were administered LNPs encapsulating human codon-optimized ARG1 mRNA every 3 d. Mice demonstrated 100% survival with no signs of hyperammonemia or weight loss to beyond 11 wk, compared with controls that perished by day 22. Plasma ammonia, arginine, and glutamine demonstrated good control without elevation of guanidinoacetic acid, a guanidino compound. Evidence of urea cycle activity restoration was demonstrated by the ability to fully metabolize an ammonium challenge and by achieving near-normal ureagenesis; liver arginase activity achieved 54% of wild type. Biochemical and microscopic data showed no evidence of hepatotoxicity. These results suggest that delivery of ARG1 mRNA by liver-targeted nanoparticles may be a viable gene-based therapeutic for the treatment of arginase deficiency.
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Soria LR, Allegri G, Melck D, Pastore N, Annunziata P, Paris D, Polishchuk E, Nusco E, Thöny B, Motta A, Häberle J, Ballabio A, Brunetti-Pierri N. Enhancement of hepatic autophagy increases ureagenesis and protects against hyperammonemia. Proc Natl Acad Sci U S A 2018; 115:391-6. [PMID: 29279371 DOI: 10.1073/pnas.1714670115] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Ammonia is a potent neurotoxin that is detoxified mainly by the urea cycle in the liver. Hyperammonemia is a common complication of a wide variety of both inherited and acquired liver diseases. If not treated early and thoroughly, it results in encephalopathy and death. Here, we found that hepatic autophagy is critically involved in systemic ammonia homeostasis by providing key urea-cycle intermediates and ATP. Hepatic autophagy is triggered in vivo by hyperammonemia through an α-ketoglutarate-dependent inhibition of the mammalian target of rapamycin complex 1, and deficiency of autophagy impairs ammonia detoxification. In contrast, autophagy enhancement by means of hepatic gene transfer of the master regulator of autophagy transcription factor EB or treatments with the autophagy enhancers rapamycin and Tat-Beclin-1 increased ureagenesis and protected against hyperammonemia in a variety of acute and chronic hyperammonemia animal models, including acute liver failure and ornithine transcarbamylase deficiency, the most frequent urea-cycle disorder. In conclusion, hepatic autophagy is an important mechanism for ammonia detoxification because of its support of urea synthesis, and its enhancement has potential for therapy of both primary and secondary causes of hyperammonemia.
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Diez-Fernandez C, Häberle J. Targeting CPS1 in the treatment of Carbamoyl phosphate synthetase 1 (CPS1) deficiency, a urea cycle disorder. Expert Opin Ther Targets 2017; 21:391-399. [PMID: 28281899 DOI: 10.1080/14728222.2017.1294685] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
INTRODUCTION Carbamoyl phosphate synthetase 1 (CPS1) deficiency (CPS1D) is a rare autosomal recessive urea cycle disorder (UCD), which can lead to life-threatening hyperammonemia. Unless promptly treated, it can result in encephalopathy, coma and death, or intellectual disability in surviving patients. Over recent decades, therapies for CPS1D have barely improved leaving the management of these patients largely unchanged. Additionally, in many cases, current management (protein-restriction and supplementation with citrulline and/or arginine and ammonia scavengers) is insufficient for achieving metabolic stability, highlighting the importance of developing alternative therapeutic approaches. Areas covered: After describing UCDs and CPS1D, we give an overview of the structure- function of CPS1. We then describe current management and potential novel treatments including N-carbamoyl-L-glutamate (NCG), pharmacological chaperones, and gene therapy to treat hyperammonemia. Expert opinion: Probably, the first novel CPS1D therapies to reach the clinics will be the already commercial substance NCG, which is the standard treatment for N-acetylglutamate synthase deficiency and has been proven to rescue specific CPS1D mutations. Pharmacological chaperones and gene therapy are under development too, but these two technologies still have key challenges to be overcome. In addition, current experimental therapies will hopefully add further treatment options.
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Affiliation(s)
- Carmen Diez-Fernandez
- a Division of Metabolism , University Children's Hospital Zurich and Children's Research Center , Zurich , Switzerland
| | - Johannes Häberle
- a Division of Metabolism , University Children's Hospital Zurich and Children's Research Center , Zurich , Switzerland
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