title: Chondrocytes Derived From Mesenchymal Stromal Cells and Induced Pluripotent Cells of Patients With Familial Osteochondritis Dissecans Exhibit an Endoplasmic Reticulum Stress Response and Defective Matrix Assembly.
abstract: : Familial osteochondritis dissecans (FOCD) is an inherited skeletal defect characterized by the development of large cartilage lesions in multiple joints, short stature, and early onset of severe osteoarthritis. It is associated with a heterozygous mutation in the ACAN gene, resulting in a Val-Met replacement in the C-type lectin domain of aggrecan. To understand the cellular pathogenesis of this condition, we studied the chondrogenic differentiation of patient bone marrow mesenchymal stromal cells (BM-MSCs). We also looked at cartilage derived from induced pluripotent stem cells (iPSCs) generated from patient fibroblasts. Our results revealed several characteristics of the differentiated chondrocytes that help to explain the disease phenotype and susceptibility to cartilage injury. First, patient chondrogenic pellets had poor structural integrity but were rich in glycosaminoglycan. Second, it was evident that large amounts of aggrecan accumulated within the endoplasmic reticulum of chondrocytes differentiated from both BM-MSCs and iPSCs. In turn, there was a marked absence of aggrecan in the extracellular matrix. Third, it was evident that matrix synthesis and assembly were globally dysregulated. These results highlight some of the abnormal aspects of chondrogenesis in these patient cells and help to explain the underlying cellular pathology. The results suggest that FOCD is a chondrocyte aggrecanosis with associated matrix dysregulation. The work provides a new in vitro model of osteoarthritis and cartilage degeneration based on the use of iPSCs and highlights how insights into disease phenotype and pathogenesis can be uncovered by studying differentiation of patient stem cells.
  
  
  
  The isolation and study of patient stem cells and the development of methods for the generation of iPSCs have opened up exciting opportunities in understanding causes and exploring new treatments for major diseases. This technology was used to unravel the cellular phenotype in a severe form of inherited osteoarthritis, termed familial osteochondritis dissecans. The phenotypic abnormalities that give rise to cartilage lesions in these patients were able to be described via the generation of chondrocytes from bone marrow-derived mesenchymal stromal cells and iPSCs, illustrating the extraordinary value of these approaches in disease modeling.
authors.affiliation: Regenerative Medicine Institute, National University of Ireland Galway, Galway, Ireland.
authors.forename: Maojia
authors.initials: M
authors.lastname: Xu
authors.affiliation: Department of Immunology, Genetics, and Pathology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden.
authors.forename: Eva-Lena
authors.initials: EL
authors.lastname: Stattin
authors.affiliation: Regenerative Medicine Institute, National University of Ireland Galway, Galway, Ireland.
authors.forename: Georgina
authors.initials: G
authors.lastname: Shaw
authors.affiliation: Department of Clinical Sciences, Rheumatology, and Molecular Skeletal Biology, Lund University, Lund, Sweden.
authors.forename: Dick
authors.initials: D
authors.lastname: Heinegård
authors.affiliation: Norwegian Center for Stem Cell Research, Oslo, Norway.
authors.forename: Gareth
authors.initials: G
authors.lastname: Sullivan
authors.affiliation: Medical Research Council Centre for Regenerative Medicine, University of Edinburgh, Edinburgh, United Kingdom.
authors.forename: Ian
authors.initials: I
authors.lastname: Wilmut
authors.affiliation: A*STAR Institute of Medical Biology, Singapore.
authors.forename: Alan
authors.initials: A
authors.lastname: Colman
authors.affiliation: Department of Clinical Sciences, Rheumatology, and Molecular Skeletal Biology, Lund University, Lund, Sweden.
authors.forename: Patrik
authors.initials: P
authors.lastname: Önnerfjord
authors.affiliation: Department of Clinical Sciences, Rheumatology, and Molecular Skeletal Biology, Lund University, Lund, Sweden.
authors.forename: Areej
authors.initials: A
authors.lastname: Khabut
authors.affiliation: Department of Clinical Sciences, Rheumatology, and Molecular Skeletal Biology, Lund University, Lund, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Aspberg
authors.affiliation: Anatomy, School of Medicine, National University of Ireland Galway, Galway, Ireland.
authors.forename: Peter
authors.initials: P
authors.lastname: Dockery
authors.affiliation: Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences University of Manchester, Manchester, United Kingdom.
authors.forename: Timothy
authors.initials: T
authors.lastname: Hardingham
authors.affiliation: Regenerative Medicine Institute, National University of Ireland Galway, Galway, Ireland.
authors.forename: Mary
authors.initials: M
authors.lastname: Murphy
authors.affiliation: Regenerative Medicine Institute, National University of Ireland Galway, Galway, Ireland frank.barry@nuigalway.ie.
authors.forename: Frank
authors.initials: F
authors.lastname: Barry
mesh_terms: D000328:Adult; D053674:Aggrecans / Q000235:genetics; D000818:Animals; D002356:Cartilage / Q000378:metabolism; D018929:Cell Culture Techniques / Q000379:methods; D019902:Chondrocytes / Q000378:metabolism / Q000473:pathology*; D020219:Chondrogenesis / Q000502:physiology; D059865:Endoplasmic Reticulum Stress / Q000502:physiology*; D005109:Extracellular Matrix / Q000473:pathology*; D006801:Humans; D007150:Immunohistochemistry; D057026:Induced Pluripotent Stem Cells / Q000166:cytology; D008297:Male; D013058:Mass Spectrometry; D059630:Mesenchymal Stem Cells / Q000166:cytology; D051379:Mice; D046529:Microscopy, Electron, Transmission; D008875:Middle Aged; D010008:Osteochondritis Dissecans / Q000151:congenital* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D010641:Phenotype
chemical_list: D053674:Aggrecans
keywords: Aggrecan mutation; Cellular pathology; Endoplasmic reticulum stress; Familial osteochondritis dissecans; Induced pluripotent stem cells; Mesenchymal stromal cells; Osteoarthritis; Stem cell disease models