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.

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.

Glycolaldehyde-Derived High-Molecular-Weight Advanced Glycation End-Products Induce Cardiac Dysfunction through Structural and Functional Remodeling of Cardiomyocytes.

BACKGROUND/AIMS: High-molecular-weight advanced glycation end-products (HMW-AGEs) are abundantly present in our Western diet. There is growing evidence reporting that HMW-AGEs contribute to the development of cardiovascular dysfunction in vivo, next to the well-known low-molecular-weight AGEs. The goal of our study is to assess the ultrastructure and function of cardiomyocytes after chronic exposure to HMW-AGEs. A better understanding of underlying mechanisms is essential to create new opportunities for further research on the specific role of HMW-AGEs in the development and progression of cardiovascular diseases. METHODS: Adult male rats were randomly assigned to daily intraperitoneal injection for six weeks with either HMW-AGEs (20 mg/kg/day) or a control solution. Hemodynamic measurements were performed at sacrifice. Single cardiomyocytes from the left ventricle were obtained by enzymatic dissociation through retrograde perfusion of the aorta. Unloaded cell shortening, time to peak and time to 50% relaxation were measured during field stimulation and normalized to diastolic length. L-type Ca2+ current density (ICaL) and steady-state inactivation of ICaL were measured during whole-cell ruptured patch clamp. Myofilament functional properties were measured in membrane-permeabilized cardiomyocytes. Ultrastructural examination of cardiac tissue was performed using electron microscopy. RESULTS: Rats injected with HMW-AGEs displayed in vivo cardiac dysfunction, characterized by significant changes in left ventricular peak rate pressure rise and decline accompanied with an increased heart mass. Single cardiomyocytes isolated from the left ventricle revealed concentric hypertrophy, indicated by the increase in cellular width. Unloaded fractional cell shortening was significantly reduced in cells derived from the HMW-AGEs group and was associated with slower kinetics. Peak L-type Ca2+ current density was significantly decreased in the HMW-AGEs group.L-type Ca2+ channel availability was significantly shifted towards more negative potentials after HMW-AGEs injection. The impact of HMW-AGEs on myofilament function was measured in membrane-permeabilized cardiomyocytes showing a reduction in passive force, maximal Ca2+ activated force and rate of force development. Ultrastructural examination of cardiac tissue demonstrated adverse structural remodeling in HMW-AGEs group characterized by a disruption of the cyto-architecture, a decreased mitochondrial density and altered mitochondrial function. CONCLUSION: Our data indicate that HMW-AGEs induce structural and functional cellular remodeling via a different working mechanism as the well-known LMW-AGEs. Results of our research open the door for new strategies targeting HMW-AGEs to improve cardiac outcome.

Acute exposure to glycated proteins reduces cardiomyocyte contractile capacity.

NEW FINDINGS: What is the central question of this study? Does acute exposure to high molecular weight advanced glycation end products (HMW-AGEs) alter cardiomyocyte contractile function? What is the main finding and its importance? Ventricular cardiomyocytes display reduced Ca2+ influx, resulting in reduced contractile capacity, after acute exposure to HMW-AGEs, independent of activation of their receptor. Given that HMW-AGEs are abundantly present in our Western diet, a better understanding of underlying mechanisms, especially in patients already displaying altered cardiac function, should be gained for these compounds. ABSTRACT: Sustained elevated levels of high molecular weight advanced glycation end products (HMW-AGEs) are known to promote cardiac dysfunction. Recent data suggest that acutely elevated levels of AGEs occur in situations of increased oxidative stress. Whether this increase might have detrimental effects on cardiac function remains unknown. In this study, we investigated whether acute exposure to HMW-AGEs affects cardiomyocyte function via activation of their receptor (RAGE) signalling pathway. Single cardiomyocytes from the left ventricle of adult male rats were obtained by enzymatic dissociation through retrograde perfusion of the aorta. Functional experiments were performed in cardiomyocytes pre-incubated with or without an anti-RAGE antibody. Unloaded cell shortening and L-type Ca2+ current amplitude were evaluated in the presence or absence of HMW-AGEs (200 µg ml-1 ). Expression of RAGE, c-Jun N-terminal kinase (JNK) and phosphorylated JNK (pJNK) were assessed by western blot. Experiments were performed at room temperature. After 4 min application of HMW-AGEs, unloaded cell shortening was significantly reduced. This impaired contractile function was related to reduced Ca2+ influx. These alterations were also observed in cardiomyocytes pre-incubated with anti-RAGE antibody. Our study demonstrates that acute exposure to elevated levels of HMW-AGEs leads to direct and irreversible cardiomyocyte dysfunction, independent of RAGE activation.

The reverse remodeling response to sacubitril/valsartan therapy in heart failure with reduced ejection fraction.

BACKGROUND: Major classes of medical therapy for heart failure with reduced ejection fraction (HFrEF) induce reverse remodeling. The revere remodeling response to sacubitril/valsartan remains unstudied. METHODS: We performed a single-center, prospective assessor-blinded study to determine the reverse remodeling response of sacubitril/valsartan therapy in HFrEF patients with a class I indication (New York heart Association [NYHA]-class II-IV, Left ventricular ejection fraction [LVEF] < 35%, optimal dose with Renin-Angiotensin-System-Blocker [RAS-blocker]). Doses of sacubitril/valsartan were optimized to individual tolerance. Echocardiographic images were assessed offline by 2 investigators blinded to both the clinical data and timing of echocardiograms. RESULTS: One-hundred-twenty-five HFrEF patients (66 ± 10 years) were prospectively included. The amount of RAS-blocker before and after switch to sacubitril/valsartan was similar(P = .290), indicating individual optimal dosing of sacubitril/valsartan. Over a median(IQR) follow-up of 118(77-160) days after initiation of sacubitril/valsartan, LVEF improved (29.6 ± 6% vs 34.8 ± 6%; P < .001) and Left ventricular end-systolic (LVESV) and end-diastolic volume (LVEDV) decreased (LVESV; 147 ± 57 mL vs 129 ± 55 mL; P < .001 and LVEDV; 206 ± 71 mL vs197 ± 72 mL; P = .027). Volumetric remodeling was associated with a reduction in the degree of mitral regurgitation (1.59 ± 1.0 vs 1.11 ± 0.8; P < .001; [scale from 0-4]). Metrics of diastolic function improved; including a drop in the E/A-wave ratio (1.75 ± 1.13 vs 1.38 ± 0.88; P = .002) and diastolic filling time (% of cycle length) prolonged (48 ± 9% vs 52 ± 1%; P = .005). The percent of patients with a restrictive mitral filling pattern dropped from 47% to 23% (P = .004). A dose-dependent effect was noted for changes in LVEF (P < .001) and LVESV (P = .031), with higher doses of sacubitril/valsartan leading to more reverse remodeling. CONCLUSION: Switching therapy in eligible HFrEF patients from a RAS-blocker to sacubitril/valsartan induces beneficial reverse remodeling of both metrics of systolic as diastolic function.

Insights into implementation of sacubitril/valsartan into clinical practice.

BACKGROUND: Sacubitril/valsartan significantly reduced heart failure hospitalization and mortality in PARADIGM-HF (Prospective Comparison of Angiotensin Receptor-Neprilysin Inhibitor With an Angiotensin-Converting Enzyme Inhibitor to Determine Impact on Global Mortality and Morbidity in Heart Failure). However, real-world data from its use are lacking. METHODS AND RESULTS: We retrospectively assessed all baseline and follow-up data of consecutive heart failure patients with reduced ejection fraction receiving therapy with sacubitril/valsartan for Class I recommendation between December 2016 and July 2017. Baseline characteristics and dose titration of sacubitril/valsartan were compared between patients in clinical practice and in PARADIGM-HF. A total of 120 patients (81% male) were switched from angiotensin-converting enzyme inhibitor or angiotensin receptor blocker to sacubitril/valsartan. A total of 20.1% of patients received dose uptitration. Patients were treated with an equipotential dose of renin-angiotensin system blockers before and after uptitration of sacubitril/valsartan (57 ± 29% vs. 53 ± 29% of target dose indicated by European Society of Cardiology guidelines; P = 0.286). However, they received a lower dose of sacubitril/valsartan in comparison with those in the PARADIGM-HF (219 ± 12 vs. 375 ± 75 mg; P < 0.001). In comparison with the patients receiving sacubitril/valsartan in PARADIGM-HF, patients in clinical practice were older and had a higher serum creatinine, higher New York Heart Association functional classification, and lower left ventricular ejection fraction (all P-value <0.05). Even in comparison with patients who experienced dropout during the run-in phase of PARADIGM-HF, real-world patients exhibited baseline characteristics indicative of more disease severity. Patients were at high absolute baseline risk for adverse outcome as illustrated by the EMPHASIS-HF (Eplerenone in Mild Patients Hospitalization and Survival Study in Heart Failure) risk score of 6 (inter-quartile range 3), in comparison with 5 (inter-quartile range 4) in PARADIGM-HF. After initiation of sacubitril/valsartan, New York Heart Association class significantly improved (P < 0.001), but systolic blood pressure dropped more than was reported in PARADIGM-HF (7.1 ± 8.0 vs. 3.2 ± 0.4 mmHg; P < 0.001). CONCLUSIONS: Patients in clinical practice exhibit baseline characteristics associated with more severe disease, which might lead to prescription of lower doses. Nevertheless, patients in clinical practice are at high risk of adverse outcome as illustrated by the EMPHASIS-HF risk score, underscoring the large potential for sacubitril/valsartan therapy to reduce the risk of heart failure hospitalization and all-cause mortality.

Prebending of osteosynthesis plate using 3D printed models to treat symptomatic os acromiale and acromial fracture.

BACKGROUND: A symptomatic os acromiale can lead to impingement syndrome and rotator cuff tendinopathy. An acromion fracture is often part of a more complex scapular trauma that needs stabilisation. METHODS: We developed a new technique using a three-dimensional (3D) model and a distal clavicle reconstruction plate to treat os acromiale and acromion fractures. Our hypothesis was that such an approach would be a useful addition to the existing techniques. First, a 3D model of the acromion was printed, then an osteosynthesis plate was pre-bent to fit the exact shape and curve of the acromion. We tested this technique and present reports on five patients, three with os acromiales and two with acromial fractures. We followed these patients during their rehabilitation and evaluated them using the Constant-Murley and the Disabilities of the Arm, Shoulder and Hand scores. RESULTS: In every case the fracture or non-union healed. If the surgery was performed before additional damage (such as an impingement syndrome) occurred, we saw that the patient's pain completely disappeared. This new technique also has other advantages because the surgeon can prepare the entire operation in advance, which reduces the duration of surgery. Another advantage of using a 3D model is that it can also be used to inform the patient and the surgical team about the planned operation. CONCLUSION: This new technique using a preoperative patient-customized plate is a good alternative for use in open reduction and internal fixation, particularly if the patient has no other conditions.