Functional characterization of TRPV4 as an osmotically sensitive ion channel in porcine articular chondrocytes

Arthritis Rheum. 2009 Oct;60(10):3028-37. doi: 10.1002/art.24799.


Objective: Transient receptor potential vanilloid 4 (TRPV4) is a Ca(2+)-permeable channel that can be gated by tonicity (osmolarity) and mechanical stimuli. Chondrocytes, the cells in cartilage, respond to their osmotic and mechanical environments; however, the molecular basis of this signal transduction is not fully understood. This study was undertaken to demonstrate the presence and functionality of TRPV4 in chondrocytes.

Methods: TRPV4 protein expression was measured by immunolabeling and Western blotting. In response to TRPV4 agonist/antagonists, osmotic stress, and interleukin-1 (IL-1), changes in Ca(2+) signaling, cell volume, and prostaglandin E(2) (PGE(2)) production were measured in porcine chondrocytes using fluorescence microscopy, light microscopy, or immunoassay, respectively.

Results: TRPV4 was expressed abundantly at the RNA and protein levels. Exposure to 4alpha-phorbol 12,13-didecanoate (4alphaPDD), a TRPV4 activator, caused Ca(2+) signaling in chondrocytes, which was blocked by the selective TRPV4 antagonist, GSK205. Blocking TRPV4 diminished the chondrocytes' response to hypo-osmotic stress, reducing the fraction of Ca(2+) responsive cells, the regulatory volume decrease, and PGE(2) production. Ca(2+) signaling was inhibited by removal of extracellular Ca(2+) or depletion of intracellular stores. Specific activation of TRPV4 restored the defective regulatory volume decrease caused by IL-1. Chemical disruption of the primary cilium eliminated Ca(2+) signaling in response to either 4alphaPDD or hypo-osmotic stress.

Conclusion: Our findings indicate that TRPV4 is present in articular chondrocytes, and chondrocyte response to hypo-osmotic stress is mediated by this channel, which involves both an extracellular Ca(2+) and intracellular Ca(2+) release. TRPV4 may also be involved in modulating the production or influence of proinflammatory molecules in response to osmotic stress.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / metabolism
  • Cartilage, Articular / metabolism*
  • Cartilage, Articular / pathology
  • Cell Size
  • Cells, Cultured
  • Chondrocytes / metabolism*
  • Chondrocytes / pathology
  • Dinoprostone / metabolism
  • Interleukin-1 / metabolism
  • Models, Animal
  • Osmosis / physiology*
  • Phorbol Esters / pharmacology
  • Signal Transduction / physiology
  • Swine
  • TRPV Cation Channels / antagonists & inhibitors
  • TRPV Cation Channels / drug effects
  • TRPV Cation Channels / metabolism*


  • Interleukin-1
  • Phorbol Esters
  • TRPV Cation Channels
  • phorbol-12,13-didecanoate
  • Dinoprostone
  • Calcium