RT Journal Article
SR Electronic
T1 Articular chondrocyte network mediated by gap junctions: role in metabolic cartilage homeostasis
JF Annals of the Rheumatic Diseases
JO Ann Rheum Dis
FD BMJ Publishing Group Ltd and European League Against Rheumatism
SP 275
OP 284
DO 10.1136/annrheumdis-2013-204244
VO 74
IS 1
A1 Mayan, Maria D
A1 Gago-Fuentes, Raquel
A1 Carpintero-Fernandez, Paula
A1 Fernandez-Puente, Patricia
A1 Filgueira-Fernandez, Purificacion
A1 Goyanes, Noa
A1 Valiunas, Virginijus
A1 Brink, Peter R
A1 Goldberg, Gary S
A1 Blanco, Francisco J
YR 2015
UL http://ard.bmj.com/content/74/1/275.abstract
AB Objective This study investigated whether chondrocytes within the cartilage matrix have the capacity to communicate through intercellular connections mediated by voltage-gated gap junction (GJ) channels.Methods Frozen cartilage samples were used for immunofluorescence and immunohistochemistry assays. Samples were embedded in cacodylate buffer before dehydration for scanning electron microscopy. Co-immunoprecipitation experiments and mass spectrometry (MS) were performed to identify proteins that interact with the C-terminal end of Cx43. GJ communication was studied through in situ electroporation, electrophysiology and dye injection experiments. A transwell layered culture system and MS were used to identify and quantify transferred amino acids.Results Microscopic images revealed the presence of multiple cellular projections connecting chondrocytes within the matrix. These projections were between 5 and 150 µm in length. MS data analysis indicated that the C-terminus of Cx43 interacts with several cytoskeletal proteins implicated in Cx trafficking and GJ assembly, including α-tubulin and β-tubulin, actin, and vinculin. Electrophysiology experiments demonstrated that 12-mer oligonucleotides could be transferred between chondrocytes within 12 min after injection. Glucose was homogeneously distributed within 22 and 35 min. No transfer was detected when glucose was electroporated into A549 cells, which have no GJs. Transwell layered culture systems coupled with MS analysis revealed connexins can mediate the transfer of L-lysine and L-arginine between chondrocytes.Conclusions This study reveals that intercellular connections between chondrocytes contain GJs that play a key role in cell–cell communication and a metabolic function by exchange of nutrients including glucose and essential amino acids. A three-dimensional cellular network mediated through GJs might mediate metabolic and physiological homeostasis to maintain cartilage tissue.