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Published on: May 26, 2023
Apelin receptor (APJ) expression during cardiopulmonary bypass in children undergoing surgical repair
Susan Walker1, Mark H D Danton2, Alexander D Lang1
1Institute of Medical Genetics, University of Glasgow School of Medicine, Royal Hospital for Sick Children, Glasgow, United Kingdom.
Insights
Apelin APJ receptor (APJ) is present in infant heart tissue. Longer ischemia during surgery increased APJ expression, correlating with oxygen levels, but cyanosis or oxygen levels did not impact expression.
Area of Science:
- Cardiovascular Science
- Pediatric Cardiology
- Molecular Biology
Background:
- The Apelin-APJ system is implicated in cardiovascular function and heart failure in adults and animals.
- Investigating the Apelin APJ receptor (APJ) in pediatric myocardium is crucial for understanding congenital heart defect repair.
Purpose of the Study:
- To examine the expression and oxygen regulation of the Apelin APJ receptor (APJ) in pediatric myocardium.
- To determine the relationship between APJ expression, ischemia duration, and post-operative outcomes in children undergoing heart surgery.
Main Methods:
- Western blotting and Real-time PCR were employed to analyze APJ expression in infant myocardial samples.
- APJ mRNA expression was compared between cyanotic and acyanotic patients.
- In vitro experiments assessed the effect of hypoxic, normoxic, and hyperoxic conditions on APJ mRNA levels.
Main Results:
- APJ was detected in all myocardial samples, with higher levels observed after longer ischemia and cardioplegia durations (p<0.05).
- A significant correlation was found between APJ expression (after 10 min) and oxygen extraction ratio (p=0.021) and mixed venous oxygen saturation (p=0.028).
- No significant differences in APJ expression were noted between cyanotic and acyanotic patients, nor with varying oxygen re-perfusion levels.
Conclusions:
- Apelin APJ receptor (APJ) expression in pediatric myocardium changes during cardiopulmonary bypass.
- Further research is needed to elucidate the specific mechanisms driving these observed changes in APJ expression.
Background And Aims:
In human adults, and animals, the Apelin-APJ ligand-receptor system is emerging as having a role in the pathogenesis of cardiovascular function and heart failure. The aim was to investigate expression, and regulation by oxygen, of the Apelin APJ receptor (APJ) in myocardium obtained from children undergoing corrective surgery with cardiopulmonary bypass for repair of congenital heart defects.
Methods:
Western blotting and Real-time PCR were used to determine if APJ was expressed in the infant myocardium, if expression was influenced by the duration of myocardial ischemia and if any relationship existed between APJ expression and early post-operative outcome. The next aim was to determine if there was a difference in mRNA expression of APJ in myocardium from cyanotic patients compared with acyanotic patients and if re-perfusing myocardium in vitro with either hypoxic, normoxic or hyperoxic oxygen affected APJ mRNA expression.
Results:
APJ was expressed in all myocardial samples and myocardium exposed to longer durations of ischemia and cardioplegia expressed higher levels of APJ (p<0.05). There was a significant correlation between APJ expression in myocardium resected after 10 min with both oxygen extraction ratio (p=0.021, rho= -0.523) and mixed venous oxygen saturation (p=0.028, rho 0.52). This association did not exist for myocardium collected before 10 min. There was no difference in APJ expression between cyanotic and acyanotic patients. No difference was found in APJ expression whether re-perfused with low, normal or high oxygen.
Conclusions:
Changes in APJ expression were observed during cardiopulmonary bypass in children and the reasons for this require further investigation.
