title: Aberrant Calreticulin Expression in Articular Cartilage of Dio2 Deficient Mice.
abstract: To identify intrinsic differences in cartilage gene expression profiles between wild-type- and Dio2-/--mice, as a mechanism to investigate factors that contribute to prolonged healthy tissue homeostasis.
  
  
  
  Previously generated microarray-data (Illumina MouseWG-6 v2) of knee cartilage of wild-type and Dio2 -/- -mice were re-analyzed to identify differential expressed genes independent of mechanical loading conditions by forced treadmill-running. RT-qPCR and western blot analyses of overexpression and knockdown of Calr in mouse chondro-progenitor cells (ATDC5) were applied to assess the direct effect of differential Calr expression on cartilage deposition.
  
  
  
  Differential expression analyses of articular cartilage of Dio2-/- (N = 9) and wild-type-mice (N = 11) while applying a cutoff threshold (P < 0.05 (FDR) and FC > |1,5|) resulted in 1 probe located in Calreticulin (Calr) that was found significantly downregulated in Dio2-/- mice (FC = -1.731; P = 0.044). Furthermore, overexpression of Calr during early chondrogenesis in ATDC5 cells leads to decreased proteoglycan deposition and corresponding lower Aggrecan expression, whereas knocking down Calr expression does not lead to histological differences of matrix composition.
  
  
  
  We here demonstrate that the beneficial homeostatic state of articular cartilage in Dio2-/- mice is accompanied with significant lower expression of Calr. Functional analyses further showed that upregulation of Calr expression could act as an initiator of cartilage destruction. The consistent association between Calr and Dio2 expression suggests that enhanced expression of these genes facilitate detrimental effects on cartilage integrity.
authors.affiliation: Department of Molecular Epidemiology, LUMC, Leiden, Netherlands.
authors.forename: Nils
authors.initials: N
authors.lastname: Bomer
authors.affiliation: Laboratory of Tissue Homeostasis and Disease, Skeletal Biology and Engineering Research Centre, KU Leuven, Leuven, Belgium.
authors.forename: Frederique M F
authors.initials: FM
authors.lastname: Cornelis
authors.affiliation: Department of Molecular Epidemiology, LUMC, Leiden, Netherlands.
authors.forename: Yolande F M
authors.initials: YF
authors.lastname: Ramos
authors.affiliation: Department of Molecular Epidemiology, LUMC, Leiden, Netherlands.
authors.forename: Wouter
authors.initials: W
authors.lastname: den Hollander
authors.affiliation: Department of Molecular Epidemiology, LUMC, Leiden, Netherlands.
authors.forename: Nico
authors.initials: N
authors.lastname: Lakenberg
authors.affiliation: Department of Molecular Epidemiology, LUMC, Leiden, Netherlands.
authors.forename: Ruud
authors.initials: R
authors.lastname: van der Breggen
authors.affiliation: Laboratory of Tissue Homeostasis and Disease, Skeletal Biology and Engineering Research Centre, KU Leuven, Leuven, Belgium.
authors.forename: Lies
authors.initials: L
authors.lastname: Storms
authors.affiliation: Department of Molecular Epidemiology, LUMC, Leiden, Netherlands.
authors.forename: P Eline
authors.initials: PE
authors.lastname: Slagboom
authors.affiliation: Laboratory of Tissue Homeostasis and Disease, Skeletal Biology and Engineering Research Centre, KU Leuven, Leuven, Belgium.|Division of Rheumatology, University Hospitals Leuven, Leuven, Belgium.
authors.forename: Rik J U
authors.initials: RJ
authors.lastname: Lories
authors.affiliation: Department of Molecular Epidemiology, LUMC, Leiden, Netherlands.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Meulenbelt
mesh_terms: D053674:Aggrecans / Q000235:genetics / Q000378:metabolism; D000818:Animals; D037282:Calreticulin / Q000235:genetics* / Q000378:metabolism; D002358:Cartilage, Articular / Q000378:metabolism* / Q000473:pathology; D019902:Chondrocytes / Q000378:metabolism / Q000473:pathology; D005080:Exercise Test; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D007453:Iodide Peroxidase / Q000172:deficiency / Q000235:genetics*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D020411:Oligonucleotide Array Sequence Analysis; D010003:Osteoarthritis / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D057071:Patellofemoral Joint / Q000378:metabolism* / Q000473:pathology; D011509:Proteoglycans / Q000235:genetics / Q000378:metabolism; D013234:Stem Cells / Q000378:metabolism / Q000473:pathology; D000097564:Iodothyronine Deiodinase Type II
chemical_list: D053674:Aggrecans; D037282:Calreticulin; D007453:Iodide Peroxidase; D011509:Proteoglycans; D000097564:Iodothyronine Deiodinase Type II