Epidermal transient receptor potential vanilloid 1 in idiopathic small nerve fibre disease, diabetic neuropathy and healthy human subjects.
OBJECTIVE
The transient receptor potential vanilloid 1 (TRPV1) plays an important role in mediating pain and heat. In painful neuropathies, intraepidermal TRPV1 nerve fibre expression is low or absent, suggesting that pain generated is not directly related to sensory nerve fibres. Recent evidence suggests that keratinocytes may act as thermal receptors via TRPV1. The aim was to investigate epidermal TRPV1 expression in patients with neuropathic conditions associated with pain.


RESULTS
In a prospective study of distal small nerve fibre neuropathy (DISN; n = 13) and diabetic neuropathy (DN; n = 12) intraepidermal nerve fibre density was assessed using the pan axonal marker PGP 9.5 and epidermal TPVR1 immunoreactivity compared with controls (n = 9). Intraepidermal nerve fibres failed to show TRPV1 immunoreactivity across all groups. There was moderate and strong TRPV1 reactivity of epidermal keratinocytes in 41.8% and 6% for DISN, 32.9% and 2.9% for DN and 25.4% and 5.1% for controls, respectively. Moderate keratinocyte TRPV1 expression was significantly increased in DISN compared with controls (P = 0.01).


CONCLUSIONS
Our study suggests that in human painful neuropathies, epidermal TRPV1 expression is mainly in keratinocytes.
Wilder-Smith
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EP
Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore. mdcwse@nus.edu.sg
Ong
W-Y
WY
Guo
Y
Y
Chow
A W-L
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D003929:Diabetic Neuropathies / Q000378:metabolism*; D004817:Epidermis / Q000294:innervation / Q000378:metabolism; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism* / Q000473:pathology; D009412:Nerve Fibers / Q000378:metabolism*; D009437:Neuralgia / Q000378:metabolism*; D011446:Prospective Studies; D050916:TRPV Cation Channels / Q000378:metabolism*
D050916:TRPV Cation Channels; C494482:TRPV1 protein, human