Early cell loss associated with mesenchymal stem cell cardiomyoplasty

Background: Human mesenchymal stem cells (hMSCs) show potential for therapeutic cellular cardiomyoplasty. However, a range of delivery methods, including direct intramyocardial injection, have resulted in poor engraftment in vivo. We used the in vivo rat heart model to study hMSC engraftment and retention in a normal beating heart. Materials and Methods: HMSCs transfected with green fluorescent protein were injected into the left ventricle (LV) of immunocompetent rats. Hearts were cryopreserved 30 minutes (Group A), 24 hours (Group B), and 5 days (Group C) post hMSC delivery. HMSC retention was estimated using confocal fluorescence microscopy and immunohistochemistry. Measured values were compared to projected GFP-positive cellular volumes. Immunohistochemical analyses probed for the presence of human cells with human prolyl hydroxylase beta (p4hβ) and an immune response with murine monocyte/macrophage antigen (CD68). Results: HMSC retention decreased significantly from 30 minutes to 5 days (p<0.05). In Group A the projected GFP positive cellular volume of 31% correlated with measured values and was significantly greater than the 1% predicted cellular volume in Group C. Moreover, human p4hβ was detected in Groups A and B, and not in Group C. Conversely, CD68 was detected in Groups B and C and not in Group A. Conclusions: In immunocompetent rats, engraftment and retention of hMSCs delivered intramyocardially significantly declines over a five day period. The influx of monocytes/macrophages suggests an unfavorable micro-environment for exogenous stem cell survival, confirmed by the absence of human cells detected five days post injection

Quantum dot labeling of mesenchymal stem cells

<p>Abstract</p> <p>Background</p> <p>Mesenchymal stem cells (MSCs) are multipotent cells with the potential to differentiate into bone, cartilage, fat and muscle cells and are being investigated for their utility in cell-based transplantation therapy. Yet, adequate methods to track transplanted MSCs <it>in vivo </it>are limited, precluding functional studies. Quantum Dots (QDs) offer an alternative to organic dyes and fluorescent proteins to label and track cells <it>in vitro </it>and <it>in vivo</it>. These nanoparticles are resistant to chemical and metabolic degradation, demonstrating long term photostability. Here, we investigate the cytotoxic effects of <it>in vitro </it>QD labeling on MSC proliferation and differentiation and use as a cell label in a cardiomyocyte co-culture.</p> <p>Results</p> <p>A dose-response to QDs in rat bone marrow MSCs was assessed in Control (no-QDs), Low concentration (LC, 5 nmol/L) and High concentration (HC, 20 nmol/L) groups. QD yield and retention, MSC survival, proinflammatory cytokines, proliferation and DNA damage were evaluated in MSCs, 24 -120 hrs post QD labeling. In addition, functional integration of QD labeled MSCs in an <it>in vitro </it>cardiomyocyte co-culture was assessed. A dose-dependent effect was measured with increased yield in HC vs. LC labeled MSCs (93 ± 3% vs. 50% ± 15%, p < 0.05), with a larger number of QD aggregates per cell in HC vs. LC MSCs at each time point (p < 0.05). At 24 hrs >90% of QD labeled cells were viable in all groups, however, at 120 hrs increased apoptosis was measured in HC vs. Control MSCs (7.2% ± 2.7% vs. 0.5% ± 0.4%, p < 0.05). MCP-1 and IL-6 levels doubled in HC MSCs when measured 24 hrs after QD labeling. No change in MSC proliferation or DNA damage was observed in QD labeled MSCs at 24, 72 and 120 hrs post labeling. Finally, in a cardiomyocyte co-culture QD labeled MSCs were easy to locate and formed functional cell-to-cell couplings, assessed by dye diffusion.</p> <p>Conclusion</p> <p>Fluorescent QDs label MSC effectively in an <it>in vitro </it>co-culture model. QDs are easy to use, show a high yield and survival rate with minimal cytotoxic effects. Dose-dependent effects suggest limiting MSC QD exposure.</p

Monoamine Oxidase is a Major Determinant of Redox Balance in Human Atrial Myocardium and is Associated With Postoperative Atrial Fibrillation

BACKGROUND: Onset of postoperative atrial fibrillation (POAF) is a common and costly complication of heart surgery despite major improvements in surgical technique and quality of patient care. The etiology of POAF, and the ability of clinicians to identify and therapeutically target high-risk patients, remains elusive. METHODS AND RESULTS: Myocardial tissue dissected from right atrial appendage (RAA) was obtained from 244 patients undergoing cardiac surgery. Reactive oxygen species (ROS) generation from multiple sources was assessed in this tissue, along with total glutathione (GSHt) and its related enzymes GSH-peroxidase (GPx) and GSH-reductase (GR). Monoamine oxidase (MAO) and NADPH oxidase were observed to generate ROS at rates 10-fold greater than intact, coupled mitochondria. POAF risk was significantly associated with MAO activity (Quartile 1 [Q1]: adjusted relative risk [ARR]=1.0; Q2: ARR=1.8, 95% confidence interval [CI]=0.84 to 4.0; Q3: ARR=2.1, 95% CI=0.99 to 4.3; Q4: ARR=3.8, 95% CI=1.9 to 7.5; adjusted Ptrend=0.009). In contrast, myocardial GSHt was inversely associated with POAF (Quartile 1 [Q1]: adjusted relative risk [ARR]=1.0; Q2: ARR=0.93, 95% confidence interval [CI]=0.60 to 1.4; Q3: ARR=0.62, 95% CI=0.36 to 1.1; Q4: ARR=0.56, 95% CI=0.34 to 0.93; adjusted Ptrend=0.014). GPx also was significantly associated with POAF; however, a linear trend for risk was not observed across increasing levels of the enzyme. GR was not associated with POAF risk. CONCLUSIONS: Our results show that MAO is an important determinant of redox balance in human atrial myocardium, and that this enzyme, in addition to GSHt and GPx, is associated with an increased risk for POAF. Further investigation is needed to validate MAO as a predictive biomarker for POAF, and to explore this enzyme's potential role in arrhythmogenesis

Reduction of Ischemia/Reperfusion Injury With Bendavia, a Mitochondria-Targeting Cytoprotective Peptide

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Enhanced Uridine Bioavailability Following Administration of a Triacetyluridine-Rich Nutritional Supplement

Uridine is a therapy for hereditary orotic aciduria and is being investigated in other disorders caused by mitochondrial dysfunction, including toxicities resulting from treatment with nucleoside reverse transcriptase inhibitors in HIV. Historically, the use of uridine as a therapeutic agent has been limited by poor bioavailability. A food supplement containing nucleosides, NucleomaxX®, has been reported to raise plasma uridine to supraphysiologic levels

Effects of amylin and other peptide hormones on Na+–K+ transport and contractility in rat skeletal muscle

In skeletal muscle, catecholamines and calcitonin gene-related peptide (CGRP) increase the content of cAMP, which mediates stimulation of the Na+–K+ pump. Amylin is structurally very similar to CGRP and also increases cAMP in muscle.In isolated rat soleus and extensor digitorum longus muscle, amylin produced a rapid and marked decrease in intracellular Na+, which was maintained for several hours. In soleus, amylin was found to induce a 45 % stimulation of Na+ efflux, a 43 % increase in 86Rb influx and a rise in intracellular K+. All these effects were abolished by ouabain, indicating that amylin produces acute stimulation of the Na+–K+ pump.In contrast, neither the closely related peptides islet amyloid polypeptide (IAPP) and adrenomedullin nor other peptide hormones (C peptide, neuropeptide Y or substance P) produced any detectable change in intracellular Na+ or K+ uptake in soleus.When contractility in soleus was inhibited by increasing extracellular K+ to 12.5 mm, amylin (10−8m) and insulin (0.7 × 10−8m) both induced partial recovery of force. These effects were additive, and in combination the two hormones elicited 63 and 80 % recovery of tetanic and twitch force, respectively. Higher concentrations produced even larger increases, and all effects were blocked by ouabain.In buffer containing 12.5 mm K+, dibutyryl cAMP induced 71 % force recovery, which was increased by theophylline. The results indicate that amylin (like catecholamines, cAMP, CGRP and insulin) stimulates the Na+–K+ pump and thereby improves the contractility of depolarized skeletal muscle cells. This adds further support to the concept that the Na+–K+ pump is important for the maintenance of excitability in skeletal muscle

Early cell loss associated with mesenchymal stem cell cardiomyoplasty

Background: Human mesenchymal stem cells (hMSCs) show potential for therapeutic cellular cardiomyoplasty. However, a range of delivery methods, including direct intramyocardial injection, have resulted in poor engraftment in vivo. We used the in vivo rat heart model to study hMSC engraftment and retention in a normal beating heart. Materials and Methods: HMSCs transfected with green fluorescent protein were injected into the left ventricle (LV) of immunocompetent rats. Hearts were cryopreserved 30 minutes (Group A), 24 hours (Group B), and 5 days (Group C) post hMSC delivery. HMSC retention was estimated using confocal fluorescence microscopy and immunohistochemistry. Measured values were compared to projected GFP-positive cellular volumes. Immunohistochemical analyses probed for the presence of human cells with human prolyl hydroxylase beta (p4hβ) and an immune response with murine monocyte/macrophage antigen (CD68). Results: HMSC retention decreased significantly from 30 minutes to 5 days(p&lt;0.05). In Group A the projected GFP positive cellular volume of 31% correlated with measured values and was significantly greater than the 1% predicted cellular volume in Group C. Moreover, human p4hβ was detected in Groups A and B, and not in Group C. Conversely, CD68 was detected in Groups B and C and not in Group A. Conclusions: In immunocompetent rats, engraftment and retention of hMSCs delivered intramyocardially significantly declines over a five day period. The influx of monocytes/macrophages suggests an unfavorable micro-environment for exogenous stem cell survival, confirmed by the absence of human cells detected five days post injection