Impaired Endothelial Function of the Umbilical Artery After Fetal Cardiac Bypass

Tissue-specific metabolomic profiling after cardiopulmonary bypass in fetal sheep

Objective

Fetal cardiopulmonary bypass (CPB) is essential to fetal heart surgery, while its development is limited by vital organ dysfunction after CPB. Studying organ metabolism may help to solve this problem. The objective of this study was to describe the tissue-specific metabolic fingerprints of fetal sheep under CPB and to associate them with organ functions.

Methods

Ten pregnant ewes at 90-120 days of gestation were randomly divided into two groups. The bypass group underwent a 1-h fetal CPB, whereas the control group underwent only a fetal sternotomy. During bypass, echocardiography, blood gases, and blood biochemistry were measured. After bypass, lambs were sacrificed, and tissues of the heart, liver, brain, kidney, and placenta were harvested. The metabolites extracted from these tissues were analyzed using non-targeted metabolomics based on liquid chromatography-mass spectrometry techniques.

Results

All tissues except the placenta displayed significant metabolic changes, and the fetal heart displayed obvious functional changes. Fetal sheep that underwent CPB had common and tissue-specific metabolic signatures. These changes can be attributed to dysregulated lipid metabolism, altered amino acid metabolism, and the accumulation of plasticizer metabolism.

Conclusion

Fetal CPB causes tissue-specific metabolic changes in fetal sheep. Studying these metabolic changes, especially cardiac metabolism, is of great significance for the study of fetal CPB.

Central and Peripheral Cannulation for Cardiopulmonary Bypass in Fetal Sheep: A Comparative Study

Objective:In-utero correction is an option for treatment of critical congenital heart diseases (CHDs). Fetal cardiac surgery for CHDs is dependent on the reliable use of fetal cardiopulmonary bypass (CPB), but this technology remains experimental. In this study, we established fetal CPB models with central and peripheral cannulation to explore the differences between the two cannulation strategies.

Methods: Ten fetal sheep with 90–110 gestational days were randomized into central cannulation (n = 5) and peripheral cannulation (n = 5) groups. All fetal CPB models were successfully established. At each time point (0, 30, and 60 min after initiation of CPB), echocardiography was performed. Blood samples were also collected for blood gas analysis and tests of myocardial enzymes and liver and kidney function.

Results: In the central cannulation group, right ventricular Tei index significantly increased (p = 0.016) over time. Compared with the peripheral cannulation group, the left ventricular Tei index of the central cannulation group was significantly higher (1.96 ± 0.31 vs. 0.45 ± 0.19, respectively; p = 0.028) and the stroke volume was lower (0.46 ± 0.55 vs. 2.13 ± 0.05, respectively; p = 0.008) at 60 min after CPB. Levels of liver and kidney injury markers and of acid-base balance, including alanine aminotransferase (ALT), aspartate aminotransferase/ALT ratio, blood urea nitrogen (BUN), BUN/creatinine ratio, base excess and bicarbonates, were significantly higher for peripheral than for central cannulation. Other important physiologic parameters, including heart rate, blood pressure, myocardial enzymes, umbilical artery beat index and resistance index, left ventricular Tei index, and left and right ventricular stroke volume, were comparable between the two groups.

Conclusions: Both central and peripheral cannulations can be used to establish fetal CPB models. Central cannulation causes more adverse impacts for cardiac function, whereas peripheral cannulation is more susceptible to complications related to inadequate organ perfusion.

Assessing the impact of total extracorporeal circulation on hemodynamics in an ovine fetal model

The present study aimed to evaluate the impact of total extracorporeal circulation on hemodynamics and placental function in an ovine fetal model. Mid-term ovine fetuses (n=6) underwent extracorporeal circulation (30 min), cardioplegic arrest (20 min) and monitoring (120 min). The ascending aorta and umbilical cords of the fetuses were occluded during the bypass and an extracorporeal membrane oxygenator was used as the oxygen source. Biventricular intracardiac pressures, echocardiographic data, blood gas levels and placental function variables were recorded, and statistical analysis was performed using the repeated-measure analysis of variance test. The data indicated that fetal heart rate and blood pressure at 30, 60, 90 and 120 min following the bypass were stable relative to pre-arrest baseline (pre-bypass) values (P>0.05). However, end diastolic pressures in the ovine right ventricles post-bypass were significantly increased at 30, 60, 90 and 120 min relative to pre-bypass pressures (P<0.05). The pulsatility index also increased at 30 min post-bypass relative to the pre-bypass score (0.91±0.06 vs. 0.61±0.14; P=0.007). The mean resistivity index at all time points post-bypass was consistent with the pre-bypass score (P>0.05), while the mean Tei index values for the left and right ventricles post-bypass were significantly higher at all time points relative to pre-bypass values (P<0.05). The pre-bypass fetal blood pH, SaO₂, base excess and lactate values were maintained during arrest (P>0.05). Fetal hemodynamics and placental function additionally remained stable for up to 2 h upon reperfusion following total extracorporeal circulation and cardioplegic arrest. Collectively these data suggest that the reproducible ovine fetal model may be useful in the evaluation of fetal cardiac surgery.

MicroRNA-34a targets regulator of calcineurin 1 to modulate endothelial inflammation after fetal cardiac bypass in goat placenta

INTRODUCTION

Placental dysfunction characterized by vascular endothelial inflammation is one of the most notable responses to fetal cardiac bypass. Regulator of calcineurin 1 (RCAN1) is an important regulator of inflammatory responses. MicroRNAs (miRNAs) are essential post-transcriptional modulators of gene expression, and miRNA-34a (miR-34a) was showed to activate vascular endothelial inflammation. We hypothesized that miR-34a may be a key regulator of placental dysfunction after fetal cardiac bypass.

METHODS

We evaluated miRNA expression in goat placentas via small RNA sequencing, quantitative real-time polymerase chain reaction (qRT-PCR) and in situ hybridization. Expression of miRNA target genes was determined via bioinformatics analyses and dual luciferase reporter assays. Furthermore, human umbilical vein endothelial cells (HUVECs) were transfected with miR-34a or a control sequence. The RCAN1, nuclear factor of activated T-cells (NFATC1) and nuclear factor kappa-B (NF-κB) levels in HUVECs and placentas were evaluated via Western blot and qRT-PCR.

RESULTS

We demonstrated that miR-34a was highly enriched in goat placenta after cardiopulmonary bypass. Moreover, RCAN1 was identified as a novel direct target of miR-34a. Transfection of miR-34a led to decreased RCAN1 expression and increased NFATC1 and NF-κB expression in HUVECs. Conversely, inhibition of miR-34a rescued RCAN1 expression and reduced NFATC1 and NF-κB expression in HUVECs.

CONCLUSIONS

We demonstrated a remarkable role of miR-34a as a regulator of NFATC1-associated placental inflammation through direct targeting of RCAN1. MiR-34a could serve as a novel therapeutic target for limiting the progression of placental inflammation after fetal cardiac bypass.

Changes in atrial natriuretic peptide levels during cardiac bypass in the fetal goat

The aim of this study is to evaluate the effect of fetal cardiac bypass on the production and secretion of fetal atrial natriuretic peptide (ANP) in the goat. Eighteen pregnant goats, at days 120 to 140 of gestation, were randomly divided into control (n = 8) and bypass (n = 10) groups. The control group underwent a sham procedure involving fetal sternotomy and cannulation. The bypass group underwent fetal cardiac bypass using a centrifugal pump for 30 min. Fetuses in the bypass group exhibited hypoxia, hypercapnia, and acidosis during and after cardiac bypass. The pulse index (PI) of the umbilical artery in the bypass group increased significantly after cardiac bypass compared with the control group. Tei indices of the left and right ventricles in the bypass group increased remarkably after cardiac bypass. Plasma troponin I levels in the bypass group increased significantly compared with that of the control group. Plasma ANP levels increased markedly in the bypass group after cardiac bypass, and the difference between two groups was significant. Transcriptional levels of ANP mRNA in the fetal heart elevated remarkably in the bypass group compared with the control group at 2 h after the bypass. A significant positive correlation between plasma ANP levels and Tei indices of the ventricles, plasma troponin I was observed (left ventricular Tei index, r = 0.606, P < 0.01; right ventricular Tei index, r = 0.581, P < 0.01; plasma troponin I, r = 0.275, P < 0.05). In conclusion, fetal cardiac bypass promoted the production and secretion of ANP and was associated with fetal cardiac dysfunction.

Cardiopulmonary bypass in the immature fetus through novel use of a mini-centrifugal pump

The concept that the natural history of certain heart defects could be positively modified through in utero intervention has stimulated extensive research in fetal cardiac intervention and surgery since the early 1980s. Since the management of certain defects would require the use of cardiopulmonary support, extensive studies have been directed toward the application of a variety of perfusion circuits. The unique features of the fetal patient have directed the focus of many of these designs toward miniaturization of components and minimization of prime volume. Large extracorporeal surface contact areas and prime volumes have been identified as potential contributors to a frequently observed placental dysfunction following fetal cardiopulmonary bypass (CPB). We set out to develop means of CPB using a centrifugal micro-system that would not require supplemental prime volume. We describe the unique application of an adult right heart assist device, primarily used for 'off-pump' coronary revascularization for fetal cardiopulmonary support. Finally, while previous fetal experiments have used late-gestation mature fetuses, we studied more immature fetuses of mid-gestation, relevant to current clinical attempts in fetal therapy.