Arterial elastase activity after balloon angioplasty and effects of elafin, an elastase inhibitor.

Increased proteolytic activity may be a factor in intimal hyperplasia after balloon angioplasty (BA). The objectives of this study were to assess elastase activity after BA in a rabbit arterial double-injury model and the effects of elastase inhibition. Elastase activity increased immediately after BA, reached an 8-fold peak at 1 week, and declined to baseline levels by 4 weeks. Elastin zymography showed that the elastase activity was associated predominantly with a molecular mass of 25 kDa. Elastase activity was significantly inhibited in vitro by elafin and phenylmethylsulfonyl fluoride, selective inhibitors of serine elastases. A second group of animals was transfected after BA with a plasmid containing the cDNA for either elafin or a control (chloramphenicol acetyltransferase, CAT) construct by using a hemagglutinating virus of Japan-liposome transfection technique. Arterial segments were obtained at 48 hours, 1 week, and 4 weeks to assess transgene expression, arterial wall elastase activity, and intimal cross-sectional area, respectively. Elafin transgene expression was evident at 48 hours and resulted in a significant (80%) inhibition of elastase activity compared with chloramphenicol acetyltransferase-transfected arteries. There was a 43% reduction in intimal cross-sectional area in elafin-transfected arteries (0.28+/-0.22 versus 0.16+/-0.07 mm(2) for CAT-transfected versus elafin-transfected arteries, respectively; P<0.05). These data suggest that an early increase in serine elastase activity after BA contributes to intimal hyperplasia. Serine elastase inhibition may be a potential therapeutic approach to inhibit intimal hyperplasia.

Hemodynamic unloading leads to regression of pulmonary vascular disease in rats.

OBJECTIVE: Treatment options for patients with advanced pulmonary vascular disease caused by a congenital heart defect are still mainly limited to heart-lung transplantation or lung transplantation with repair of the cardiac lesion. Because we have previously shown that the structural changes associated with pulmonary hypertension can be reversed by stress unloading in an organ culture model, we now investigate whether hemodynamic unloading will lead to regression of pulmonary vascular disease in the intact animal. METHODS: Right middle and lower lobectomy and monocrotaline injection were performed in Lewis rats (n = 22) to cause pulmonary vascular disease from a combined hemodynamic and toxic injury. Twenty-eight days later the left lungs were examined (n = 10) or exposed to normal pulmonary artery pressure for an additional 14 (n = 5) or 28 (n = 7) days by transplantation into healthy recipients. Pulmonary artery pressure, ventricular weight, and pulmonary artery morphology were evaluated in each group. RESULTS: Pulmonary hypertension (50 vs 16 mm Hg; P <.001) and right ventricular hypertrophy (right ventricular/left ventricular weight 0.69 vs 0.32; P <.001) associated with pulmonary artery medial hypertrophy (28.2% vs 7.2% wall thickness; P <.001) and muscularization of small pulmonary arteries (92.3% vs 19.4%; P <.001) developed by day 28 (compared with untreated controls). However, transplantation into healthy recipients effectively unloaded the lungs (mean pulmonary artery pressure 17 and 24 mm Hg at 14 and 28 days after transplantation) and resulted in progressive normalization of medial hypertrophy (15.6% and 12.1% at 14 and 28 days) and muscularization (65.1% and 42.2% at 14 and 28 days) relative to nontransplanted controls (P <.005 in each case). CONCLUSIONS: Hemodynamic unloading of lungs with pulmonary vascular disease results in progressive normalization of pulmonary artery structure. These results are the first to provide a rationale for attempting to induce regression of pulmonary vascular disease by pressure unloading of the pulmonary circulation. Methods to mechanically unload the pulmonary circulation should be critically evaluated as a strategy for staged surgical repair of congenital heart defects despite presumed irreversible pulmonary hypertension.

Gene transfer of the serine elastase inhibitor elafin protects against vein graft degeneration.

BACKGROUND: Leukocyte infiltration and serine elastase activity lead to smooth muscle cell proliferation in association with posttransplant coronary arteriopathy and may also be involved in vein graft neointimal formation. A number of therapies have targeted cellular proliferation, but the inhibition of serine elastase-mediated extracellular matrix remodeling has not been investigated as a potential strategy to prevent neointimal formation and subsequent atherosclerotic degeneration in vein grafts. METHODS AND RESULTS: We studied jugular vein grafts 48 hours after interposition into the carotid arteries of rabbits and demonstrated inflammatory cell infiltration and elevated serine elastase activity, a stimulus for matrix remodeling and deposition of elastin. Therefore, elastolytic activity in vein grafts was targeted through transient expression of the selective serine elastase inhibitor elafin with hemagglutinating virus of Japan liposome-mediated gene transfer. Elafin transfection reduced inflammation by 60% at 48 hours and neointimal formation by approximately 50% at 4 weeks after implantation. At 3 months, a 74% decrease in neointimal elastin deposition correlated with protection against cholesterol-induced macrophage infiltration and lipid accumulation, which were both reduced by approximately 50% in elafin-transfected grafts relative to controls. CONCLUSIONS: Gene transfer of the selective serine elastase inhibitor elafin in vein grafts is effective in reducing the early inflammatory response. Although transient expression of elafin delays neointimal formation, it is also sufficient to cause an alteration in elastin content of the extracellular matrix, making it relatively resistant to atherosclerotic degeneration.

Suppressed smooth muscle proliferation and inflammatory cell invasion after arterial injury in elafin-overexpressing mice.

Elastases degrade the extracellular matrix, releasing growth factors and chemotactic peptides, inducing glycoproteins such as tenascin, and thereby promoting vascular cell proliferation and migration. Administration of serine elastase inhibitors reduces experimentally induced vascular disease. The ability to mount an intrinsic anti-elastase response may, therefore, protect against intimal/medial thickening after vascular injury. To investigate this, we showed that wire-induced endothelial denudation of the carotid artery is associated with transient elevation in elastase activity and confirmed that this is abolished in transgenic mice overexpressing the serine elastase inhibitor, elafin, targeted to the cardiovascular system. Ten days after injury, nontransgenic littermates show vessel enlargement, intimal thickening, increased medial area and cellularity, and 2-fold increase in tenascin. Injured vessels in transgenic mice become enlarged but are otherwise similar to sham-operated controls. Injury-induced vessel wall thickening, which is observed only in nontransgenic mice, is related to foci of neutrophils and macrophages, in addition to smooth muscle cells that fail to stain for alpha-actin and are likely dedifferentiated. Our study therefore suggests that a major determinant of the vascular response to injury is the early transient induction of serine elastase activity, which leads to cellular proliferation and inflammatory cell migration.

Gene transfer in utero biologically engineers a patent ductus arteriosus in lambs by arresting fibronectin-dependent neointimal formation.

Closure of the ductus arteriosus requires prenatal formation of intimal cushions, which occlude the vessel lumen at birth. Survival of newborns with severe congenital heart defects, however, depends on ductal patency. We used a gene transfer approach to create a patent ductus arteriosus by targeting the fibronectin-dependent smooth muscle cell migration required for intimal cushion formation. Fetal lamb ductus arteriosus was transfected in utero with hemagglutinating virus of Japan liposomes containing plasmid encoding 'decoy' RNA to sequester the fibronectin mRNA binding protein. Fibronectin translation was inhibited and intimal cushion formation was prevented. We thus established the essential role of fibronectin-dependent smooth muscle cell migration in intimal cushion formation in the intact animal and the feasibility of incorporating biological engineering in the management of congenital heart disease.

Atrioventricular septal defect with tetralogy of Fallot: results of surgical correction.

BACKGROUND: The outcome of surgical correction of complete atrioventricular septal defect with tetralogy of Fallot has improved in recent years. Controversy exists about the optimal approach to this complex lesion. Our experience over the past 8 years with a single technique is reviewed. The important anatomic features of this lesion are discussed in relation to our method of repair. METHODS: Between 1988 and 1996, 11 consecutive patients underwent correction of complete atrioventricular septal defect with tetralogy of Fallot. Nine patients had undergone prior palliative shunts. The two-patch technique for atrioventricular septal defect was used. The ventricular septal defect was closed through a right ventriculotomy in each case. The commissure between the superior and inferior bridging leaflets of the left portion of the common atrioventricular valve was closed in each patient. Management of the right ventricular outflow tract was individualized. RESULTS: There was one mortality in the early postoperative period. One patient required reoperation for closure of a dehiscent left atrioventricular valve cleft. All survivors are currently in New York Heart Association functional class I or II at follow-up ranging from 2 to 101 months. CONCLUSIONS: Atrioventricular septal defect with tetralogy of Fallot can be corrected with low mortality using the two-patch technique and closure of the ventricular septal defect through a combined approach using a right ventriculotomy and right atriotomy. Routine closure of the commissure of the left portion of the atrioventricular valve results in a low incidence of regurgitation. A good functional result can be achieved in most patients at intermediate-term follow-up.

Tetralogy of Fallot with anomalous LAD: repair without conduit.

We report a case of anomalous origin of left anterior descending coronary artery in a patient with tetralogy of Fallot, absent pulmonary valve cusps, and origin of left pulmonary artery from the ascending aorta. Pulmonary outflow tract obstruction was successfully treated by direct anastomosis of the main pulmonary artery to the right ventricle. This approach prevented injury to the anomalous coronary artery and avoided the use of an extracardiac conduit.

Effects of acutely raising intracranial pressure on cardiac sympathetic efferent neuron function.

OBJECTIVE: To determine whether acutely raising intracranial pressure modifies the function of cardiac efferent autonomic neurons. METHODS: The effects of suddenly raising intracranial pressure above systemic vascular pressure on heart rate, left atrial and left ventricular chamber pressures, as well as right and left ventricular intramyocardial pressures, were studied following removal of the adrenal glands from the circulation. Cardiac effects induced by systemic administration of nicotine, tyramine or isoproterenol were investigated before and after raising intracranial pressure: (1) in 9 dogs with neurally intact hearts in which cardiac release of catecholamines and intrinsic cardiac neuronal activity were studied; (2) in another 8 dogs in which intrathoracic autonomic neurons were disconnected from central neurons; (3) in another 8 dogs after decentralizing intrathoracic sympathetic but not parasympathetic neurons; (4) in 2 animals after decentralizing intrathoracic parasympathetic, not sympathetic neurons. RESULTS: Increasing intracranial pressure in neurally intact preparations induced ventricular augmentation followed by depression such that after 12 min of cerebral ischemia left ventricular systolic pressure was 62 +/- 5 mmHg. Isoproterenol and tyramine augmented right ventricular inotropism similarly before and after raising intracranial pressure, their effects on left ventricular systolic pressures being reduced secondary to the systemic vascular hypotension. Although nicotine excited intrinsic cardiac neurons similarly before and after raising intracranial pressure, it failed to enhance cardiac liberation of noradrenaline after compared to before raising intracranial pressure. Nicotine-induced ventricular augmentation was obtunded after brain death despite the fact that ventricular myocytes underwent no detectable histological changes. In contrast, nicotine induced similar cardiac augmentation before and after raising intracranial pressure when intrathoracic autonomic neurons or when intrathoracic sympathetic, not parasympathetic neurons, were decentralized. CONCLUSION: Cardiac sympathetic efferent neuronal function is obtained by acutely raising intracranial pressure.

Capacity of intrinsic cardiac neurons to modify the acutely autotransplanted mammalian heart.

The capacity of the intrinsic cardiac nervous system to modify the acutely autotransplanted heart was investigated in eight anesthetized open-chest canine preparations in which the adrenal glands had been removed from the circulation. Cardiac effects elicited by isoproterenol and nicotine were also examined before and after heart-lung transplantation. Cardiac augmentation induced by isoproterenol was similar before and immediately after cardiopulmonary transplantation, indicating that the surgery did not obtund cardiac myocyte function significantly. The initial bradycardia induced by nicotine was greater before transplantation. The subsequent augmentation in left atrial systolic pressure, as well as right and left ventricular intramyocardial systolic pressures, induced by nicotine were similar before and after transplantation. When nicotine was administered to transplanted preparations after atropine administration, cardiac augmentation was induced. Cardiac augmentation was not induced by nicotine after subsequent beta-adrenergic blockade. These data indicate that nicotine-sensitive adrenergic neurons which accompany the transplanted heart are capable of inducing considerable cardiac augmentation. Power spectral analysis of heart rate and left ventricular chamber rate of pressure rise variability indicated an almost complete lack of power in these indexes after, as opposed to before, transplantation. Together with intrinsic cardiac cholinergic neurons, intrinsic cardiac adrenergic neurons may be responsible for physiologically and pharmacologically induced alterations in cardiac variables that occur in acutely transplanted hearts.

Functional capacity of nicotine-sensitive canine intrinsic cardiac neurons to modify the heart.

The capacity of intrinsic cardiac efferent parasympathetic and sympathetic neurons to modify the heart was investigated in nine anesthetized open-chest dogs with adrenal glands removed from the circulation. The effects elicited by intravenously administered isoproterenol, tyramine, and nicotine on cardiac variables were examined before and after acute decentralization of the heart. Major vessels, as well as other tissues at the base of the heart, were denuded by means of an ultrasonic aspirator that removed neural elements without damaging muscles or blood vessels. The efficacy of the acute decentralization was assured by testing cardiac responses elicited by right and left stellate ganglia and cervical vagosympathetic complex stimulations after surgery. Heart rate, atrial force, and both right and left ventricular intramyocardial systolic pressures were augmented similarly by isoproterenol and tyramine before and after acute decentralization, indicating that the surgery necessary to decentralize the heart did not obtund cardiac myocyte function. Power spectral analysis of heart rate and left ventricular chamber pressure rate of change indicated an almost complete lack of variability of these indexes after, but not before, acute decentralization. Despite these changes, similar cardiac augmentation was elicited by nicotine before and after acute decentralization. Cardiac augmentation was elicited by nicotine in acutely decentralized preparations after atropine administration but not after beta-adrenergic blockade. These data indicate that the canine intrinsic cardiac nervous system contains a significant population of nicotine-sensitive adrenergic neurons that modulate the heart. Furthermore, the intrinsic cardiac nervous system does not appear to be primarily responsible for the heart rate and ventricular pressure variability found in intact hearts.