Biology subjects

Tessier, A.

Publications and source records attributed to Tessier, A..

9 recordsLinked to original sources

bioRxiv2026

Repeated Neuromuscular Electrical Stimulation Protocol Disrupts Muscle-to-Brain Signaling in Rats

Objective. Neuromuscular electrical stimulation (NMES) is increasingly used to preserve or restore muscle function in patients unable to exercise, and acute NMES improves cognitive performance and increases hippocampal mature brain-derived neurotrophic factor (BDNF). However, the consequences of repeated sessions for muscle-to-brain signaling remain poorly understood. We examined whether seven consecutive days of quadriceps NMES would reproduce this acute response. Methods. Male Wistar rats received daily 30-min quadriceps NMES or SHAM sessions under isoflurane for seven consecutive days. Blood was collected immediately after the final session and 24 h later, when muscle and hippocampal tissues were also collected. An independent cohort underwent behavioral testing. Results. Repeated NMES increased serum creatine kinase activity and quadriceps fibrillar collagen deposition without altering muscle mass, myofiber size, or degeneration-regeneration markers. These changes were accompanied by low-grade systemic inflammation and corticosterone elevation persisting 24 h after the final session. In the hippocampus, NMES increased inflammatory cytokine expression, astrocytic and microglial markers, and glucocorticoid receptor phosphorylation. Mature BDNF, TrkB phosphorylation and ERK1/2 signaling decreased, whereas proBDNF, p75NTR and JNK signaling increased; Akt and mTOR phosphorylation were unchanged. Synaptophysin, GAP43 and PSD95 also decreased. NMES increased marble burying and forced-swim immobility, without detectable changes in locomotion, recognition memory, or neuronal profile density. Conclusions. Repeated daily NMES engaged a distinct, maladaptive mode of muscle-to-brain signaling rather than reproducing the benefits reported after acute stimulation. Stimulation parameters and recovery intervals that avoid this response need to be defined before repeated NMES can be recommended as an exercise substitute.

physiology↗

bioRxiv2026

Nav1.5 regulates intrinsic cardiac neuronal excitability and expands the cellular basis of SCN5A channelopathies

Background: Loss- and gain-of-function variants in SCN5A, encoding the cardiac sodium channel Nav1.5, are major causes of inherited cardiac channelopathies. Their pathophysiology has almost exclusively been attributed to altered cardiomyocyte excitability and cardiac conduction. However, growing evidence indicates that autonomic dysfunction contributes to these disorders, raising the possibility that Nav1.5 dysfunction may also affect the intrinsic cardiac nervous system. Objectives: We investigated whether Nav1.5 is functionally expressed in murine intrinsic cardiac neurons and evaluated its contribution to neuronal excitability. Methods: Scn5a expression was investigated by digital PCR and immunocytochemistry in isolated murine intracardiac neurons. Whole-cell patch-clamp recordings were used to characterize sodium currents and action potential properties in wild-type and Scn5a+/- mice. Results: Scn5a transcripts and Nav1.5 protein were detected in intrinsic cardiac neurons. Voltage-clamp recordings identified a tetrodotoxin-resistant sodium current accounting for approximately 8% of the total sodium current and displaying pharmacological and biophysical properties consistent with Nav1.5. Activation and inactivation analyses indicated that Nav1.5 is the predominant sodium conductance available at most polarized membrane potentials. Accordingly, Scn5a haploinsufficiency selectively altered action potential threshold, maximal upstroke velocity, overshoot and duration in neurons resting below -60 mV, whereas more depolarized neurons were essentially unaffected. No structural or neurochemical remodeling of intrinsic cardiac ganglia was detected. Conclusion: Nav1.5 is a functional determinant of intrinsic cardiac neuronal excitability. These findings identify the intrinsic cardiac nervous system as a new cellular target of SCN5A dysfunction and suggest that inherited cardiac sodium channelopathies could involve alterations in both myocardial and intrinsic neuronal electrophysiology.

physiology↗

bioRxiv2026

Desmin p.R406W mutation is associated with arrhythmias through structural and electrophysiological remodeling

Background and AimsMutations in the desmin (DES) gene cause a variety of cardiomyopathies associated with arrhythmias, yet the electrophysiological consequences of these variants remain largely uncharacterized. The aim of this study was to investigate the pathogenic mechanisms of the de novo DES p.R406W variant, which was identified in a 9-year-old patient who suffered from severe ventricular arrhythmias and sudden cardiac death without overt structural heart disease. MethodsHuman induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) carrying the DES p.R406W variant (including the patients line) were compared to isogenic controls. Action potentials (AP) of hiPSC-CMs were recorded using patch-clamp. Furthermore, 3D engineered heart tissues (EHTs) were generated from hiPSC-CMs and their APs were recorded with sharp microelectrodes. Analytical techniques also included transmission electron microscopy (TEM) and integrated transcriptomic and proteomic profiling. Finally, a heterozygous knock-in (KI) mouse model carrying the Des p.R405W ortholog was evaluated through surface ECG, echocardiography and ex vivo cardiac optical mapping. ResultsThe DES p.R406W mutation prolonged AP duration in IM-R406W hiPSC-CMs and EHTs vs Control ones. Multi-omics analysis of EHTs revealed a dysregulation of genes and proteins involved in contractile function, cell adhesion, and electrical activity. TEM imaging revealed changes in Z-disc architecture in mutant tissues. Twenty-week-old Des p.R405W KI mice exhibited ventricular conduction slowing (prolonged QRS) and a high susceptibility to ventricular tachyarrhythmias, likely due to reentrant mechanisms. Mild hypertrophy was also observed, but only in females. ConclusionThe DES p.R406W variant is highly pathogenic, causing electrical and structural remodeling of the myocardium. This study highlights the effectiveness of hiPSC-CMs and EHTs in recapitulating the clinical phenotype of desminopathy, providing a platform for investigating the mechanisms of early-onset cardiac arrhythmias and SCD.

pathology↗

bioRxiv2025

Late INa activation of cardiac TTX-sensitive sodium channels by AaH-II induces an arrhythmogenic phenotype

AimsLate sodium current (INaL) is a key contributor to cardiac arrhythmias, but its precise origin and arrhythmogenic potential from tetrodotoxin-sensitive (TTX-S) sodium (Nav) channels remain unclear. While the FDA-endorsed toxin ATX-II has been widely used to model INaL-associated arrhythmogenesis, it lacks selectivity, limiting its utility in dissecting the roles of individual Nav channel subtypes. This study investigates the proarrhythmic impact of TTX-S Nav channel activation using AaH-II*, a scorpion venom-derived peptide with selective efficacy for TTX-S channels. Methods and ResultsUsing automated patch-clamp recordings, we characterized AaH-II* selectivity across human Nav isoforms and demonstrated potent, preferential activation of INaL in hNav1.1, 1.2, 1.3, and 1.6 over the TTX-resistant cardiac isoform hNav1.5. Calcium imaging in isolated adult rat cardiomyocytes showed that low nanomolar concentrations of AaH-II* induced spontaneous calcium release events and arrhythmogenic calcium transients, even in the absence of Nav1.5 activation. Ex vivo multielectrode array recordings in Langendorff-perfused rat hearts confirmed dose-dependent ventricular conduction slowing, prolonged repolarization, and increased arrhythmia burden, all mitigated by TTX. In vivo, intravenous AaH-II* administration in rats elicited QTc prolongation, atrioventricular block, and ventricular tachyarrhythmias, which were significantly suppressed by TTX pretreatment. ConclusionWe identify AaH-II* as a powerful and selective tool to study INaL from TTX-S Nav channels in cardiac tissue. Our findings reveal that TTX-S channel-mediated INaL alone is sufficient to induce arrhythmias and that pharmacological inhibition of these channels offers a promising antiarrhythmic strategy. These results advocate for broader consideration of TTX-S Nav channels as targets in arrhythmia research and drug safety screening.

physiology↗

bioRxiv2024

Assessment of non-linear mixed effects model-based approaches to test for drug effect using simulated data: type I error and power properties

1Pharmacometric approaches achieves higher power to detect a drug effect compared to traditional statistical hypothesis tests. Known drawbacks come from the model building process where multiple testing and model misspecification are major causes for type I error inflation. IMA is a new approach using mixture models and the likelihood ratio test (LRT) to test for drug effect. It previously showed type I error control and unbiased drug estimates in the context of two-arms balanced designs using real placebo data, in comparison to the standard approach (STD). The aim of this study was to extend the assessment of IMA and STD regarding type I error, power, and bias in the drug effect estimates under various types of model misspecification, with or without LRT calibration. Two classical statistical approaches, t-test and Mixed-Effect Model Repeated Measure (MMRM), were also added to the comparison. The focus was a simulation study where the extent of the model misspecification is known, using a response model with or without drug effect as motivating example in two sample size scenarios. The IMA performances were overall not impacted by the sample size or the LRT calibration, contrary to STD which had better type I error results with the larger sample size and calibrated LRT. In terms of power STD required LRT calibration to outperform IMA. T-test and MMRM had both controlled type I error. The t-test had a lower power than both STD and IMA while MMRM had power predictions similar to IMA. IMA and STD had similarly unbiased drug effect estimates, with few exceptions. IMA showed again encouraging performances (type I error control and unbiased drug estimates) and presented reasonable power predictions. The IMA performances were overall more robust towards model mis-specification compared to STD. IMA confirmed its status of promising NLMEM-based approach for hypothesis testing of the drug effect and could be used in the future, after further evaluations, as primary analysis in confirmatory trials.

pharmacology and toxicology↗

bioRxiv2023

Microencapsulation of mesenchymal stromal cells in covalent alginate hydrogels for cell therapy

Osteoarthritis (OA) is the most common inflammatory joint disease and currently lacks an effective curative treatment. Intra-articular injection of mesenchymal stromal cells (MSCs) has gained attention as a relevant therapeutic approach for OA treatment due to the MSCs ability to secrete anti-inflammatory and immunomodulatory factors. Given their limited viability post- intraarticular injection and the potential leakage of cells out of the injection site, encapsulating MSCs in hydrogels is considered a promising strategy to protect them and provide a suitable 3D microenvironment to support their biological activities. Calcium-cross-linked alginate hydrogels are commonly used for MSC encapsulation, but their long-term in vivo stability remains uncertain. On the other hand, alginate cross-linking by the strain-promoted azide- alkyne cycloaddition (SPAAC) reaction would create a network unaffected by an ionic environment. Hence, this study aimed to develop an alginate-based hydrogel cross-linked via stable and cytocompatible covalent bonds for cell encapsulation. We established for the first time the formation of covalent alginate hydrogels between two SPAAC precursors, namely alginate-BCN and alginate-N3. These hydrogels exhibited in vitro stability and enabled the diffusion of molecules of interest. We then generated alginate-based SPAAC microgels of 170 m in mean diameter, suitable for intra-articular injection. We next encapsulated human adipose MSCs (hASCs) in these alginate-based SPAAC microgels and confirmed their cytocompatibility, with over 90 % of cells remaining viable after 14 days in culture. Finally, the microencapsulated hASCs maintained their biological properties and were able to secrete anti-inflammatory factors (IDO, PGE2, and HGF) when exposed to pro-inflammatory cytokines (TNF- and IFN-{gamma}). In the end, human-activated lymphocytes were cultured in contact with microencapsulated hASCs, and CD3+ T cell proliferation was quantified by flow cytometry. We demonstrated that the encapsulation process did not impair the hASC immunomodulatory activity. Overall, our findings show the potential of alginate-based SPAAC hydrogels for microencapsulating hASCs for cell therapy.

bioengineering↗

bioRxiv2023

Optical control of cardiac rhythm by in vivo photoactivation of an ERG channel peptide inhibitor

RATIONALECardiac rhythm, conduction and synchronization of electrical activity require the coordinated action of different types of ion channels that differ according to transmural and regional specificities. Classical pharmacology affects these ion channels in a non-regionalized way which explains why treating arrhythmias, that often occur in specific foci, has often limited efficacy in addition to negative side-effects on non-targeted organs. Photopharmacology is an emergent technology that has the potential to counteract all the negative aspects of classical pharmacology by restricting drug activity in a spatio-temporal manner. OBJECTIVEWe tested the potential of photopharmacology in specifically regulating heart activity by using a caged derivative of a natural peptide inhibitor of the ERG channel, BeKm1. The peptide was uncaged and activity monitored in vitro on a cell line expressing the hERG channel, on human cardiomyocytes derived from iPS cells, and ex vivo and in vivo on zebrafish larvae and rat hearts. METHODS AND RESULTSCaged BeKm-1 is inactive and fully active upon uncaging. Uncaging of the peptide on human iPS-derived cardiomyocytes enlarges the action potential duration and triggers arrhythmias. Uncaging also triggers bradycardia and disturbs cardiac conduction within the atria in perfused rat hearts upon illumination. The potency of photopharmacology for cardiac electrical modulation was further validated in zebrafish larvae where illumination of the caged compound induces bradycardia and atrio-ventricular desynchrony. Finally, in anesthetized rats, illumination of the caged peptide in the right atria, containing the sino-atrial node, leads to bradycardia without arrhythmia. CONCLUSIONSThis report demonstrates that photopharmacology, using the caged peptide strategy, can be used for dynamically regulating cardiac electrical activity in vivo and that spatial illumination restriction can dissociate the bradycardic effect from the arrhythmic one. The technology is applicable to all kinds of cardiac ion channels and regions of interest to create arrhythmogenic models or investigate new clinical applications.

pharmacology and toxicology↗

bioRxiv2022

Production of recombinant heterotrimeric mini-procollagen I and homotrimeric II mini-procollagen II reveals new cleavage sites for BMP-1

The proteolytic conversion of soluble procollagens into mature collagen monomers is a critical step to decrease their solubility and trigger collagen fibril formation. In the case of collagens I, II and III, this maturation process is driven by several extracellular metalloproteinases such as BMP-1, tolloid-like proteinases, meprin , meprin {beta}, ADAMTS-2 and ADAMTS-14 but the extensive characterization of these proteolytic events has been hampered by the lack of recombinant procollagens. We previously reported the production and partial characterization of recombinant homotrimeric proteins derived from procollagen III (mini-procollagens III) and, in this study, we describe how we have extended this previous work to the production of heterotrimeric mini-procollagen I and homotrimeric mini-procollagen II. These mini-procollagens include truncated triple helices and intact C-telopeptide and C-propeptide domains and were produced in suspension in HEK293-F cells with yields ranging from 2.5 mg/L to 10 mg/L after purification. They proved very useful tools to analyze the effect of calcium on the stability of the procollagen C-terminal region and to compare the procollagen C-proteinase activity of BMP-1 on the three major fibrillar procollagens or their ability to interact with various partners such as PCPE-1. Using mass spectrometry to map BMP-1 cleavage sites on the mini-procollagens, we confirmed all previously described sites but also revealed two additional cleavage sites in the 1 chain of procollagens I and II. This result shows that the mini-procollagen toolkit offers a broad range of perspectives to make functional studies but also possibly structural analyses or to develop drug screening assays.

biochemistry↗

bioRxiv2022

MHC-II expressing neutrophils circulate in blood and milk during mastitis and show high microbicidal activity

Bovine mastitis are mainly caused by bacterial infection. They are responsible for economic losses and have an impact on the health and welfare of animals. The increase in the somatic cell count in milk during mastitis is mainly due to the influx of neutrophils which have a crucial role in the elimination of pathogens. For a long time, these first line defenders has been view as microbes killers with limited role in the orchestration of the immune response. However, their role is more complex and we recently characterized a MHC-II expressing neutrophil subset with regulatory capacities in cattle. In this study, we questioned the implication of different neutrophils subsets in the mammary gland immunity during clinical and subclinical mastitis. Here, we described for the first time that, in blood as in milk, neutrophils are a heterogeneous population and encompass at least two subsets distinguishable with their expression of MHC-II. We observed higher bactericidal capacities of milk MHC-IIpos neutrophils as compared to their classical counterparts, due to a higher production of ROS and phagocytosis ability. MHC-IIpos neutrophils are enriched in milk during a subclinical mastitis as compared to blood. Moreover, we observed a positive and highly significant correlation between MHC-IIpos neutrophils and T lymphocytes present in milk during subclinical mastitis. To conclude, our study could open the way to the discovery of new biomarkers of mastitis inflammation.

immunology↗