title: Patient-Specific Induced Pluripotent Stem Cell-Derived RPE Cells: Understanding the Pathogenesis of Retinopathy in Long-Chain 3-Hydroxyacyl-CoA Dehydrogenase Deficiency.
abstract: OBJECTIVE
  Retinopathy is an important manifestation of trifunctional protein (TFP) deficiencies but not of other defects of fatty acid oxidation. The common homozygous mutation in the TFP α-subunit gene HADHA (hydroxyacyl-CoA dehydrogenase), c.1528G>C, affects the long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) activity of TFP and blindness in infancy. The pathogenesis of the retinopathy is unknown. This study aimed to utilize human induced pluripotent stem cell (hiPSC) technology to create a disease model for the disorder, and to derive clues for retinopathy pathogenesis.
  
  
  METHODS
  We implemented hiPSC technology to generate LCHAD deficiency (LCHADD) patient-specific retinal pigment epithelial (RPE) monolayers. These patient and control RPEs were extensively characterized for function and structure, as well as for lipid composition by mass spectrometry.
  
  
  RESULTS
  The hiPSC-derived RPE monolayers of patients and controls were functional, as they both were able to phagocytose the photoreceptor outer segments in vitro. Interestingly, the patient RPEs had intense cytoplasmic neutral lipid accumulation, and lipidomic analysis revealed an increased triglyceride accumulation. Further, patient RPEs were small and irregular in shape, and their tight junctions were disorganized. Their ultrastructure showed decreased pigmentation, few melanosomes, and more melanolysosomes.
  
  
  CONCLUSIONS
  We demonstrate that the RPE cell model reveals novel early pathogenic changes in LCHADD retinopathy, with robust lipid accumulation, inefficient pigmentation that is evident soon after differentiation, and a defect in forming tight junctions inducing apoptosis. We propose that LCHADD-RPEs are an important model for mitochondrial TFP retinopathy, and that their early pathogenic changes contribute to infantile blindness of LCHADD.
authors.affiliation: Research Program of Molecular Neurology, Biomedicum 1, University of Helsinki, Helsinki, Finland.
authors.forename: Padmini P
authors.initials: PP
authors.lastname: Polinati
authors.affiliation: Institute of Biomedical Technology, University of Tampere, Tampere, Finland 3BioMediTech, Tampere, Finland.
authors.forename: Tanja
authors.initials: T
authors.lastname: Ilmarinen
authors.affiliation: Research Program of Molecular Neurology, Biomedicum 1, University of Helsinki, Helsinki, Finland.
authors.forename: Ras
authors.initials: R
authors.lastname: Trokovic
authors.affiliation: Valtion Teknillinen Tutkimuskeskus (VTT) Technical Research Centre of Finland, Tietotie 2, Espoo, Finland.
authors.forename: Tuulia
authors.initials: T
authors.lastname: Hyotylainen
authors.affiliation: Research Program of Molecular Neurology, Biomedicum 1, University of Helsinki, Helsinki, Finland 5Children's Hospital, Helsinki University Central Hospital, Helsinki, Finland.
authors.forename: Timo
authors.initials: T
authors.lastname: Otonkoski
authors.affiliation: Research Program of Molecular Neurology, Biomedicum 1, University of Helsinki, Helsinki, Finland 5Children's Hospital, Helsinki University Central Hospital, Helsinki, Finland.
authors.forename: Anu
authors.initials: A
authors.lastname: Suomalainen
authors.affiliation: Institute of Biomedical Technology, University of Tampere, Tampere, Finland 3BioMediTech, Tampere, Finland.
authors.forename: Heli
authors.initials: H
authors.lastname: Skottman
authors.affiliation: Research Program of Molecular Neurology, Biomedicum 1, University of Helsinki, Helsinki, Finland 5Children's Hospital, Helsinki University Central Hospital, Helsinki, Finland.
authors.forename: Tiina
authors.initials: T
authors.lastname: Tyni
mesh_terms: D015415:Biomarkers / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D007150:Immunohistochemistry; D057026:Induced Pluripotent Stem Cells / Q000166:cytology*; D008055:Lipids / Q000032:analysis; D063989:Long-Chain-3-Hydroxyacyl-CoA Dehydrogenase / Q000172:deficiency*; D013058:Mass Spectrometry; D008928:Mitochondria / Q000201:enzymology; D012164:Retinal Diseases / Q000378:metabolism / Q000473:pathology*; D055213:Retinal Pigment Epithelium / Q000378:metabolism / Q000473:pathology*
chemical_list: D015415:Biomarkers; D008055:Lipids; D063989:Long-Chain-3-Hydroxyacyl-CoA Dehydrogenase