Basement membrane heparan sulfate in atherogenesis and intimal hyperplasia

Cardiovascular disease due to atherosclerosis has become the leading cause of mortality in the world. Atherosclerosis is a progressive disease characterized by the accumulation of lipids, inflammatory cells, smooth muscle cells (SMCs) and extracellular matrix in the wall of large and medium-sized arteries. Surgical treatment of atherosclerosis cause mechanical injury to the vessel wall, which in many cases leads to restenosis and graft stenosis and recurrence of symptoms. Intimal SMC proliferation contributes to the stability of atherosclerotic plaques but it is also the main feature of intimal hyperplasia, which contributes to restenosis. It is therefore important to understand the mechanisms that control SMC growth in order to achieve a balanced healing response following interventions. This can be illustrated by the use of stents that elute anti-proliferative drugs, which has recently been associated with a higher risk of late stent thrombosis due to impaired intimal healing. Here, the role of basement membrane heparan sulfate (HS) in intimal hyperplasia and atherogenesis was investigated. Exogenously added heparin and HS are known inhibitors of SMC proliferation. However, the role of perlecan, which is the major arterial HS proteoglycan, in vascular disease was previously largely unknown. In vitro, the HS chains of perlecan lead to altered interactions between SMCs and fibronectin, possibly due to conformational changes in the fibronectin molecule. Such interactions may influence SMC function in atherogenesis and vascular repair processes. The use of transgenic mice expressing an HS-deficient perlecan showed increased SMC proliferation in vitro and increased intimal hyperplasia in vivo, confirming a growth inhibitory role for perlecan HS. A possible mechanism is decreased bioavailability of heparin-binding growth factors like FGF-2 at the cell surface due to sequestering in the basement membrane. In order to study the role of HS in atherogenesis the HS-deficient mice were cross-bred with apolipoprotein E null mice, which develop atherosclerosis. The results from that study indicate that the perlecan HS chains are pro-atherogenic in mice through increased lipoprotein retention, and the ability of HS to inhibit SMC growth may contribute to lesion instability. However, when binding and retention are not limiting factors, the perlecan HS chains may be anti-atherogenic by reducing endothelial permeability to lipoproteins. To investigate how perlecan can be pharmacologically regulated we explored the effect of all-trans-retinoic acid (AtRA) on perlecan expression in SMCs. AtRA was shown to up-regulate perlecan and the inhibition of SMC proliferation by AtRA is secondary to an increased expression of perlecan and dependent upon its HS chains. In summary, the role of basement membrane HS in vascular disease is complex. It may enhance lipoprotein retention, but also decrease endothelial permeability to lipoproteins. In addition, it can reduce restenosis, but maybe also cause plaque instability. This makes perlecan a difficult but very intriguing target for pharmacological interventions

Outpatient prescription of pulmonary vasodilator therapy to preterm children with bronchopulmonary dysplasia

Aim: The use of pulmonary vasodilator therapy in children born preterm is largely unknown. Our aim was to map prescription patterns in children with bronchopulmonary dysplasia in Sweden. Methods: This was a descriptive national registry-based study of children <7 years who had been prescribed a pulmonary vasodilator during 2007–2017, were born preterm and classified as having bronchopulmonary dysplasia. Information on prescriptions, patient characteristics and comorbidities were retrieved from the Swedish Prescribed Drug Register and linked to other national registers. Results: The study included 74 children, 54 (73%) born at 22–27 weeks' gestation and 20 (27%) at 28–36 weeks. Single therapy was most common, n = 64 (86.5%), and sildenafil was prescribed most frequently, n = 69 (93%). Bosentan, iloprost, macitentan and/or treprostinil were used mainly for combination therapies, n = 10 (13.5%). Patent ductus arteriosus or atrial septal defect were present in 29 (39%) and 25 (34%) children, respectively, and 20 (69%) versus 3 (12%) underwent closure. Cardiac catheterisation was performed in 19 (26%) patients. Median duration of therapy was 4.6 (1.9-6.8, 95% CI) months. Mortality was 9%. Conclusion: Preterm children with bronchopulmonary dysplasia were prescribed pulmonary vasodilators, often without prior catheterisation. Sildenafil was most commonly used. Diagnostic tools, effects, and drug safety need further evaluation

Pulmonary Vasodilator Therapy in Children with Single Ventricle Physiology : Effects on Saturation and Pulmonary Arterial Pressure

In children with single ventricle physiology, increased pulmonary vascular resistance may impede surgical progression or result in failing single ventricle physiology. The use of pulmonary vasodilators has been suggested as a potential therapy. However, knowledge on indication, dosage, and effect is limited. A retrospective case notes review of all (n = 36) children with single ventricle physiology, treated with pulmonary vasodilators by the UK Pulmonary Hypertension Service for Children 2004–2017. Therapy was initiated in Stage 1 (n = 12), Glenn (n = 8), or TCPC (n = 16). Treatment indications were high mean pulmonary arterial pressure, cyanosis, reduced exercise tolerance, protein-losing enteropathy, ascites, or plastic bronchitis. Average dose of sildenafil was 2.0 mg/kg/day and bosentan was 3.3 mg/kg/day. 56% had combination therapy. Therapy was associated with a reduction of the mean pulmonary arterial pressure from 19 to 14 mmHg (n = 17, p < 0.01). Initial therapy with one or two vasodilators was associated with an increase in the mean saturation from 80 to 85%, (n = 16, p < 0.01). Adding a second vasodilator did not give significant additional effect. 5 of 12 patients progressed from Stage 1 to Glenn, Kawashima, or TCPC, and 2 of 8 from Glenn to TCPC during a mean follow-up time of 4.7 years (0–12.8). Bosentan was discontinued in 57% and sildenafil in 14% of treated patients and saturations remained stable. Pulmonary vasodilator therapy was well tolerated and associated with improvements in saturation and mean pulmonary arterial pressure in children with single ventricle physiology. It appears safe to discontinue when no clear benefit is observed

Vasodilator therapy for pulmonary hypertension in children : a national study of patient characteristics and current treatment strategies

Pulmonary vasodilator therapy is still often an off-label treatment for pulmonary hypertension in children. The aim of this nationwide register-based study was to assess patient characteristics and strategies for pulmonary vasodilator therapy in young Swedish children. Prescription information for all children below seven years of age at treatment initiation, between 2007 and 2017, was retrieved from the National Prescribed Drug Register, and medical information was obtained by linkage to other registers. All patients were categorized according to the WHO classification of pulmonary hypertension. In total, 233 patients had been prescribed pulmonary vasodilators. The treatment was initiated before one year of age in 61% (N = 143). Sildenafil was most common (N = 224 patients), followed by bosentan (N = 29), iloprost (N = 14), macitentan (N = 4), treprostinil (N = 2) and riociguat (N = 2). Over the study period, the prescription rate for sildenafil tripled. Monotherapy was most common, 87% (N = 203), while 13% (N = 20) had combination therapy. Bronchopulmonary dysplasia (N = 82, 35%) and/or congenital heart defects (N = 156, 67%) were the most common associated conditions. Eight percent (N = 18) of the patients had Down syndrome. Cardiac catheterization had been performed in 39% (N = 91). Overall mortality was 13% (N = 30) during the study period. This study provides an unbiased overview of national outpatient use of pulmonary vasodilator therapy in young children. Few cases of idiopathic pulmonary arterial hypertension were found, but a large proportion of pulmonary hypertension associated with congenital heart defects or bronchopulmonary dysplasia. Despite treatment, mortality was high, and additional pediatric studies are needed for a better understanding of underlying pathologies and evidence of treatment effects

Radiopaque dyes allow vessel imaging in lung tissue using laboratory phase contrast micro-CT

Phase contrast micro-CT is a powerful technique allowing imaging of soft tissue at synchrotrons or using lab- oratory sources. The use of contrast agents is a useful approach when imaging vascular structures. However, common x-ray contrast agents typically rely on heavy metals to increase absorption, which may affect the phase contrast and cause artifacts in the reconstructed volumes. Thus, utilizing an agent with lower attenuation similar to soft tissue is clearly advantageous. Here, we evaluated different colored radiopaque solutions (tissue marking dyes) which had been injected into the vascular system of bovine lung samples, prior to embedding in paraffin. Scans were performed using a micro-focus x-tube calibrated to 10 µm spot size at 70 kV and a photon counting detector with a silicon sensor and 75 µm pixels. The resulting volumes have a voxel size of (25 µm)3, limited by the size of the samples, but sufficient to resolve the vascular system. Experiments confirmed that sufficient perfusion of the vessels with the dyes could be achieved, and the different dyes could be clearly discerned in the reconstructed volumes without causing artifacts allowing to clearly identify features in the soft tissue. Further, the findings were confirmed by histology.Keywords