Monday, January 13, 2014

TRPV1 and Osteoarthritis Related Pain

Our TRPV Antibodies are widely used and frequently published. Many of these feature TRPVs' role in nociceptive pain. Specifically they play important roles in the detection of noxious stimuli and inflammatory hyperalgesia.

TRPV1 has been implicated in OA pain, both in animal models and by the finding that TRPV1 genetic variants are associated with the risk of symptomatic knee OA in humans: S Kelly, R J Chapman, S Woodhams, D R Sagar, J Turner, J J Burston, C Bullock, K Paton, J Huang, A Wong, D F McWilliams, B N Okine, D A Barrett, G J Hathway, D A Walsh, V Chapman. Increased function of pronociceptive TRPV1 at the level of the joint in a rat model of osteoarthritis pain. Ann Rheum Dis doi:10.1136/annrheumdis-2013-203413.
Methods: Rat spinal cord sections from MIA- and saline-treated rats (n=5/group) (see online supplemental methods) were incubated with a polyclonal guinea pig anti-TRPV1 antibody (1 : 500, Neuromics, Edina, Minnesota, USA catalogue number GP14100) and then with Alexa 568-conjugated goat anti-guinea pig secondary antibody (1:300, Molecular Probes). TRPV1 immunostaining was visualised with a Leica DMRB/DM4000 B fluorescence microscope and images were acquired using Openlab software (PerkinElmer)...

Images: Transient receptor potential vanilloid 1 (TRPV1) immunoreactivity in the spinal cord. TRPV1 immunofluorescence detected in superficial dorsal horn (10× magnification) in rat lumbar (L3–L5) spinal cord at day 28 post-intra-articular injection of saline (A) or mono-iodoacetate (MIA) (B). Minimum and maximum brightness values were altered (32.01 min and 90.14 max) using Image J so as to highlight the area of TRPV1 positive staining. (C) Quantification of TRPV1 immunofluorescence in superficial dorsal horn of spinal cord taken from rats at 14 or 28 days following intra-articular injection of MIA and at day 28 following intra-articular injection of saline. Data are expressed as mean and SEM (n=5 per group).

Clinical trials of oral TRPV1 antagonists have been limited by on-target-induced hyperthermia. Here experimental evidence for increased functional role of TRPV1 at the level of the joint in a model of OA pain and the demonstration that blockade of joint TRPV1 ablates sensory afferent sensitization and pain behaviour support future targeted site-specific investigations of the therapeutic potential of TRPV1 for OA pain associated with synovitis. This could be good news for OA sufferers.

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