title: The expression and function of microRNAs in chondrogenesis and osteoarthritis.
abstract: OBJECTIVE
  To use an in vitro model of chondrogenesis to identify microRNAs (miRNAs) with a functional role in cartilage homeostasis.
  
  
  METHODS
  The expression of miRNAs was measured in the ATDC5 cell model of chondrogenesis using microarray and was verified using quantitative reverse transcription-polymerase chain reaction. MicroRNA expression was localized by in situ hybridization. Predicted miRNA target genes were validated using 3'-untranslated region-Luc reporter plasmids containing either wild-type sequences or mutants of the miRNA target sequence. Signaling through the Smad pathway was measured using a (CAGA)(12) -Luc reporter.
  
  
  RESULTS
  The expression of several miRNAs was regulated during chondrogenesis. These included 39 miRNAs that are coexpressed with miRNA-140 (miR-140), which is known to be involved in cartilage homeostasis and osteoarthritis (OA). Of these miRNAs, miR-455 resides within an intron of COL27A1 that encodes a cartilage collagen. When human OA cartilage was compared with cartilage obtained from patients with femoral neck fractures, the expression of both miR-140-5p and miR-455-3p was increased in OA cartilage. In situ hybridization showed miR-455-3p expression in the developing limbs of chicks and mice and in human OA cartilage. The expression of miR-455-3p was regulated by transforming growth factor β (TGFβ) ligands, and miRNA regulated TGFβ signaling. ACVR2B, SMAD2, and CHRDL1 were direct targets of miR-455-3p and may mediate its functional impact on TGFβ signaling.
  
  
  CONCLUSIONS
  MicroRNA-455 is expressed during chondrogenesis and in adult articular cartilage, where it can regulate TGFβ signaling, suppressing the Smad2/3 pathway. Diminished signaling through this pathway during the aging process and in OA chondrocytes is known to contribute to cartilage destruction. We propose that the increased expression of miR-455 in OA exacerbates this process and contributes to disease pathology.
authors.affiliation: University of East Anglia, Norwich, UK.
authors.forename: Tracey E
authors.initials: TE
authors.lastname: Swingler
authors.forename: Guy
authors.initials: G
authors.lastname: Wheeler
authors.forename: Virginia
authors.initials: V
authors.lastname: Carmont
authors.forename: Hannah R
authors.initials: HR
authors.lastname: Elliott
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Barter
authors.forename: Muhammad
authors.initials: M
authors.lastname: Abu-Elmagd
authors.forename: Simon T
authors.initials: ST
authors.lastname: Donell
authors.forename: Raymond P
authors.initials: RP
authors.lastname: Boot-Handford
authors.forename: Mohammad K
authors.initials: MK
authors.lastname: Hajihosseini
authors.forename: Andrea
authors.initials: A
authors.lastname: Münsterberg
authors.forename: Tamas
authors.initials: T
authors.lastname: Dalmay
authors.forename: David A
authors.initials: DA
authors.lastname: Young
authors.forename: Ian M
authors.initials: IM
authors.lastname: Clark
mesh_terms: D016475:3T3 Cells; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D002358:Cartilage, Articular / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D019902:Chondrocytes / Q000378:metabolism* / Q000473:pathology; D020219:Chondrogenesis / Q000502:physiology*; D005260:Female; D006621:Hip Joint / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D008297:Male; D051379:Mice; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000235:genetics / Q000378:metabolism* / Q000473:pathology
chemical_list: D035683:MicroRNAs