title: Dynamic compression of chondrocyte-agarose constructs reveals new candidate mechanosensitive genes.
abstract: Articular cartilage is physiologically exposed to repeated loads. The mechanical properties of cartilage are due to its extracellular matrix, and homeostasis is maintained by the sole cell type found in cartilage, the chondrocyte. Although mechanical forces clearly control the functions of articular chondrocytes, the biochemical pathways that mediate cellular responses to mechanical stress have not been fully characterised. The aim of our study was to examine early molecular events triggered by dynamic compression in chondrocytes. We used an experimental system consisting of primary mouse chondrocytes embedded within an agarose hydrogel; embedded cells were pre-cultured for one week and subjected to short-term compression experiments. Using Western blots, we demonstrated that chondrocytes maintain a differentiated phenotype in this model system and reproduce typical chondrocyte-cartilage matrix interactions. We investigated the impact of dynamic compression on the phosphorylation state of signalling molecules and genome-wide gene expression. After 15 min of dynamic compression, we observed transient activation of ERK1/2 and p38 (members of the mitogen-activated protein kinase (MAPK) pathways) and Smad2/3 (members of the canonical transforming growth factor (TGF)-β pathways). A microarray analysis performed on chondrocytes compressed for 30 min revealed that only 20 transcripts were modulated more than 2-fold. A less conservative list of 325 modulated genes included genes related to the MAPK and TGF-β pathways and/or known to be mechanosensitive in other biological contexts. Of these candidate mechanosensitive genes, 85% were down-regulated. Down-regulation may therefore represent a general control mechanism for a rapid response to dynamic compression. Furthermore, modulation of transcripts corresponding to different aspects of cellular physiology was observed, such as non-coding RNAs or primary cilium. This study provides new insight into how chondrocytes respond to mechanical forces.
authors.affiliation: Université Lyon 1, Univ Lyon, CNRS, FRE 3310 - Dysfonctionnement de l'Homéostasie Tissulaire et Ingénierie Thérapeutique, IBCP, Lyon, France.
authors.forename: Carole
authors.initials: C
authors.lastname: Bougault
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Aubert-Foucher
authors.forename: Anne
authors.initials: A
authors.lastname: Paumier
authors.forename: Emeline
authors.initials: E
authors.lastname: Perrier-Groult
authors.forename: Ludovic
authors.initials: L
authors.lastname: Huot
authors.forename: David
authors.initials: D
authors.lastname: Hot
authors.forename: Martine
authors.initials: M
authors.lastname: Duterque-Coquillaud
authors.forename: Frédéric
authors.initials: F
authors.lastname: Mallein-Gerin
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D019902:Chondrocytes / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D015536:Down-Regulation; D051766:Early Growth Response Protein 1 / Q000235:genetics / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000378:metabolism; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000235:genetics; D040542:Mechanotransduction, Cellular / Q000235:genetics; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D012685:Sepharose / Q000378:metabolism*; D015398:Signal Transduction; D051785:Smad Proteins / Q000235:genetics / Q000378:metabolism; D013314:Stress, Mechanical; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: D051766:Early Growth Response Protein 1; C486109:Egr1 protein, mouse; D016326:Extracellular Matrix Proteins; D051785:Smad Proteins; D018808:Transcription Factor AP-1; D016212:Transforming Growth Factor beta; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D012685:Sepharose; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases