Underlying molecular mechanisms of DIO2 susceptibility in symptomatic osteoarthritis.
OBJECTIVE
To investigate how the genetic susceptibility gene DIO2 confers risk to osteoarthritis (OA) onset in humans and to explore whether counteracting the deleterious effect could contribute to novel therapeutic approaches.


METHODS
Epigenetically regulated expression of DIO2 was explored by assessing methylation of positional CpG-dinucleotides and the respective DIO2 expression in OA-affected and macroscopically preserved articular cartilage from end-stage OA patients. In a human in vitro chondrogenesis model, we measured the effects when thyroid signalling during culturing was either enhanced (excess T3 or lentiviral induced DIO2 overexpression) or decreased (iopanoic acid).


RESULTS
OA-related changes in methylation at a specific CpG dinucleotide upstream of DIO2 caused significant upregulation of its expression (β=4.96; p=0.0016). This effect was enhanced and appeared driven specifically by DIO2 rs225014 risk allele carriers (β=5.58, p=0.0006). During in vitro chondrogenesis, DIO2 overexpression resulted in a significant reduced capacity of chondrocytes to deposit extracellular matrix (ECM) components, concurrent with significant induction of ECM degrading enzymes (ADAMTS5, MMP13) and markers of mineralisation (ALPL, COL1A1). Given their concurrent and significant upregulation of expression, this process is likely mediated via HIF-2α/RUNX2 signalling. In contrast, we showed that inhibiting deiodinases during in vitro chondrogenesis contributed to prolonged cartilage homeostasis as reflected by significant increased deposition of ECM components and attenuated upregulation of matrix degrading enzymes.


CONCLUSIONS
Our findings show how genetic variation at DIO2 could confer risk to OA and raised the possibility that counteracting thyroid signalling may be a novel therapeutic approach.
Department of Molecular Epidemiology, LUMC, Leiden, The Netherlands IDEAL, The Netherlands.
Nils
N
Bomer
Department of Molecular Epidemiology, LUMC, Leiden, The Netherlands.
Wouter
W
den Hollander
Department of Molecular Epidemiology, LUMC, Leiden, The Netherlands.
Yolande F M
YF
Ramos
Department of Molecular Epidemiology, LUMC, Leiden, The Netherlands Genomics Initiative, sponsored by the NCHA, Leiden, The Netherlands.
Steffan D
SD
Bos
Department of Molecular Epidemiology, LUMC, Leiden, The Netherlands.
Ruud
R
van der Breggen
Department of Molecular Epidemiology, LUMC, Leiden, The Netherlands.
Nico
N
Lakenberg
Department of Human Genetics, LUMC, Leiden, The Netherlands.
Barry A
BA
Pepers
Department of Molecular Epidemiology, LUMC, Leiden, The Netherlands.
Annelies E
AE
van Eeden
Department of Imaging & BioInformatics, LIACS, Leiden, The Netherlands.
Arash
A
Darvishan
Department of Molecular Epidemiology, LUMC, Leiden, The Netherlands IDEAL, The Netherlands.
Elmar W
EW
Tobi
Department of Orthopaedics, LUMC, Leiden, The Netherlands.
Bouke J
BJ
Duijnisveld
Department of Molecular Epidemiology, LUMC, Leiden, The Netherlands The Delft Bioinformatics Lab, Delft University of Technology, Delft, The Netherlands.
Erik B
EB
van den Akker
Department of Molecular Epidemiology, LUMC, Leiden, The Netherlands Genomics Initiative, sponsored by the NCHA, Leiden, The Netherlands.
Bastiaan T
BT
Heijmans
Department of Human Genetics, LUMC, Leiden, The Netherlands.
Willeke Mc
WM
van Roon-Mom
Department of Imaging & BioInformatics, LIACS, Leiden, The Netherlands.
Fons J
FJ
Verbeek
Department of Orthopaedics, Erasmus MC, Rotterdam, The Netherlands Deptartment of Otorhinolaryngology, Erasmus MC, Rotterdam, The Netherlands.
Gerjo J V M
GJ
van Osch
Department of Orthopaedics, LUMC, Leiden, The Netherlands.
Rob G H H
RG
Nelissen
Department of Molecular Epidemiology, LUMC, Leiden, The Netherlands IDEAL, The Netherlands Genomics Initiative, sponsored by the NCHA, Leiden, The Netherlands.
P Eline
PE
Slagboom
Department of Molecular Epidemiology, LUMC, Leiden, The Netherlands Genomics Initiative, sponsored by the NCHA, Leiden, The Netherlands.
Ingrid
I
Meulenbelt
D002358:Cartilage, Articular / Q000201:enzymology / Q000503:physiopathology; D020219:Chondrogenesis / Q000235:genetics; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D005786:Gene Expression Regulation; D020868:Gene Silencing / Q000502:physiology; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D006801:Humans; D007453:Iodide Peroxidase / Q000235:genetics*; D019656:Loss of Heterozygosity; D010003:Osteoarthritis / Q000235:genetics* / Q000503:physiopathology; D015207:Osteoarthritis, Hip / Q000235:genetics; D020370:Osteoarthritis, Knee / Q000235:genetics; D013963:Thyroid Hormones / Q000502:physiology; D015854:Up-Regulation / Q000502:physiology; D000097564:Iodothyronine Deiodinase Type II
D007453:Iodide Peroxidase; D013963:Thyroid Hormones; D000097564:Iodothyronine Deiodinase Type II