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Early alterations of Hedgehog signaling pathway in vascular endothelial cells after peripheral nerve injury elicit blood-nerve barrier disruption, nerve inflammation, and neuropathic pain development

Moreau, Nathan; Mauborgne, Annie; Bourgoin, Sylvie; Couraud, Pierre-Olivier; Romero, Ignacio A.; Weksler, Babette B.; Villanueva, Luis; Pohl, Michel; Boucher, Yves

doi: 10.1097/j.pain.0000000000000444
Research Paper

Changes in the nerve's microenvironment and local inflammation resulting from peripheral nerve injury participate in nerve sensitization and neuropathic pain development. Taking part in these early changes, disruption of the blood–nerve barrier (BNB) allows for infiltration of immunocytes and promotes the neuroinflammation. However, molecular mechanisms engaged in vascular endothelial cells (VEC) dysfunction and BNB alterations remain unclear. In vivo, BNB permeability was assessed following chronic constriction injury (CCI) of the rat sciatic nerve (ScN) and differential expression of markers of VEC functional state, inflammation, and intracellular signaling was followed from 3 hours to 2 months postinjury. Several mechanisms potentially involved in functional alterations of VEC were evaluated in vitro using human VEC (hCMEC/D3), then confronted to in vivo physiopathological conditions. CCI of the ScN led to a rapid disruption of endoneurial vascular barrier that was correlated to a decreased production of endothelial tight-junction proteins and an early and sustained alteration of Hedgehog (Hh) signaling pathway. In vitro, activation of Toll-like receptor 4 in VEC downregulated the components of Hh pathway and altered the endothelial functional state. Inhibition of Hh signaling in the ScN of naive rats mimicked the biochemical and functional alterations observed after CCI and was, on its own, sufficient to evoke local neuroinflammation and sustained mechanical allodynia. Alteration of the Hh signaling pathway in VEC associated with peripheral nerve injury, is involved in BNB disruption and local inflammation, and could thus participate in the early changes leading to the peripheral nerve sensitization and, ultimately, neuropathic pain development.

Local blockade of Hedgehog signaling in rat sciatic nerve mimicked enhanced endoneurial vascular permeability, local neuroinflammation, and mechanical allodynia emergence typically evoked by nerve injury.

aUFR d'Odontologie, Université Paris Descartes, Hôpital Bretonneau, Paris, France

bCentre de Psychiatrie et Neurosciences, INSERM U894, Université Paris Descartes, Hôpital Sainte-Anne, Paris, France

cUniversité Paris Descartes, Institut Cochin, Paris, France

dDepartment of Biological Sciences, The Open University, Walton Hall, Milton Keynes, United Kingdom

eWeill Medical College of Cornell University, New York, NY, USA

fUFR d'Odontologie, Université Paris Diderot, Hôpital Pitié Salpêtrière, Paris, France

Corresponding author. Address: UFR d'Odontologie, Université Paris Diderot, 5 rue garanciere, Paris 75006, France. Tel.: 0033695619036. E-mail address: (Y. Boucher).

Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article.

Received June 28, 2015

Received November 04, 2015

Accepted November 20, 2015

© 2016 International Association for the Study of Pain
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