Alvine Bissery

Transplantation of cardiac-committed mouse embryonic stem cells to infarcted sheep myocardium: a preclinical study

BACKGROUND Heart failure develops after myocardial infarction and is a major cause of morbidity and mortality. The ability to direct differentiation of embryonic stem cells (ESC) towards a cardiomyogenic phenotype makes them an attractive therapeutic option for cardiac repair, but species-specific and individual-specific immunological imprinting remains a hurdle. Our aim was to ascertain whether the purported immune privilege of ESC allows for their cross-species engraftment in a clinically relevant large-animal model. METHODS We studied engraftment and differentiation of cardiac-committed mouse ESC in 18 sheep in which a myocardial infarction had been induced; nine controls received medium and nine sheep (five of which were immunosuppressed) received ESC. The gain in myocardial function was measured by echocardiography 1 month after cell transplantation. FINDINGS Cardiac-committed murine ESC engrafted in infarcted myocardium of immunosuppressed and immunocompetent sheep, and differentiated into mature cardiomyocytes that expressed connexins. Colonisation of the scar area by ESC was accompanied by a functional benefit of the damaged myocardium. Left-ventricular ejection fraction deteriorated in the control group by a median of 9.9% (range -20 to 0.3) relative to baseline (p=0.011) whereas in the treated group it improved by 6.6% (-5.7 to 50.8; comparison between groups p=0.002). INTERPRETATION These findings obtained in a clinically relevant large-animal model of heart failure strengthen the potential therapeutic use of ESC to regenerate the severely dysfunctional myocardium and bring additional evidence for an immune privilege of these cells.

Pharmacologic Demonstration of the Synergistic Effects of a Combination of the Renin Inhibitor Aliskiren and the AT1 Receptor Antagonist Valsartan on the Angiotensin II–Renin Feedback Interruption

Interrupting the renin-angiotensin system (RAS) with a usual daily dose of a single-site RAS inhibitor does not achieve complete and long-lasting pharmacologic blockade. Hormonal and BP effects were compared for 48 h after administration of single oral doses of 300 mg (high dose) of the renin inhibitor aliskiren (A300) and 160 mg (standard antihypertensive dose) of the AT1 receptor antagonist valsartan (V160) and their combination each at half dose (A150+V80) in 12 mildly sodium-depleted normotensive individuals. In this double-blind, placebo-controlled, randomized, four-period crossover study, A300 decreased plasma renin activity and angiotensin I and II levels for 48 h, stimulated immunoreactive active renin release more strongly than V160, and decreased urinary aldosterone excretion for a longer duration than V160. In contrast to V160, the A150+V80 combination did not increase plasma angiotensins. The renin and aldosterone effects of the A150+V80 combination were similar to those of A300 and greater than those of V160. When plasma drug concentrations were taken into account, the A150 +V80 combination had a synergistic effect on renin release. The A150+V80 combination lowered BP at least as effectively as either higher dose monotherapy. In conclusion, in mildly sodium-depleted normotensive individuals, the long-lasting effects of aliskiren alone or in combination with valsartan on plasma immunoreactive active renin and urinary aldosterone effects demonstrate strong and prolonged blockade of angiotensin II at the kidney and the adrenal level. Moreover, a renin inhibitor and AT1R antagonist combination may provide synergistic effects on RAS hormone levels.

Does the Functional Efficacy of Skeletal Myoblast Transplantation Extend to Nonischemic Cardiomyopathy

Background—The benefits of skeletal myoblast (SM) transplantation on infarcted myocardium have been investigated extensively; however, little is known about its effects in nonischemic cardiomyopathy models. To address this issue, we tested SM transplantation in CHF147 Syrian hamsters, a strain characterized by a &dgr;-sarcoglycan deficiency that phenotypically features the human setting of primary dilated cardiomyopathy. Methods and Results—Cell culture techniques were used to prepare ≈5×106 muscle cells from autologous tibialis anterior muscle, of which 50% were SMs (desmin staining). The cells were injected in 6 sites across the left ventricular wall (n=14). Control animals (n=12) received equivalent volumes of culture medium. Left ventricular systolic function was assessed in a blinded fashion from 2D echocardiographic left ventricular fractional area change, before transplantation, and 4 weeks later. Explanted hearts were processed for the detection of myotubes and quantification of fibrosis. Baseline functional data did not differ between the 2 groups. Four weeks after transplantation, 6 of the 10 surviving grafted hamsters were improved compared with 0 of the 8 survivors of the control group. This translated into a 6% decrease in fractional area change in controls compared with a 24% increase in cell-transplanted hamsters (P=0.001). Engrafted myotubes were consistently detected in all SM transplanted hearts by immunohistochemistry, whereas fibrosis was not worsened by cell injections. Conclusions—These data suggest that the functional benefits of SM transplantation might extend to nonischemic cardiomyopathy.

Arterial and renal consequences of partial genetic deficiency in tissue kallikrein activity in humans

Tissue kallikrein (TK), the major kinin-forming enzyme, is synthesized in several organs, including the kidney and arteries. A loss-of-function polymorphism of the human TK gene (R53H) induces a substantial decrease in enzyme activity. As inactivation of the TK gene in the mouse induces endothelial dysfunction, we investigated the vascular, hormonal, and renal phenotypes of carriers of the 53H allele. In a crossover study, 30 R53R-homozygous and 10 R53H-heterozygous young normotensive white males were randomly assigned to receive both a low sodium-high potassium diet to stimulate TK synthesis and a high sodium-low potassium diet to suppress TK synthesis, each for 1 week. Urinary kallikrein activity was 50-60% lower in R53H subjects than in R53R subjects. Acute flow-dependent vasodilatation and endothelium-independent vasodilatation of the brachial artery were both unaffected in R53H subjects. In contrast, R53H subjects consistently exhibited an increase in wall shear stress and a paradoxical reduction in artery diameter and lumen compared with R53R subjects. Renal and hormonal adaptation to diets was unaffected in R53H subjects. The partial genetic deficiency in TK activity is associated with an inward remodeling of the brachial artery, which is not adapted to a chronic increase in wall shear stress, indicating a new form of arterial dysfunction affecting 5-7% of white people.

Hormonal and Hemodynamic Effects of Aliskiren and Valsartan and Their Combination in Sodium-Replete Normotensive Individuals

BACKGROUND AND OBJECTIVES An AT1 receptor antagonist induces a counterregulatory renin release whose intensity and duration reflect the magnitude of the renin-angiotensin blockade. We investigated whether a renin inhibitor may neutralize this counterregulation and amplify the effects of AT1 receptor antagonists. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS In 12 normotensive male individuals who were on a high-sodium diet, a double-blind, placebo-controlled, randomized, crossover design was used to study the hormonal and BP effects of single oral administrations of 300 mg of the renin inhibitor aliskiren, 320 mg of valsartan, and a combination of these two drugs, each at half dosage (150 mg of aliskiren and 160 mg of valsartan). RESULTS Valsartan (320 mg) increased plasma renin activity and angiotensin I and angiotensin II levels, but 300 mg of aliskiren decreased them for 48 h. Aliskiren (300 mg) stimulated immunoreactive renin release more strongly than 320 mg of valsartan, decreased urinary aldosterone excretion for longer than 320 mg of valsartan, and had a similar BP-lowering effect as 320 mg of valsartan. In combination, 150 mg of aliskiren neutralized the valsartan (160 mg)-induced increase in plasma angiotensins for 48 h. The renin and aldosterone effects of the combination of 150 mg of aliskiren and 160 mg of valsartan were similar to those of 300 mg of aliskiren and greater than those of 320 mg of valsartan. When plasma drug concentrations were taken into account, the combination of 150 mg of aliskiren and 160 mg of valsartan had a synergistic effect on renin release. The BP-lowering effect of 150 mg of aliskiren and 160 mg of valsartan was similar to that of 300 mg of aliskiren and 320 mg of valsartan at peak but was more prolonged. CONCLUSION The stronger and longer lasting effects on plasma active renin and urinary aldosterone of aliskiren, alone or in combination, demonstrate a more effective blockade of the renin-angiotensin system than that obtained with 320 mg of valsartan alone.

Investigation of aldosterone-synthase inhibition in rats

Background In-vivo investigation of aldosterone-synthase inhibitors requires experimental models to characterize the biological effects of these compounds. Methods Seven successive experiments were performed in groups of 2-month-old male spontaneously hypertensive rats. Urinary free aldosterone was the main end-point measured during two contrasted diets: low sodium–high potassium (LS), inducing high urinary aldosterone (839 pmol/24 h, 95% confidence interval 654–1077), and high sodium–normal potassium (HS), inducing low urinary aldosterone (38.1 pmol/24 h; 95% confidence interval, 32.4–44.9). Results FAD 286 A (10 and 30 mg/kg) decreased urinary free aldosterone by 53 and 87% on the LS diet, and 50 and 75% on the HS. Plasma renin concentration increased three-fold after a 4-week treatment of 30 mg/kg FAD 286 A on the LS diet and did not change on the HS. The combination of FAD 286 A (30 mg/kg) and spironolactone (30 mg/kg) on the LS diet induced a biological picture of severe hypoaldosteronism and was not tolerated, whereas the HS diet prevented these abnormalities. The combination of FAD 286 A (30 mg/kg) and furosemide (30 mg/kg) on the HS diet corrected the diuretic-induced hypokalemia (4.1 ± 0.2 versus 3.7 ± 2.2 mEq/l, P < 0.033). Conclusion This experimental model will be useful to screen future aldosterone-synthase inhibitors and study their biological effects in various experimental conditions.

Integrating Drug Pharmacokinetics for Phenotyping Individual Renin Response to Angiotensin II Blockade in Humans

Abstract—Renin release into plasma has been used to investigate the drug dose-dependence of renin-angiotensin system inhibition because it is proportional to the interruption of the permanent negative feedback loop of angiotensin II on renin secretion. We investigated the 24-hour between-subject differences in renin profiles by analyzing the time-dependence of individual renin responses in 16 mildly sodium-depleted normotensive subjects exposed in a 4-period crossover study to single oral doses of 8- and 16-mg (C8 and C16) candesartan cilexetil and 80- and 160-mg (V80 and V160) valsartan. C8 had a similar effect to V160 in terms of the increase in active renin concentration and decrease in blood pressure. C16 had the strongest effect and V80 the weakest effect on renin release. Within- and between-subject variability was more marked for valsartan pharmacokinetics than for candesartan pharmacokinetics and influenced variability in renin response. To eliminate some of the variability caused by the pharmacokinetics of each drug, we corrected the area under time curve of plasma renin levels by that of plasma drug levels to obtain an individual normalized index of renin release or “renin/pharmacokinetic index”. In these experimental conditions, this index was found to be a reproducible individual characteristic affecting renin response, in addition to the pharmacokinetics and pharmacological properties of angiotensin II type-1 receptor antagonists. The pharmacokinetic–pharmacodynamic model of renin release described here could be of value for the identification and investigation of renin release abnormalities in patients with hypertension and for the comparison of renin-angiotensin system blockers.

Pharmacokinetics and pharmacodynamics of the vasopeptidase inhibitor AVE7688 in humans

Our objective was to define the pharmacodynamic profile of the new dual neutral endopeptidase (NEP)/angiotensin‐converting enzyme (ACE) inhibitor AVE7688.

Physiologic Consequences of Vasopeptidase Inhibition in Humans: Effect of Sodium Intake

The in vivo inhibition of angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP) were monitored simultaneously by sequentially measuring the urinary excretion of N-Acetyl-Ser-Asp-Lys-Pro and of the atrial natriuretic factor to compare the magnitude and the duration of action of a vasopeptidase inhibitor, omapatrilat, and an ACE inhibitor, fosinopril. Single oral doses of 40 or 80 mg of omapatrilat or 20 mg of fosinopril were administered to 24 normotensive, sodium-depleted or -replete volunteers in a placebo-controlled crossover study. ACE inhibition persisted longer after treatment with omapatrilat than with fosinopril, and there was no major difference between the effects of 40 and 80 mg of omapatrilat. The duration of NEP inhibition by omapatrilat was shorter than that of ACE inhibition. Although omapatrilat effectively inhibited NEP, it had a mild and transient natriuretic effect and did not increase natriuresis more than fosinopril. Omapatrilat induced a decrease in BP and an increase in plasma renin more rapidly and more effectively than fosinopril. The BP and renin effects of omapatrilat persisted despite high sodium intake, which neutralized the effects of fosinopril. The simultaneous inhibition of ACE and NEP may be more effective in reducing BP than the inhibition of ACE alone and less dependent on sodium balance.

Pharmacodynamic effects of single oral doses of omapatrilat (40 and 80 mg) and fosinopril (20 mg) during salt depletion and salt repletion in normotensive subjects

To investigate the effects of Valsartan on left ventricular function and its antihypertensive efficacy. Echocardiography was performed in 89 patients with essential hypertension who were treated with Valsartan before and after 4 weeks treatment 36 patients with essential hypertension were control. After 4 weeks treatment, the systolic and diastolic blood pressure decreased obviously, peak flow velocity and time velocity integral of atrial contraction decreasd P 0.001 and 0.05), and E/A ratio significantly increased (P 0.01). There were no changes in systolic function in patients treated by Valsartan and in control subjects. Valsartan could effectively decrease blood pressure and improve left ventricular diastolic function in patients with essential hypertension.