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Endothelial apoptosis and circulating endothelial cells after bypass grafting with and without cardiopulmonary bypass
Franz-Xaver Schmid1, Nalini Vudattu, Bernhard Floerchinger
1Department of Cardiothoracic and Vascular Surgery, University Hospital of Regensburg, Franz-Josef-Strauss-Allee 11, D-93053 Regensburg, Germany. fx.schmid@klinik.uni.regensburg.de
Insights
Off-pump coronary artery bypass grafting (CABG) is associated with lower levels of circulating endothelial cells (CEC) and reduced endothelial cell death compared to on-pump CABG. These findings suggest less endothelial damage during off-pump procedures.
Area of Science:
- Cardiovascular Surgery
- Endothelial Biology
- Surgical Outcomes
Background:
- Coronary artery bypass grafting (CABG) involves significant physiological stress.
- Endothelial cells (EC) play a crucial role in vascular health and are susceptible to damage during surgical procedures.
- Circulating endothelial cells (CEC) and endothelial cell apoptosis are indicators of endothelial activation and injury.
Purpose of the Study:
- To compare the levels of circulating endothelial cells (CEC) and the serum's capacity to induce human endothelial cell (hEC) apoptosis between on-pump and off-pump CABG patients.
- To evaluate the impact of cardiopulmonary bypass (CPB) on endothelial response during CABG surgery.
Main Methods:
- A comparative study involving 30 CABG patients, randomly assigned to either off-pump (n=15) or on-pump (n=15) procedures.
- Blood samples were collected preoperatively and at multiple time points up to 48 hours post-surgery.
- CEC were quantified using immunomagnetic separation, and serum-induced hEC apoptosis was assessed via tissue culture assays and microscopy.
Main Results:
- Both on-pump and off-pump CABG led to significant elevations in CEC numbers and hEC apoptosis post-surgery (p<0.01).
- Patients undergoing off-pump CABG exhibited significantly lower CEC levels (p=0.04) and reduced hEC apoptosis (p=0.03) compared to the on-pump group.
- Peak CEC counts and hEC apoptosis were observed at 6 hours and 4 hours post-surgery, respectively, with elevated levels persisting up to 48 hours in both groups.
Conclusions:
- Elevated CEC and endothelial apoptosis serve as markers of endothelial activation and damage following CABG.
- CABG utilizing cardiopulmonary bypass (on-pump) is associated with a more pronounced endothelial response than off-pump CABG (OPCAB) in the immediate postoperative period.
- Off-pump CABG may offer a protective effect on the endothelium compared to on-pump procedures.
Objective:
We compared profiles of the numbers of circulating endothelial cells (CEC) and the apoptosis-inducing capacity of serum samples on human endothelial cells (hEC) in on-pump and off-pump coronary artery bypass grafting (CABG) patients.
Methods:
Blood samples from 30 patients undergoing CABG (randomly assigned to two groups: 15 patients off-pump and 15 on-pump (cardiopulmonary bypass, CPB)) were collected after induction of anesthesia (preoperatively), at weaning from CPB/end of bypass grafting (0 h), and 1, 6, 12, 24, and 48 h afterwards. CEC were isolated with immunomagnetic anti-CD146-coated Dynabeads, and counted in a Nageotte chamber. The apoptosis-inducing activity of serum samples on hEC was examined by a tissue culture assay system. Apoptotic and normal cells were identified using phase contrast/fluorescence microscopy after DNA dye staining.
Results:
CEC numbers and proportions of apoptotic hEC were significantly elevated during and after surgery in both groups (p<0.01). Compared with the on-pump group, CEC and proportions of apoptotic hEC were significantly lower (p=0.04 and p=0.03, respectively) in patients having CABG performed off-pump. Starting at comparable baseline levels, the mean CEC-number was highest at 6h postoperatively with 81.9 ml(-1) (range, 44-141) for on-pump patients and 63.3 ml(-1) (range, 48-105) for off-pump patients. hEC apoptosis peaked also at T4: 16.5+/-2.8% versus 11.3+/-2.2%. In both groups, CEC numbers and proportions of endothelial apoptosis were still elevated at 48 h after surgery.
Conclusion:
The number of circulating endothelial cells and apoptotic endothelial cell death are markers of endothelial activation and damage during CABG. This study provides evidence that CABG with the use of CPB in comparison to OPCAB surgery is associated with a significantly more pronounced endothelial response in the immediate postoperative period.
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