Thèse la Dynamique Calcique Dépendante d'Orai1 Nouvelle Cible Prometteuse pour Traiter l'Insuffisance Cardiaque Gauche H/F - Doctorat.Gouv.Fr

Établissement : Université Paris-Saclay GS Santé et médicaments École doctorale : Innovation thérapeutique : du fondamental à l'appliqué Laboratoire de recherche : Signalisation et physiopathologie cardiovasculaire Direction de la thèse : Jessica SABOURIN ORCID 0000000229808455 Début de la thèse : 2026-10-01 Date limite de candidature : 2026-04-28T23:59:59 L'insuffisance cardiaque (IC) est un fléau sanitaire et économique croissant dans le monde, soulignant le besoin de développer des thérapies plus efficaces et complémentaires. Les traitements actuels visent à soulager les symptômes plutôt que les anomalies moléculaires. Une approche prometteuse consiste à contrer les effets indésirables d'une dérégulation de l'homéostasie calcique cellulaire impliquée dans la pathogenèse de l'IC. Orai1, en tant qu'archétype des canaux calciques SOCs (store-operated Ca2+ channels), pourrait constituer une nouvelle cible thérapeutique attractive. En effet, nous avons fourni la preuve de concept selon laquelle Orai1 est un nouveau candidat thérapeutique potentiel pour l'IC gauche et droite. Le projet vise donc à établir des bases précliniques solides grâce à un suivi approfondi dans différents modèles expérimentaux d'IC à fraction d'éjection réduite ou préservée (HFrEF et HFpEF) afin de confirmer la pertinence de l'inhibition d'Orai1 en tant que thérapie innovante. La nature révolutionnaire du projet repose sur la possibilité de développer une nouvelle thérapie ciblant les canaux ioniques afin de lutter contre ce syndrome cardiaque dévastateur. Cardiovascular diseases (CVDs) are the number one killer of men and women worldwide. Although CVDs have declined over the last 40 years, there has been a shift in the occurrence of CVD cases towards younger age-groups. Among CVDs, heart failure (HF) is an increasingly prevalent multifactorial syndrome in which abnormal cardiac function leads to inadequate supply of blood to tissues and organs for their metabolic demands. As a leading cardiovascular cause of death in worldwide, HF has been singled out as an epidemic and is a staggering clinical and public health problem associated with significant mortality and morbidity rates, particularly in patients aged 65 years and older. The burden is increasing over time. Recent estimates suggest that there are 64.3 million patients worldwide with HF and more than a million and a half people in France (epidemiological data from Fédération Française de Cardiologie). Despite significant therapeutic advances, mortality rates remain high, with almost half of patients with HF dying within 5 years of diagnosis. In the developed countries, coronary artery diseases and systemic arterial hypertension are the predominant etiologies. Traditionally, left HF has been divided into distinct phenotypes based on the left ventricular (LV) ejection fraction (EF) measurement: HF with reduced EF (HFrEF 40%); HF with mildly reduced EF (HFmrEF 41-49%), and HF with preserved EF (HFpEF 50%)[1]. HFpEF, the most common form of HF, differs from HFrEF in that HFpEF patients are older and predominantly women. The diagnosis of HFpEF is complex because of the multiple associated cardiac and non-cardiac comorbidities, such as obesity, diabetes mellitus, and chronic obstructive pulmonary disease (COPD).[2]
As a multifactorial clinical syndrome, HF still represents an epidemic threat, highlighting the need to further understand the cellular and molecular mechanisms involved in the pathogenesis of HF to develop innovative therapeutic strategies.
Ca2+ mishandling as a central cause of contractile dysfunction and arrhythmias is a hallmark of HF and has been the subject of a large body of research to understand how cardiac stress alters Ca2+ homeostasis in cardiomyocytes. Indeed, Ca2+ is a universal signaling ion that is essential for most cardiomyocyte functions, ranging from excitation-contraction coupling to the regulation of gene expression and energy metabolism. This is orchestrated by ion channels, transporters, and exchangers working in synergy with Ca2+ binding proteins. Despite decades of research, the source of Ca2+ that induces these alterations in HF remains incompletely understood. It is therefore essential to elucidate the mechanisms that maintain intracellular Ca2+ homeostasis.
Functional alterations in plasmalemmal Ca2+ channels, notably store-operated channels (SOCs), may be a cornerstone of HF. Although several studies suggested that the voltage-independent cationic transient receptor potential canonical 1-7 (TRPC) channels might be the candidates for SOCs, the Orai1 channels, voltage-independent selective Ca2+ channels recapitulate the archetypical SOC current termed Ca2+ release-activated Ca2+ (CRAC) channel. The stromal interaction molecule (STIM) as the endo/sarcoplasmic reticulum (ER/SR) Ca2+ sensor communicates information of the stores Ca2+ content to the SOCs. Upon ER Ca2+ depletion, STIMs oligomerize and translocate to ER/PM junctions, where they interact with and activate Orai1, thereby inducing SOCE. The latter subsequently allows intracellular Ca2+ stores to refill and is instrumental in many cellular and physiological functions. The importance of SOCE through the Orai1 channel activated by STIM1 has been highlighted in immune cells, in which inheritable autosomal recessive mutations of Orai1 have been linked to devastating immunodeficiency diseases termed CRAC channelopathy[3].
Orai1/STIM1-mediated SOCE contributes to Ca2+ influx in cardiac cells, thereby regulating diastolic and SR Ca2+ homeostasis, which is crucial for postnatal cardiac growth.[4-6] Although its activity appears less prominent at the adult stage, Orai1 regulates the sarcomere organization and activity, the electrical-mechanical coupling, and pacemaker function. Importantly, convergent experimental results have identified Orai1-dependent SOCE as a critical mediator of Ca2+ signaling and cardiac remodeling in the context of HF and arrhythmias.[4] Notably, we showed that Orai1 is upregulated during the development of LHF and RHF in animal models.[7-9] Thus, the Orai1 Ca2+ channel is a new Ca2+ actor involved in the pathophysiology of HF. Moreover, we recently provided proof-of-concept evidence that the Orai1 Ca2+ channel may be a new therapeutic candidate for LHF secondary to pressure overload and for RHF due to pulmonary hypertension.[7-9] However, Orai1 blockers used in these studies are not suitable in the clinic. Critical next steps include extensive follow-up to confirm the benefit of Orai1 inhibition across preclinical models of HF (HFrEF and HFpEF) with other etiologies and with cardiac and non-cardiac comorbidities, taking into account sex-related disparities.
Through multidisciplinary approaches that conduct synergistic, state-of-the-art research in ion channel pharmacology and cardiac function, the global objective is to lay strong preclinical foundations for a potential Orai1 therapy, bringing a new therapeutic arsenal to patient benefit and to mechanistically understand the Orai1-dependent Ca2+ signalling associated with HF.
This project will take advantage of a unique, selective, efficient, tolerable, and safe Orai1 inhibitor used in human clinical trials (for acute pancreatitis, acute kidney failure, and COVID-19 pneumonia): CM4620 developed, and CM5480 being developed for human clinical trials, thanks to the strong partnership with the American CRAC channel platform company (CalciMedica®). We will use different experimental animal models of left HF (LHF).
Translational relevance of Orai1 inhibition in preclinical models of LHF
As mentioned before, HF is secondary to many diseases, like coronary artery disease and systemic arterial hypertension, as predominant etiologies. Thus, identification of Orai1 inhibition as an HF therapeutic target requires validation in multiple relevant preclinical models. We will extend our previous study on the beneficial effects of Orai1 inhibition, using clinically available Orai1 inhibitors from Calcimedica® for chronic inflammatory diseases, in several preclinical HF animal models with different etiologies or comorbidities. Of interest, sex differences will also be explored.Task1: To test selective Orai1 inhibition on HFrEF models
Acute and chronic LHF with reduced ejection fraction (HFrEF) will be induced by myocardial infarction (MI) in mice with permanent ligation of the left main descending coronary artery (LCA) for 1 or 3 weeks. Age-matched sham-operated rats will be submitted to the same surgery except for the LCA ligation.

Task2: To test selective Orai1 inhibition on HFpEF models
A double-hit model of HFpEF (metabolic syndrome+hemodynamic stress) will be used to mimic comorbidities in patients: db/db mice that develop obesity and type II diabetes (at 12 weeks old) that undergo a 4-week chronic infusion of aldosterone. The inclusion criteria for HFpEF are HF symptoms, concentric hypertrophy, LV diastolic dysfunction, and inflammation/fibrosis. The exclusion criteria are systolic dysfunction with a reduced EF.

Task 1 &2: Via a curative strategy, after LHF induction, the mice will be randomly and blindly assigned to the delivery of Orai1 inhibitor (CM5480 (10 mg/kg)) or vehicle via daily oral administration, and will be followed weekly by echocardiography. In vivo functional exploration of the animals will be performed in all groups before and during hypertrophic stresses using the Vevo 3100 echocardiography system for systolic and diastolic function (M-Mode, Strain, Doppler, and pressure-volume (PV) loop) and ECG telemetry for cardiac electrical function. At the sacrifice, anatomical parameters (heart weight-to-body weight (HW/BW) or tibia length (HW/TL) ratios) and cardiac morphology (myocyte size and fibrosis by histological analysis) will be assessed. Transcriptomic, proteomic, and bioinformatic analyses by RNA sequencing and mass spectrometry approaches will document changes in the transcriptome comprising the expression of classical hypertrophic markers genes (ANP, BNP, skeletal -actin), as well as fibrotic genes (type I and III collagen), apoptotic markers (caspase-3 and -9, cytochrome c, BAD-BAX-Bcl-2), capillary density markers (CD31) and Orai, TRPCs and STIM isoforms in ventricle tissues.

In vitro functional exploration of left ventricular (LV) tissue and isolated LV cardiomyocytes from sham and LHF animals will be conducted.
1) Molecular analysis by qRT-PCR and western-blot will analyze the abundance of Orai1 mRNA and protein.
2) Orai1-mediated SOCE and ISOC current using conventional microscopy with Fura-2 and the whole-cell configuration of the patch-clamp will be investigated.
3) Localization of Orai and STIM isoforms and all molecular interactions will be studied by immunocyto- and histochemistry, co-immunoprecipitation, and proximity ligation duolink assay.
4) Underlying Orai1-dependent pro-hypertrophic signaling pathways will be characterized (Calcineurin/NFAT, ERK1/2 or CaMKII).
5) The cell contraction (fractional shortening), amplitude and kinetics of [Ca2+]i transients, spontaneous Ca2+ release events (sparks and waves), sarcoplasmic Ca2+ load in Fluo-4 loaded and electrically-paced cardiomyocytes using a laser scanning confocal microscope will be measured.
6) The electrophysiological properties of the action potential recorded by patch-clamp from ventricular cardiomyocytes will be also examined.
7) The occurrence of pro-arrhythmic spontaneous Ca2+ waves and delayed afterdepolarization events will be quantified.

Le candidat doit pratiquer l'expérimentation animale (microchirurgie) et, si possible, avoir des connaissances sur la physiologie et la pathologie cardiaque ainsi que sur les canaux ioniques. La connaissance et la pratique des techniques d'électrophysiologie, d'imagerie calcique, de biologie moléculaire et cellulaire ainsi que de biochimie sont également recommandées.