Effects of transient microglial depletion on functional recovery and tissue integrity after spinal cord injury : translational analysis from murines to non-human primates

Les déficits moteurs et sensitifs induits par une lésion de la moelle épinière (LME) ne bénéficient d’aucun traitement curatif. Après une lésion médullaire, un processus complexe d'activation microgliale survient, incluant une prolifération. La réponse microgliale joue un rôle essentiel dans la récupération fonctionnelle. Nous avons d’abord étudié si une réduction pharmacologique transitoire de la prolifération microgliale après une LME est bénéfique pour la récupération fonctionnelle chez les souris, ensuite dans un objectif de transposition à la clinique, nous avons étendu notre approche aux primates non-humains. L'intégrité structurelle des tissus peut être évaluée, entre autres, grâce à la myéline. De nombreuses techniques permettent de caractériser la structure de la myéline dans le système nerveux des mammifères. En particulier, grâce à la teneur élevée en lipides des gaines de myéline, la spectroscopie Raman cohérente anti-Stokes (CARS) est une méthode sans marquage permettant d'identifier et de caractériser la myéline. Méthodes. Le récepteur CSF1R (Colony Stimulating Factor 1) régule la prolifération, la différenciation et la survie de la microglie. Nous avons administré par voie orale du GW2580, un inhibiteur du CSF1R qui inhibe spécifiquement la prolifération microgliale. Chez les souris et les primates non-humains, nous avons ensuite analysé les effets du traitement sur la récupération motrice par des tests comportementaux et la structure tissulaire de la moelle épinière par imagerie par résonance magnétique (IRM) et par histologie. Nous avons également utilisé une analyse transcriptomique pour identifier les changements moléculaires induits par le GW2580 dans la microglie. En parallèle, pour compléter nos études, à l'aide du CARS, nous avons caractérisé plus en détail la myéline de la moelle épinière dans trois espèces différentes, à savoir ; souris, lémurien et humain. Dans toutes les espèces, nous avons analysé les funiculi dorsal et latéral de la moelle épinière saine thoracique adulte. Résultats. Premièrement, l'administration transitoire de GW2580 post-lésion chez la souris améliore la récupération motrice, favorise la préservation et/ou la réorganisation des tissus et module la réactivité gliale. Deuxièmement, le traitement par GW2580 chez la souris a induit une diminution de l’expression des gènes associés à la prolifération et des gènes associés à l'inflammation dans la microglie, ce qui peut expliquer la réduction de la neuro-inflammation et l'amélioration de la récupération fonctionnelle après une LME. Enfin, le traitement par GW2580 post-lésion chez les primates non humains réduit la prolifération de la microglie, améliore la récupération motrice et favorise la protection des tissus. De plus, nos analyses comparatives entre espèces en CARS ont permis de montrer de fortes similarités entre la structure myélinique de la moelle épinière chez les primates non-humains et les humains confirmant le grand intérêt de l’utilisation de ce modèle animal dans le cadre d'une recherche à visée de transposition à la clinique. Conclusion. Un traitement oral transitoire au GW2580 après une LME pourrait constituer une stratégie thérapeutique prometteuse pour les patients lésés médullaires et pourrait également être étendu à d'autres atteintes traumatiques voir chroniques du système nerveux central associées à une activation de la microglie.Motor and sensory deficits induced by spinal cord injury (SCI) do not benefit from any curative treatment. After SCI, a complex process of microglial activation occurs, including proliferation. The microglial response plays an essential role in motor recovery. We first assessed if, a transient pharmacological reduction in microglial proliferation after SCI is beneficial for recovery in mice, then we extended our approach to non-human primates with the aim of a clinical transposition. The structural integrity of tissues can be evaluated, among other things, through myelin. There are many techniques for showing the structure of myelin in the mammalian nervous system. In particular, due to the high lipid content of myelin sheaths, anti-Stokes coherent Raman spectroscopy (CARS) is a non-labeling method to identify and characterize myelin.Methods. The CSF1 receptor (Colony Stimulating Factor 1) regulates the proliferation, differentiation and survival of microglia. We orally administered GW2580, a CSF1R inhibitor that specifically inhibits microglial proliferation. In mice and non-human primates, we then analyzed the effects of the treatment on motor recovery by behavioral testing and spinal cord tissue structure by magnetic resonance imaging (MRI) and histology. We also used transcriptomic analysis to identify molecular changes induced by GW2580 in microglia. In parallel, to complete our studies , we further characterized the myelin of the spinal cord in three different species: mouse, lemur and human using CARS. In all species, we analyzed the dorsal and lateral funiculi of the healthy adult thoracic spinal cord.Results. First, post-injury transient administration of GW2580 in mice improves motor recovery, promotes tissue preservation and / or reorganization, and modulates glial reactivity. Second, GW2580 in mice induced a decrease in the expression of genes associated with proliferation and genes associated with inflammation in the microglia, which may explain the reduction of neuroinflammation and improvement of functional recovery after SCI. Finally, post-injury treatment with GW2580 in non-human primates reduces microglia proliferation, improves motor recovery and promotes tissue protection. In addition, our comparative CARS analyzes between species demonstrated strong similarities between the myelin structure of the spinal cord in non-human primates and humans, confirming the great interest of this animal model in the context of transposition to the clinic.Conclusion. Transient oral treatment with GW2580 after SCI could be a promising therapeutic strategy for patients and could also be extended to other traumatic or even chronic damages to the central nervous system associated with activation of the microglia

Dentate Nucleus as Target for Deep Brain Stimulation in Dystono-Dyskinetic Syndromes

International audiencePurpose: To discuss the potential of deep brain stimulation (DBS) of the dentate nucleus as a treatment for dystono-dyskinetic syndromes.Methods: An extensive literature review covered the anatomy and physiology of the dentate nucleus and the experimental evidence for its involvement in the pathophysiology of dystonia and dyskinesia.Results: Evidence from animal models and from functional imaging in humans is strongly in favor of involvement of the dentate nucleus in dystono-dyskinetic syndromes. Results from previous surgical series of dentate nucleus stimulation were promising but precise description of movement disorders being treated were lacking and outcome measures were generally not well defined.Conclusions: In the light of new evidence regarding the involvement of the dentate nucleus in dystono-dyskinetic syndromes, we present a review of the current literature and discuss why the question of dentate nucleus stimulation deserves to be revisited

Huge heterogeneity in survival in a subset of adult patients with resected, wild-type isocitrate dehydrogenase status, WHO grade II astrocytomas

OBJECTIVE World Health Organization grade II gliomas are infiltrating tumors that inexorably progress to a higher grade of malignancy. However, the time to malignant transformation is quite unpredictable at the individual patient level. A wild-type isocitrate dehydrogenase (IDH-wt) molecular profile has been reported as a poor prognostic factor, with more rapid progression and a shorter survival compared with IDH-mutant tumors. Here, the oncological outcomes of a series of adult patients with IDH-wt, diffuse, WHO grade II astrocytomas (AII) who underwent resection without early adjuvant therapy were investigated. METHODS A retrospective review of patients extracted from a prospective database who underwent resection between 2007 and 2013 for histopathologically confirmed, IDH-wt, non\textendash1p19q codeleted AII was performed. All patients had a minimum follow-up period of 2 years. Information regarding clinical, radiographic, and surgical results and survival were collected and analyzed. RESULTS Thirty-one consecutive patients (18 men and 13 women, median age 39.6 years) were included in this study. The preoperative median tumor volume was 54 cm 3 (range 3.5\textendash180 cm 3 ). The median growth rate, measured as the velocity of diametric expansion, was 2.45 mm/year. The median residual volume after surgery was 4.2 cm 3 (range 0\textendash30 cm 3 ) with a median volumetric extent of resection of 93.97% (8 patients had a total or supratotal resection). No patient experienced permanent neurological deficits after surgery, and all patients resumed a normal life. No immediate postoperative chemotherapy or radiation therapy was given. The median clinical follow-up duration from diagnosis was 74 months (range 27\textendash157 months). In this follow-up period, 18 patients received delayed chemotherapy and/or radiotherapy for tumor progression. Five patients (16%) died at a median time from radiological diagnosis of 3.5 years (range 2.6\textendash4.5 years). Survival from diagnosis was 77.27% at 5 years. None of the 21 patients with a long-term follow-up greater than 5 years have died. There were no significant differences between the clinical, radiological, or molecular characteristics of the survivors relative to the patients who died. CONCLUSIONS Huge heterogeneity in the survival data for a subset of 31 patients with resected IDH-wt AII tumors was observed. These findings suggest that IDH mutation status alone is not sufficient to predict risk of malignant transformation and survival at the individual level. Therefore, the therapeutic management of AII tumors, in particular the decision to administer early adjuvant chemotherapy and/or radiation therapy following surgery, should not solely rely on routine molecular markers

Deep Brain Stimulation and Hypoxemic Perinatal Encephalopathy: State of Art and Perspectives

Cerebral palsy (CP) is a heterogeneous group of non-progressive syndromes with lots of clinical variations due to the extent of brain damages and etiologies. CP is majorly defined by dystonia and spasticity. The treatment of acquired dystonia in CP is very difficult. Many pharmacological treatments have been tried and surgical treatment consists of deep brain stimulation (continuous electrical neuromodulation) of internal globus pallidus (GPi). A peculiar cause of CP is neonatal encephalopathy due to an anoxic event in the perinatal period. Many studies showed an improvement of dystonia in CP patients with bilateral GPi DBS. However, it remains a variability in the range of 1% to 50%. Published case-series concerned mainly small population with a majority of adult patients. Selection of patients according to the clinical pattern, to the brain lesions observed on classical imaging and to DTI is the key of a high success rate of DBS in children with perinatal hypoxemic encephalopathy. Only a large retrospective study with a high number of patients in a homogeneous pediatric population with a long-term follow-up or a prospective multicenter trial investigation could answer with a high degree of certitude of the real interest of this therapeutic in children with hypoxemic perinatal encephalopathy

Unlike Brief Inhibition of Microglia Proliferation after Spinal Cord Injury, Long-Term Treatment Does Not Improve Motor Recovery

International audienceMicroglia are major players in scar formation after an injury to the spinal cord. Microglia proliferation, differentiation, and survival are regulated by the colony-stimulating factor 1 (CSF1). Complete microglia elimination using CSF1 receptor (CSF1R) inhibitors worsens motor function recovery after spinal injury (SCI). Conversely, a 1-week oral treatment with GW2580, a CSF1R inhibitor that only inhibits microglia proliferation, promotes motor recovery. Here, we investigate whether prolonged GW2580 treatment further increases beneficial effects on locomotion after SCI. We thus assessed the effect of a 6-week GW2580 oral treatment after lateral hemisection of the spinal cord on functional recovery and its outcome on tissue and cellular responses in adult mice. Long-term depletion of microglia proliferation after SCI failed to improve motor recovery and had no effect on tissue reorganization, as revealed by ex vivo diffusion-weighted magnetic resonance imaging. Six weeks after SCI, GW2580 treatment decreased microglial reactivity and increased astrocytic reactivity. We thus demonstrate that increasing the duration of GW2580 treatment is not beneficial for motor recovery after SCI

Negative Impact of Sigma-1 Receptor Agonist Treatment on Tissue Integrity and Motor Function Following Spinal Cord Injury

International audienceIn traumatic spinal cord injury, the initial trauma is followed by a cascade of impairments, including excitotoxicity and calcium overload, which ultimately induces secondary damages. The sigma-1 receptor is widely expressed in the central nervous system and is acknowledged to play a key role in calcium homeostasis. Treatments with agonists of the sigma-1 receptor induce beneficial effects in several animal models of neurological diseases. In traumatic injury the use of an antagonist of the sigma-1 receptor reversed several symptoms of central neuropathic pain. Here, we investigated whether sigma-1 receptor activation with PRE-084 is beneficial or detrimental following SCI in mice. First, we report that PRE-084 treatment after injury does not improve motor function recovery. Second, using ex vivo diffusion weighted magnetic resonance imaging completed by histological analysis, we highlight that σ1R agonist treatment after SCI does not limit lesion size. Finally, PRE-084 treatment following SCI decreases NeuN expression and increases astrocytic reactivity. Our findings suggest that activation of sigma-1 receptor after traumatic spinal cord injury is detrimental on tissue preservation and motor function recovery in mice

Partial Vertebrectomies without Instrumented Stabilization During En Bloc Resection of Primary Bronchogenic Carcinomas Invading the Spine: Feasibility Study and Results on Spine Balance

International audienceOBJECTIVE:It is unknown whether spinal instrumentation is required to prevent deformity after partial vertebrectomy in the treatment of primary bronchogenic carcinomas invading the spine (PBCIS). In this study, we focus on the postoperative spine deformity in patients who underwent operation for partial vertebrectomies without instrumentation during en bloc PBCIS resection. Our objective was to determine whether deformity depends on the type of vertebral resection and if any vertebral resection threshold can be observed to justify additional spinal instrumentation.METHODS:This is a retrospective study, including all patients with PBCIS operated without spinal instrumentation from 2009 to 2018. Partial vertebrectomies were classified into categories A, B, and C depending on vertebral resection. Patients had long-term radiologic follow-up to assess the spine deformity evolution.RESULTS:Eighteen patients were included. The median follow-up was 27 months. Four patients underwent a secondary posterior instrumentation surgical procedure due to progressive spinal deformity. A low-risk group of deformation was characterized as type A resection and type B resection on less than 3 vertebrae.CONCLUSIONS:There are no validated criteria to justify a systematic spinal instrumentation when performing a partial vertebrectomy during en bloc resection of PBCIS. Performed alone without spine instrumentation, both type A and type B resections on less than 3 resected vertebrae were not subject to sagittal and coronal deformity even after a long follow-up, emphasizing that a systematic stabilization is not needed in this low-risk group. These results could help to reduce the perioperative morbidity of these procedures that are usually long and complex

Persistence of FoxJ1+ Pax6+ Sox2+ ependymal cells throughout life in the human spinal cord

International audienceEpendymal cells lining the central canal of the spinal cord play a crucial role in providing a physical barrier and in the circulation of cerebrospinal fluid. These cells express the FOXJ1 and SOX2 transcription factors in mice and are derived from various neural tube populations, including embryonic roof and floor plate cells. They exhibit a dorsal-ventral expression pattern of spinal cord developmental transcription factors (such as MSX1, PAX6, ARX, and FOXA2), resembling an embryonic-like organization. Although this ependymal region is present in young humans, it appears to be lost with age. To re-examine this issue, we collected 17 fresh spinal cords from organ donors aged 37-83 years and performed immunohistochemistry on lightly fixed tissues. We observed cells expressing FOXJ1 in the central region in all cases, which co-expressed SOX2 and PAX6 as well as RFX2 and ARL13B, two proteins involved in ciliogenesis and cilia-mediated sonic hedgehog signaling, respectively. Half of the cases exhibited a lumen and some presented portions of the spinal cord with closed and open central canals. Co-staining of FOXJ1 with other neurodevelopmental transcription factors (ARX, FOXA2, MSX1) and NESTIN revealed heterogeneity of the ependymal cells. Interestingly, three donors aged > 75 years exhibited a fetal-like regionalization of neurodevelopmental transcription factors, with dorsal and ventral ependymal cells expressing MSX1, ARX, and FOXA2. These results provide new evidence for the persistence of ependymal cells expressing neurodevelopmental genes throughout human life and highlight the importance of further investigation of these cells

Coherent Anti-Stokes Raman Scattering Microscopy: A Label-Free Method to Compare Spinal Cord Myelin in Different Species

International audienceMany histological techniques are used to identify and characterize myelin in the mammalian nervous system. Due to the high content of lipids in myelin sheaths, coherent anti-stokes Raman scattering (CARS) microscopy is a label-free method that allows identifying myelin within tissues. CARS excites the CH 2 vibrational mode at 2845 cm −1 and CH 2 bonds are found in lipids. In this study, we have used CARS for a new biological application in the field of spinal cord analysis. We have indeed compared several parameters of spinal cord myelin sheath in three different species, i.e ., mouse, lemur, and human using a label-free method. In all species, we analyzed the dorsal and the lateral funiculi of the adult thoracic spinal cord. We identified g-ratio differences between species. Indeed, in both funiculi, g-ratio was higher in mice than in the two primate species, and the myelin g-ratio in lemurs was higher than in humans. We also detected a difference in g-ratio between the dorsal and the lateral funiculi only in humans. Furthermore, species differences between axon and fiber diameters as well as myelin thickness were observed. These data may reflect species specificities of conduction velocity of myelin fibers. A comparison of data obtained by CARS imaging and fluoromyelin staining, a method that, similar to CARS, does not require resin embedding and dehydration, displays similar results. CARS is, therefore, a label-free alternative to other microscopy techniques to characterize myelin in healthy and neurological disorders affecting the spinal cord