Combining stem cells in myocardial infarction: The road to superior repair?

Myocardial infarction irreversibly destroys millions of cardiomyocytes in the ventricle, making it the leading cause of heart failure worldwide. Over the past two decades, many progenitor and stem cell types were proposed as the ideal candidate to regenerate the heart after injury. The potential of stem cell therapy has been investigated thoroughly in animal and human studies, aiming at cardiac repair by true tissue replacement, by immune modulation, or by the secretion of paracrine factors that stimulate endogenous repair processes. Despite some successful results in animal models, the outcome from clinical trials remains overall disappointing, largely due to the limited stem cell survival and retention after transplantation. Extensive interest was developed regarding the combinational use of stem cells and various priming strategies to improve the efficacy of regenerative cell therapy. In this review, we provide a critical discussion of the different stem cell types investigated in preclinical and clinical studies in the field of cardiac repair. Moreover, we give an update on the potential of stem cell combinations as well as preconditioning and explore the future promises of these novel regenerative strategies.

Combinational Therapy of Cardiac Atrial Appendage Stem Cells and Pyridoxamine: The Road to Cardiac Repair?

Myocardial infarction (MI) occurs when the coronary blood supply is interrupted. As a consequence, cardiomyocytes are irreversibly damaged and lost. Unfortunately, current therapies for MI are unable to prevent progression towards heart failure. As the renewal rate of cardiomyocytes is minimal, the optimal treatment should achieve effective cardiac regeneration, possibly with stem cells transplantation. In that context, our research group identified the cardiac atrial appendage stem cells (CASCs) as a new cellular therapy. However, CASCs are transplanted into a hostile environment, with elevated levels of advanced glycation end products (AGEs), which may affect their regenerative potential. In this study, we hypothesize that pyridoxamine (PM), a vitamin B6 derivative, could further enhance the regenerative capacities of CASCs transplanted after MI by reducing AGEs' formation. Methods and Results: MI was induced in rats by ligation of the left anterior descending artery. Animals were assigned to either no therapy (MI), CASCs transplantation (MI + CASCs), or CASCs transplantation supplemented with PM treatment (MI + CASCs + PM). Four weeks post-surgery, global cardiac function and infarct size were improved upon CASCs transplantation. Interstitial collagen deposition, evaluated on cryosections, was decreased in the MI animals transplanted with CASCs. Contractile properties of resident left ventricular cardiomyocytes were assessed by unloaded cell shortening. CASCs transplantation prevented cardiomyocyte shortening deterioration. Even if PM significantly reduced cardiac levels of AGEs, cardiac outcome was not further improved. Conclusion: Limiting AGEs' formation with PM during an ischemic injury in vivo did not further enhance the improved cardiac phenotype obtained with CASCs transplantation. Whether AGEs play an important deleterious role in the setting of stem cell therapy after MI warrants further examination.

Advanced Glycation End Products Impair Cardiac Atrial Appendage Stem Cells Properties.

BACKGROUND: During myocardial infarction (MI), billions of cardiomyocytes are lost. The optimal therapy should effectively replace damaged cardiomyocytes, possibly with stem cells able to engraft and differentiate into adult functional cardiomyocytes. As such, cardiac atrial appendage stem cells (CASCs) are suitable candidates. However, the presence of elevated levels of advanced glycation end products (AGEs) in cardiac regions where CASCs are transplanted may affect their regenerative potential. In this study, we examine whether and how AGEs alter CASCs properties in vitro. METHODS AND RESULTS: CASCs in culture were exposed to ranging AGEs concentrations (50 µg/mL to 400 µg/mL). CASCs survival, proliferation, and migration capacity were significantly decreased after 72 h of AGEs exposure. Apoptosis significantly increased with rising AGEs concentration. The harmful effects of these AGEs were partially blunted by pre-incubation with a receptor for AGEs (RAGE) inhibitor (25 µM FPS-ZM1), indicating the involvement of RAGE in the observed negative effects. CONCLUSION: AGEs have a time- and concentration-dependent negative effect on CASCs survival, proliferation, migration, and apoptosis in vitro, partially mediated through RAGE activation. Whether anti-AGEs therapies are an effective treatment in the setting of stem cell therapy after MI warrants further examination.

The Impact of Advanced Glycation End-Products (AGEs) on Proliferation and Apoptosis of Primary Stem Cells: A Systematic Review.

Stem cell-based regenerative therapies hold great promises to treat a wide spectrum of diseases. However, stem cell engraftment and survival are still challenging due to an unfavorable transplantation environment. Advanced glycation end-products (AGEs) can contribute to the generation of these harmful conditions. AGEs are a heterogeneous group of glycated products, nonenzymatically formed when proteins and/or lipids become glycated and oxidized. Our typical Western diet as well as cigarettes contain high AGEs content. AGEs are also endogenously formed in our body and accumulate with senescence and in pathological situations. Whether AGEs have an impact on stem cell viability in regenerative medicine remains unclear, and research on the effect of AGEs on stem cell proliferation and apoptosis is still ongoing. Therefore, this systematic review provides a clear overview of the effects of glycated proteins on cell viability in various types of primary isolated stem cells used in regenerative medicine.

Differentiation of Human Cardiac Atrial Appendage Stem Cells into Adult Cardiomyocytes: A Role for the Wnt Pathway?

Human cardiac stem cells isolated from atrial appendages based on aldehyde dehydrogenase activity (CASCs) can be expanded in vitro and differentiate into mature cardiomyocytes. In this study, we assess whether Wnt activation stimulates human CASC proliferation, whereas Wnt inhibition induces cardiac maturation. CASCs were cultured as described before. Conventional PCR confirmed the presence of the Frizzled receptors. Small-molecule inhibitors (IWP2, C59, XAV939, and IWR1-endo) and activator (CHIR99021) of the Wnt/ß -catenin signaling pathway were applied, and the effect on ß-catenin and target genes for proliferation and differentiation was assessed by Western blot and RT-qPCR. CASCs express multiple early cardiac differentiation markers and are committed toward myocardial differentiation. They express several Frizzled receptors, suggesting a role for Wnt signaling in clonogenicity, proliferation, and differentiation. Wnt activation increases total and active ß-catenin levels. However, this does not affect CASC proliferation or clonogenicity. Wnt inhibition upregulated early cardiac markers but could not induce mature myocardial differentiation. When CASCs are committed toward myocardial differentiation, the Wnt pathway is active and can be modulated. However, despite its role in cardiogenesis and myocardial differentiation of pluripotent stem-cell populations, our data indicate that Wnt signaling has limited effects on CASC clonogenicity, proliferation, and differentiation.

How to Stimulate Myocardial Regeneration in Adult Mammalian Heart: Existing Views and New Approaches.

Stem cell-based therapy has been considered as a promising option in the treatment of ischemic heart disease. Although stem cell administration resulted in the temporary improvement of myocardial contractility in the majority of studies, the formation of new cardiomyocytes within the injured myocardium has not been conclusively demonstrated. Consequently, the focus of research in the field has since shifted to stem cell-derived paracrine factors, including cytokines, growth factors, mRNA, and miRNA. Notably, both mRNA and miRNA can enter into the extracellular space either in soluble form or packed into membrane vesicles. Stem cell-derived paracrine factors have been shown to suppress inflammation and apoptosis, stimulate angiogenesis, and amplify the proliferation and differentiation of resident cardiac stem cells (CSCs). Such features have led to exosomes being considered as potential drug candidates affording myocardial regeneration. The search for chemical signals capable of stimulating cardiomyogenesis is ongoing despite continuous debates regarding the ability of mature cardiomyocytes to divide or dedifferentiate, transdifferentiation of other cells into cardiomyocytes, and the ability of CSCs to differentiate into cardiomyocytes. Future research is aimed at identifying novel cell candidates capable of differentiating into cardiomyocytes. The observation that CSCs can undergo intracellular development with the formation of "cell-in-cell structure" and subsequent release of transitory amplifying cells with the capacity to differentiate into cardiomyocytes may provide clues for stimulating regenerative cardiomyogenesis.

Muscle wasting after coronary artery bypass graft surgery: impact on post-operative clinical status and effect of exercise-based rehabilitation.

Background: Coronary artery bypass graft (CABG) surgery is known to induce significant muscle wasting. It remains to be investigated whether muscle wasting after CABG surgery relates to a worse clinical status at entry of rehabilitation and exercise-based rehabilitation remediates such muscle wasting.Design: Prospective observational study.Methods: In 21 males, changes in lean tissue mass (LTM) after CABG surgery were assessed and during a 12-week endurance exercise-based rehabilitation intervention. Changes in blood parameters and cardiopulmonary exercise capacity were assessed, and relations with changes in LTM were analysed.Results: LTM decreased by -1.9 ± 2.5 kg (p < .05) within 3 weeks after CABG surgery: greater LTM loss related to a lower ventilatory threshold at entry of rehabilitation (r = 0.58-0.61, p < .05). LTM was fully restored (+2.1 ± 2.4 kg, p < .05) during rehabilitation.Conclusion: In males, CABG-induced LTM reduction was associated with a worse aerobic exercise tolerance at entry of rehabilitation, but this LTM reduction was fully remediated by endurance exercise-based rehabilitation.

A randomized, controlled trial of Veriset™ hemostatic patch in halting cardiovascular bleeding.

BACKGROUND: Obtaining hemostasis during cardiovascular procedures can be a challenge, particularly around areas with a complex geometry or that are difficult to access. While several topical hemostats are currently on the market, most have caveats that limit their use in certain clinical scenarios such as pulsatile arterial bleeding. The aim of this study was to assess the effectiveness and safety of Veriset™ hemostatic patch in treating cardiovascular bleeding. METHODS: Patients (N=90) scheduled for cardiac or vascular surgery at 12 European institutions were randomized 1:1 to treatment with either Veriset™ hemostatic patch (investigational device) or TachoSil® (control). After application of the hemostat, according to manufacturer instructions for use, time to hemostasis was monitored. Follow-up occurred up to 90 days post-surgery. RESULTS: Median time to hemostasis was 1.5 min with Veriset™ hemostatic patch, compared to 3.0 min with TachoSil® (p<0.0001). Serious adverse events within 30 days post-surgery were experienced by 12/44 (27.3%) patients treated with Veriset™ hemostatic patch and 10/45 (22.2%) in the TachoSil® group (p=0.6295). None of these adverse events were device-related, and no reoperations for bleeding were required within 5 days post-surgery in either treatment group. CONCLUSION: This study reinforces the difference in minimum recommended application time between Veriset™ hemostatic patch and TachoSil® (30 s versus 3 min respectively). When compared directly at 3 min, Veriset™ displayed no significant difference, showing similar hemostasis and safety profiles on the cardiovascular bleeding sites included in this study.

A comparison between minimized extracorporeal circuits and conventional extracorporeal circuits in patients undergoing aortic valve surgery: is 'minimally invasive extracorporeal circulation' just low prime or closed loop perfusion ?

INTRODUCTION: Even though results have been encouraging, an unequivocal conclusion on the beneficial effect of minimally invasive extracorporeal circulation (MiECC) in patients undergoing aortic valve surgery cannot be derived from previous publications. Long-term outcomes are rarely reported and a significant decrease in operative mortality has not been shown. Most studies have a limited number of patients and are underpowered. They merely report on short-term results of a heterogeneous intraoperative group using different types of ECC system in aortic valve surgery. The aim of the present study was to determine whether MiECC systems are more beneficial than conventional extracorporeal systems (CECC) with regard to mortality, hospital stay and inflammation and with only haemodilution and blood-air interface as differences. METHODS: We retrospectively analysed data regarding mortality, hospital stay and inflammation in patients undergoing isolated aortic valve surgery. Forty patients were divided into two groups based on the type of extracorporeal system used; conventional (n=20) or MiECC (n=20). RESULTS: Perioperative blood product requirements were significantly lower in the MiECC group (MiECC: 0.2±0.5 units vs CECC: 0.9±1.2 units, p=0.004). No differences were seen postoperatively regarding mortality (5% vs 5%, p=0.99), total length of hospital stay (10.6±7.2 days (MiECC) vs 12.1±5.9 days (CECC), p=0.39) or inflammation markers (CRP: MiECC: 7.09±13.62 mg/L vs CECC: 3.4±3.2 mg/L, p=0.89). CONCLUSION: MiECC provides circulatory support that is equally safe and feasible as conventional extracorporeal circuits. No differences in mortality, hospital stay or inflammation markers were observed.

Compromised Cardiopulmonary Exercise Capacity in Patients Early After Endoscopic Atraumatic Coronary Artery Bypass Graft: Implications for Rehabilitation.

OBJECTIVE: The purpose of this work was to test the hypothesis that cardiopulmonary exercise tolerance is better preserved early after endoscopic atraumatic coronary artery bypass graft (endo-ACAB) surgery versus coronary artery bypass graft (CABG) surgery. DESIGN: Twenty endo-ACAB surgery patients, 20 CABG surgery patients, and 15 healthy subjects executed a maximal cardiopulmonary exercise test, with assessment and comparison of cycling power output, O2 uptake, CO2 output, respiratory gas exchange ratio, end-tidal O2 and CO2 pressures, equivalents for O2 uptake and CO2 output, heart rate, O2 pulse, expiratory volume, tidal volume, respiratory rate, at peak exercise and ventilatory threshold. In patients, forced expiratory volume and forced vital capacity were measured. RESULTS: Oxygen uptake, CO2 output, expiratory and tidal volume, equivalents for O2 uptake and CO2 output, end-tidal O2 and CO2 pressures at peak exercise (matched peak respiratory gas exchange ratio between patient groups), and ventilatory threshold were significantly worse in patients versus healthy controls (P < 0.05; observed power, >0.80). All these parameters, and lung function, were, however, comparable between CABG and endo-ACAB surgery patients (P > 0.10). CONCLUSIONS: Exercise tolerance and ventilatory function during exercise seems, in contrast to expectation, equally compromised early after endo-ACAB surgery as opposed to after CABG surgery. These data may signify the need for exercise-based rehabilitation intervention early after endo-ACAB surgery.

Outcome after PORT in ypN2 or R1/R2 versus no PORT in ypN0 Stage III-N2 NSCLC after Induction Chemotherapy and Resection.

INTRODUCTION: We investigated patients with contemporarily staged and treated stage III-N2 NSCLC treated with induction chemotherapy and surgery with or without postoperative radiotherapy (PORT). We focused on survival and toxicity and investigated what additional PORT may offer in patients with ypN2 status or incomplete resection. METHODS: We identified 161 patients with pathologically proven, resectable stage III-N2 NSCLC from our prospective database who were treated between 1998 and 2012. Of these patients, 150 without progressive disease after chemotherapy underwent resection. Patients with ypN2 status or R1/2 resection received three-dimensional PORT (n = 70) to a dose of 50 to 66 Gy in 2-Gy fractions. RESULTS: The mean follow-up time was 49 months. The 5-year overall survival (OS) rate was 35.1% in intention-to-treat analysis; relapse-free survival was 31.8%, the cumulative local recurrence (LR) rate was 50.9%, and the distant metastasis rate was 63.4%. The 5-year OS, relapse-free survival, and cumulative LR and distant metastasis rates were 32.0%, 32.9%, 47.0%, and 63.9% in the PORT group versus 38.1%, 30.7%, 54.1%, and 63.2% in the non-PORT group. These results were not significantly different, even though patients in the PORT group had worse prognostic features. Cardiac toxicity was higher in the non-PORT group (p = 0.02), but pulmonary toxicity was similar (p = 0.15). There was no difference between the two groups regarding dyspnea (p = 0.32), cough (p = 0.37), forced expiratory volume in 1 second (p = 0.30), and diffusing capacity of the lung for carbon monoxide (p = 0.61). CONCLUSIONS: A similar outcome (OS, LR, and toxicity) was seen in both patient groups (PORT versus non-PORT group). Despite the limitations of this retrospective study, PORT can be both effective and safe for patients with stage III-N2 NSCLC with an R1/R2 resection or yN2 after induction chemotherapy and surgery.

Patterns of Locoregional Relapses in Patients with Contemporarily Staged Stage III-N2 NSCLC Treated with Induction Chemotherapy and Resection: Implications for Postoperative Radiotherapy Target Volumes.

OBJECTIVES: Our aim was to evaluate locoregional relapse (LR) patterns after induction chemotherapy and surgery for stage III-N2 NSCLC staged with current standard methods and their impact on radiation target volumes for postoperative radiotherapy (PORT). METHODS: A total of 150 patients with stage III-N2 NSCLC from a prospective database of patients who underwent surgical resection at the University Hospitals of Leuven or the Oncologic Centre Limburg between 1998 and 2012 were included. Patients were staged with fluorodeoxyglucose F 18 positron emission tomography/computed tomography and brain imaging and treated with induction chemotherapy and surgery. PORT was performed for incomplete resection (R1/R2) and/or persistent nodal disease (ypN2). For the non-PORT group, we created a virtual planning target volume (PTV). In general, the clinical target volume encompassed the bronchial stump, the ipsilateral hilum, the subcarinal region (station 7), and the initially involved mediastinal lymph nodes. RESULTS: After a mean follow-up time of 49 months, the 5-year overall survival was 35.1% in all patients; disease-free survival was 31.8%. PORT was delivered to 70 patients. LR was seen in 26 patients in the PORT group (37%) and 32 in the non-PORT group (40%). Fifty-eight nodal relapse sites were seen in the PORT group (2.2 sites per patient) versus 113 in the non-PORT group (3.5 sites per patient) (p < 0.01). In the PORT group, the most frequent sites of LR were the ipsilateral hilum (21%), lymph node station 7 (15%), ipsilateral station 4 (9%), ipsilateral station 5 (9%) and ipsilateral station 6 (9%). For the non-PORT group these were station 7 (19%), ipsilateral 4 (16%), and ipsilateral hilum (14%). The dominant pattern of failure was inside (inside or both inside and outside) the PTV. Regarding the out-of-PTV relapses, 47% and 69% of LRs occurred in the contralateral mediastinum for the PORT and non-PORT groups, respectively. Out-of-PTV relapses occurred mostly in initially left-sided tumors. CONCLUSIONS: Despite the limitations of this retrospective study, our data support the role of PORT in decreasing local relapses. Because of the large number of out-of-PTV relapses in the contralateral mediastinum, inclusion of elective contralateral lymph node stations in the PTV could be considered in left-sided tumors. However, prospective randomized trials are needed to verify this.

Cardiac atrial appendage stem cells promote angiogenesis in vitro and in vivo.

Cardiac atrial appendage stem cells (CASCs) show extraordinary myocardial differentiation properties, making them ideal candidates for myocardial regeneration. However, since the myocardium is a highly vascularized tissue, revascularization of the ischemic infarct area is essential for functional repair. Therefore, this study assessed if CASCs contribute to cardiac angiogenesis via paracrine mechanisms. First, it was demonstrated that CASCs produce and secrete high levels of numerous angiogenic growth factors, including vascular endothelial growth factor (VEGF), endothelin-1 (ET-1) and insulin-like growth factor binding protein 3 (IGFBP-3). Functional in vitro assays with a human microvascular endothelial cell line (HMEC-1) and CASC CM showed that CASCs promote endothelial cell proliferation, migration and tube formation, the most important steps of the angiogenesis process. Addition of inhibitory antibodies against identified growth factors could significantly reduce these effects, indicating their importance in CASC-induced neovascularization. The angiogenic potential of CASCs and CASC CM was also confirmed in a chorioallantoic membrane assay, demonstrating that CASCs promote blood vessel formation in vivo. In conclusion, this study shows that CASCs not only induce myocardial repair by cardiomyogenic differentiation, but also stimulate blood vessel formation by paracrine mechanisms. The angiogenic properties of CASCs further strengthen their therapeutic potential and make them an optimal stem cell source for the treatment of ischemic heart disease.

From Bone Marrow to Cardiac Atrial Appendage Stem Cells for Cardiac Repair: A Review.

Traditionally the heart is considered a terminally differentiated organ. However, at the beginning of this century increased mitotic activity was reported in ischemic and idiopathic dilated cardiomyopathy hearts, compared to healthy controls, underscoring the potential of regeneration after injury. Due to the presence of adult stem cells in bone marrow and their purported ability to differentiate into other cell lineages, this cell population was soon estimated to be the most suited candidate for cardiac regeneration. Clinical trials with autologous bone marrow-derived mononuclear cells, using either an intracoronary or direct intramyocardial injection approach consistently showed only minor improvement in global left ventricular ejection fraction. This was explained by their limited cardiomyogenic differentiation potential. To obtain more convincing improvement in cardiac function, based on true myocardial regeneration, the focus of research has shifted towards resident cardiac progenitor cells. Several isolation procedures have been described: the c-kit surface marker was the first to be used, however experimental research has clearly shown that c-kit+ cells only marginally contribute to regeneration post myocardial infarction. Sphere formation was used to isolate the so-called cardiosphere derived cells (CDC), and also in this cell population cardiomyogenic differentiation is a rare event. Recently a new type of stem cells derived from atrial tissue (cardiac atrial stem cells - CASCs) was identified, based on the presence of the enzyme aldehyde dehydrogenase (ALDH). Those cells significantly improve both regional and global LV ejection fraction, based on substantial engraftment and consistent differentiation into mature cardiomyocytes (98%).

Reduction in pulmonary function after CABG surgery is related to postoperative inflammation and hypercortisolemia.

UNLABELLED: Pulmonary function is significantly reduced in the acute phase after coronary artery bypass graft (CABG) surgery. Because pulmonary function partly depends on respiratory muscle strength, we studied whether reductions in pulmonary function are related to postoperative alterations in circulatory factors that affect muscle protein synthesis. METHODS: Slow vital capacity (SVC) was assessed in 22 subjects before and 9 ± 3 days after CABG surgery. Blood testosterone, cortisol, insulin-like growth factor-1 (IGF-1), growth hormone, sex-hormone binding globulin (SHBG), glucose, insulin, c-peptide, c-reactive protein (CRP) content, and free androgen index, cortisol/testosterone ratio, HOMA-IR index were assessed before surgery and during the first three days after surgery. Intubation, surgery time and cumulative chest tube drainage were measured. Correlations between changes in SVC and blood parameters after surgery or subject characteristics were studied. This was a prospective observational study. RESULTS: After CABG surgery SVC decreased by 37 ± 18% (P < 0.01). Free androgen index, blood SHBG, testosterone and IGF-1 content decreased, while HOMA-IR index, cortisol/testosterone ratio, blood growth hormone, insulin and CRP content increased (P < 0.0025) in the first three days after surgery. Decrease in SVC was independently (P < 0.05) related to higher preoperative SVC (SC ß = 0.66), and greater increase in blood cortisol (SC ß = 0.54) and CRP (SC ß = 0.37) content after surgery. CONCLUSIONS: Larger reductions in pulmonary function after CABG surgery are present in patients experiencing greater postoperative increases in blood CRP and cortisol levels. Decrements in pulmonary function after CABG surgery are, at least in part, thus related to alterations in circulatory factors that affect muscle protein synthesis.

Cardiac atrial appendage stem cells engraft and differentiate into cardiomyocytes in vivo: A new tool for cardiac repair after MI.

BACKGROUND: This study assessed whether autologous transplantation of cardiac atrial appendage stem cells (CASCs) preserves cardiac function after myocardial infarction (MI) in a minipig model. METHODS AND RESULTS: CASCs were isolated from right atrial appendages of Göttingen minipigs based on high aldehyde dehydrogenase activity and expanded. MI was induced by a 2h snare ligation of the left anterior descending coronary artery. Upon reperfusion, CASCs were intramyocardially injected under NOGA guidance (MI-CASC, n=10). Non-transplanted pigs (MI, n=8) received sham treatment. 3D electromechanical mapping (EMM) and cardiac MRI were performed to assess left ventricular (LV) function. MI pigs developed LV dilatation at 2 months (2M), while in the MI-CASC group volumes remained stable. Global LV ejection fraction decreased by 16 ± 8% in MI animals vs 3 ± 10% in MI-CASC animals and regional wall thickening in border areas was better preserved in the MI-CASC group. EMM showed decreased viability and wall motion in the LV for both groups POST-MI, whereas at 2M these parameters only improved in the MI-CASC. Substantial cell retention was accompanied by cardiomyogenic differentiation in 98±1% of the transplanted CASCs, which functionally integrated. Second harmonic generation microscopy confirmed the formation of mature sarcomeres in transplanted CASCs. Absence of cardiac arrhythmias indicated the safety of CASC transplantation. CONCLUSION: CASCs preserve cardiac function by extensive engraftment and cardiomyogenic differentiation. Our data indicate the enormous potential of CASCs in myocardial repair.

Magnitude of muscle wasting early after on-pump coronary artery bypass graft surgery and exploration of aetiology.

NEW FINDINGS: What is the central question of this study? It remains uncertain whether significant fat-free mass wasting occurs early after coronary artery bypass graft surgery, and the aetiology of this wasting in these particular conditions is unexplored. What is the main finding and its importance? Significant fat-free mass wasting is present after coronary artery bypass graft surgery, and this wasting effect is greater in younger patients and in patients with greater increments in blood cortisol-to-testosterone ratios after surgery. The magnitude and aetiology of muscle wasting early after coronary artery bypass graft (CABG) surgery remains unknown. In the present study, we assessed changes in fat-free mass early after CABG surgery and explored the possible aetiology (relationships with postsurgical changes in blood hormones, insulin resistance, subject characteristics and inflammation) for these changes. Fat-free mass was assessed before and 23 (range: 25) days after CABG surgery in 25 subjects. Blood testosterone, cortisol, insulin-like growth factor-1, growth hormone, sex hormone-binding globulin, glucose, insulin, C-peptide and C-reactive protein concentrations were determined, and free androgen index, cortisol-to-testosterone ratio and HOMA-IR index were all calculated before surgery, during the first 3 days after surgery and at reassessment of body composition. Relationships between changes in fat-free mass and changes in blood parameters after surgery or subject characteristics were studied. After surgery, free androgen index and blood sex hormone-binding globulin, testosterone and insulin-like growth factor-1 concentrations decreased significantly, while HOMA-IR index, cortisol-to-testosterone ratio, blood growth hormone, insulin and C-reactive protein concentrations increased significantly (P < 0.0025, observed α > 0.80). Whole-body fat-free mass decreased significantly [by -1.9 (range: 9.1) kg, P < 0.0025, observed α = 0.99] after surgery. According to regression analysis, greater absolute loss of fat-free mass was observed after CABG surgery in subjects who were younger, who experienced a greater increase in blood cortisol-to-testosterone ratio after surgery and/or who underwent earlier reassessment of body composition (P < 0.05). Significant decrements in fat-free mass were observed early after CABG surgery, especially in younger subjects and/or subjects with elevated blood cortisol-to-testosterone ratios after surgery. Interventions to preserve fat-free mass soon after CABG surgery are thus warranted.

Mesenchymal stem cell secreted platelet derived growth factor exerts a pro-migratory effect on resident Cardiac Atrial appendage Stem Cells.

Mesenchymal stem cells (MSCs) modulate cardiac healing after myocardial injury through the release of paracrine factors, but the exact mechanisms are still unknown. One possible mechanism is through mobilization of endogenous cardiac stem cells (CSCs). This study aimed to test the pro-migratory effect of MSC conditioned medium (MSC-CM) on endogenous CSCs from human cardiac tissue. By using a three-dimensional collagen assay, we found that MSC-CM improved migration of cells from human cardiac tissue. Cell counts, perimeter and area measurements were utilized to quantify migration effects. To examine whether resident stem cells were among the migrating cells, specific stem cell properties were investigated. The migrating cells displayed strong similarities with resident Cardiac Atrial appendage Stem Cells (CASCs), including a clonogenic potential of ~21.5% and expression of pluripotency associated genes like Oct-4, Nanog, c-Myc and Klf-4. Similar to CASCs, migrating cells demonstrated high aldehyde dehydrogenase activity and were able to differentiate towards cardiomyocytes. Receptor tyrosine kinase analysis and collagen assays performed with recombinant platelet derived growth factor (PDGF)-AA and Imatinib Mesylate, a PDGF receptor inhibitor, suggested a role for the PDGF-AA/PDGF receptor α axis in enhancing the migration process of CASCs. In conclusion, our findings demonstrate that factors present in MSC-CM improve migration of resident stem cells from human cardiac tissue. These data open doors towards future therapies in which MSC secreted factors, like PDGF-AA, can be utilized to enhance the recruitment of CASCs towards the site of myocardial injury.