Surgical Swine Model of Chronic Cardiac Ischemia Treated by Off-Pump Coronary Artery Bypass Graft Surgery

Improving long-term postoperative survival in a porcine cardiac valve surgery model utilizing cardiopulmonary bypass via left thoracotomy: a single-center experience sharing insights

Objective

The objective of this study was to improve long-term postoperative survival in a porcine cardiac valve surgery model by utilizing cardiopulmonary bypass (CPB) via left thoracotomy. The study aimed to share refined techniques and insights accumulated over years at a single-center animal clinical trial facility.

Method

A total of 196 Chinese Large White pigs weighing between 60 and 75 kg were used in the study. All animals underwent cardiac valve surgeries via left thoracotomy with CPB. Surgical techniques included mitral valve replacement, mitral valve repair, aortic valve replacement, OZAKI procedure, ascending aorta replacement, and left ventricular assist device implantation. Anesthesia and CPB protocols were optimized to minimize stress and complications. Postoperative care was standardized to enhance recovery and survival.

Result

All 196 pigs survived the surgical procedures, with no deaths reported. The mean surgical duration was 168.55 ± 38.75 min, CPB time was 114.89 ± 32.11 min, and aortic cross-clamp time was 76.75 ± 21.33 min. Automatic heart resumption occurred in 63.8% of pigs, while the remainder required electrical defibrillation or cardiac massage. The postoperative mechanical ventilation time was 2.44 ± 0.58 min, and the average drainage volume at 2 h postoperatively was 27.50 ± 9.70 ml. There were no cases of postoperative hemorrhage complications or blood transfusions, and surgical site infections occurred in only 1.5% of pigs.

Conclusion

The surgical approach utilizing left thoracotomy with CPB has proven effective in significantly enhancing long-term survival rates in porcine heart surgeries. The refined techniques and standardized operational procedures described in this study offer valuable insights for researchers aiming to improve the success of porcine heart valve surgical models. However, due to differences in animal anatomy, the applicability of this surgical approach to other animal models still requires further exploration.

CoQ10 enhances PGC1α and increases expression of mitochondrial antioxidant proteins in chronically ischemic swine myocardium

Background

Expression of mitochondrial proteins is reduced within hibernating myocardium (HM). It is unclear whether dietary supplementation with CoQ₁₀ can increase expression of mitochondrial electron transport chain (ETC) and antioxidant proteins within this tissue. In a swine model of HM, we tested whether dietary administration of CoQ₁₀ for four weeks enhances the expression of ETC and antioxidant proteins within the mitochondria via increased PGC1α signaling.

Methods

12 swine were instrumented with a fixed constrictor around the LAD artery to induce gradual stenosis. At three months, transthoracic ECHO was performed to confirm the presence of a wall motion abnormality in the anterior wall. Animals were then randomly assigned to receive daily dietary supplements of either CoQ₁₀ (10 mg/kg/day) or placebo for four weeks. At this time, animals underwent a final ECHO and terminal procedure. Expression of nuclear-bound PGC1α (Western blots) and mitochondrial proteins (Tandem Mass Tag) were determined.

Results

Mitochondrial and nuclear membranes were isolated from the LAD region. Nuclear-bound PGC1α levels were > 200-fold higher with administration of four weeks of CoQ₁₀ treatment (p = 0.016). Expression of ETC proteins was increased in those animals that received CoQ₁₀. Compared with mitochondria in the LAD region from placebo-treated pigs, CoQ₁₀-treated pigs had higher levels of Complex I (p = 0.03), Complex IV (p = 0.04) and Complex V (p = 0.028) peptides.

Conclusions

Four weeks of dietary CoQ₁₀ in HM pigs enhances active, nuclear-bound PGC1α and increases the expression of ETC proteins within mitochondria of HM tissue.

Mitochondrial Respiratory Capacity is Restored in Hibernating Cardiomyocytes Following Co-Culture with Mesenchymal Stem Cells

Hibernating myocardium is a subset of ischemic cardiac disease characterized by viable but dysfunctional tissue. Standard treatment for hibernating myocardium is coronary artery bypass graft, which reduces arrhythmias and improves survival but does not fully restore function, presenting a gap in currently available treatments. Large animal studies of hibernating myocardium have identified impaired mitochondrial dynamics as a root cause of persistent cardiac dysfunction despite surgical revascularization. This study presents a novel in vitro model of hibernating myocardium cardiomyocytes to study active mitochondrial respiration in hibernating myocardium cells, and to test the paracrine effect of mesenchymal stem cells on impaired mitochondrial function. Exposure of cardiomyocytes to hypoxic conditions of 1% oxygen for 24 hours resulted in a phenotype consistent with hibernating myocardium cardiac tissue, including decreased respiratory capacity under high work states, decreased expression of mitochondrial proteins, and preserved cellular viability. Co-culture of hibernating myocardium cardiomyocytes with mesenchymal stem cells restored mitochondrial respiratory function, potentially via an increase in proliferator-activated receptor gamma coactivator 1-alpha-driven mitochondrial biogenesis. Co-culture treatment of hibernating myocardium cardiomyocytes with mesenchymal stem cells shows improvement in both mitochondrial function and ATP production, both of which are critical for effectively functioning cardiac tissue. These results suggest that mesenchymal stem cell therapy as an adjunct treatment to revascularization may address the current gap in treatment for hibernating myocardium patients.