Électroarthrographie : mesure et analyse des potentiels électriques à la surface du genou pour l’évaluation de l’arthrose

RÉSUMÉ L’électroarthrographie (EAG) est une technique qui fut récemment découverte par un groupe de chercheurs de l’École Polytechnique de Montréal pour enregistrer et analyser les signaux électriques à la surface du genou qui sont produits par la compression du cartilage articulaire. Auparavant, il fut démontré que des potentiels électriques dits ‘d’écoulement’ peuvent être mesurés directement sur le cartilage articulaire lors de mesures invasives, et que ces potentiels diminuent lorsqu’il y a une dégradation du cartilage produite par une réduction de la concentration de glycosaminoglycanes ou lorsque le collagène perd de son intégrité. L’électroarthrographie constitue alors une méthode non-invasive de mesure des potentiels d’écoulement qui reflètent l’état de santé du cartilage articulaire. Le premier objectif de ce mémoire était de concevoir un protocole de prise de mesures EAG répétable et adapté à des populations gériatriques. Pour ce faire, nous avons fait des études de cas selon plusieurs protocoles différents. Pour le protocole qui a été retenu, la mise en charge du cartilage articulaire se fait par un simple transfert de poids d’une jambe à l’autre, alors que le sujet se tient debout. Ce transfert de poids est répété durant deux minutes pour permettre de réduire le niveau de bruit en calculant des valeurs EAG moyennes. Les potentiels électriques sont mesurés à l’aide d’électrodes collées sur la surface du genou en utilisant un système d’enregistrement sans fil comprenant huit canaux en courant continu. Pour traiter les signaux mesurés, un programme avec une interface graphique fut mis au point pour filtrer les signaux, corriger la dérive de la ligne de base et moyenner les multiples épisodes de mise en charge. La répétabilité des potentiels moyennés pour chacune des électrodes fut évaluée par une procédure de test-retest pour 14 sujets. Il s’est avéré que quatre sites de mesure, situés surtout au niveau de la ligne d’articulation, ont montré des coefficients de corrélation intra-classe statistiquement significatifs. Le deuxième objectif était de déterminer la provenance des signaux et d’évaluer la sensibilité de l’EAG à la dégradation du cartilage. Pour ce faire, nous avons comparé deux populations; un groupe Contrôle, avec des genoux sains, et un groupe dont un des genoux était diagnostiqué arthrosique, tandis que le genou controlatéral portait une prothèse totale du genou. Chaque groupe comprenait vingt sujets. Dans le groupe Contrôle, l’amplitude moyenne des signaux EAG était statistiquement plus élevée du côté médial que du côté latéral, ce qui reflète des forces au niveau de l’articulation qui sont reconnues être plus élevées du côté médial que du----------ABSTRACT Electroarthrography (EAG) is a technique that was recently discovered by a group of researchers from the Ecole Polytechnique de Montreal, to record and analyze the electrical signals on the surface of the knee that are produced by the compression of articular cartilage. Previously, it has been shown that electrical potentials called 'streaming potentials' can be measured directly on the surface of the articular cartilage and that cartilage degradation, produced by a reduction in the concentration of glycosaminoglycans or collagen content, can decrease the amplitude of the streaming potentials. Eectroarthrography is therefore a non-invasive method for measuring electrical potential that reflect streaming potentials and the status of articular cartilage. The first objective of this project was to design a protocol that can provide repeatable EAG measurements and that is suitable for geriatric populations. To do this, we performed case studies using several different protocols. For our final protocol, the loading of articular cartilage is performed with a simple transfer of weight from one leg to another while the subject is standing. This weight transfer is repeated for two minutes to reduce the noise level by calculating average EAG values. Electrical potentials are measured with electrodes placed on the surface of the knee using a wireless recording system with eight channels. To process the measured signals, a program with a graphic user interface was developed to filter the signals, correct the baseline drift and average the multiple loading episodes. The repeatability of the averaged EAG for each of the electrodes was evaluated by a test-retest procedure for 14 subjects. We found that four measurement sites, mostly located over the joint line, showed statistically significant intraclass correlation coefficients. The second objective was to determine the origin of the EAG signals and to evaluate the sensitivity of the EAG for the detection of cartilage degradation. We thus compared two populations: a control group with healthy knees and a group of patients with osteoarthritis diagnosed for one knee, while the contralateral knee had a total knee replacement. Each group consisted of twenty subjects. In the control group, the mean amplitude of the EAG signal was statistically higher for the medial side than for the lateral side, reflecting joint forces that are known to be higher in the medial side than on the lateral side. For EAG signals recorded over the total knee replacement, their mean amplitude was statistically zero, reflecting the absence of cartilage. For signals collected over the arthritic knees, their mean amplitude was statisticall

Subjective sleep quality in non-demented elderly adults with and without cognitive impairment

Objective: Sleep problems are prevalent among older adults who are at risk of developing dementia. Until now, there have been relatively few studies investigating subjective sleep quality in these individuals. The first objective of this study was to compare seniors with cognitive impairment no dementia (CIND) and older adults without cognitive impairment (non‐CIND) on several subjective sleep measures. The second objective was to verify whether sleep parameters associated with CIND differ between men and women. Methods: The population sample consisted of 2287 French‐speaking older adults from Québec (Canada) aged between 65 and 96 years. Participants were classified as CIND or non‐CIND on the basis of their mini mental state examination score using sex, age, and education‐stratified normative data. All participants completed the Pittsburgh Sleep Quality Index, and responses of CIND and non‐CIND individuals were compared. A series of confounding variables (age, education, chronic diseases, mood disorders, anxiety disorders, and use of psychotropic drugs) were statistically controlled for. Student's t ‐tests were performed to compare characteristics of CIND and non‐CIND individuals; data from male and female participants were analyzed separately. Moreover, the association between each sleep variable and CIND was measured by odds ratios based on logistic regression. Results: On the whole, analyses revealed no significant association between subjective sleep parameters and CIND. Moreover, no difference was observed between men and women regarding subjective sleep quality. Conclusions: Overall, these results suggest that subjective measures of sleep do not allow differentiating cognitively impaired older individuals from those with normal cognition. Copyright © 2014 John Wiley & Sons, Ltd

Optimization of RNA extraction methods from human metabolic tissue samples of the COMET biobank

International audienceConstitution of biobank of human tissues requires careful handling and storage of biological material, to guarantee the quality of samples. Tissue preparation is also critical for further applications such as transcriptomic profiling. In this study, our aim was to evaluate the impact of different disruption techniques (FastPrep-24 instrument, GentleMACS dissociator, and syringe/needle) and homogenizing buffers (RLT versus QIAzol) on RNA purity and quality of metabolic tissues (adipose tissues, liver and skeletal muscle) present in the COMET Biobank. For all homogenization methods used and tissue types, the A260/280 ratios reached values ≥ 1.8, which are in the range of what is found in human tissues and cell lines, while the A260/230 ratios were however ≤ 1.8, with the lowest value obtained with GentleMACS Dissociator. In addition, GentleMACS Dissociator combined with QIAzol reagent gave the highest RIN value and 28S/18S ratio for all tissues tested, except for muscle. Performing RT-qPCR, Ct values for different housekeeping genes can be influenced by extraction methods and RNA quality of samples. In conclusion, we have demonstrated that different disruption techniques and homogenizing buffers impact the purity and some quality markers of RNA, and can also impact quantification of mRNAs by RT-qPCR in human metabolic tissues

Addressing the quality challenge of a human biospecimen biobank through the creation of a quality management system.

BackgroundThe objective of the COMET (COllection of MEtabolic Tissues) biobank project is to create a high-quality collection of insulin-sensitive tissues (liver, muscle, adipose tissues, and epiploic artery) and blood sample derivatives (plasma, serum, DNA and RNA), collected from 270 grade 2-3 obese patients undergoing bariatric surgery. Relevant data on patient such as clinical/biological characteristics and sample handling are also collected. For this, our aim was to establish a Quality Management System (QMS) to meet the reliability and quality requirements necessary for its scientific exploitation.Materials and methodsThe COMET QMS includes: (1) Quality Assurance to standardize all stages of the biobanking process, (2) Quality Controls on samples from the first patients included in order to validate the sample management process and ensure reproducible quality; and 3) "in process" Quality Controls to ensure the reliability of the storage procedures and the stability of the samples over time.ResultsFor serum and plasma, several corrective actions, such as temperature handling and centrifugation conditions, were made to the protocol and led to improvement of the volume and quality of samples. Regarding DNA, all samples evaluated achieved a satisfactory level of purity and integrity and most of them yielded the required DNA quantity. All frozen tissue samples had RNAs of good purity. RNA quality was confirmed by RIN, achieving values in most cases over 7 and efficient amplification of housekeeping genes by RT-qPCR, with no significant differences among samples from the same tissue type. In the "in process" Quality Controls, DNA, RNA, and histological integrity of tissues showed no differences among samples after different preservation times.ConclusionQuality Control results have made it possible to validate the entire biobank process and confirm the utility of implementing QMS to guarantee the quality of a biospecimen collection