Apport des nouveaux biomarqueurs sur la physiopathologie, le diagnostic et le pronostic de l'angiopathie amyloïde cérébrale

L'angiopathie amyloïde cérébrale (AAC) sporadique est une microangiopathie cérébrale, dont l'intérêt auprès des cliniciens et des chercheurs est grandissant. L'AAC est fréquente chez les sujets âgés et constitue une cause majeure et croissante d'hémorragie intracérébrale et de démence. Des avancées importantes ont été réalisées ces dernières années dans ce champ de recherche, permettant d'identifier de nouveaux biomarqueurs de la maladie, grâce aux progrès réalisés en neuroimagerie structurelle, fonctionnelle et moléculaire. Des thérapies anti-amyloïdes sont en cours de développement et des essais cliniques évaluant la meilleure stratégie vis à vis des traitements anticoagulants chez ces patients ont débuté, laissant entrevoir des possibilités thérapeutiques. Ainsi, l'évaluation de ces nouveaux biomarqueurs d'AAC semble particulièrement importante. L'objectif principal de cette thèse était d'apporter de nouvelles connaissances sur les biomarqueurs de neuroimagerie les plus récents et leurs applications potentielles en pratique clinique chez les patients avec AAC. Nous avons pour cela conduit 6 études de recherche clinique explorant des nouveaux biomarqueurs hémorragiques (hémosidérose corticale, hémorragie sous arachnoïdienne de la convexité) et non hémorragiques (espaces périvasculaires dilatés, TEP amyloïde et réseau de connectivité cérébrale) de la maladie. Nous évaluons ces biomarqueurs comme outils diagnostiques et leur pertinence clinique comme facteur pronostique.Sporadic cerebral amyloid angiopathy (CAA) is a common cerebral small vessel disease with growing interest among clinicians and researchers. CAA occurs frequently in elderly subjects and is a major and increasing cause of intracerebral hemorrhage and dementia. Over the last several years, important advances have been made in this research field, with the development of new biomarkers for the disease, thanks to advances in structural, functional and molecular neuroimaging. Anti-amyloid therapies are currently in development and clinical trial assessing anticoagulant strategy in these patients are ongoing, raising the perspective of future treatments. Hence, evaluating these new biomarkers of CAA seems particularly important. The main objective of this PhD thesis was to get insights into novel neuroimaging biomarkers and their potential clinical applications in patients with CAA. We conducted 6 clinical research studies exploring new hemorrhagic (cortical superficial siderosis, convexity subarachnoid hemorrhage) and non-hemorrhagic (enlarged perivascular spaces, amyloid PET, brain network connectivity) markers of the disease. Biomarkers are evaluated as diagnostic tools and their clinical relevance, as prognostic markers are investigated

The actin-based motor protein myosin II regulates MHC class II trafficking and BCR-driven antigen presentation

Antigen (Ag) capture and presentation onto major histocompatibility complex (MHC) class II molecules by B lymphocytes is mediated by their surface Ag receptor (B cell receptor [BCR]). Therefore, the transport of vesicles that carry MHC class II and BCR–Ag complexes must be coordinated for them to converge for processing. In this study, we identify the actin-associated motor protein myosin II as being essential for this process. Myosin II is activated upon BCR engagement and associates with MHC class II–invariant chain complexes. Myosin II inhibition or depletion compromises the convergence and concentration of MHC class II and BCR–Ag complexes into lysosomes devoted to Ag processing. Accordingly, the formation of MHC class II–peptides and subsequent CD4 T cell activation are impaired in cells lacking myosin II activity. Therefore, myosin II emerges as a key motor protein in BCR-driven Ag processing and presentation

Pigmentation Pathway Evolution after Whole-Genome Duplication in Fish

Whole-genome duplications (WGDs) have occurred repeatedly in the vertebrate lineage, but their evolutionary significance for phenotypic evolution remains elusive. Here, we have investigated the impact of the fish-specific genome duplication (FSGD) on the evolution of pigmentation pathways in teleost fishes. Pigmentation and color patterning are among the most diverse traits in teleosts, and their pigmentary system is the most complex of all vertebrate groups

Decompressive surgery in cerebral venous sinus thrombosis due to vaccine-induced immune thrombotic thrombocytopenia

Background and purpose: Cerebral venous sinus thrombosis due to vaccine-induced im-mune thrombotic thrombocytopenia (CVST-VITT) is an adverse drug reaction occurring after severe acute respiratory syndrome coronavirus 2 (SARS-CoV- 2) vaccination. CVST-VITT patients often present with large intracerebral haemorrhages and a high proportion undergoes decompressive surgery. Clinical characteristics, therapeutic management and outcomes of CVST-VITT patients who underwent decompressive surgery are described and predictors of in- hospital mortality in these patients are explored.Methods: Data from an ongoing international registry of patients who developed CVST within 28 days of SARS-CoV- 2 vaccination, reported between 29 March 2021 and 10 May 2022, were used. Definite, probable and possible VITT cases, as defined by Pavord et al. (N Engl J Med 2021; 385: 1680–1689), were included. Results: Decompressive surgery was performed in 34/128 (27%) patients with CVST- VITT. In- hospital mortality was 22/34 (65%) in the surgical and 27/94 (29%) in the non- surgical group (p< 0.001). In all surgical cases, the cause of death was brain herniation. The highest mortality rates were found amongst patients with preoperative coma (17/18, 94% vs. 4/14, 29% in the non-comatose; p< 0.001) and bilaterally absent pupillary re-flexes (7/7, 100% vs. 6/9, 67% with unilaterally reactive pupil, and 4/11, 36% with bi-laterally reactive pupils; p= 0.023). Postoperative imaging revealed worsening of index haemorrhagic lesion in 19 (70%) patients and new haemorrhagic lesions in 16 (59%) pa-tients. At a median follow-up of 6 months, 8/10 of surgical CVST-VITT who survived ad-mission were functionally independent.Conclusions: Almost two-thirds of surgical CVST-VITT patients died during hospital ad-mission. Preoperative coma and bilateral absence of pupillary responses were associated with higher mortality rates. Survivors often achieved functional independence.Peer reviewe

The Boston criteria version 2.0 for cerebral amyloid angiopathy:a multicentre, retrospective, MRI–neuropathology diagnostic accuracy study

BACKGROUND: Cerebral amyloid angiopathy (CAA) is an age-related small vessel disease, characterised pathologically by progressive deposition of amyloid β in the cerebrovascular wall. The Boston criteria are used worldwide for the in-vivo diagnosis of CAA but have not been updated since 2010, before the emergence of additional MRI markers. We report an international collaborative study aiming to update and externally validate the Boston diagnostic criteria across the full spectrum of clinical CAA presentations. METHODS: In this multicentre, hospital-based, retrospective, MRI and neuropathology diagnostic accuracy study, we did a retrospective analysis of clinical, radiological, and histopathological data available to sites participating in the International CAA Association to formulate updated Boston criteria and establish their diagnostic accuracy across different populations and clinical presentations. Ten North American and European academic medical centres identified patients aged 50 years and older with potential CAA-related clinical presentations (ie, spontaneous intracerebral haemorrhage, cognitive impairment, or transient focal neurological episodes), available brain MRI, and histopathological assessment for CAA diagnosis. MRI scans were centrally rated at Massachusetts General Hospital (Boston, MA, USA) for haemorrhagic and non-haemorrhagic CAA markers, and brain tissue samples were rated by neuropathologists at the contributing sites. We derived the Boston criteria version 2.0 (v2.0) by selecting MRI features to optimise diagnostic specificity and sensitivity in a prespecified derivation cohort (Boston cases 1994-2012, n=159), then externally validated the criteria in a prespecified temporal validation cohort (Boston cases 2012-18, n=59) and a geographical validation cohort (non-Boston cases 2004-18; n=123), comparing accuracy of the new criteria to the currently used modified Boston criteria with histopathological assessment of CAA as the diagnostic standard. We also assessed performance of the v2.0 criteria in patients across all cohorts who had the diagnostic gold standard of brain autopsy. FINDINGS: The study protocol was finalised on Jan 15, 2017, patient identification was completed on Dec 31, 2018, and imaging analyses were completed on Sept 30, 2019. Of 401 potentially eligible patients presenting to Massachusetts General Hospital, 218 were eligible to be included in the analysis; of 160 patient datasets from other centres, 123 were included. Using the derivation cohort, we derived provisional criteria for probable CAA requiring the presence of at least two strictly lobar haemorrhagic lesions (ie, intracerebral haemorrhages, cerebral microbleeds, or foci of cortical superficial siderosis) or at least one strictly lobar haemorrhagic lesion and at least one white matter characteristic (ie, severe visible perivascular spaces in centrum semiovale or white matter hyperintensities in a multispot pattern). The sensitivity and specificity of these criteria were 74·8% (95% CI 65·4-82·7) and 84·6% (71·9-93·1) in the derivation cohort, 92·5% (79·6-98·4) and 89·5% (66·9-98·7) in the temporal validation cohort, 80·2% (70·8-87·6) and 81·5% (61·9-93·7) in the geographical validation cohort, and 74·5% (65·4-82·4) and 95·0% (83·1-99·4) in all patients who had autopsy as the diagnostic standard. The area under the receiver operating characteristic curve (AUC) was 0·797 (0·732-0·861) in the derivation cohort, 0·910 (0·828-0·992) in the temporal validation cohort, 0·808 (0·724-0·893) in the geographical validation cohort, and 0·848 (0·794-0·901) in patients who had autopsy as the diagnostic standard. The v2.0 Boston criteria for probable CAA had superior accuracy to the current Boston criteria (sensitivity 64·5% [54·9-73·4]; specificity 95·0% [83·1-99·4]; AUC 0·798 [0·741-0854]; p=0·0005 for comparison of AUC) across all individuals who had autopsy as the diagnostic standard. INTERPRETATION: The Boston criteria v2.0 incorporate emerging MRI markers of CAA to enhance sensitivity without compromising their specificity in our cohorts of patients aged 50 years and older presenting with spontaneous intracerebral haemorrhage, cognitive impairment, or transient focal neurological episodes. Future studies will be needed to determine generalisability of the v.2.0 criteria across the full range of patients and clinical presentations. FUNDING: US National Institutes of Health (R01 AG26484)

Detection of cannabinoid receptor type 2 in native cells and zebrafish with a highly potent, cell-permeable fluorescent probe.

Despite its essential role in the (patho)physiology of several diseases, CB2R tissue expression profiles and signaling mechanisms are not yet fully understood. We report the development of a highly potent, fluorescent CB2R agonist probe employing structure-based reverse design. It commences with a highly potent, preclinically validated ligand, which is conjugated to a silicon-rhodamine fluorophore, enabling cell permeability. The probe is the first to preserve interspecies affinity and selectivity for both mouse and human CB2R. Extensive cross-validation (FACS, TR-FRET and confocal microscopy) set the stage for CB2R detection in endogenously expressing living cells along with zebrafish larvae. Together, these findings will benefit clinical translatability of CB2R based drugs

Radiology

Background: A target mismatch profile can identify good clinical response to recanalization after acute ischemic stroke, but does not consider region specificities. Purpose: To test whether location-weighted infarction core and mismatch, determined from diffusion and perfusion MRI performed in patients with acute stroke, could improve prediction of good clinical response to mechanical thrombectomy compared with a target mismatch profile. Materials and Methods: In this secondary analysis, two prospectively collected independent stroke data sets (2012–2015 and 2017–2019) were analyzed. From the brain before stroke (BBS) study data (data set 1), an eloquent map was computed through voxel-wise associations between the infarction core (based on diffusion MRI on days 1–3 following stroke) and National Institutes of Health Stroke Scale (NIHSS) score. The French acute multimodal imaging to select patients for mechanical thrombectomy (FRAME) data (data set 2) consisted of large vessel occlusion–related acute ischemic stroke successfully recanalized. From acute MRI studies (performed on arrival, prior to thrombectomy) in data set 2, target mismatch and eloquent (vs noneloquent) infarction core and mismatch were computed from the intersection of diffusion- and perfusion-detected lesions with the coregistered eloquent map. Associations of these imaging metrics with early neurologic improvement were tested in multivariable regression models, and areas under the receiver operating characteristic curve (AUCs) were compared. Results: Data sets 1 and 2 included 321 (median age, 69 years [IQR, 58–80 years]; 207 men) and 173 (median age, 74 years [IQR, 65–82 years]; 90 women) patients, respectively. Eloquent mismatch was positively and independently associated with good clinical response (odds ratio [OR], 1.14; 95% CI: 1.02, 1.27; P =.02) and eloquent infarction core was negatively associated with good response (OR, 0.85; 95% CI: 0.77, 0.95; P =.004), while noneloquent mismatch was not associated with good response (OR, 1.03; 95% CI: 0.98, 1.07; P =.20). Moreover, adding eloquent metrics improved the prediction accuracy (AUC, 0.73; 95% CI: 0.65, 0.81) compared with clinical variables alone (AUC, 0.65; 95% CI: 0.56, 0.73; P =.01) or a target mismatch profile (AUC, 0.67; 95% CI: 0.59, 0.76; P =.03). Conclusion: Location-weighted infarction core and mismatch on diffusion and perfusion MRI scans improved the identification of patients with acute stroke who would benefit from mechanical thrombectomy compared with the volume-based target mismatch profile. © RSNA, 2022.Translational Research and Advanced Imaging Laborator

Management of Cerebral Venous Thrombosis Due to Adenoviral COVID-19 Vaccination

Objective Cerebral venous thrombosis (CVT) caused by vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare adverse effect of adenovirus-based severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) vaccines. In March 2021, after autoimmune pathogenesis of VITT was discovered, treatment recommendations were developed. These comprised immunomodulation, non-heparin anticoagulants, and avoidance of platelet transfusion. The aim of this study was to evaluate adherence to these recommendations and its association with mortality. Methods We used data from an international prospective registry of patients with CVT after the adenovirus-based SARS-CoV-2 vaccination. We analyzed possible, probable, or definite VITT-CVT cases included until January 18, 2022. Immunomodulation entailed administration of intravenous immunoglobulins and/or plasmapheresis. Results Ninety-nine patients with VITT-CVT from 71 hospitals in 17 countries were analyzed. Five of 38 (13%), 11 of 24 (46%), and 28 of 37 (76%) of the patients diagnosed in March, April, and from May onward, respectively, were treated in-line with VITT recommendations (p < 0.001). Overall, treatment according to recommendations had no statistically significant influence on mortality (14/44 [32%] vs 29/55 [52%], adjusted odds ratio [OR] = 0.43, 95% confidence interval [CI] = 0.16-1.19). However, patients who received immunomodulation had lower mortality (19/65 [29%] vs 24/34 [70%], adjusted OR = 0.19, 95% CI = 0.06-0.58). Treatment with non-heparin anticoagulants instead of heparins was not associated with lower mortality (17/51 [33%] vs 13/35 [37%], adjusted OR = 0.70, 95% CI = 0.24-2.04). Mortality was also not significantly influenced by platelet transfusion (17/27 [63%] vs 26/72 [36%], adjusted OR = 2.19, 95% CI = 0.74-6.54). Conclusions In patients with VITT-CVT, adherence to VITT treatment recommendations improved over time. Immunomodulation seems crucial for reducing mortality of VITT-CVT. ANN NEUROL 2022Peer reviewe