ITGB2 is a central hub-gene associated with inflammation and early fibro-atheroma development in a swine model of atherosclerosis.

Background and aim: The complex dynamic interplay between different biological pathways involved in atherosclerosis development has rendered the identification of specific therapeutic targets a challenging quest. We aimed to identify specific genes and mechanistic pathways associated with the early development of fibro-atheromas in a swine model of atherosclerosis. Methods: The Wisconsin Miniature Swine™ model of Familial Hypercholesterolemia (WMS-FH, n = 11) and genetically related WMS controls (WMS-N, n = 11) were used. The infrarenal aorta was harvested from both groups for histopathologic and transcriptomic profiling at 12 months. Bioinformatic analysis was performed to identify hub genes and pathways central to disease pathophysiology. The expression of ITGB2, the top ranked hub gene, was manipulated in cell culture and the expression of interconnected genes was tested. Results: Fibro-atheromatous lesions were documented in all WMS-FH aortic tissues and displayed internal elastic lamina (IEL) disruption, significant reduction of myofibroblast presence and disorganized collagen deposition. No fibro-atheromas were observed in the control group. A total of 266 differentially expressed genes (DEGs) were upregulated in WMS-FH aortic tissues, while 29 genes were downregulated. Top identified hub genes included ITGB2, C1QA, LCP2, SPI1, CSF1R, C5AR1, CTSS, MPEG1, C1QC, and CSF2RB. Overexpression of ITGB2 resulted in elevated expression of other interconnected genes expressed in porcine endothelial cells. Conclusion: In a swine translational model of atherosclerosis, transcriptomic analysis identified ITGB2 as a central hub gene associated inflammation and early fibroatheroma development making it a potential therapeutic target at this stage of disease.

Longitudinal dynamics of circulating miRNAs in a swine model of familial hypercholesterolemia during early atherosclerosis.

Atherosclerosis is a complex progressive disease involving intertwined biological mechanisms. We aimed to identify miRNA expression dynamics at the early stages of atherosclerosis using a large swine model (Wisconsin Miniature Swine, WMS). A total of 18 female pigs; 9 familial hypercholesterolemic (WMS-FH) and 9 normal control swine (WMS-N) were studied. miRNA sequencing was performed on plasma cell-free RNA at 3, 6, and 9 months of age. RT-qPCR validated DE miRNAs in a new cohort of animals (n = 30) with both sexes. Gene ontology and mRNA targets for DE miRNAs were identified. In vivo multimodality imaging and histopathology were performed to document the presence of atherosclerosis at termination. 20, 19, and 9 miRNAs were significantly DE between the groups at months 3, 6, and 9, respectively. Most DE miRNAs and their target genes are involved in human atherosclerosis development. Coronary atherosclerosis was documented in 7/9 WMS-FH pigs. Control animals had no lesions. miR-138, miR-152, miR-190a, and miR-196a showed a significant diagnostic power at month 3, whereas miR-486, miR-126-3p, miR-335, and miR-423-5p were of significant diagnostic power at month 9. In conclusion, specific DE miRNAs with significant discriminatory power may be promising biomarkers for the early detection of coronary atherosclerosis.

Design and construction of three-dimensional physiologically-based vascular branching networks for respiratory assist devices.

Microfluidic lab-on-a-chip devices are changing the way that in vitro diagnostics and drug development are conducted, based on the increased precision, miniaturization and efficiency of these systems relative to prior methods. However, the full potential of microfluidics as a platform for therapeutic medical devices such as extracorporeal organ support has not been realized, in part due to limitations in the ability to scale current designs and fabrication techniques toward clinically relevant rates of blood flow. Here we report on a method for designing and fabricating microfluidic devices supporting blood flow rates per layer greater than 10 mL min-1 for respiratory support applications, leveraging advances in precision machining to generate fully three-dimensional physiologically-based branching microchannel networks. The ability of precision machining to create molds with rounded features and smoothly varying channel widths and depths distinguishes the geometry of the microchannel networks described here from all previous reports of microfluidic respiratory assist devices, regarding the ability to mimic vascular blood flow patterns. These devices have been assembled and tested in the laboratory using whole bovine or porcine blood, and in a porcine model to demonstrate efficient gas transfer, blood flow and pressure stability over periods of several hours. This new approach to fabricating and scaling microfluidic devices has the potential to address wide applications in critical care for end-stage organ failure and acute illnesses stemming from respiratory viral infections, traumatic injuries and sepsis.

Preclinical in vivo long-term evaluation of the novel Mitra-Spacer technology: experimental validation in the ovine model.

AIMS: The Mitra-Spacer (Cardiosolutions, Bridgewater, MA, USA) is designed to treat mitral regurgitation by introducing a dynamic spacer that constantly adapts to the changing haemodynamic conditions during the cardiac cycle. We aimed to evaluate the performance and safety of this device in the chronic ovine model. METHODS AND RESULTS: Eight sheep were enrolled in this study. Through a left thoracotomy, the Mitra-Spacer was inserted via the transapical approach and advanced into the left atrium (LA) under imaging guidance. Device performance and safety were evaluated up to 90 days using fluoroscopy, echocardiography and histopathology. The volume within the balloon spacer shifted during the cardiac cycle in all cases. Seven animals survived up to 90 days for terminal imaging and tissue harvest. Echocardiography showed no change in left ventricle (LV) ejection fraction from baseline to 90 days. There were no observations of changes in LV diastolic function, pulmonary vein inflow, or tricuspid valve function. Histological analysis demonstrated no significant injury to the mitral apparatus. CONCLUSIONS: In the healthy ovine model, Mitra-Spacer implantation was feasible and safe. At 90 days, no evidence of structural damage to the mitral apparatus or deterioration of cardiac performance was demonstrated.

Stenting and Adjunctive Delivery of Paclitaxel Via Balloon Coating Versus Durable Polymeric Matrix for De Novo Coronary Lesions: Clinical and Angiographic Results from the Prospective Randomized Trial.

BACKGROUND: There is limited comparative clinical data regarding the safety and efficacy profile of paclitaxel delivery via balloon versus stent-polymer matrix. In this study, we aimed to compare the clinical and angiographic results of two different methods of paclitaxel delivery among patients undergoing percutaneous coronary intervention (PCI) for single de novo coronary lesions. METHODS: A total of 202 patients undergoing PCI due to symptomatic heart disease and at least one significant coronary artery lesion were prospectively enrolled in a multicenter non-inferiority trial. Eligible patients were randomized to a revascularization with either a paclitaxel eluting stent (PES = Coroflex Please, B.Braun) or a bare metal stent (BMS) followed by a paclitaxel coated balloon (PCB) dilation (BMS = Coroflex + PCB = Sequent Please, B.Braun). Clinical follow-up was obtained at 9 months in all patients, whereas angiographic in a subset of 94 (46.5%) patients. RESULTS: The baseline characteristics were well balanced between groups. At 9 months, the primary endpoint of in-stent late lumen loss in BMS + PCB was comparable and non-inferior to PES (0.21 ± 0.5 vs. 0.30 ± 0.7 mm, respectively. P(non-inf) < 0.05). At 9 months, the incidence of MACE (7.0 vs. 6.9%, HR = 1, 95%CI: 0.3-2.8; P = 0.99), comprising the occurrence of myocardial infarction (4.9 vs. 3.0%, HR = 1.62, 95%CI: 0.4-6.5; P = 0.32), target lesion revascularization (6.9 vs. 5.0%, HR = 1.42, 95%CI: 0.4-4.4; p = 0.54) and stent thrombosis (4.9 vs. 3.0%, HR = 2.01, 95%CI: 0.5-7.4; P = 0.74) was comparable between BMS + PCB and PES, respectively. In the BMS + PCB group, thrombosis tended to occur within 30 days (3.9 vs. 1.0%; P = 0.38). CONCLUSIONS: Paclitaxel delivery via drug coated balloon or polymer-stent matrix achieved comparable angiographic and clinical results among patients with de novo coronary lesions. BMS + PCB revascularization was associated with a higher rate of stent thrombosis when compared to newer generation drug eluting stents, therefore, should be recommended as a bail-out for PCB alone angioplasty.

Early feasibility evaluation of thoracoscopically assisted transcatheter ventricular reconstruction in an experimental model of ischaemic heart failure with left anteroapical aneurysm.

AIMS: To test the feasibility of a thoracoscopically assisted, off-pump, transcatheter ventricular reconstruction (TCVR) approach in an ovine model of left ventricular (LV) anteroapical aneurysm. METHODS AND RESULTS: Myocardial infarction (MI) was induced by coil occlusion of the middle left anterior descending artery and diagonals. Two months after MI creation, TCVR was performed via a minimal thoracotomy in eight sheep. Under endoscopic and fluoroscopic guidance, trans-interventricular septal puncture was performed from the LV epicardial scar. A guidewire was externalised via a snare placed in the right ventricle from the external jugular vein. An internal anchor was inserted over the wire and positioned on the right ventricular septum and an external anchor was deployed on the LV anterior epicardium. Serial pairs of anchors were placed and plicated together to exclude the scar completely. Immediately after TCVR, echocardiography showed LV end-systolic volume decreased from pre-procedure 58.8±16.6 ml to 25.1±7.6 ml (p<0.01) and the ejection fraction increased from 32.0±7.3% to 52.0±7.5% (p<0.01). LV twist significantly improved (3.83±2.21 vs. pre-procedure -0.41±0.94, p=0.01) and the global peak-systolic longitudinal strain increased from -5.64% to -10.77% (p<0.05). CONCLUSIONS: TCVR using minimally invasive access techniques on the off-pump beating heart is feasible and resulted in significant improvement in LV performance.

Experimental evaluation of pharmacokinetic profile and biological effect of a novel paclitaxel microcrystalline balloon coating in the iliofemoral territory of swine.

BACKGROUND: New paclitaxel coated balloons (PCB) developments have been proposed to maintain therapeutic levels of drug in the tissue while decreasing particle release. In this series of studies, we evaluated the pharmacokinetic profile and biological effects after paclitaxel delivery via novel microcrystalline PCB coating (mcPCB, Pax®, Balton) in porcine iliofemoral arteries. METHODS: Ten domestic swine were enrolled yielding 24 iliofemoral segments for evaluation. In the pharmacokinetic study, nine mcPCBs were dilated for 60 sec and animals sacrificed after 1 hr, 3 and 7 days. Studied segments were harvested and tissue paclitaxel concentration was analyzed utilizing HPLC. In the biological response evaluation, self-expandable stents were implanted followed by post dilation with either mcPCB (n = 10) or POBA (n = 5). After 28 days, angiography was performed, animals were sacrificed and stented segments harvested for histopathological evaluation. RESULTS: The 1-hr, 3 and 7 days vessel paclitaxel concentrations were 152.9 ± 154.5, 36.5 ± 49.5, and 0.9 ± 0.7 ng/mg respectively. In the biological response study, stents in the mcPCB group presented lower angiographic measures of neointimal hyperplasia as expressed by late loss when compared to POBA (-0.43 ± 0.9 vs. 0.23 ± 1.2; P = 0.24) at 28 days. In the histopathological evaluation, percent area of stenosis (%AS) was reduced by 42% in the mcPCB group (P < 0.05). The healing process in mcPCB group was comparable to POBA with regard to fibrin deposition (0.7 vs. 0.7; P = ns), neointimal maturity (1.97 vs. 1.93; P = ns), inflammation score (0.92 vs. 1; P = ns) and endothelialization score (1.77 vs. 1.73; P = ns). The mcPCB group did however display a greater tendency of medial cell loss and mineralization (60% vs. 0; P = 0.08). CONCLUSIONS: Delivery of paclitaxel via a novel mcPCB resulted in low long-term tissue retention of paclitaxel. However, this technological approach displayed reduced neointimal proliferation and favorable healing profile.

Tissue uptake, distribution, and healing response after delivery of paclitaxel via second-generation iopromide-based balloon coating: a comparison with the first-generation technology in the iliofemoral porcine model.

OBJECTIVES: This study sought to evaluate vascular drug uptake, distribution and response of second-generation paclitaxel coated balloon (PCB) (Cotavance, MEDRAD Interventional, Indianola, Pennsylvania) and compare it with first-generation technology, containing identical excipient and drug concentration. BACKGROUND: Original PCB technologies displayed a heterogeneous deposition of crystalline paclitaxel-iopromide inside the balloon folds, whereas second-generation PCBs consisted of more homogeneous, circumferential coatings. METHODS: Paclitaxel tissue uptake was assessed in 20 iliofemoral arteries of a domestic swine. Vascular healing response was assessed in the familial hypercholesterolemic model of iliofemoral in-stent restenosis. Three weeks after bare-metal stent implantation, vascular segments were randomly revascularized with first-generation PCBs (n = 6), second-generation PCBs (n = 6), or plain balloon angioplasty (PBA) (n = 6). At 28 days, angiographic and histological evaluation was performed in all treated segments. RESULTS: One-hour paclitaxel tissue uptake was 42% higher in the second-generation PCBs (p = 0.03) and resulted in more homogeneous segment-to-segment distribution compared with first-generation PCBs. Both angiography (percentage of diameter stenosis: second-generation 11.5 ± 11% vs. first-generation 21.9 ± 11% vs. PBA 46.5 ± 10%; p < 0.01) and histology (percentage of area stenosis: second-generation 50.5 ± 7% vs. first-generation 54.8 ± 18% vs. PBA 78.2 ± 9%; p < 0.01) showed a decrease in neointimal proliferation in both PCB groups. Histological variance of the percentage of area stenosis was lower in second-generation compared with first-generation PCBs (51.7 vs. 328.3; p = 0.05). The presence of peristrut fibrin deposits (0.5 vs. 2.4; p < 0.01) and medial smooth muscle cell loss (0 vs. 1.7; p < 0.01) were lower in the second-generation compared with first-generation PCBs. CONCLUSIONS: In the experimental setting, second-generation PCB showed a comparable efficacy profile and more favorable vascular healing response when compared to first-generation PCB. The clinical implications of these findings require further investigation.

Comparable clinical safety and efficacy of biodegradable versus durable polymer paclitaxel eluting stents despite shorter dual antiplatelet therapy: insights from a multicenter, propensity score-matched registry.

BACKGROUND: The biodegradable polymer drug-eluting stents have been proposed as an alternative to durable polymer DES, theoretically improving vessel healing and reducing the need for prolonged double anti platelet therapy (DAPT), however clinical significance of this technology is under debate. Therefore, we sought to compare the clinical outcomes of two Paclitaxel eluting stents (PES) containing different polymer-based eluting matrices. METHODS: In this multicenter registry of 392 consecutive patients who underwent PCI between June 2006 and September 2008, we included patients with stable angina or NSTE-ACS displaying at least one significant lesion (>50% diameter stenosis) in native coronary arteries. RESULTS: Biodegradable polymer PES (BP-PES, LUC Chopin(2) , Balton, Poland) was implanted in 206 patients, whereas durable polymer PES (DP-PES, Taxus, Boston Scientific, USA) was implanted in 186 patients. There were no significant differences in baseline characteristics between groups with the exception of increased diabetes and number of lesions for BP-PES. In risk-unadjusted analysis at 1-year follow-up, there were no significant differences in TLR (BP-PES: 8.4% vs. DP-PES: 6%; P = 0.36), TVR (BP-PES: 11.1% vs. DP-PES: 8.4%; P = 0.36) and incidence of stent thromboses (BP-PES: 2.15% vs. DP-PES: 3.4%; P = 0.42) between groups. There was also no difference in MACCE between groups (17.6% vs. 14.4%, P = 0.49). The mean dual antiplatelet therapy (DAPT) compliance at 1 year was 77% for BP-PES versus 92% for DP-PES (P = 0.03). Kaplan-Meier analysis showed a significantly higher long-term stroke free survival in BP-PES (P = 0.04). After adjustment, this was sustained with an additional tendency toward higher MI free survival for BP-PES (P = 0.059). CONCLUSIONS: In this observational analysis, BP-PES were comparable to DP-PES, with regard to incidence of repeated revascularizations, stent thromboses and MACCE despite earlier DAPT discontinuation.

Mechanism of gender-specific differences in aortic stiffness with aging in nonhuman primates.

BACKGROUND: Our hypothesis was that the changes in vascular properties responsible for aortic stiffness with aging would be greater in old male monkeys than old female monkeys. METHODS AND RESULTS: We analyzed the effects of gender differences in aging on in vivo measurements of aortic pressure and diameter and on extracellular matrix of the thoracic aorta in young adult (age, 6.6+/-0.5 years) versus old adult (age, 21.2+/-0.2 years) monkeys (Macaca fascicularis). Aortic stiffness, as represented by the pressure strain elastic modulus (Ep), increased more in old male monkeys (5.08+/-0.81; P<0.01) than in old females (3.06+/-0.52). In both genders, collagen density was maintained, collagen-bound glycation end products increased, and collagen type 1 decreased. However, elastin density decreased significantly (from 22+/-1.5% to 15+/-1.2%) with aging (P<0.05) only in males. Furthermore, only old males were characterized by a decrease (P<0.05) in collagen type 3 (an isoform that promotes elasticity) and an increase in collagen type 8 (an isoform that promotes the neointimal migration of vascular smooth muscle cells). In contrast to the data in monkeys, collagen types 1 and 3 both increased significantly in aging rats. CONCLUSIONS: There are major species differences in the effects of aging on aortic collagen types 1 and 3. Furthermore, because alterations in collagen density, collagen content, hydroxyproline, and collagen advanced glycation end products were similar in both old male and female monkeys, these factors cannot be responsible for the greater increase in stiffness in old males. However, changes in collagen isoforms and the decrease in elastin observed only in old males likely account for the greater increase in aortic stiffness.

Increased apoptosis and myocyte enlargement with decreased cardiac mass; distinctive features of the aging male, but not female, monkey heart.

We studied gender-specific changes in aging cardiomyopathy in a primate model, Macaca fascicularis, free of the major human diseases, complicating the interpretation of data specific to aging in humans. Left ventricular (LV) weight/body weight decreased, p<0.05, in old males but did not change in old females. However, despite the decrease in LV weight, mean myocyte cross-sectional area in the old males increased by 51%. This increase in myocyte size was not uniform in old males, i.e., it was manifest in only 20-30% of all the myocytes from old males. In old males there was a 4-fold increase in frequency of myocyte apoptosis without any increase in proliferation-capable myocytes assessed by Ki-67 expression. Apoptosis was unchanged in old female monkey hearts, whereas the frequency of myocytes expressing Ki-67 declined 90%. These results, opposite to findings from rodent studies, indicate distinct differences in which male and female monkeys maintain functional heart mass during aging. The old male hearts demonstrated increased apoptosis, which more than offset the myocyte hypertrophy. Interestingly, the hypertrophy was not uniform and there was no significant increase in myocyte proliferation.

Telomere dynamics in macaques and humans.

In humans, telomere length in proliferating tissues shortens with age--a process accelerated with age-related diseases. Thus, telomere length and attrition with age in the nonhuman primate may serve as a useful paradigm for understanding telomere biology in humans. We examined telomere parameters in tissues of young and old Macaca fascicularis and compared them with several tissues from humans. Macaque telomeres were variable in length and exhibited partial synchrony (equivalence) within animals. They were longer than humans, partially because of longer subtelomeric segments. As skeletal muscle telomere length was unchanged with age, we used it as an internal reference to offset interanimal variation in telomere length. We identified age-dependent telomere attrition in lung, pancreas, skin, and thyroid. Similar to humans, telomerase activity was detected in spleen, thymus, digestive tract, and gonads. We conclude that factors that modify telomere attrition and aging in humans may also operate in the macaque.

Sex-specific regulation of gene expression in the aging monkey aorta.

Although increased vascular stiffness is more prominent in aging males than females, and males are more prone to vascular disease with aging, no study has investigated the genes potentially responsible for sex differences in vascular aging. We tested the hypothesis that the transcriptional adaptation to aging differs in males and females using a monkey model, which is not only physiologically and phylogenetically closer to humans than the more commonly studied rodent models but also is not afflicted with the most common forms of vascular disease that accompany the aging process in humans, e.g., atherosclerosis, hypertension, and diabetes. The transcriptional profile of the aorta was compared by high-density microarrays between young and old males or females (n = 6/group). About 600 genes were expressed differentially when comparing old versus young animals. Surprisingly, <5% of these genes were shared between males and females. Radical differences between sexes were especially apparent for genes regulating the extracellular matrix, which relates to stiffness. Aging males were also more prone than females to genes switching smooth muscle cells from the "contractile" to "secretory" phenotype. Other sex differences involved genes participating in DNA repair, stress response, and cell signaling. Therefore, major differences of gene regulation exist between males and females in vascular aging, which may underlie the physiological differences characterizing aging arteries in males and females. Furthermore, the analyses in young monkeys demonstrated differences in genes regulating vascular structure, implying that the sex differences in vascular stiffness that develop with aging are programmed at an early age.

Obligatory role of cardiac nerves and alpha1-adrenergic receptors for the second window of ischemic preconditioning in conscious pigs.

We tested the hypothesis that cardiac nerves may mediate ischemic preconditioning. Pigs were chronically instrumented to measure aortic, left atrial and left ventricular pressures, and regional myocardial function (wall thickening). Hemodynamic variables, area at risk, and tissue blood flows (radioactive microspheres) were similar among groups. Myocardial infarct size following 60 minutes coronary artery occlusion and 4 days reperfusion, expressed as a fraction of the area at risk, was 42+/-4.0%, in innervated pigs and similar in pigs with regional cardiac denervation (CD, 41+/-2.5%). Infarct size in innervated pigs during the first window of preconditioning (first window) was markedly reduced (6+/-1.8%, P<0.01), as it was in the second window of preconditioning (second window) (16+/-3.3%, P<0.01). Although infarct size was still reduced in pigs with CD and first window preconditioning (9+/-1.8%, P<0.01), the protective effects of second window were abrogated in pigs with CD resulting in an infarct size of 38+/-5.6%. In another group of innervated pigs during pharmacological alpha(1)-adrenergic receptor (AR) blockade, infarct size was also not reduced during the second window (48+/-3.2%). Additionally, Western blot analysis of inducible nitric oxide synthase and cyclooxygenase-2 proteins demonstrated significant (P<0.05) upregulation following the second window in innervated pigs, but not in pigs with CD or alpha(1)-AR blockade. Thus, the mechanism of protection during the second window, but not the first window, appears to be dependent on cardiac nerves and alpha(1)-AR stimulation.

Cardiac nerves affect myocardial stunning through reactive oxygen and nitric oxide mechanisms.

The goal of this study was to investigate the role of cardiac nerves on the response to 90-minute coronary artery stenosis (CAS), which reduced coronary blood flow by 40% for 90 minutes, and subsequent myocardial stunning after reperfusion in chronically instrumented conscious pigs. In pigs with regional cardiac denervation (CD), myocardial stunning was intensified, ie, at 12 hours reperfusion wall thickening (WT) was depressed more, P<0.05, in CD (-46+/-5%) as compared with intact pigs (-31+/-3%) and remained depressed in CD at 24 hours reperfusion (-45+/-6%). Although the TTC technique was negative for infarct, histopathological analysis revealed patchy necrosis present in 11+/-2% of the area at risk. In intact pigs, WT had essentially recovered at 24 hours without infarct. In CD pigs treated with either an antioxidant, N-2-mercaptopropionyl glycine (MPG, 100 mg/kg per hour) or systemic nitric oxide synthase inhibition using N(omega)-nitro-L-arginine (L-NA, 30 mg/kg for 3 days), recovery of wall thickening was similar to that in pigs with intact nerves and without evidence of infarct. Immunohistochemistry analysis for 3-nitrotyrosine in tissue after CAS and 1 hour reperfusion demonstrated enhanced peroxynitrite-related protein nitration in pigs with regional CD compared with pigs with intact cardiac nerves, and pigs with regional CD and MPG or L-NA. Thus, reperfusion after myocardial ischemia in the setting of CD results in enhanced stunning and development of infarct. The underlying mechanism appears to involve nitric oxide and reactive oxygen species.

Gender differences on the effects of aging on cardiac and peripheral adrenergic stimulation in old conscious monkeys.

We examined the effects of gender and aging on cardiac and peripheral hemodynamic responses to beta-adrenergic receptor (beta-AR) stimulation in young (male = 5.9 +/- 0.4 yr old and female = 6.5 +/- 0.7 yr old) and old (male = 19.8 +/- 0.7 yr old and female = 21.2 +/- 0.2 yr old) conscious monkeys (Macaca fascicularis), chronically instrumented for measurements of left ventricular (LV) and arterial pressures as well as cardiac output. Baseline LV pressure, the first derivative of LV pressure (LV dP/dt), cardiac index, mean arterial pressure, total peripheral resistance (TPR), and heart rate in conscious monkeys were not different among the four groups. Increases in LV dP/dt in response to 0.1 microg/kg isoproterenol (Iso) were diminished (P < 0.05) in old males (+99 +/- 11%) compared with young males (+194 +/- 18%). In addition, the inotropic responses to norepinephrine (NE) and forskolin (FSK) were significantly depressed (P < 0.05) in old males. Iso-induced reductions of TPR were less (P < 0.05) in old males (-28 +/- 2%) than in young males (-49 +/- 2%). The changes of TPR in response to NE and FSK were also significantly attenuated (P < 0.05) in old males. However, the LV dP/dt responses to BAY y 5959 (15 microg. kg-1. min-1), a Ca2+ channel promotor independent of beta-AR signaling, were not significantly different between old and young males. In contrast to results in male monkeys, LV dP/dt and TPR responses to Iso, NE, and FSK in old females were similar to those observed in young females. Thus both cardiac contractile and peripheral vascular dynamic responses to beta-AR stimulation are preserved in old female but not old male monkeys. This may explain, in part, the reduced cardiovascular risk in the older female population.

Persistent stunning induces myocardial hibernation and protection: flow/function and metabolic mechanisms.

To test the hypothesis that persistent myocardial stunning can lead to hibernating myocardium, 13 pigs were chronically instrumented, and persistent stunning was induced regionally by 6 repetitive episodes of 90-minute coronary stenosis (CS) (30% reduction in baseline coronary blood flow [CBF]) followed by full reperfusion every 12 hours. During the 1st CS, CBF fell from 43+/-2 to 31+/-2 mL/min, and anterior wall thickening (AWT) fell by 54+/-8%, but posterior WT did not change. AWT never recovered fully and remained depressed by 31+/-7% before the 6th CS, reflecting persistent myocardial stunning, but baseline CBF was not changed. Surprisingly, during the 6th CS, AWT did not fall further despite a similar reduction in CBF during CS, as occurred with the 1st episode. Regional Mo2 fell similarly during the 1st and 6th CS. During the 1st CS, plasma glucose uptake increased, whereas free fatty acid (FFA) uptake was reduced. Before the 6th CS, glucose uptake remained elevated, whereas FFA uptake remained reduced. Histology revealed enhanced glycogen deposition, which could be explained by decreased glycogen synthase kinase (GSK)-3beta protein levels and activity. These results indicate that persistent stunning, even in the absence of chronic ischemia, can recapitulate the phenotype of myocardial hibernation. This results in a shift in the flow/function relationship where a 30% decrease in CBF is no longer accompanied by a fall in myocardial function, which could be explained, in part, by a shift in substrate utilization. These hemodynamic/metabolic adjustments could facilitate survival of hibernating myocardium.