Stereological assessment of the blood-air barrier and the surfactant system after mesenchymal stem cell pretreatment in a porcine non-heart-beating donor model for lung transplantation.

More frequent utilization of non-heart-beating donor (NHBD) organs for lung transplantation has the potential to relieve the shortage of donor organs. In particular with respect to uncontrolled NHBD, concerns exist regarding the risk of ischaemia/reperfusion (IR) injury-related graft damage or dysfunction. Due to their immunomodulating and tissue-remodelling properties, bone-marrow-derived mesenchymal stem cells (MSCs) have been suspected of playing a beneficial role regarding short- and long-term survival and function of the allograft. Thus, MSC administration might represent a promising pretreatment strategy for NHBD organs. To study the initial effects of warm ischaemia and MSC application, a large animal lung transplantation model was generated, and the structural organ composition of the transplanted lungs was analysed stereologically with particular respect to the blood-gas barrier and the surfactant system. In this study, porcine lungs (n = 5/group) were analysed. Group 1 was the sham-operated control group. In pigs of groups 2-4, cardiac arrest was induced, followed by a period of 3 h of ventilated ischaemia at room temperature. In groups 3 and 4, 50 × 106 MSCs were administered intravascularly via the pulmonary artery and endobronchially, respectively, during the last 10 min of ischaemia. The left lungs were transplanted, followed by a reperfusion period of 4 h. Then, lungs were perfusion-fixed and processed for light and electron microscopy. Samples were analysed stereologically for IR injury-related structural parameters, including volume densities and absolute volumes of parenchyma components, alveolar septum components, intra-alveolar oedema, and the intracellular and intra-alveolar surfactant pool. Additionally, the volume-weighted mean volume of lamellar bodies (lbs) and their profile size distribution were determined. Three hours of ventilated warm ischaemia was tolerated without eliciting histological or ultrastructural signs of IR injury, as revealed by qualitative and quantitative assessment. However, warm ischaemia influenced the surfactant system. The volume-weighted mean volume of lbs was reduced significantly (P = 0.024) in groups subjected to ischaemia (group medians of groups 2-4: 0.180-0.373 µm³) compared with the sham control group (median 0.814 µm³). This was due to a lower number of large lb profiles (size classes 5-15). In contrast, the intra-alveolar surfactant system was not altered significantly. No significant differences were encountered comparing ischaemia alone (group 2) or ischaemia plus application of MSCs (groups 3 and 4) in this short-term model.

Localization of Exogenous Mesenchymal Stem Cells in a Pig Model of Lung Transplantation.

BACKGROUND: Mesenchymal stem cells (MSCs) have a great potential for the treatment of acute lung injury. This study provides a detailed immunohistochemical and stereological analysis of the localization and distribution of exogenous MSC in a pig model of lung transplantation after intravascular or endobronchial application. METHODS: MSC derived from human bone marrow were labeled by DiI and administered intravascularly or endobronchially to the lungs of donor pigs after a period of 3 hours warm and 3 hours cold ischemia. The left lung was transplanted to a recipient pig and reperfused for 4 hours before fixation. The right donor lung was fixed for microscopic analysis directly after the ischemia time. RESULTS: After both administration routes, a similar number of exogenous MSC was found in the lungs. Within each animal, the heterogeneity of MSC distribution was high both with respect to left and right lung as well as to the different lobes of each lung. After endobronchial application, MSC were found in alveolar and bronchial/bronchiolar lumen, whereas after intravascular administration, they were mainly observed in blood vessels. CONCLUSION: Although the administration of exogenous MSC is possible by endobronchial or intravascular application, it yields a heterogeneous distribution in the lungs which may warrant strategies to improve a more homogeneous distribution.

Long-term results after lung transplantation using organs from circulatory death donors: a propensity score-matched analysis†.

OBJECTIVES: Due to organ shortage in lung transplantation (LTx), donation after circulatory death (DCD) has been implemented in several countries, contributing to an increasing number of organs transplanted. We sought to assess long-term outcomes after LTx with organs procured following circulatory death in comparison with those obtained from donors after brain death (DBD). METHODS: Between January 2007 and November 2013, 302 LTxs were performed in our institution, whereby 60 (19.9%) organs were retrieved from DCD donors. We performed propensity score matching (DCD:DBD = 1:2) based on preoperative donor and recipient factors that were significantly different in univariate analysis. RESULTS: After propensity matching, there were no statistically significant differences between the groups in terms of demographics and preoperative donor and recipient characteristics. There were no significant differences regarding intraoperative variables and total ischaemic time. Patients from the DCD group had significantly higher incidence of primary graft dysfunction grade 3 at the end of the procedure (P = 0.014), and significantly lower pO2/FiO2 ratio during the first 24 h after the procedure (P = 0.018). There was a trend towards higher incidence of the need for postoperative extracorporeal life support in the DCD group. Other postoperative characteristics were comparable. While the overall cumulative survival was not significantly different, the DCD group had significantly poorer results in terms of bronchiolitis obliterans syndrome (BOS)-free survival in the long-term follow-up. CONCLUSIONS: Long-term results after LTx with organs procured following DCD are in general comparable with those obtained after DBD LTx. However, patients transplanted using organs from DCD donors have a predisposition for development of BOS in the longer follow-up.

Endothelial Injury Associated with Cold or Warm Blood Cardioplegia during Coronary Artery Bypass Graft Surgery.

The aim of this investigation was to analyze the impact of intermittent cold blood cardioplegia (ICC) and intermittent warm blood cardioplegia (IWC) on endothelial injury in patients referred to elective on-pump coronary artery bypass graft (CABG) surgery. Patients undergoing CABG procedures were randomized to either ICC or IWC. Myocardial injury was assessed by CK-MB and cardiac troponin T (cTnT). Endothelial injury was quantified by circulating endothelial cells (CECs), von Willebrand factor (vWF), and soluble thrombomodulin (sTM). Perioperative myocardial injury (PMI) and major adverse cardiac events (MACE) were recorded. Demographic data and preoperative risk profile of included patients (ICC: n = 32, IWC: n = 36) were comparable. No deaths, PMI, or MACE were observed. Levels of CK-MB and cTnT did not show intergroup differences. Concentrations of CECs peaked at 6 h postoperatively with significantly higher values for IWC-patients at 1 h (ICC: 10.1 ± 3.9/mL; IWC: 18.4 ± 4.1/mL; P = 0.012) and 6 h (ICC: 19.3 ± 6.2/mL; IWC: 29.2 ± 6.7/mL; P < 0.001). Concentrations of vWF (ICC: 178.4 ± 73.2 U/dL; IWC: 258.2 ± 89.7 U/dL; P < 0.001) and sTM (ICC: 3.2 ± 2.1 ng/mL; IWC: 5.2 ± 2.4 ng/mL; P = 0.011) were significantly elevated in IWC-group at 1 h postoperatively. This study shows that the use of IWC is associated with a higher extent of endothelial injury compared to ICC without differences in clinical endpoints.

Preconditioning of skeletal myoblast-based engineered tissue constructs enables functional coupling to myocardium in vivo.

OBJECTIVE: Skeletal myoblasts fuse to form functional syncytial myotubes as an integral part of the skeletal muscle. During this differentiation process, expression of proteins for mechanical and electrical integration is seized, which is a major drawback for the application of skeletal myoblasts in cardiac regenerative cell therapy, because global heart function depends on intercellular communication. METHODS: Mechanically preconditioned engineered tissue constructs containing neonatal mouse skeletal myoblasts were transplanted epicardially. A Y-chromosomal specific polymerase chain reaction (PCR) was undertaken up to 10 weeks after transplantation to confirm the presence of grafted cells. Histologic and electrophysiologic analyses were carried out 1 week after transplantation. RESULTS: Cells within the grafted construct expressed connexin 43 at the interface to the host myocardium, indicating electrical coupling, confirmed by sharp electrode recordings. Analyses of the maximum stimulation frequency (5.65 ± 0.37 Hz), conduction velocity (0.087 ± 0.011 m/s) and sensitivity for pharmacologic conduction block (0.736 ± 0.080 mM 1-heptanol) revealed effective electrophysiologic coupling between graft and host cells, although significantly less robust than in native myocardial tissue (maximum stimulation frequency, 11.616 ± 0.238 Hz, P < .001; conduction velocity, 0.300 ± 0.057 m/s, P < .01; conduction block, 1.983 ± 0.077 mM 1-heptanol, P < .001). CONCLUSIONS: Although untreated skeletal myoblasts cannot couple to cardiomyocytes, we confirm that mechanical preconditioning enables transplanted skeletal myoblasts to functionally interact with cardiomyocytes in vivo and, thus, reinvigorate the concept of skeletal myoblast-based cardiac cell therapy.

Risk factors predictive of one-year mortality after lung transplantation.

OBJECTIVES: Lung transplantation (LTx) is a life-saving therapy for patients with end-stage lung disease. However, there remains a significant postoperative complication rate and mortality in this extreme patient group. The aim of the present study was to identify donor, recipient and perioperative risk factors for one-year mortality after LTx. METHODS: A total of 252 LTxs were performed in our institution between 2007 and 2013. Donor and recipient demographics and clinical characteristics of 1-year survivors and non-survivors were collected and compared retrospectively. Multivariate logistic regression analysis was performed on univariate predictors for 1-year mortality with an entry criterion of P < 0.05. RESULTS: Multivariate analysis revealed female-to-male transplantation (95% CI: 0.088-0.767; P = 0.015), lower pO2/FiO2-ratio at 72 h postoperatively (95% CI: 0.988-0.999; P = 0.024), need for postoperative extracorporeal membrane oxygenation (ECMO) support (95% CI: 0.035-0.658; P = 0.012) and on-pump technique (95% CI: 0.007-0.944; P = 0.045) as the only independent predictors for 1-year mortality. Mainly unplanned intraoperative conversion to cardiopulmonary bypass contributed to poorer survival in patients who underwent LTx using cardiopulmonary bypass (P < 0.001). CONCLUSIONS: Our results show that the unplanned use of CPB (conversion from off- to on-pump) might adversely affect outcome after LTx. Also, the negative impact of female-to-male transplantation should not be underestimated during recipient selection. Furthermore, poor early postoperative oxygenation, particularly with the need for extracorporeal oxygenation, might be a very strong negative prognostic factor after LTx.

Mesenchymal stem cell pretreatment of non-heart-beating-donors in experimental lung transplantation.

BACKGROUND: Lung transplantation (LTx) is still limited by organ shortage. To expand the donor pool, lung retrieval from non-heart-beating donors (NHBD) was introduced into clinical practice recently. However, primary graft dysfunction with inactivation of endogenous surfactant due to ischemia/reperfusion-injury is a major cause of early mortality. Furthermore, donor-derived human mesenchymal stem cell (hMSC) expansion and fibrotic differentiation in the allograft results in bronchiolitis obliterans syndrome (BOS), a leading cause of post-LTx long-term mortality. Therefore, pretreatment of NHBD with recipient-specific bone-marrow-(BM)-derived hMSC might have the potential to both improve the postischemic allograft function and influence the long-term development of BOS by the numerous paracrine, immunomodulating and tissue-remodeling properties especially on type-II-pneumocytes of hMSC. METHODS: Asystolic pigs (n = 5/group) were ventilated for 3 h of warm ischemia (groups 2-4). 50x106 mesenchymal-stem-cells (MSC) were administered in the pulmonary artery (group 3) or nebulized endobronchially (group 4) before lung preservation. Following left-lung-transplantation, grafts were reperfused, pulmonary-vascular-resistance (PVR), oxygenation and dynamic-lung-compliance (DLC) were monitored and compared to control-lungs (group 2) and sham-controls (group 1). To prove and localize hMSC in the lung, cryosections were counter-stained. Intra-alveolar edema was determined stereologically. Statistics comprised ANOVA with repeated measurements. RESULTS: Oxygenation (p = 0.001) and PVR (p = 0.009) following endovascular application of hMSC were significantly inferior compared to Sham controls, whereas DLC was significantly higher in endobronchially pretreated lungs (p = 0.045) with overall sham-comparable outcome regarding oxygenation and PVR. Stereology revealed low intrapulmonary edema in all groups (p > 0.05). In cryosections of both unreperfused and reperfused grafts, hMSC were localized in vessels of alveolar septa (endovascular application) and alveolar lumen (endobronchial application), respectively. CONCLUSIONS: Preischemic deposition of hMSC in donor lungs is feasible and effective, and endobronchial application is associated with significantly better DLC as compared to sham controls. In contrast, transvascular hMSC delivery results in inferior oxygenation and PVR. In the long term perspective, due to immunomodulatory, paracrine and tissue-remodeling effects on epithelial and endothelial restitution, an endobronchial NHBD allograft-pretreatment with autologous mesenchymal-stem-cells to attenuate limiting bronchiolitis-obliterans-syndrome in the long-term perspective might be promising in clinical lung transplantation. Subsequent work with chronic experiments is initiated to further elucidate this important field.

Outcomes after implantation of partial-support left ventricular assist devices in inotropic-dependent patients: Do we still need full-support assist devices?

OBJECTIVES: Partial-support left ventricular assist devices (LVADs) represent a novel strategy for heart failure treatment. The Synergy Pocket Micro-pump (HeartWare Inc, Framingham, Mass), the smallest surgically implanted long-term LVAD, provides partial flow up to 4.25 L/min and was primarily designed for "less sick" patients with severe heart failure. This device is implanted minimally invasively without sternotomy or cardiopulmonary bypass. Early implantation in patients with Interagency Registry for Mechanically Assisted Circulatory Support class 4 and higher was shown to be feasible and associated with significantly improved hemodynamics and quality of life. The aim of this study was to present our experience with implementation of long-term partial circulatory support as a bridge to transplantation in patients with more advanced heart failure who were dependent preoperatively on inotropic support or intra-aortic balloon pump. METHODS: In this observational study, only inotropic or intra-aortic balloon pump-dependent patients with end-stage heart failure were included (n = 12). These patients underwent Synergy device implantation between February 2012 and August 2013. RESULTS: The mean preoperative Interagency Registry for Mechanically Assisted Circulatory Support class was 2.17 ± 0.84 (class 1, 25%; class 2, 33%; class 3, 42%). The mean age was 46 ± 15 years, and 33% were female. Preoperatively, 4 patients (33%) had at least 1 previous sternotomy, 3 patients (25%) were supported with a balloon pump, 1 patient (8%) had a previous full-support LVAD, and 4 patients (33%) had cerebrovascular events in the past. After device implantation, there were no right ventricular failures, device-related infections, hemorrhagic strokes, arterial or venous thromboembolisms, or worsenings of aortic and mitral regurgitation observed over the follow-up. The mean follow up was 174 ± 171 days (range, 5-764 days; cumulative, 3199 days). One patient (8%) died, 3 patients (25%) successfully underwent transplantation, 1 device (8%) was explanted after myocardial recovery, and 5 patients (42%) are still on ongoing support. Two patients (17%) were upgraded to a full-support LVAD after 65 days of mean support. A total of 11 of 12 patients (92%) were discharged from the hospital and are presently alive. Left ventricular end-diastolic diameter was significantly reduced 3 months after device implantation. CONCLUSIONS: Partial LVAD support may be clinically efficacious in inotropic and intra-aortic balloon pump-dependent patients. On the basis of our experience and evidence of previous research, such patients may benefit from minimally invasive access, no need for sternotomy and cardiopulmonary bypass, a short implantation time, an easy exchange if necessary, and a lower risk of subsequent heart transplantation. Because the implantation is performed without sternotomy, device upgrade is feasible with a comparatively low operative risk and good clinical outcome. Our preliminary results show that partial-support devices may have the potential to replace full-support LVADs in the near future.

Outcomes after different non-sternotomy approaches to left single-vessel revascularization: a comparative study with up to 10-year follow-up.

OBJECTIVES: Various non-sternotomy approaches have been used for left internal mammary artery (LIMA) grafting in left single-vessel revascularization. The aim of this study was to evaluate the impact of three different non-sternotomy techniques on long-term outcomes after left single-vessel revascularization. METHODS: A total of 502 patients having single-vessel LAD disease treated from April 2003 to May 2013 by minimally invasive direct coronary artery bypass grafting (MIDCAB), endoscopically assisted coronary artery bypass grafting (EACAB) or robotically assisted direct coronary artery bypass grafting (RADCAB) were reviewed. In all cases, distal anastomoses were performed through anterolateral minithoracotomy incisions. In-hospital and long-term (10-year) outcomes were compared using standard and propensity score-adjusted analyses. RESULTS: One hundred and eighty-nine patients had MIDCAB, 76 had EACAB and 236 had RADCAB. After propensity score matching, RADCAB patients had significantly longer operative duration (P < 0.001), whereas MIDCAB and RADCAB patients had significantly higher incidence of postoperative angina over the follow-up (P = 0.034). The groups were comparable regarding in-hospital mortality and reintervention rate as well as incidence of myocardial infarction, reoperations, reinterventions and cardiac death. All groups showed comparable long-term survival (P = 0.943). CONCLUSIONS: MIDCAB, EACAB and RADCAB are associated with similar long-term survival and incidence of major adverse cardiac events (MACEs) in single-vessel surgical revascularization. However, the endoscopic approach was found to be free from the disadvantages of longer operating duration observed in RADCAB or higher incidence of angina and shorter freedom from MACEs observed in both MIDCAB and RADCAB groups.

A novel treatment strategy of new onset atrial fibrillation after cardiac surgery: an observational prospective study.

OBJECTIVE: The aim of this prospective observational study was to evaluate the efficiency of a new escalating treatment strategy with vernakalant, flecainide and electrical cardioversion (EC) in patients with new onset atrial fibrillation (AF) after cardiac surgery. MATERIAL AND METHODS: 24 patients with new onset AF after aortic valve surgery, coronary artery bypass surgery or combined procedures were evaluated in this study. Additional including criteria were age between 18 and 80, duration of AF less than four days, body weight less than 100 kg and no previous treatment with class I or III antiarrhythmic drugs. Exclusion criteria were poor left ventricular ejection fraction (LVEF < 40%) and history of myocardial infarction within 30 days. The patients were divided into converters and non-converters according to their response to combination treatment with vernakalant and flecainide, and the groups were compared. RESULTS: The mean age of the population was 69.6 ± 6.3 years and 26.1% of patients were female. There were no statistically significant differences between the two groups in terms of height, weight, gender distribution, comorbidities, preoperative medication, left ventricular function and left atrium diameter. Interventricular septum (IVS) in the non-converted group was significantly thicker compared to the converted group: 14.0 ± 1.00 vs. 10.40 ± 2.59 mm (p = 0.036). While 14 patients (60.9%) were successfully converted into stable sinus rhythm by pharmacological treatment with vernakalant and flecainide, 9 patients (39.1%, non-converted group) remained in AF. However, seven of them could be converted after additional EC. CONCLUSION: The combination of vernakalant and flecainide improves the conversion rate into a stable sinus rhythm in postcardiotomy patients with new onset AF compared to single drug therapy. Furthermore it might be an excellent precondition for successful EC in patients who are not converted after using both antiarrhtythmic drugs. Furthermore, left ventricular hypertrophy might be a potential negative predictor of successful pharmacological cardioversion.

Less invasive coronary artery revascularization with a minimized extracorporeal circulation system: preliminary results of a comparative study with off-pump-procedures.

BACKGROUND: Coronary-artery-bypass-grafting (CABG) with conventional extracorporeal circulation (CECC) is associated with adverse effects such as systemic inflammatory response leading to a decrease in systemic vascular resistance and hemodynamic instability. Modern "less invasive" procedures have been established recently which potentially avoid negative side effects of CECC. The aim of this study was to compare perioperative outcome following coronary revascularization using either a minimized extracorporeal circuit (Mini-HLM) or off-pump technique (OPCAB). METHODS: In this prospective ethics-approved trial, 120 patients referred for CABG were randomly assigned either to off-pump coronary artery bypass (OPCAB) or to a Mini-HLM procedure. Patient demographics, preoperative characteristics and extensive postoperative outcome were analyzed for both groups. Hemodynamic data were measured at seven time points perioperatively. RESULTS: Operation-time was longer in the Mini-HLM group (178,3 ± 32,9 min) compared to OPCAB (133,2 ± 32,7 min, p < 0,001) with higher graft numbers in Mini-HLM group (3,11 ± 0,7 vs. 1,78 ± 0,7, p < 0.001). There were no significant differences in perioperative hemodynamic criteria, catecholaminergic support, hospital (p = 0,534) and intensive care unit stay (p = 0,880), ventilation time (p = 0,113), blood loss (p = 0,570), transfusion requirements, postoperative atrial fibrillation rate (p = 0,706) and neurocognitive disturbance (p = 0,297). No deaths and no myocardial infarctions were observed. CONCLUSIONS: Coronary revascularisation with Mini-HLM represents a suitable and "less invasive" procedure which achieves all benefits of OPCAB but may allow for less demanding revascularisation than OPCAB in special patients with complex coronary anatomy and can therefore be used both on a routine basis and in all "conversion" cases of OPCAB.

Noninvasive in vivo tracking of mesenchymal stem cells and evaluation of cell therapeutic effects in a murine model using a clinical 3.0 T MRI.

Cardiac cell therapy with mesenchymal stem cells (MSCs) represents a promising treatment approach for end-stage heart failure. However, little is known about the underlying mechanisms and the fate of the transplanted cells. The objective of the presented work is to determine the feasibility of magnetic resonance imaging (MRI) and in vivo monitoring after transplantation into infarcted mouse hearts using a clinical 3.0 T MRI device. The labeling procedure of bone marrow-derived MSCs with micron-sized paramagnetic iron oxide particles (MPIOs) did not affect the viability of the cells and their cell type-defining properties when compared to unlabeled cells. Using a clinical 3.0 T MRI scanner equipped with a dedicated small animal solenoid coil, 10(5) labeled MSCs could be detected and localized in the mouse hearts for up to 4 weeks after intramyocardial transplantation. Weekly ECG-gated scans using T1-weighted sequences were performed, and left ventricular function was assessed. Histological analysis of hearts confirmed the survival of labeled MSCs in the target area up to 4 weeks after transplantation. In conclusion, in vivo tracking of labeled MSCs using a clinical 3.0 T MRI scanner is feasible. In combination with assessment of heart function, this technology allows the monitoring of the therapeutic efficacy of regenerative therapies in a small animal model.

Intraoperative stress in cardiac surgery: attendings versus residents.

BACKGROUND: Performing cardiac surgery is associated with stress for surgeons. We investigated stress levels of experienced surgeons and trainees during coronary artery bypass graft teaching procedures. METHODS: We assessed heart rate (HR) and sympathovagal balance (SVB) of experienced surgeons (attendings; n = 7) and residents enrolled in a training program (residents; n = 3) using a one-lead electrocardiogram during a total of 109 elective isolated coronary artery bypass graft procedures. We measured HR and SVB for baseline values at rest and at prespecified phases during the procedure in the role as primary surgeons (n = 10) and assistants (n = 9). RESULTS: All participants were healthy men with a mean age of 41.4 ± 4.3 y. For patients operated on during this study, demographic and intraoperative data were homogeneous. Compared with rest, mean HR and SVB for the whole procedure were higher for surgeons and assistants, with significant differences for HR values (surgeons, 83.7 ± 8.8 beats/min [bpm]; assistants, 85.4 ± 12.7 bpm, P < 0.05 versus 62.3 ± 5.1 bpm). Courses of HR and SVB were comparable for attending and resident groups but values were higher throughout for attendings compared with residents in their role as surgeons during the total procedure, and as assistants during cardiopulmonary bypass. Mean HR and SVB values of attendings assisting the procedure were higher compared with those of residents performing the operation. CONCLUSIONS: Surgical experience is not associated with reduced stress levels. Supervising a teaching case in cardiac surgery can be linked with more stress compared with the resident performing the procedure.

Mechanical preconditioning enables electrophysiologic coupling of skeletal myoblast cells to myocardium.

OBJECTIVE: The effect of mechanical preconditioning on skeletal myoblasts in engineered tissue constructs was investigated to resolve issues associated with conduction block between skeletal myoblast cells and cardiomyocytes. METHODS: Murine skeletal myoblasts were used to generate engineered tissue constructs with or without application of mechanical strain. After in vitro myotube formation, engineered tissue constructs were co-cultured for 6 days with viable embryonic heart slices. With the use of sharp electrodes, electrical coupling between engineered tissue constructs and embryonic heart slices was assessed in the presence or absence of pharmacologic agents. RESULTS: The isolation and expansion procedure for skeletal myoblasts resulted in high yields of homogeneously desmin-positive (97.1% ± 0.1%) cells. Mechanical strain was exerted on myotubes within engineered tissue constructs during gelation of the matrix, generating preconditioned engineered tissue constructs. Electrical coupling between preconditioned engineered tissue constructs and embryonic heart slices was observed; however, no coupling was apparent when engineered tissue constructs were not subjected to mechanical strain. Coupling of cells from engineered tissue constructs to cells in embryonic heart slices showed slower conduction velocities than myocardial cells with the embryonic heart slices (preconditioned engineered tissue constructs vs embryonic heart slices: 0.04 ± 0.02 ms vs 0.10 ± 0.05 ms, P = .011), lower maximum stimulation frequencies (preconditioned engineered tissue constructs vs embryonic heart slices: 4.82 ± 1.42 Hz vs 10.58 ± 1.56 Hz; P = .0009), and higher sensitivities to the gap junction inhibitor (preconditioned engineered tissue constructs vs embryonic heart slices: 0.22 ± 0.07 mmol/L vs 0.93 ± 0.15 mmol/L; P = .0004). CONCLUSIONS: We have generated skeletal myoblast-based transplantable grafts that electrically couple to myocardium.

Enhanced gap junction expression in myoblast-containing engineered tissue.

Transplantation of skeletal myoblasts (SMs) has been investigated as a potential cardiac cell therapy approach. SM are available autologously, predetermined for muscular differentiation and resistant to ischemia. Major hurdles for their clinical application are limitations in purity and yield during cell isolation as well as the absence of gap junction expression after differentiation into myotubes. Furthermore, transplanted SMs do not functionally or electrically integrate with the host myocardium. Here, we describe an efficient method for isolating homogeneous SM populations from neonatal mice and demonstrate persistent gap junction expression in an engineered tissue. This method resulted in a yield of 1.4 × 10(8) high-purity SMs (>99% desmin positive) after 10 days in culture from 162.12 ± 11.85 mg muscle tissue. Serum starvation conditions efficiently induced differentiation into spontaneously contracting myotubes that coincided with loss of gap junction expression. For mechanical conditioning, cells were integrated into engineered tissue constructs. SMs within tissue constructs exhibited long term survival, ordered alignment, and a preserved ability to differentiate into contractile myotubes. When the tissue constructs were subjected to passive longitudinal tensile stress, the expression of gap junction and cell adherence proteins was maintained or increased throughout differentiation. Our studies demonstrate that mechanical loading of SMs may provide for improved electromechanical integration within the myocardium, which could lead to more therapeutic opportunities.

The influence of cardiovascular risk factors on bone marrow mesenchymal stromal cell fitness.

BACKGROUND AIMS: In the past, cell transplantation strategies for the treatment of heart failure have shown promising results in experimental and clinical studies. Bone marrow (BM)-derived stem cells represent the most frequently used cell population. Within this heterogeneous cell population, mesenchymal stromal cells (MSC) have been identified to induce therapeutic effects, mainly through paracrine mechanisms. Because of their low frequency in native tissues, in vitro cell culture expansion is mandatory prior to transplantation. We sought to identify patient-specific cardiovascular risk factors influencing the proliferative potential of MSC. METHODS: BM aspirates from 51 patients undergoing elective cardiac surgery were analyzed for MSC frequency and cell culture expansion potential. Fibroblastic colony-forming units (CFU-F) were quantified for culture conditions applying autologous (AS) or fetal bovine serum (FBS) and different basic media. Univariate and multivariate analyzes were performed in order to determine the impact of patient-specific factors on CFU-F numbers. RESULTS: Expanded MSC showed a specific immune phenotype and displayed adipogenic, chondrogeneic and osteogeneic differentiation potential. CFU-F numbers did not differ under AS or FBS supplementation. Elevated numbers of mononuclear cells, diabetes mellitus, steroid treatment, chronic obstructive pulmonary disease, renal failure, high euroSCORE and impaired left ventricular function were significant determinants for higher CFU-F numbers. CONCLUSIONS: The impact of specific cardiovascular risk factors on MSC fitness could be determined. These results may help to establish patient profiling in order to identify patients suitable for autologous MSC transplantation, and might lead to the identification of disease-related mechanisms of stem cell activation.

Off-pump or minimized on-pump coronary surgery--initial experience with Circulating Endothelial Cells (CEC) as a supersensitive marker of tissue damage.

BACKGROUND: Off-pump-coronary-artery-bypass-grafting (OPCAB) and minimized-extracorporeal-circulation (Mini-HLM) have been proposed to avoid harmful effects of cardiopulmonary-bypass (CPB). Controversies exist whether OPCAB is still superior in perioperative outcome. Circulating endothelial cells (CEC) are sensitive markers of endothelial damage and are significantly elevated in conventional-CPB-procedures as compared to Mini-HLM-revascularisation. Therefore, CEC might be of specific value in evaluating effectiveness of Mini-HLM and OPCAB as currently applied less-invasive coronary procedures. METHODS: 76 coronary patients were randomly assigned either to OPCAB (n = 34) or to Mini-HLM (ROCsafe™, Terumo Inc., n = 42) procedures. Perioperative data, clinical and serological outcome and measurements of CEC-release and parameters of endothelial function (v.Willebrand-Factor, soluble-thrombomodulin) perioperatively (pre-operative-baseline, post-Mini-HLM/release of OPCAB-stabilizer, 6 h, 12 h, 24 h and 5 days postoperatively) were obtained and compared by ANOVA models including repeated-measures-analysis. RESULTS: Mean graft-number was 3.06 ± 0.72 in Mini-HLM-patients and 1.89 ± 0.74 in OPCAB-patients (p < 0.001). However, ventilation-, ICU- and total-hospital duration were comparable between groups as well as chest-tube-drainage, transfusion requirements, hemodynamics and catecholaminergic support (p > 0.05). CEC-release did not differ between groups (p = 0.274) and was generally within normal limits, Troponin-T levels where not significanty different (p = 0.108). No myocardial infarctions, strokes or deaths occurred, neuron specific enolase (NSE) did not show any differences between groups (p = 0.194). CONCLUSION: Conceptional advantages of minimized CPB systems (ROCsafe™) result in morbidity and mortality comparable with OPCAB procedures. Mini-HLM therefore minimizes CPB-related systemic and organ injury as demonstrated by low CEC-values which indicates intact endothelial integrity. Furthermore, Mini-HLM combines OPCAB-benefits with low morbidity in high-risk patients while facilitating more complete revascularization in complex patients.

Logistic risk model predicting postoperative renal failure requiring dialysis in cardiac surgery patients.

OBJECTIVE: Renal failure requiring dialysis represents a serious complication following cardiac surgery. This study was designed to determine the incidence and predictors of renal failure requiring dialysis in a contemporary patient population. We also aimed to create a model based on these risk factors that could serve as a tool for the prediction of renal failure requiring dialysis. METHODS: Between October 2007 and June 2009, 2511 consecutive patients (mean age 69 ± 12 years, 68% male) underwent on-pump cardiac surgery at our institution. The main outcome investigated was postoperative renal failure requiring temporary or permanent dialysis. Other postoperative parameters included in the analysis were hospital mortality, major morbidity, length of hospital stay, and discharge condition. Predictors of renal failure requiring dialysis were determined using multivariate regression models. The discriminatory power was evaluated by calculating the area under the receiver-operating-characteristic (ROC) curves (c-statistic). RESULTS: Renal failure requiring dialysis occurred in 3.9% (n = 98) of patients. Hospital mortality among patients with dialysis-dependent renal failure was 37.8% compared with a mortality rate of 1.3% in patients without this complication (p<0.001). Multivariate analysis revealed pulmonary hypertension (odds ratio (OR) = 8.1), preoperative renal dysfunction (creatinine >2.0 mg dl⁻¹) (OR=4.6), cardiopulmonary bypass (CPB) time >120 min (OR=3.9), peripheral vascular disease (OR = 3.1), previous myocardial infarction (OR=3.0), atrial fibrillation (OR = 2.8), age > 75 years (OR = 2.6), New York Heart Association (NYHA) class IV (OR = 2.5), and diabetes (OR = 2.0) as independent predictors for postoperative renal failure requiring dialysis. A logistic equation including the coefficients of the regression analysis accurately predicted individual patient's risk for the occurrence of renal failure requiring dialysis (area under the ROC curve: 0.829, 95% confidence interval 0.78-0.86). CONCLUSIONS: Renal failure requiring dialysis remains a serious complication, particularly in patients with pulmonary hypertension and previous renal dysfunction. Our logistic risk model allows the prediction of renal failure requiring dialysis, based on the individual presentation of risk factors and, therefore, helps to determine the perioperative risk in cardiac surgery patients.

Clinical benefits of partial circulatory support in New York Heart Association Class IIIB and Early Class IV patients.

OBJECTIVE: Full mechanical support with a left-ventricular assist device (LVAD) is generally limited to end-stage heart-failure patients. We have been studying the safety and efficacy of the partial support Synergy® Pocket Micro-pump as bridge-to-transplant in a less-sick group of patients as a prelude to a study of its use for destination therapy. METHODS: The CircuLite® Synergy device is implanted via a small right-sided thoracotomy with an inflow cannula in the left atrium and an outflow graft connected to the right subclavian artery without the use of extracorporeal circulation. The micro-pump is the size of an AA battery, sits in the 'pacemaker' pocket subcutaneously in the right clavicular groove and pumps up to 3.0 l min⁻¹ from the left atrium to the right subclavian artery. RESULTS: The device has been implanted in 27 patients awaiting cardiac transplant (22 males), age 54.8 ± 10.0 years with ejection fraction (EF) 21 ± 6%, mean arterial pressure 73.5 ± 8.8 mm Hg, pulmonary capillary wedge pressure (PCWP) 27.5 ± 7.8 mm Hg and cardiac index (CI) 2.0 ± 0.4 l min⁻¹ m⁻². Duration of support has ranged from 6 to 281 days. Right-heart catheterization showed significant hemodynamic improvement in the short- and intermediate term after implant, with increases in CI from 2.0 ± 0.4 to 2.8 ± 0.6 l min⁻¹ m⁻² (p < 0.001) and reductions in PCWP from 28 ± 6 to 18 ± 7 mm Hg (p = 0.002) at an average of 9.5 ± 5.5 weeks. CONCLUSIONS: The Synergy device provides partial hemodynamic support and its use is associated with significantly improved hemodynamics, thus appearing to interrupt and partially reverse the progressive hemodynamic deterioration typical of end-stage heart failure. Ongoing efforts are aimed at demonstrating additional clinical benefits and continuing to further improve the risk/benefit ratio.