Nodes of Ranvier and Paranodes in Chronic Acquired Neuropathies Carmen Cifuentes-Diaz1,2,3, Odile Dubourg4,5, Theano Irinopoulou1,2,3, Marc Vigny1,2,3, Sylvie Lachkar1,2,3, Laurence Decker6, Patrick Charnay6, Natalia Denisenko1,2,3, Thierry Maisonobe4,7, Jean- Marc Le´ ger5, Karine Viala7, Jean-Jacques Hauw2,4, Jean-Antoine Girault1,2,3* 1 Institut National de la Sante´ et de la Recherche Me´dicale (Inserm), Unite´ Mixte de Recherche en Sante´ (UMR-S) 839, Paris, France, 2 Universite´ Pierre et Marie Curie (UPMC), Paris, France, 3 Institut du Fer a` Moulin, Paris, France, 4 Laboratoire de Neuropathologie Raymond-Escourolle, Pitie´-Salpeˆtrie`re Hospital, Assistance Publique des Hoˆ pitaux de Paris (AP-HP), Paris, France, 5 Consultation de Pathologie Neuromusculaire, Centre de Re´fe´rence de Paris Est, Pitie´-Salpeˆtrie`re Hospital, AP-HP, Paris, France, 6 Institut de Biologie de l’Ecole Normale Supe´rieure (IBENS), Inserm U1024, Centre National de la Recherche Scientifique (CNRS) UMR 8197, Ecole Normale Supe´rieure, Paris, France, 7 Fe´de´ration de Neurophysiologie Clinique and Fe´de´ration de Neurologie, Pitie´-Salpeˆtrie`re Hospital, AP-HP, Paris, France Abstract Chronic acquired neuropathies of unknown origin are classified as chronic inflammatory demyelinating polyneuropathies (CIDP) and chronic idiopathic axonal polyneuropathies (CIAP). The diagnosis can be very difficult, although it has important therapeutic implications since CIDP can be improved by immunomodulating treatment. The aim of this study was to examine the possible abnormalities of nodal and paranodal regions in these two types of neuropathies. Longitudinal sections of superficial peroneal nerves were obtained from biopsy material from 12 patients with CIDP and 10 patients with CIAP and studied by immunofluorescence and in some cases electron microscopy. Electron microscopy revealed multiple alterations in the nodal and paranodal regions which predominated in Schwann cells in CIDP and in axons in CIAP. In CIDP paranodin/Caspr immunofluorescence was more widespread than in control nerves, extending along the axon in internodes where it appeared intense. Nodal channels Nav and KCNQ2 were less altered but were also detected in the internodes. In CIAP paranodes, paranodin labeling was irregular and/or decreased. To test the consequences of acquired primary Schwann cells alteration on axonal proteins, we used a mouse model based on induced deletion of the transcription factor Krox-20 gene. In the demyelinated sciatic nerves of these mice we observed alterations similar to those found in CIDP by immunofluorescence, and immunoblotting demonstrated increased levels of paranodin. Finally we examined whether the alterations in paranodin immunoreactivity could have a diagnosis value. In a sample of 16 biopsies, the study of paranodin immunofluorescence by blind evaluators led to correct diagnosis in 7064% of the cases. This study characterizes for the first time the abnormalities of nodes of Ranvier in CIAP and CIDP, and the altered expression and distribution of nodal and paranodal proteins. Marked differences were observed between CIDP and CIAP and the alterations in paranodin immunofluorescence may be an interesting tool for their differential diagnosis. Citation: Cifuentes-Diaz C, Dubourg O, Irinopoulou T, Vigny M, Lachkar S, et al. (2011) Nodes of Ranvier and Paranodes in Chronic Acquired Neuropathies. PLoS ONE 6(1): e14533. doi:10.1371/journal.pone.0014533 Editor: Mark A. Tarnopolsky, McMaster University, Canada Received June 29, 2010; Accepted December 10, 2010; Published January 18, 2011 Copyright: 2011 Cifuentes-Diaz et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The work was supported by funding from Institut National de la Sante´ et de la Recherche Me´dicale (Inserm) and from Assistance Publique - Hoˆ pitaux de Paris (AP-HP). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: jean-antoine.girault@inserm.fr Introduction Chronic polyneuropathy is a highly prevalent condition with various etiologies, including hereditary, metabolic, toxic or immune-mediated origins. For hereditary polyneuropathies, termed Charcot-Marie-Tooth (CMT) diseases, recent advances in the identification of the responsible genes allow a genetic diagnosis in a growing number of cases [1]. Acquired neuropathies are more frequent than hereditary neuropathies and their diagnosis is based on a combination of clinical, electrophysiolog- ical, biological and, when necessary, histopathological evidence. Despite thorough investigations, no cause is found in 10–15% of patients with chronic polyneuropathies [2]. Here, we studied two types of chronic acquired polyneuropathies whose diagnosis can be challenging, chronic inflammatory demyelinating polyneuropathy (CIDP) and chronic idiopathic axonal polyneuropathy (CIAP). The distinction is important since specific treatment options are available for CIDP [3], whereas there is none of proven efficacy for CIAP [4]. CIDP is an immune-mediated disorder of peripheral nerves, with a progressive or relapsing course [5,6]. Its diagnosis is based mainly on clinical and electrophysiological features [5,7]. In its most common clinical presentation, CIDP combines motor deficits involving proximal and/or distal segments of the limbs, and superficial and/or deep sensory loss, progressing for at least two months [5]. Cerebrospinal fluid (CSF) examination often shows increased protein levels without cells. However, CIDP clinical presentation may be atypical [8], and electrodiagnostic criteria for demyelination may be missing because segmental demyelination affects only a few myelinated fibers or proximal segments not easily studied by electroneuromyography (ENMG). CIAPs are slowly progressive distal polyneuropathies, involving sensory or motor and sensory modalities, for which no cause is found after a thorough biological investigation [9]. In some cases, CIDP may be PLoS ONE | www.plosone.org 1 January 2011 | Volume 6 | Issue 1 | e14533