Effects of gradual coronary artery occlusion and exercise training on gene expression in swine heart

Mild exercise along with limb blood-flow restriction modulates the electrocardiogram, angiotensin, and apelin receptors of the heart in aging rats

OBJECTIVES

Considering the lack of information, the effects of mild endurance exercise plus blood flow restriction (BFR) on electrocardiographic parameters, hypertrophy index, and expression of angiotensin II receptors type 1 (AT1R) and type 2 (AT2R) and apelin receptor (APJ) were assessed in hearts of old male rats.

MATERIALS AND METHODS

Animal were grouped as control (CTL), Sham (Sh), lower extremities blood flow restriction (BFR), exercise (Ex), Sham + exercise (Sh + Ex), and blood flow restriction + exercise (BFR + Ex).

RESULTS

Exercise plus BFR significantly decreased the corrected QT (QTc) interval (P<0.01 vs CTL and Sh groups) and increased the heart hypertrophy index (P<0.05 vs CTL and BFR groups). Exercise alone increased expression of the APJ (P<0.01, vs CTL, Sh, and BFR groups) and AT2 receptors (P<0.001, vs Sh, CTL, BFR, and BFR + exercise groups), whereas it reduced expression of AT1R (P<0.01 in comparison with CTL, Sh, and BFR groups). Exercise plus BFR caused a significant increase in APJ (P<0.05 vs Ex, Sh+Ex and P<0.001 vs CTL, Sh, and BFR groups) and also expression of AT1R (P<0.001 vs Ex, Sh + Ex, CTL, Sh, and P<0.01 vs BFR groups). Accompaniment of exercise with BFR destroyed the effect of exercise on the expression of AT2R.

CONCLUSION

Mild endurance exercise plus BFR can alter the expression of angiotensin II and apelin receptors that leads to cardiac hypertrophy and improves the ventricular conductivity of aging rats.

Calcification or Not. This Is the Question. A 1-Year Study of Bovine Pericardial Vascular Patches (CardioCel) in Minipigs

A main problem with bioprosthesis used for surgical correction of congenital cardiac malformation is its tendency to shrink and to calcify. Recently, a new material, that is, decellularized bovine pericardium (CardioCel), was introduced in clinics. It was proposed that this new patch material should not calcify and should be particularly suitable for the correction of vascular defects in inborn cardiac diseases. The aim of our chronic minipig study was to evaluate the performance of CardioCel patches implanted in aortic and pulmonary artery position, respectively. Ten minipigs aged 3 months were operated on. A CardioCel patch was implanted in the aorta ascendens and arteria pulmonalis, respectively. Seven minipigs completed the 12 months' follow-up. Angiography of both vessels, measurement of pressure gradients, and histologic evaluation of the implanted patches were carried out. Angiography of both great vessels revealed a good clinical outcome without stenosis. However, histologic examination of the patches showed calcification and neo-formation of hyaline cartilage in both vessel types. Staining of collagen and elastic fibers as well as α-smooth muscle actin demonstrated that the patches did not remodel into an anatomic vascular structure during the 1 year of implantation. In our chronic piglet model, CardioCel patches, when implanted in the ascending aorta and the pulmonary artery, led to calcification and neo-formation of hyaline cartilage in both vessel types 1 year after implantation. The present study indicates that the ideal patch biomaterial for repair of inborn cardiac diseases is still a goal not achieved yet.

The porcine innate immune system: an update

Over the last few years, we have seen an increasing interest and demand for pigs in biomedical research. Domestic pigs (Sus scrofa domesticus) are closely related to humans in terms of their anatomy, genetics, and physiology, and often are the model of choice for the assessment of novel vaccines and therapeutics in a preclinical stage. However, the pig as a model has much more to offer, and can serve as a model for many biomedical applications including aging research, medical imaging, and pharmaceutical studies to name a few. In this review, we will provide an overview of the innate immune system in pigs, describe its anatomical and physiological key features, and discuss the key players involved. In particular, we compare the porcine innate immune system to that of humans, and emphasize on the importance of the pig as model for human disease.

Physiological performance of a detergent decellularized heart valve implanted for 15 months in Vietnamese pigs: surgical procedure, follow-up, and explant inspection

This study features the longest experimental follow-up for decellularized heart valves implanted in an animal model. Porcine aortic heart valves were decellularized according to a disclosed standardized method in which TRITON X-100 and sodium cholate (TRICOL) are used in succession, followed by a further treatment with the endonuclease Benzonase to completely remove the nucleic acid remnants. Experimental animals (n = 17), represented by Vietnamese pigs (VPs), received a decellularized aortic allograft as a substitute for the replacement of their right ventricular outflow tract. The surgical implantation of the TRICOL-treated aortic valve conduit was successful in 11 VPs, while perioperative or postoperative complications occurred in the remaining six animals. In the sham-operated group (n = 4), the native pulmonary root was excised and immediately reimplanted orthotopically in the same animal. Echocardiography demonstrated a satisfactory hemodynamic performance of the TRICOL-treated valves during follow-up as well as the absence of relevant leaflet alterations concerning thickness and motility or valve insufficiency. At explantation, macroscopic inspection of tissue-engineered heart valve conduits did not evidence calcifications and showed a decreased wall thickness, comparable to that of the reimplanted native pulmonary roots. Noteworthy, extended functional performance, recovery of DNA content, and active extracellular matrix precursor incorporation are apparently compatible with the properties of a living self-supporting substitute.

Ca²⁺ sensitization of cardiac myofilament proteins contributes to exercise training-enhanced myocardial function in a porcine model of chronic occlusion

Exercise training has been shown to improve cardiac dysfunction in both patients and animal models of coronary artery disease; however, the underlying cellular and molecular mechanisms have not been completely understood. We hypothesized that exercise training would improve force generation in the myocardium distal to chronic coronary artery occlusion via altered intracellular Ca(2+) concentration ([Ca(2+)](i)) cycling and/or Ca(2+) sensitization of myofilaments. Ameroid occluders were surgically placed around the proximal left circumflex coronary artery of adult female Yucatan pigs. Twenty-two weeks postoperatively, the myocardium was isolated from nonoccluded (left anterior descending artery dependent) and collateral-dependent (formerly left circumflex coronary artery dependent) regions of sedentary (pen confined) and exercise-trained (treadmill run, 5 days/wk for 14 wk) pigs. Force measurements in myocardial strips showed that the percent change in force at stimulation frequencies of 3 and 4 Hz relative to 1 Hz was significantly higher in exercise-trained pigs compared with sedentary pigs. β-Adrenergic stimulation with dobutamine significantly improved force kinetics in myocardial strips of sedentary but not exercise-trained pigs at 1 Hz. Additionally, time to peak and half-decay of intracellular Ca(2+) (340-to-380-nm fluoresence ratio) responses at 1 Hz were significantly decreased in the collateral-dependent region of exercise-trained pigs with no difference in peak [Ca(2+)](i) between groups. Furthermore, the skinned myocardium from exercise-trained pigs showed an increase in Ca(2+) sensitivity compared with sedentary pigs. Immunoblot analysis revealed that the relative levels of cardiac troponin T and β(1)-adrenergic receptors were decreased in hearts from exercise-trained pigs independent of occlusion. Also, the ratio of phosphorylated to total myosin light chain-2, basal phosphorylation levels of cardiac troponin I (Ser(23) and Ser(24)), and cardiac myosin binding protein-C (Ser(282)) were unaltered by occlusion or exercise training. Thus, our data demonstrate that exercise training-enhanced force generation in the nonoccluded and collateral-dependent myocardium was associated with improved Ca(2+) transients, increased Ca(2+) sensitization of myofilament proteins, and decreased expression levels of β(1)-adrenergic receptors and cardiac troponin T.

Signaling responses after exposure to 5 alpha-dihydrotestosterone or 17 beta-estradiol in norepinephrine-induced hypertrophy of neonatal rat ventricular myocytes

Androgens appear to enhance, whereas estrogens mitigate, cardiac hypertrophy. However, signaling pathways in cells for short (3 min) and longer term (48 h) treatment with 17beta-estradiol (E2) or 5 alpha-dihydrotestosterone (DHT) are understudied. We compared the effect of adrenergic stimulation by norepinephrine (NE; 1 microM) alone or in combination with DHT (10 nM) or E2 (10 nM) treatment in neonatal rat ventricular myocytes (NRVMs) by cell area, protein synthesis, sarcomeric structure, gene expression, phosphorylation of extracellular signal-regulated (ERK), and focal adhesion kinases (FAK), and phospho-FAK nuclear localization. NE alone elicited the expected hypertrophy and strong sarcomeric organization, and DHT alone gave a similar but more modest response, whereas E2 did not alter cell size. Effects of NE dominated when used with either E2 or DHT with all combinations. Both sex hormones alone rapidly activated FAK but not ERK. Long-term or brief exposure to E2 attenuated NE-induced FAK phosphorylation, whereas DHT had no effect. Neither hormone altered NE-elicited ERK activation. Longer term exposure to E2 alone reduced FAK phosphorylation and reduced nuclear phospho-FAK, whereas its elevation was seen in the presence of NE with both sex hormones. The mitigating effects of E2 on the NE-elicited increase in cell size and the hypertrophic effect of DHT in NRVMs are in accordance with results observed in whole animal models. This is the first report of rapid, nongenomic sex hormone signaling via FAK activation and altered FAK trafficking to the nucleus in heart cells.

Advances in swine biomedical model genomics

This review is a short update on the diversity of swine biomedical models and the importance of genomics in their continued development. The swine has been used as a major mammalian model for human studies because of the similarity in size and physiology, and in organ development and disease progression. The pig model allows for deliberately timed studies, imaging of internal vessels and organs using standard human technologies, and collection of repeated peripheral samples and, at kill, detailed mucosal tissues. The ability to use pigs from the same litter, or cloned or transgenic pigs, facilitates comparative analyses and genetic mapping. The availability of numerous well defined cell lines, representing a broad range of tissues, further facilitates testing of gene expression, drug susceptibility, etc. Thus the pig is an excellent biomedical model for humans. For genomic applications it is an asset that the pig genome has high sequence and chromosome structure homology with humans. With the swine genome sequence now well advanced there are improving genetic and proteomic tools for these comparative analyses. The review will discuss some of the genomic approaches used to probe these models. The review will highlight genomic studies of melanoma and of infectious disease resistance, discussing issues to consider in designing such studies. It will end with a short discussion of the potential for genomic approaches to develop new alternatives for control of the most economically important disease of pigs, porcine reproductive and respiratory syndrome (PRRS), and the potential for applying knowledge gained with this virus for human viral infectious disease studies.