Rationale: Although many familial cases of pulmonary arterial hypertension (PAH) exhibit an autosomal dominant mode of inheritance with the majority having mutations in essential constituents of the bone morphogenetic protein (BMP) signaling, the specific contribution of the long-term loss of signal transduction triggered by the type 2 BMP receptor (BMPR2) remains poorly characterized. Objective: To investigate the role of BMP9, the main ligand of ALK1/BMPR2 heterocomplexes, in pulmonary hypertension (PH). Method and Results: The absence of BMP9 in Bmp9-/-mice and its inhibition in C57BL/6 mice using neutralizing anti-BMP9 antibodies substantially prevent against chronic hypoxia induced PH judged by right ventricular systolic pressure (RVSP) measurement, right ventricular hypertrophy, and pulmonary distal arterial muscularization. In agreement with these observations, we found that the BMP9/BMP10 ligand trap ALK1ECD administered in monocrotaline (MCT) or Sugen/hypoxia (SuHx) rats substantially attenuate proliferation of pulmonary vascular cells, inflammatory cell infiltration and regresses established PH in rats. Our data obtained in human pulmonary endothelial cells derived from controls and PAH patients indicate that BMP9 can affect the balance between endothelin-1, apelin and adrenomedullin. We reproduced these in vitro observations in mice chronically exposed to hypoxia, with Bmp9-/-mice exhibiting lower mRNA levels of the vasoconstrictor peptide endothelin (ET)-1 and higher levels of the two potent vasodilator factors apelin and adrenomedullin (ADM) compared with Bmp9 +/+ littermates. Conclusion: Taken together, our data indicate that the loss of BMP9, by deletion or inhibition, has beneficial effects against PH onset and progression.

Aims  The progressive accumulation of cells in pulmonary vascular walls is a key pathological feature of pulmonary arterial hypertension (PAH) that results in narrowing of the vessel lumen, but treatments targeting this mechanism are lacking. The C-X-C motif chemokine 12 (CXCL12) appears to be crucial in these processes. We investigated the activity of two CXCL12 neutraligands on experimental pulmonary hypertension (PH), using two complementary animal models. Methods and results  Male Wistar rats were injected with monocrotaline (MCT) or were subjected to SU5416 followed by 3-week hypoxia to induce severe PH. After PH establishment, assessed by pulsed-wave Doppler echocardiography, MCT-injected or SU5416 plus chronic hypoxia (SuHx) rats were randomized to receive CXCL12 neutraligands chalcone 4 or LIT-927 (100 mg/kg/day), the C-X-C motif chemokine receptor 4 (CXCR4) antagonist AMD3100 (5 mg/kg/day), or vehicle, for 2 or 3 weeks, respectively. At the end of these treatment periods, echocardiographic and haemodynamic measurements were performed and tissue samples were collected for protein expression and histological analysis. Daily treatment of MCT-injected or SuHx rats with established PH with chalcone 4 or LIT-927 partially reversed established PH, reducing total pulmonary vascular resistance, and remodelling of pulmonary arterioles. Consistent with these observations, we found that neutralization of CXCL12 attenuates right ventricular hypertrophy, pulmonary vascular remodelling, and decreases pulmonary artery smooth muscle cell (PA-SMC) proliferation in lungs of MCT-injected rats and SuHx rats. Importantly, CXCL12 neutralization with either chalcone 4 or LIT-927 inhibited the migration of PA-SMCs and pericytes in vitro with a better efficacy than AMD3100. Finally, we found that CXCL12 neutralization decreases vascular pericyte coverage and macrophage infiltration in lungs of both MCT-injected and SuHx rats. Conclusion  We report here a greater beneficial effect of CXCL12 neutralization vs. the conventional CXCR4 blockade with AMD3100 in the MCT and SuHx rat models of severe PH, supporting a role for CXCL12 in the progression of vascular complications in PH and opening to new therapeutic options.

Objective: Excessive accumulation of resident cells within the pulmonary vascular wall represents the hallmark feature of the remodeling occurring in pulmonary arterial hypertension (PAH). Furthermore, we have previously demonstrated that pulmonary arterioles are excessively covered by pericytes in PAH, but this process is not fully understood. The aim of our study was to investigate the dynamic contribution of pericytes in PAH vascular remodeling. Approach and Results: In this study, we performed in situ, in vivo, and in vitro experiments. We isolated primary cultures of human pericytes from controls and PAH lung specimens then performed functional studies (cell migration, proliferation, and differentiation). In addition, to follow up pericyte number and fate, a genetic fate-mapping approach was used with an NG2CreER;mT/mG transgenic mice in a model of pulmonary arteriole muscularization occurring during chronic hypoxia. We identified phenotypic and functional abnormalities of PAH pericytes in vitro, as they overexpress CXCR (C-X-C motif chemokine receptor)-7 and TGF (transforming growth factor)-βRII and, thereby, display a higher capacity to migrate, proliferate, and differentiate into smooth muscle-like cells than controls. In an in vivo model of chronic hypoxia, we found an early increase in pericyte number in a CXCL (C-X-C motif chemokine ligand)-12-dependent manner whereas later, from day 7, activation of the canonical TGF-β signaling pathway induces pericytes to differentiate into smooth muscle-like cells. Conclusions: Our findings reveal a pivotal role of pulmonary pericytes in PAH and identify CXCR-7 and TGF-βRII as 2 intrinsic abnormalities in these resident progenitor vascular cells that foster the onset and maintenance of PAH structural changes in blood lung vessels.

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Heightened pulmonary artery smooth muscle cell (PA‐SMC) proliferation and migration and dynamic remodeling of the extracellular matrix are hallmark pathogenic features of pulmonary arterial hypertension (PAH). Pirfenidone (PFD) is an orally bioavailable pyridone derivative with antifibrotic, antiinflammatory, and antioxidative properties currently used in the treatment of idiopathic pulmonary fibrosis. We therefore evaluated the efficacy of curative treatments with PFD in the sugen/hypoxia (SuHx) rat model of severe pulmonary hypertension. Treatment with PFD (30 mg/kg per day by mouth 3 times a day for 3 wk) started 5 wk after sugen injection partially reversed established pulmonary hypertension, reducing total pulmonary vascular resistance and remodeling. Consistent with these observations, we found that continued PFD treatment decreases PA‐SMC proliferation and levels of extracellular matrix deposition in lungs and right ventricles in SuHx rats. Importantly, PFD attenuated the proproliferative and promigratory potentials of cultured PA‐SMCs from patients with idiopathic PAH and their capacity to produce extracellular matrix components. Finally, we found that PFD dose dependently enhanced forkhead box Ol protein levels and its nuclear translocation in cultured idiopathic PAH PA‐SMCs and in PFD‐treated SuHx rats. PFD appears to be a potential therapy for PAH worthy of investigation and evaluation for clinical use in conjunction with current PAH treatments.—Poble, P.‐B., Phan, C., Quatremare, T., Bordenave, J., Thuillet, R., Cumont, A., Huertas, A., Tu, L., Dorf muller, P., Humbert, M., Ghigna, M.‐R., Savale, L., Guignabert, C. Therapeutic effect of pirfenidone in the sugen/hypoxia rat model of severe pulmonary hypertension. FASEB J. 33,3670–3679 (2019). http://www.fasebj.org

Background: Pulmonary hypertension (PH) is a common complication of idiopathic pulmonary fibrosis (IPF) that significantly contributes to morbidity and mortality. Macrophage migration inhibitory factor (MIF) is a critical factor in vascular remodeling of the pulmonary circulation. Objectives: We tested the effects of two small molecules targeting MIF on bleomycin (BLM)-induced collagen deposition, PH, and vascular remodeling in mouse lungs. Methods: We examined the distribution pattern of MIF, CD74, and CXCR4 in the lungs of patients with IPF-PH and the lungs of BLM-injected mice. Then, treatments were realized with (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1) and N-(3-hydroxy-4-fluorobenzyl)-5 trifluoromethylbenzoxazol-2-thione 31 (20 mg/kg/day per os for 3 weeks) started 24 h after an intratracheal BLM administration. Results: More intense immunoreactivity was noted for MIF, CD74, and CXCR4 in lungs from IPF-PH patients and BLM-injected mice. Furthermore, we found that treatments of BLM-injected mice with ISO-1 or compound 31 attenuated lung collagen deposition and right ventricular systolic pressure increase. Additionally, reduced pulmonary inflammatory infiltration and pulmonary arterial muscularization were observed in the lungs of BLM-injected mice treated with ISO-1 or compound 31. Conclusions: Treatments with ISO-1 or compound 31 attenuates BLM-induced inflammation and fibrosis in lung, and prevents PH development in mice, suggesting that MIF is an important factor for IPF-PH development.

Allogeneic hematopoietic stem-cell transplantation (allo-HSCT) is the most effective treatment for selected patients with acute myeloid leukemia (AML) and relies on a "graft-versus-leukemia" effect (GVL) where donor T lymphocytes mediate control of malignant cell growth. However, relapse remains the major cause of death after allo-HSCT. In various malignancies, several immunoregulatory mechanisms have been shown to restrain antitumor immunity, including ligand-mediated engagement of inhibitory receptors on effector cells, and induction of immunosuppressive cell-subsets such as regulatory T cells (Tregs) or myeloid-derived suppressor cells (MDSCs). While relapse after HSCT remains a major therapeutic challenge, immunoregulatory mechanisms involved in restraining the GVL effect need to be better deciphered in humans. We used mass cytometry to comprehensively characterize circulating leukocytes in two cohorts of patients after allo-HSCT. We first longitudinally assessed various immunoregulatory parameters highlighting specific trends, such as opposite dynamics between MDSCs and Tregs. More generally, the immune landscape was rather stable from month-3 to 6, while many variations occurred from month-6 to 12 post-HSCT. Comparison with healthy individuals revealed that profound alterations in the immune equilibrium persisted 1-year post-HSCT. Importantly, we found that high levels of TIGIT and CD161 expression on CD4 T cells at month 3 post-HSCT were distinct features significantly associated with subsequent AML relapse in a second cross sectional cohort. Altogether, these data provide global insights into the immunoregulatory landscape reconstitution following HSCT, and highlight non-canonical inhibitory receptors associated with relapse, which could open the path towards new prognostic tools or therapeutic targets to restore subverted anti-AML immunity.

Dans l'hypertension artérielle pulmonaire (HTAP), les récentes découvertes physiopathologiques illustrent bien la complexité et l'aspect multifactoriel des mécanismes impliqués dans l'accumulation inadéquate de cellules vasculaires pulmonaires dans les parois des artères pulmonaires. Néanmoins, ces dernières avancées dans le domaine ont aussi permis de mieux comprendre les trois composantes motrices à la base de ce remodelage vasculaire pulmonaire et apportent un éclairage nouveau sur les mécanismes moléculaires et cellulaires sous-jacents. Parmi ces acteurs au centre de la pathogenèse, les perturbations des fonctions de l'endothélium pulmonaire et des processus inflammatoires jouent des rôles critiques, tout comme la perte d'activité du BMPRII et les altérations des communications entre cellules au sein des parois des artères pulmonaires.