Fanny Bajolle

An Nkx2-5/Bmp2/Smad1 Negative Feedback Loop Controls Heart Progenitor Specification and Proliferation

During heart development the second heart field (SHF) provides progenitor cells for most cardiomyocytes and expresses the homeodomain factor Nkx2-5. We now show that feedback repression of Bmp2/Smad1 signaling by Nkx2-5 critically regulates SHF proliferation and outflow tract (OFT) morphology. In the cardiac fields of Nkx2-5 mutants, genes controlling cardiac specification (including Bmp2) and maintenance of the progenitor state were upregulated, leading initially to progenitor overspecification, but subsequently to failed SHF proliferation and OFT truncation. In Smad1 mutants, SHF proliferation and deployment to the OFT were increased, while Smad1 deletion in Nkx2-5 mutants rescued SHF proliferation and OFT development. In Nkx2-5 hypomorphic mice, which recapitulate human congenital heart disease (CHD), OFT anomalies were also rescued by Smad1 deletion. Our findings demonstrate that Nkx2-5 orchestrates the transition between periods of cardiac induction, progenitor proliferation, and OFT morphogenesis via a Smad1-dependent negative feedback loop, which may be a frequent molecular target in CHD.

Immunodeficiency, autoinflammation and amylopectinosis in humans with inherited HOIL-1 and LUBAC deficiency

We report the clinical description and molecular dissection of a new fatal human inherited disorder characterized by chronic autoinflammation, invasive bacterial infections and muscular amylopectinosis. Patients from two kindreds carried biallelic loss-of-expression and loss-of-function mutations in HOIL1 (RBCK1), a component of the linear ubiquitination chain assembly complex (LUBAC). These mutations resulted in impairment of LUBAC stability. NF-κB activation in response to interleukin 1β (IL-1β) was compromised in the patients fibroblasts. By contrast, the patients mononuclear leukocytes, particularly monocytes, were hyper-responsive to IL-1β. The consequences of human HOIL-1 and LUBAC deficiencies for IL-1β responses thus differed between cell types, consistent with the unique association of autoinflammation and immunodeficiency in these patients. These data suggest that LUBAC regulates NF-κB–dependent IL-1β responses differently in different cell types.

Rotation of the Myocardial Wall of the Outflow Tract Is Implicated in the Normal Positioning of the Great Arteries

Congenital heart defects frequently involve a failure of outflow tract (OFT) formation during development. We analyzed the remodeling of the OFT, using the y96-Myf5-nlacZ-16 transgene, which marks a subpopulation of myocardial cells of the pulmonary trunk. Expression analyses of reporter transcript and protein suggest that the myocardial wall of the OFT rotates before and during the formation of the great arteries. Rotational movement was confirmed by Di-I injection experiments with cultured embryos. We subsequently examined the expression of the transgene in mouse models for OFT defects. In hearts with persistent truncus arteriosus (PTA), double outlet right ventricle (DORV), or transposition of the great arteries, rotation of the myocardial wall of the OFT is arrested or fails to initiate. This is observed in Splotch (Pax3) mutants with PTA or DORV and may be a result of defects in neural crest migration, known to affect OFT septation. However, in Pitx2&dgr;c mutant embryos, where cardiac neural crest cells are present in the heart, PTA and DORV are again associated with a rotation defect. This is also seen in Pitx2&dgr;c mutants, which have transposition of the great arteries. Because Pitx2c is involved in left–right signaling, these results suggest that embryonic laterality affects rotation of the myocardial wall during OFT maturation. We propose that failure of normal rotation of OFT myocardium may underlie major forms of congenital heart disease.

Add-On Therapy with Subcutaneous Treprostinil for Refractory Pediatric Pulmonary Hypertension

OBJECTIVEnTo evaluate the efficacy and tolerability of subcutaneous (SC) treprostinil, a prostacyclin analogue, in young children with refractory pulmonary arterial hypertension.nnnSTUDY DESIGNnEight children (median age, 4 years) received SC treprostinil therapy after failure of combined oral treatment (n = 7) or because of severe complications with intravenous epoprostenol (n = 1). Treprostinil was delivered through an SC catheter at gradually increasing doses to an average of 40 ng/kg/min, depending on the presence of adverse effects.nnnRESULTSnSeven patients demonstrated early significant improvement (in functional class, hemodynamics, and/or 6-minute walk distance; P <.05), and 6 had a sustained good response. Site pain could be effectively managed in all but one child.nnnCONCLUSIONSnTreprostinil may be a potentially valuable rescue therapy in children with refractory pulmonary arterial hypertension, but further study in a larger number of patients is needed.

Decreased Levels of Embryonic Retinoic Acid Synthesis Accelerate Recovery From Arterial Growth Delay in a Mouse Model of DiGeorge Syndrome

Rationale: Loss of Tbx1 and decrease of retinoic acid (RA) synthesis result in DiGeorge/velocardiofacial syndrome (DGS/VCFS)-like phenotypes in mouse models, including defects in septation of the outflow tract of the heart and anomalies of pharyngeal arch–derived structures including arteries of the head and neck, laryngeal–tracheal cartilage, and thymus/parathyroid. Wild-type levels of T-box transcription factor (Tbx)1 and RA signaling are required for normal pharyngeal arch artery development. Recent studies have shown that reduction of RA or loss of Tbx1 alters the contribution of second heart field (SHF) progenitor cells to the elongating heart tube. Objective: Here we tested whether Tbx1 and the RA signaling pathway interact during the deployment of the SHF and formation of the mature aortic arch. Methods and Results: Molecular markers of the SHF, neural crest and smooth muscle cells, were analyzed in Raldh2;Tbx1 compound heterozygous mutants. Our results revealed that the SHF and outflow tract develop normally in Raldh2+/−;Tbx1+/− embryos. However, we found that decreased levels of RA accelerate the recovery from arterial growth delay observed in Tbx1+/− mutant embryos. This compensation coincides with the differentiation of smooth muscle cells in the 4th pharyngeal arch arteries, and is associated with severity of neural crest cell migration defects observed in these mutants. Conclusions: Our data suggest that differences in levels of embryonic RA may contribute to the variability in great artery anomalies observed in DGS/VCFS patients.

Successful Treatment of Severe Cardiomyopathy in Glycogen Storage Disease Type III With D,L-3-Hydroxybutyrate, Ketogenic and High-Protein Diet

Glycogen storage disease type III (GSD III) due to debranching enzyme deficiency presenting usually with hepatomegaly and hypoglycemia may be responsible for severe cardiomyopathy which is often fatal. Current treatment of GSD III is based on frequent high-carbohydrate meals that have no effect on the cardiomyopathy. We describe a 2-mo-old infant presenting with a familial form of GSD III complicated with cardiomyopathy. As conventional treatment was unable to improve his sisters cardiomyopathy who was deceased at age 11 mo, we proposed an experimental treatment combining the use of synthetic ketone bodies (d,l-3-OH butyrate) as an alternative energy source, 2:1 ketogenic diet to reduce glucose intake and high-protein diet to enhance gluconeogenesis. Twenty-four months after the onset of this treatment, echocardiography showed an improvement of cardiomyopathy. Growth and liver size remained normal, and no side effects were observed. Blood glucose levels remained within the normal range and insulin levels decreased. These findings show that synthetic ketone bodies as well as low-carbohydrate, high-lipid, and high-protein diet may be a more beneficial therapeutic choice therapeutic choice for GSD III patients with cardiomyopathy. These encouraging data need to be confirmed in more GSD III patients presenting with cardiac or muscular symptoms.

Prenatal diagnosis of isolated total anomalous pulmonary venous connection: a series of 10 cases.

To report on a series of 10 fetuses with prenatally diagnosed isolated total anomalous pulmonary venous connection (TAPVC), focusing on echocardiographic features leading to diagnosis, assess accuracy of prenatal diagnosis and describe postnatal outcome.

Common arterial trunk repair: with conduit or without?

OBJECTIVEnTo compare the mid-term results of two techniques used for the reconstruction of the pulmonary outflow tract during common arterial trunk repair in infancy, with special attention paid to re-operation rate and pulmonary arterial growth.nnnMETHODSnBetween 2000 and 2006, 32 consecutive neonates or infants underwent common arterial trunk repair. In 15 patients, the pulmonary outflow tract was reconstructed using an extracardiac valved conduit (conduit group). In 17 patients, right ventricle to pulmonary artery connection was achieved without conduit, using the left atrial appendage and including a monocusp valve (non-conduit group). The decision regarding the type of ventricle to pulmonary artery connection was at the discretion of the attending surgeon. The two groups were similar in terms of age, weight, type of common arterial trunk, truncal valve dysfunction and coronary abnormalities. Follow-up was 93% complete and included echo-Doppler evaluation, catheterisation and CT scan imaging.nnnRESULTSnHospital mortality (five patients - 16%) was increased by coronary abnormalities and preoperative ventilation but did not differ between the two groups (13.3% in the conduit group vs 18% in the non-conduit group). The mean follow-up was 40+/-25 months. There were six late deaths (three in each group), yielding an actuarial survival of 76% at 5 years. One late death was procedure related (percutaneous dilatation for obstructive monocusp patch). Re-operation for right ventricular outflow tract obstruction was necessary in seven patients (five in the conduit group and two in the non-conduit group); the actuarial freedom from re-operation was higher in the non-conduit group (p=0.026). At last follow-up, the right ventricle-pulmonary artery gradient and the right ventricle/left ventricle pressure ratio were higher in the conduit group (p=0.006 and p=0.007, respectively). At late computed tomography (CT)-scan evaluation, the growth of the proximal pulmonary arterial tree had improved in the non-conduit group, as shown by a higher Nakata ostial index and right ventricular outflow tract growth.nnnCONCLUSIONSnRepair of common arterial trunk without conduit for right ventricular outflow tract reconstruction (1) does not increase mortality and morbidity, (2) decreases the need for re-intervention and (3) promotes a better growth of the proximal pulmonary arteries. These preliminary results need confirmation by further experience.

Conotruncal defects associated with anomalous pulmonary venous connections

BACKGROUNDnConotruncal defects constitute one of the major categories of congenital heart disease. Our understanding of how these defects develop has been derived from knowledge of the role of neural crest cells in heart development. However, recent studies have revealed a role for the myocardium in the formation of both the arterial and venous poles of the heart.nnnAIMnTo identify congenital heart defects that associate anomalies of the arterial and venous poles.nnnMETHODSnFrom a database spanning 27 years, we identified those patients with conotruncal defects associated with an anomalous pulmonary venous connection (APVC; total or partial). Patients with atria isomerism or atrioventricular septal defects were excluded. Patient files were reviewed for clinical presentation, family history, diagnostic and surgical procedures, and outcome.nnnRESULTSnWe identified 23 patients with conotruncal defects and APVC. Conotruncal defects were as follows : common arterial trunk, n=7; tetralogy of Fallot, n=5; discordant ventriculoarterial connections, n=4; interrupted aortic arch, n=2; subarterial ventricular septal defect, n=2; double outlet right ventricle, n=2; and right pulmonary artery from ascending aorta, n=1. Nine patients had total APVC and 14 patients had partial APVC. Recurrence of the cardiac defects in siblings was observed in three families.nnnCONCLUSIONnOur findings suggest that congenital heart defects that associate anomalies of the arterial and venous poles may have a common embryology, which results from a myocardial defect.

Acute Ischemic Cardiomyopathy after Extreme Emotional Stress in a Child

Ischemic cardiomyopathy is rare in children. It is usually caused by congenital anomalies of coronary arteries, coronary anomalies after coronary artery transfer, or Kawasaki disease. In recent years, a new cardiac syndrome-named Tako-Tsubo cardiomyopathy for the particular shape of the end systolic ventricle-has been described in adults. In the absence of coronary artery obstruction, it mimics acute myocardial infarction with chest pain and typical electrocardiography changes. Emotional or physical stress usually precedes this cardiomyopathy. At present, this entity has only been described in adults, with a strong predominance in postmenopausal women. We report a case of acute ischemic cardiomyopathy after extreme stress in a child that may share the same pathophysiology.