Articular chondrocytes express connexin 43 hemichannels and P2 receptors - a putative mechanoreceptor complex involving the primary cilium?
| Autor: | Susan R. McGlashan, CA Poole, Cynthia G. Jensen, Mariana Garcia, Martin M. Knight |
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| Rok vydání: | 2009 |
| Předmět: |
Cartilage
Articular Male Cytoplasm P2Y receptor Histology Fluorescent Antibody Technique Connexin Biology Mechanotransduction Cellular Chondrocyte Receptors Purinergic P2Y2 Receptors Purinergic P2Y1 chemistry.chemical_compound Chondrocytes medicine Animals Humans Cilia Mechanotransduction Molecular Biology Ecology Evolution Behavior and Systematics Microscopy Confocal Staining and Labeling Receptors Purinergic P2 Cilium Purinergic receptor Original Articles Cell Biology Middle Aged Isoquinolines Cell biology EGTA medicine.anatomical_structure chemistry Connexin 43 Cattle Female Mechanosensitive channels Receptors Purinergic P2X7 Anatomy Mechanoreceptors Receptors Purinergic P2X4 Receptors Purinergic P2X2 Developmental Biology |
| Zdroj: | Journal of Anatomy. 214:275-283 |
| ISSN: | 1469-7580 0021-8782 |
| DOI: | 10.1111/j.1469-7580.2008.01021.x |
| Popis: | Mechanical loading is essential for the health and homeostasis of articular cartilage, although the fundamental mechanotransduction pathways are unclear. Previous studies have demonstrated that cyclic compression up-regulates proteoglycan synthesis via an intracellular Ca(2+) signalling pathway, mediated by the release of ATP. However, the mechanism(s) of ATP release has not been elucidated. The present study examines expression of the putative mechanosensitive ATP-release channel, connexin 43 and whether it is expressed on the chondrocyte primary cilium, which acts as a mechanosensor in a variety of other cell types. In addition the study characterized the expression of a range of purine receptors through which ATP may activate downstream signalling events controlling cell function. Bovine articular chondrocytes were isolated by sequential enzyme digestion and seeded in agarose constructs. To verify the presence of functional hemichannels, Lucifer yellow (LY) uptake into viable cells was quantified following treatment with a hemichannel agonist (EGTA) and antagonist (flufenamic acid). LY uptake was observed in 45% of chondrocytes, increasing to 83% following EGTA treatment (P < 0.001). Treatment with the hemichannel blocker, flufenamic acid, significantly decreased LY uptake to less than 5% with and without EGTA. Immunofluorescence and confocal microscopy confirmed the presence of primary cilia and the expression of connexin 43. Approximately 50% of bovine chondrocyte primary cilia were decorated with connexin 43. Human chondrocytes in situ within cartilage explants also expressed connexin 43 hemichannels. However, expression was confined to the upper 200 microm of the tissue closest to the articular surface. Immunofluorescence revealed the expression of a range of P2X and P2Y receptor subtypes within human articular cartilage. In conclusion, the expression of functional hemichannels by articular chondrocytes may represent the mechanism through which mechanical loading activates ATP release as part of a purinergic mechanotransduction pathway. Furthermore, the expression of connexin 43 on the chondrocyte primary cilium suggests the possible involvement of the cilium in this pathway. |
| Databáze: | OpenAIRE |
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