Pulmonary arterial hypertension (PAH) is a rare, devastating disease with no cure. Current treatment consists of a cocktail of vasodilators which relieve symptoms of PAH but do not treat the cause. Thus, there is a need for novel drugs that target the underlying pathological causes of PAH. PAH is a multi-factorial, but one key contributor is the pro-inflammatory cytokine IL-6 which stimulates pro-inflammatory and pro-angiogenic signalling mediated by the JAK/STAT pathway. One way in which IL-6 signalling via JAK/STAT is inhibited is via SOCS3 in a type of negative feedback loop whereby IL-6 induces transcription of SOCS3, which then attenuates further JAK/STAT signalling. SOCS3 can also be induced by cAMP. This is interesting as prostanoids, a type of drug used in the treatment of PAH due to its vasodilator effects and the only type to show any efficacy improving the life expectancy of PAH patients, acts by mobilising cAMP. Thus, prostanoid stimulation of cAMP could potentially limit IL-6 signalling via the induction of SOCS3. This is a novel mechanism of prostanoids which has not previously been considered. This study investigated the capability of prostanoids to limit the pro-inflammatory/pro-angiogenic effects of IL-6 that enable PAH to develop. Initial experiments confirmed that vascular endothelial cells responded to prostanoids which increased SOCS3 and limited IL-6 signalling activity. Further experiments utilising SOCS3 KO endothelial cell models demonstrated prostanoid inhibition of IL-6 signalling was due in part to SOCS3. In conclusion, this project has confirmed that prostanoids do limit the pro-inflammatory effects induced by IL-6 and that this is in part due to SOCS3. Although the exact mechanism is yet to be discovered, it will be beneficial in the treatment of PAH as it provides currently unexploited drug targets which can be considered for future PAH therapies. / British Heart Foundation

Pulmonary Arterial Hypertension (PAH) is a rare incurable condition affecting both the cardiac and respiratory systems. Patients living with PAH face the burden of both intensive medication regimens and debilitating disease symptoms. This study’s primary aim was to identify patients’ medication-taking behaviours and beliefs using a framework derived from the extended health belief model (EHBM), and to use this information to deliver personalised interventions to improve medication-taking behaviours. A mixed-methodology longitudinal study design recorded patients’ parameters over a 12-month period. Thirteen participants from Northern Ireland completed the study. The results showed that the level of high-adherence to PAH medicines, as assessed using the MARS questionnaire was 80%, but this value differed when assessed via pill counting and interview data. There was a trend to improvement in observed and predicted medication adherence over the study duration. Participants’ beliefs showed a non-statistical increase in the specific-necessity beliefs and a reduction in general-overuse belief. This study added to the EHBM new constructs of trust and support in being able to better predict nonadherent behaviours. Key medication-taking themes were self-confidence, perceived ranking of medicines, uncertainty and knowledge. This study developed important learning that can be applied to future research on behavioural health studies. / Heart Trust Fund; Actelion Pharmaceuticals

Background: Fingolimod is the first oral immunomodulatory therapy approved for highly active relapsing remitting multiple sclerosis. Based on the distribution pattern of fingolimod interacting sphingosine-1-phosphat receptors in organism including immune system and cardiovascular system clinical monitoring of patients and evaluation of adverse events are recommended. Despite extensive data on cardiovascular safety, experience with fingolimod in patients with concomitant cardiological disease, especially within the pulmonary circulation, is rare. Case presentation: We report the case of a 46-year-old woman presented with relapsing remitting multiple sclerosis and severe idiopathic pulmonary arterial hypertension. Fingolimod was initiated because of disease activity of multiple sclerosis with two relapses and gadolinium-enhancing lesions in MRI. The patient demonstrated stable disease course of idiopathic pulmonary arterial hypertension when fingolimod was started. Fingolimod therapy did not alter or even worsen the pulmonary or cardiovascular conditions during first dose application as well as follow up of nine months. Conclusion: In this report, we present the first case of fingolimod treatment in a patient with highly active multiple sclerosis and severe idiopathic pulmonary arterial hypertension. We suggest an interdisciplinary approach with detailed cardiopulmonary monitoring for safety in such patients.

A Hipertensão Arterial Pulmonar (HAP) é uma patologia grave e incapacitante, caracterizada por modificações bioquímicas, morfofuncionais e estruturais que gera aumento progressivo da resistência vascular pulmonar (RVP), da pressão arterial pulmonar média (PAPm) e alterações no ventrículo direito (VD) que culminam com a insuficiência cardíaca direita (ICD), seguida de óbito. O efeito do exercício físico aeróbio sobre o estresse oxidativo e sobre o metabolismo do óxido nítrico (NO) e endotelina-1 (ET-1), no tecido pulmonar é desconhecido. Assim, este estudo teve como objetivo verificar a influência de um protocolo de exercício físico sobre o estresse oxidativo pulmonar e o seu papel modulador no metabolismo do NO e da ET-1 em ratos com HAP. Para isso, foram utilizados 28 ratos machos Wistar, divididos em quatro grupos experimentais (5-7 animais): CS (controle sedentário), MS (monocrotalina sedentário), CT (controle treinado) e MT (monocrotalina treinado). Os animais dos grupos CT e MT participaram de duas semanas de pré-treinamento em esteira adaptada para ratos. No final desse período, os animais dos grupos MS e MT receberam dose única (60 mg/Kg) intraperitoneal de monocrotalina (MCT), enquanto que os animais dos grupos CS e CT, receberam salina na mesma dose. Em seguida, os animais dos grupos CT e MT foram submetidos a três semanas de treinamento aeróbio, com frequência de cinco vezes por semana e utilização de 60% do VO2 máximo. Análises ecocardiográficas foram realizadas 24 horas após a última sessão de exercício físico aeróbio. Os parâmetros de tempo de aceleração/tempo de ejeção do fluxo pela artéria pulmonar (TAC/TEJ), volume sistólico (VS), débito cardíaco (DC), excursão sistólica do plano do anel da tricúspede (TAPSE), fração de enchimento (FEC), mudança da área fracional (FAC), índice de performance do miocárdio (IPM) e velocidade de enchimento rápido/lento do ventrículo direito (E/A) foram analisados e, em seguida, os ratos foram mortos por sobrecarga anestésica, confirmada por deslocamento cervical. Seus órgãos (coração, fígado e pulmão) foram coletados para realização posterior das análises. A massa do coração foi utilizada para analisar a hipertrofia cardíaca (HC) e a massa do fígado, para analisar a congestão hepática. O lobo direito do pulmão foi separado para realização das análises bioquímicas e moleculares e, o lobo esquerdo para realização das análises imuno-histoquímicas. A administração de MCT promoveu hipertrofia do VD, redução dos parâmetros TAC/TEJ, DC, VS e TAPSE, sendo que o exercício físico aeróbio acentuou essa redução nas análises do TAC/TEJ e DC. Nos demais parâmetros ecocardiográficos e na congestão hepática, não encontramos diferenças significativas entre os grupos experimentais. Nos resultados bioquímicos encontramos aumento da concentração do radical superóxido (O2.-) nos grupos MCT, principalmente no grupo MT, inalteração da concentração de peróxido de hidrogênio (H2O2) e da atividade da enzima NADPH Oxidase (NOX). Em relação às enzimas antioxidantes, encontramos redução da atividade da superóxido dismutase (SOD) nos animais que participaram do protocolo de treinamento físico e inalteração da sua expressão por Western Blot. A catalase (CAT), por sua vez, teve sua atividade reduzida nos animais que receberam MCT e também na sua expressão no grupo MS quando comparado ao CS. Já o grupo MT teve aumento da expressão da CAT quando comparado ao grupo MS.Em relação à atividade da enzima glutationa peroxidase (GPx) houve aumento nos grupos que receberam a MCT, principalmente no grupo MT. Encontramos ainda, redução nos danos oxidativos a proteínas e lipídios nos grupos que receberam MCT. O metabolismo do NO também foi afetado, uma vez que evidenciamos redução da atividade da óxido nítrico sintase (NOS) nos animais que participaram do protocolo de treinamento aeróbio e também naqueles que receberam a MCT. A concentração de nitritos totais e da expressão de enzima óxido nítrico sintase endotelial (eNOS) não apresentaram diferenças significativas entre os diferentes grupos experimentais. Houve aumento na marcação da enzima óxido nítrico sintase induzível (iNOS) e na nitrotirosina em arteríolas pulmonares dos animais que receberam MCT, sendo mais acentuada nos animais do grupo MT. Ainda, não encontramos alterações significativas na expressão do receptor A (ET-A) da ET-1, mas sim, redução da expressão do receptor B (ET-B). Em conclusão, o modelo experimental de HAP induzido por MCT, foi reproduzido nesse estudo e a realização do protocolo de treinamento físico mostrou-se incapaz de atenuar e/ou reverter as alterações no metabolismo do NO e da ET-1, bem como o aumento do estresse oxidativo causados pela droga, no tecido pulmonar. Na verdade, em muitas análises, foram encontrados efeitos prejudiciais do exercício físico, potencializando a progressão e severidade da doença. / Pulmonary arterial hypertension (PAH) is a serious and disabling condition characterized by biochemical, morphological, functional and structural alterations, which generate a progressive increase in pulmonary vascular resistance (PVR) and in mean pulmonary arterial pressure (mPAP), together with changes in right ventricle (RV). This scenario leads to right heart failure, followed by death. The effects of aerobic exercise on oxidative stress, metabolism of nitric oxide (NO) and endothelin-1 (ET-1) in lung tissue are unknown. This study aimed to verify the influence of a physical exercise protocol on pulmonary oxidative stress and also the modulatory role of exercise in the metabolism of NO and ET-1 in rats with PAH. Then, 28 male Wistar rats were used, divided into four groups (5-7 animals/group): SC (sedentary control), SM (sedentary monocrotaline), TC (trained control), and TM (trained monocrotaline). Animals of TC and TM groups participated in two weeks of pre-training on a treadmill adapted to rats. At the end of this period, the animals of TM and SM groups received a single injection (60 mg/kg, i.p.) of monocrotaline (MCT), whereas animals of SC and TC groups received saline at the same volume. Then, the animals of TC and TM groups underwent three weeks of aerobic training, five times a week, using 60% of maximum VO2. Echocardiographic analysis was performed 24 hours after the last aerobic exercise session. The parameters of acceleration /ejection time of pulmonary artery flow (AT/ET), stroke volume (SV), cardiac output (CO), tricuspid annular plane systolic excursion (TAPSE), filling fraction (FF), fractional area change (FAC), myocardial performance index (MPI) and fast/slow rate of right ventricular filling (E/A ratio) were analyzed, and then rats were euthanized with anesthetic overload, confirmed by cervical dislocation. Heart, liver and lungs were collected to perform later analysis. Heart mass was used to analyze cardiac hypertrophy (CH), and liver mass to analyze hepatic congestion. The right lobe of lung was separated to biochemical and molecular measurements and the left lobe to perform immunohistochemical analysis. The administration of MCT promoted RV hypertrophy, and reduced AT/ET, CO, SV, and TAPSE. However, aerobic exercised groups had an accentuated reduction in the analysis of the AT/ET and CO. We found no significant differences between the experimental groups in other echocardiographic parameters and liver congestion analysis. Biochemical results showed increased concentrations of superoxide radical (O2.-) in the MCT group, especially in the TM group, with no changes in hydrogen peroxide concentration (H2O2) and NADPH oxidase enzyme activity (NOX). Regarding the antioxidant enzymes, we found reduced activity of superoxide dismutase (SOD) in animals that underwent physical training protocol, with no changes in expression by Western blot. Catalase (CAT), in turn, reduced its activity in animals that received MCT and in its expression in the SM group, when compared to SC. However, animals in TM group had increased expression of CAT when compared to SM group. Regarding the activity of glutathione peroxidase enzyme (GPx) there was an increase in the groups that received MCT, mainly in the TM group. The groups that received MCT presented reduction in oxidative damage to proteins and lipids. NO metabolism was also affected, once reduction in the activity of nitric oxide synthase (NOS) was observed in animals that participated in the aerobic training protocol and also in those who received MCT. The concentration of total nitrites and the endothelial nitric oxide synthase enzyme (eNOS) expression showed no significant differences between the different experimental groups. There was an increase in the immunohistochemical analysis of the inducible nitric oxide synthase enzyme (iNOS) and nitrotyrosine in pulmonary arterioles of animals that received MCT, being more pronounced in the animals of TM group. Although no significant changes in the A receptor of ET-1 (ET-A) expression were identified, it was detected a decrease in the B receptor of ET-1 (ETB) expression. In conclusion, the experimental model of PAH induced by MCT was reproduced in this study and physical training protocol execution proved to be unable to mitigate and/or reverse changes in the metabolism of NO and ET-1, as well as the increased oxidative stress caused by the drug in lung tissue. In fact, in many analyzes, harmful effects of exercise were found, contributing to progression and severity of the disease.

L’hypertension artérielle pulmonaire (HTAP) est une maladie caractérisée par une obstruction des artères pulmonaires de petit calibre aboutissant, à terme, à une défaillance cardiaque droite. L’évolution de cette maladie est parfois émaillée d’épisodes de dégradation de l’état fonctionnel des patients, nécessitant une admission en unité de soins intensifs pour surveillance cardioscopique et administration de médicaments inotropes et/ou vasopresseurs. Peu d’éléments permettent à ce jour de guider les praticiens dans la prise en charge de ces patients et la physiopathologie de ces épisodes est assez peu connue.Dans un premier temps, nous avons retrouvé une mortalité de 41% en réanimation et testé certains facteurs pronostiques cliniques et biologiques simples issus de la pratique quotidienne dans une cohorte propective de patients avec une prise en charge standardisée. Nous avons identifié comme facteurs pronostiques la pression artérielle systémique, la natrémie, la créatininémie, la valeur de la C-reactive Proteine. Nous avons retrouvé une influence de ces épisodes sur l’évolution à moyen terme de ces épisodes. Dans un second temps nous avons testé la valeur pronostique des indices temporels de fonctionnement du ventricule gauche, suggérée par les études en imagerie par résonnance magnétique. Nous avons utilisé pour cela la tonométrie d’aplanation, outil original et non invasif. Nous avons retrouvé que la valeur de la durée d’éjection du ventricule gauche est associée au pronostic. Dans une troisième partie nous avons mesuré les conséquences et la valeur pronostique de l’épuration extra rénale en contexte d’ insuffisance rénale menaçante chez ces patients. Dans une étude rétrospective, nous avons observé 68 séances d’épuration extra-rénale continue ou discontinue. Ces séances se sont compliquées d’hypotension artérielle dans environ 50% des cas. La très haute mortalité en réanimation et à 3 mois, respectivement de 47% et 73%, soulève la question de la place de l’assistance circulatoire et de la transplantation urgente chez ces patients. Ces données soulignent la sévérité à court terme des épisodes aigus d’aggravation chez les patients porteurs d’HTAP. De plus amples données sont nécessaires pour améliorer la prise en charge de ces patients et organiser dans le meilleur délai la mise en place de thérapeutiques exceptionnelles comme l’assistance circulatoire et la transplantation pulmonaire ou cardio-pulmonaire. / Pulmonary arterial hypertension ( PAH) is a disease characterized by an obstruction of the small pulmonary arteries leading ultimately to right heart failure. The evolution of this disease is sometimes punctuated by episodes of deterioration of the functional status of patients requiring admission to intensive care unit for monitoring and administration of inotropic drugs and / or vasopressors. Few evidence to date are available to guide physicians in the care of these patients and the pathophysiology of these episodes is still elusive.In a first part, we found a mortality of 41% in the intensive care unit (ICU) and tested some simple clinical and biological prognostic factors from the daily practice in a prospective cohort of patients with a standardized management. We have identified systemic blood pressure, serum sodium, serum creatinine, serum C -reactive Protein as prognostic factors. We found an influence of these events on the medium-term evolution of the patients.In a second step we tested the prognostic value of time derived indices of left ventricular function, variables suggested by magnetic resonance imaging studies. In this purpose, we used aplanation tonometry, an original and non-invasive tool. We found that the value of the left ventricular ejection time was associated with in ICU prognosis.In the third part we measured the impact and prognostic value of renal replacement therapy in case of threatening kidney failure in these patients. In a retrospective study, we observed 68 sessions of renal replacement therapy, continuous hemofiltration and intermittent hemodialysis. These sessions were complicated by hypotension in 50 % of cases. The high in ICU mortality and three months mortilty, respectively 47% and 73%, raises the question of the role of extracorporeal life support and urgent transplantation in these patients.These data underscore the severity of acute worsening in patients with PAH. More data are needed to improve the management of these patients and determine the best timing of exceptional treatment such as circulatory support and pulmonary or cardiopulmonary transplantation.

Pulmonary arterial hypertension (PAH) is a group of diseases characterized by avascular obstruction leading to a progressive increase of the resistances in the pulmonary blood flow. The recent progress in the understanding of mechanisms at the origin of this disease underlines the role of extrapulmonary cells, such as circulating stem cells and bone marrow-derived progenitor cells in vascular remodeling and in PAH development. In this thesis we have shown implication of the progenitor cells and chemotactic axis in the vascular remodeling in human and experimental PAH. This work could help to develop new therapies allowing more specific and more effective treatments leading to improved survival of PAH patients. / L’hypertension artérielle pulmonaire (HTAP) est un groupe de maladies qui se caractérise par une obstruction vasculaire conduisant à une augmentation progressive des résistances à l’écoulement sanguin. Le remodelage vasculaire qui implique toutes les couches de la paroi du vaisseau est considéré comme un élément clé dans la pathogenèse de l'HTAP. Les progrès récents dans la compréhension des mécanismes à l'origine de cette maladie soulignent le rôle de cellules extrapulmonaires, telles que des cellules souches circulantes et des progéniteurs dérivés de la moelle osseuse, dans le remodelage vasculaire et dans le développement de l’HTAP. Les thérapeutiques ciblées sur la dysfonction endothéliale ne permettent pas à l'heure actuelle de guérir cette maladie, il est donc nécessaire d’identifier d'autres mécanismes physiopathologiques permettant de développer de nouvelles stratégies thérapeutiques. C’est pourquoi nous avons exploré l’implication des cellules progénitrices et des signaux chimiotactiques dans le remodelage vasculaire au cours de l’HTAP humaine et expérimentale. Nous avons mis en évidence un recrutement de cellules c-kit+ (incluant des progéniteurs et des mastocytes) ainsi que l’expansion de vasa vasorum dans les poumons des patients atteints d’HTAP. Grâce à l’utilisation du modèle expérimentale d’HTAP induit par l’hypoxie chez la souris, nous avons montré le rôle central de la chimiokine CXCL12 et de ses deux récepteurs CXCR4 et CXCR7 dans le recrutement des progéniteurs c-kit+. Le traitement combiné par les antagonistes AMD3100 et CCX771, grâce à leurs actions synergiques, inhibe le remodelage vasculaire pulmonaire, l’hypertrophie cardiaque droite, ainsi que le recrutement des progéniteurs c-kit+, induits par l’hypoxie. Par ailleurs, le blocage de c-kit par l’imatinib améliore également les paramètres d’hémodynamique et diminue le recrutement périvasculaire des cellules c-kit+, probablement en inhibant leurs expansion dans la moelle osseuse. Nous avons également mis en évidence une altération d’une population de progéniteurs mésenchymateux d’origine hématopoïétique, appelés fibrocytes, dans le sang des patients souffrant d’HTAP.Ce travail pourrait contribuer à développer des actions thérapeutiques ciblées permettant la mise en place de traitements à la fois plus spécifiques et plus efficaces susceptibles d’améliorer la survie des patients HTAP.

L’hypertension artérielle pulmonaire (HTAP) est une maladie rare caractérisée par un remodelage des artères pré-capillaires pulmonaires lié à une dysfonction des cellules endothéliales (CE) conduisant à une prolifération cellulaire vasculaire. Cette prolifération conduit à une obstruction progressive du lit artériel et à l’augmentation des résistances vasculaires. L’hypertension pulmonaire (HTP) qui en résulte provoque une hypertrophie du ventricule droit aboutissant à la défaillance cardiaque et à la mort du patient. Actuellement le seul recours possible est la transplantation pulmonaire. Les mécanismes responsables de ce remodelage vasculaire sont encore peu connus. Les premiers travaux présentés mettent en évidence in situ un nouveau mécanisme impliqué dans ce remodelage. Au cours de ce processus, appelé transition endothélio-mésenchymateuse (EndoMT), les CE se désolidarisent de l’endothélium vasculaire et envahissent l’espace sous endothélial. Ce mécanisme s’accompagne d’une perte progressive du phénotype endothélial et du gain d’un phénotype mésenchymateux invasif et proliférant. L’EndoMT est impliquée dans la formation des lésions intimale et plexiforme. L’inhibition de l’EndoMT a donné des résultats prometteurs dans des modèles in vivo et in vitro d’HTAP. Cette découverte ouvre une nouvelle voie pour le traitement de la maladie. Dans un second projet nous avons confirmé le lien suspecté entre les chimiothérapies et la maladie veino-occlusive pulmonaire (MVOP), une forme d’HTP touchant les veines et veinules pulmonaires. L’étude des cas rapportés de MVOP consécutive à une chimiothérapie indiquent une forte incidence des agents alkylants, notamment du cyclophosphamide (CP), sur le développement de la MVOP. L’exposition au CP a provoqué une HTP associée à des lésions post-capillaires chez 3 espèces animales (souris, rat et lapin) confirmant ce lien. Nous espérons que nos travaux aboutiront à une plus grande vigilance concernant cette complication rare et sévère de l’exposition aux agents alkylants. De plus, nos travaux in vivo ont permis de mettre au point le tout premier modèle expérimental de MVOP. Au cours du dernier projet présenté, nous avons démontré que le nebivolol, un β-bloquant (β1 antagoniste β2 et β3 agoniste ayant un effet vasodilatateur) de 3ème génération, permettait d’améliorer les paramètres hémodynamiques et morphologiques, ainsi que la dysfonction endothéliale, liés à l’HTAP dans les modèles in vivo et in vitro. Ces travaux suggèrent la nécessité de réévaluer les recommandations actuelles, basées sur l’étude de β-bloquants non spécifiques de 1ère génération, qui proscrivent leur utilisation dans l’HTAP. En revisitant plusieurs aspects du remodelage vasculaire, ma thèse contribue ainsi à l’innovation thérapeutique dans l’HTAP. / Pulmonary arterial hypertension (PAH) is a rare disease characterized by a severe modeling of the precapillary pulmonary arteries related to an endothelial cells (EC) dysfunction leading to vascular cell proliferation. This proliferation leads to a progressive obstruction of the distal pulmonary arterial bed and increases pulmonary vascular resistance. The resulting pulmonary hypertension (PH) leads to a progressive right ventricular hypertrophy, and subsequent right heart failure and death unless the patient receives a lung transplantation. The primary mechanisms that trigger the vascular remodeling remain poorly understood. In the first presented study, we discovered in situ a new pathological process involved in vascular remodeling in PAH. During this process called endothelial-to-mesenchymal transition (EndoMT), the EC lose their cell-junctions to leave the endothelium and invade the subendothelial space. This phenomenon involves the progressive loss of the endothelial phenotype and the gain of a pro-invasive and pro-proliferative mesenchymal phenotype. This process is implicated in the pathogenesis of intimal and plexiform lesions. The inhibition of EndoMT gave promising results in experimental in vivo and in vitro models of PAH. This finding may have therapeutic implications for PAH. During a second project presented, we confirmed the suspected potential link between chemotherapies and the pulmonary veino-occlusive disease (PVOD). PVOD is a PH with vein and venular lesions. The systematic review of cases of chemotherapy induced PVOD cases suggests that alkylating agents, and cyclophosphamide (CP) in particular, represents a risk factor for the development of PVOD. In experimental models, CP exposure induced PH in three different animal models (mouse, rat, and rabbit). We hope that our findings will allow achieving greater vigilance against this rare and severe complication after alkylating agents exposure. Moreover our in vivo results lead to the development of the 1st experimental model of PVOD. In the last part, we demonstrated that nebivolol, a 3rd generation β-blocker (β1 antagonist, β2 & β3 agonist with vasodilator effect), improved PAH in in vitro and in vivo models. The actual guidelines, based on results obtained with non-specific 1st generation β-blockers, advice against the use of β-blockers in PAH. Our results suggest that the recommendation against β-blockers might be reevaluated taking into consideration their generation and specificity. By revisiting many aspects of vascular remodeling, my thesis contributes to therapeutic innovation in PAH.

Mutations in the gene encoding the bone morphogenetic protein type 2 receptor (BMPR2) are the most common genetic cause of heritable pulmonary arterial hypertension (PAH). However, given the reduced penetrance of BMPR2 mutations in affected families, a major outstanding question is the identity of additional factors or pathways that are responsible for the manifestation of clinical disease. Furthermore, limited human tissue is available for study and usually only from patients with end-stage disease, making it difficult to understand how PAH is established and progresses. Alternative human models of PAH are therefore required. This thesis describes the characterisation of the first human iPSC-derived smooth muscle cell (iPSC-SMC) model of PAH and elucidates the role of BMPR2 deficiency in establishing PAH-associated phenotypes in iPSC-derived SMCs. To achieve this, I used CRISPR-Cas9 gene editing to generate wild-type and BMPR2+/- iPSC lines with isogenic backgrounds which were subsequently differentiated into lineage-specific iPSC-SMCs that displayed a gene expression profile and responses to BMP signalling akin to those present in distal pulmonary artery smooth muscle cells (PASMCs). Using these cells, I found that the introduction of a single BMPR2 mutation in iPSC-SMCs was sufficient to recapitulate the pro-proliferative and anti-apoptotic phenotype of patient-derived BMPR2+/- PASMCs. However, acquisition of the mitochondrial hyperpolarisation phenotype was enhanced by inflammatory signalling and required an interaction between BMPR2 mutations and environmental stimuli provided by exposure to serum over time. Furthermore, I showed that BMPR2+/- iPSC-SMCs had an altered differentiation state and were less contractile compared to wild-type iPSC-SMCs, phenotypes which have not been observed previously in PAH-derived PASMCs. Finally, RNA sequencing analysis identified genes that were differentially expressed between wild-type and BMPR2+/- iPSC-SMCs and may hence provide further insights into PAH pathobiology. The iPSC-SMC model described in this study will be useful for identifying additional factors involved in disease penetrance and for validating therapeutic approaches that target BMPR2.

La décompensation cardiaque se manifeste par une symptomatologie de dyspnée et de fatigue, et par une diminution de l’aptitude aérobie. La décompensation cardiaque peut être globale ou gauche (DCG), ou droite comme dans le cas de l’hypertension artérielle pulmonaire (HTAP). Les mesures fonctionnelles de repos (fonction ventriculaire gauche ou pression artérielle pulmonaire moyenne) sont peu corrélées à l’aptitude aérobie, qui est cependant un élément important de la mise au point et du suivi clinique des patients atteints de DCG ou d’HTAP. L’aptitude aérobie est évaluée par une ergospirométrie. Réalisée sur cycloergomètre ou sur tapis roulant elle mesure l’évolution des variables ventilatoires (ventilation, consommation en oxygène et production de CO2), la fréquence cardiaque et la tension artérielle lors d’un effort à intensité croissante jusqu’à l’effort maximal. Elle apporte une analyse fine du comportement à l’exercice des patients, de la cause de la limitation à l’effort et permet la détermination précise de la consommation d’oxygène maximale (VO2max). Plus simple que l’ergospirométrie, le test de marche de 6 minutes (TDM6) mesure la distance maximale parcourue en marchant 6 minutes. Il évalue la réponse intégrée des systèmes cardiovasculaire, respiratoire et musculaire à l’effort, mais, contrairement à l’ergospirométrie, il ne permet pas d’identifier les facteurs déterminants l’aptitude aérobie. Le TDM6 est corrélé de façon significative, mais non étroite, à la VO2 max et à la classe fonctionnelle telle qu’évaluée par l’échelle à 4 points de la New York Heart Association. Les travaux réunis dans le présent travail ont eu pour but de contribuer à l’étude de la pathophysiologie de l’aptitude aérobie et à la compréhension des tests utilisés pour l’évaluer dans l’HTAP et de la DCG. Dans une première étude, nous avons comparé le profil ergospirométrique et le périmètre de marche de 6 minutes chez les patients DCG ou HTAP. Les résultats montrent que la VO2 max et le TDM sont diminués dans les mêmes proportions chez des patients à handicap fonctionnel (NYHA) comparable, avec toutefois une propension plus marquée à l’hyperventilation dans l’HTAP. Dans une seconde étude, nous avons mesuré la réponse métabolique au TDM6 au moyen d’un ergospiromètre portable chez des patients HTAP. Les résultats montrent que le TDM6 est réalisé à une VO2 correspondant à la VO2max mesurée à l’ergospirométrie sur cycloergomètre, avec cependant une ventilation, un quotient respiratoire et une fréquence cardiaque inférieures. Durant le TDM6, les patients stabilisent leur effort à un quotient respiratoire légèrement inférieur à 1. Ces résultats s’expliquent soit par la cinétique de la VO2 durant l’ergospirométrie à protocole standardisé comportant un incrément de charge trop rapide par minute, soit par une différence des masses musculaires mises en œuvre durant la marche ou l’effort sur bicyclette. Ces résultats suggèrent que le TDM6 pourrait être un test plus adéquat que l’ergospirométrie pour évaluer l’aptitude aérobie dans l’HTAP. Dans un troisième travail, plus modeste, nous avons réalisé la réplique du précédent, dans la DCG. Nous y avons observé les mêmes résultats. Dans un dernier travail nous avons évalué la valeur pronostique de l’ergospirométrie et du TDM6 dans l’HTAP. Nous avons analysé les ergospirométries et TDM6 de 65 patients atteints d’HTAP et discerné un sous groupe de patients atteints d’HTAP idiopathique ou associée à la prise d’anorexigène. Le TDM6 et le produit « distance x poids » étaient pronostiques de mortalité dans le groupe entier de patients et dans le sous groupe de patients atteints d’HTAP idiopathique ou associée à la prise d’anorexigène. La pente VE/VCO2 n’était facteur pronostique de mortalité que dans le groupe de patients atteints d’HTAP idiopathique ou associée à la prise d’anorexigène. La VO2pic n’était prédictive de mortalité dans aucun des groupes de patients. En conclusion, nos travaux ont montré que la DCG et l’HTAP menaient à une diminution similaire de la capacité à l’exercice. Ils ont également contribué à montrer l’intérêt du TDM6 (avec mesures ergospirométriques) dans l’évaluation de cette amputation de l’aptitude à l’effort. Le TDM6 paraît plus adéquat pour la mesure de l’aptitude purement aérobie (quotient respiratoire < 1). Ceci permet probablement de comprendre la supériorité du TDM6 par rapport à l’ergospirométrie en tant que facteur pronostique et en sensibilité aux effets d’interventions thérapeutiques.

Pulmonary arterial hypertension (PAH) is a rare but fatal disease with an annual mortality rate of 15% despite current therapies. Uncontrolled proliferation of pulmonary artery smooth muscle cells (PASMCs) results in adverse vascular remodeling contributing to PAH. Understanding the mechanisms of PASMC proliferation may identify new targets for treatment. Chloride currents/channels (ICl) are expressed in PASMCs and their roles in proliferation have been suggested based on their importance in resting membrane potential and cell volume regulation. The present study explored the role of ICl in proliferation in rat and human PASMCs. We found that either nonspecific ICl inhibitors (DIDS or NPPB) or a putative specific blocker of swelling-activated ICl (ICl,swell) reduced proliferation of PASMCs cultured in serum-containing media. Patch-clamp studies showed that proliferating PASMCs had increased baseline ICl and ICl,swell in association with depolarized membrane potentials. Quantitative real-time RT-PCR studies identified expressions of CLC-3, a candidate gene of ICl,swell, and several other CLC genes in proliferating PASMCs. While selective knockdown of CLC-3 with lentiviral shRNA reduced PASMC proliferation, it had no effect on ICl,swell. These findings are consistent with the conclusion that ICl regulate proliferation of PASMCs and suggest that selective ICl inhibition may be useful in treating pulmonary arterial hypertension.