Differentiation of Adipose-Derived Stem Cells into Vascular Smooth Muscle Cells for Tissue Engineering Applications.

Synthetic grafts have been developed for vascular bypass surgery, however, the risks of thrombosis and neointimal hyperplasia still limit their use. Tissue engineering with the use of adipose-derived stem cells (ASCs) has shown promise in addressing these limitations. Here we further characterized and optimized the ASC differentiation into smooth muscle cells (VSMCs) induced by TGF-ß and BMP-4. TGF-ß and BMP-4 induced a time-dependent expression of SMC markers in ASC. Shortening the differentiation period from 7 to 4 days did not impair the functional property of contraction in these cells. Stability of the process was demonstrated by switching cells to regular growth media for up to 14 days. The role of IGFBP7, a downstream effector of TGF-ß, was also examined. Finally, topographic and surface patterning of a substrate is recognized as a powerful tool for regulating cell differentiation. Here we provide evidence that a non-woven PET structure does not affect the differentiation of ASC. Taken together, our results indicate that VSMCs differentiated from ASCs are a suitable candidate to populate a PET-based vascular scaffolds. By employing an autologous source of cells we provide a novel alternative to address major issues that reduces long-term patency of currently vascular grafts.

Steroids Limit Myocardial Edema During Ex Vivo Perfusion of Hearts Donated After Circulatory Death.

BACKGROUND: Normothermic ex vivo heart perfusion (EVHP) has been shown to improve the preservation of hearts donated after circulatory arrest and to facilitate clinical successful transplantation. Steroids are added to the perfusate solution in current clinical EVHP protocols; however, the impact of this approach on donor heart preservation has not been previously investigated. We sought to determine the impact of steroids on the inflammatory response and development of myocardial edema during EVHP. METHODS: Thirteen pigs were anesthetized, mechanical ventilation was discontinued, and a hypoxemic cardiac arrest ensued. A 15-minute warm-ischemic standoff period was observed, and then hearts were resuscitated with a cardioplegic solution. Donor hearts were then perfused ex vivo in a normothermic beating state for 6 hours with 500 mg of methylprednisolone (steroid: n = 5) or without (control: n = 8). RESULTS: The addition of steroids to the perfusate solution reduced the generation of proinflammatory cytokines (interleukin-6, -8, -1ß, and tumor necrosis factor-α) and the development of myocardial edema during EVHP (percentage of weight gain: control = 26% ± 7% versus steroid = 16% ± 10%, p = 0.049). Electron microscopy suggested less endothelial cell edema in the steroid group (injury score: control = 1.8 ± 0.2 versus steroid = 1.2 ± 0.2, p = 0.06), whereas perfusate troponin-I (control = 11.9 ± 1.9 ng/mL versus steroid = 9.5 ± 2.4 ng/mL, p = 0.448) and myocardial function were comparable between the groups. CONCLUSIONS: The addition of methylprednisolone to the perfusion solution minimizes the generation of proinflammatory cytokines and development of myocardial edema during normothermic ex vivo perfusion of hearts donated after circulatory arrest.

Negative pressure ventilation decreases inflammation and lung edema during normothermic ex-vivo lung perfusion.

BACKGROUND: Normothermic ex-vivo lung perfusion (EVLP) using positive pressure ventilation (PPV) and both acellular and red blood cell (RBC)-based perfusate solutions have increased the rate of donor organ utilization. We sought to determine whether a negative pressure ventilation (NPV) strategy would improve donor lung assessment during EVLP. METHODS: Thirty-two pig lungs were perfused ex vivo for 12 hours in a normothermic state, and were allocated equally to 4 groups according to the mode of ventilation (positive pressure ventilation [PPV] vs NPV) and perfusate composition (acellular vs RBC). The impact of ventilation strategy on the preservation of 6 unutilized human donor lungs was also evaluated. Physiologic parameters, cytokine profiles, lung injury, bullae and edema formation were compared between treatment groups. RESULTS: Perfused lungs demonstrated acceptable oxygenation (partial pressure of arterial oxygen/fraction of inspired oxygen ratio >350 mm Hg) and physiologic parameters. However, there was less generation of pro-inflammatory cytokines (tumor necrosis factor-α, interleukin-6 and interleukin-8) in human and pig lungs perfused, irrespective of perfusate solution used, when comparing NPV with PPV (p < 0.05), and a reduction in bullae formation with an NPV modality (p = 0.02). Pig lungs developed less edema with NPV (p < 0.01), and EVLP using an acellular perfusate solution had greater edema formation, irrespective of ventilation strategy (p = 0.01). Interestingly, human lungs perfused with NPV developed negative edema, or "drying" (p < 0.01), and lower composite acute lung injury (p < 0.01). CONCLUSIONS: Utilization of an NPV strategy during extended EVLP is associated with significantly less inflammation, and lung injury, irrespective of perfusate solution composition.

Hypoxia enhances the therapeutic potential of superparamagnetic iron oxide-labeled adipose-derived stem cells for myocardial infarction.

Adipose-derived stem cells (ASCs) induce therapeutic angiogenesis due to pro-angiogenic cytokines secretion. Superparamagnetic iron oxide (SPIO) nanoparticles are critical for magnetic resonance (MR) tracking of implanted cells. Hypoxia is a powerful stimulus for angiogenic activity of ASCs. In this study, we investigated whether therapeutic potency could be enhanced by implantation of hypoxia-preconditioned SPIO-labeled ASCs (SPIOASCs) into the infarcted myocardium. ASCs and SPIOASCs were cultured under 2% O2 (hypoxia) or 95% air (normoxia). Cells were intramyocardially injected into the infarcted myocardium after 48-h culture. We found that hypoxia culture increased the mRNA expression of hypoxia-inducible factor-1 alpha (HIF-1α) and vascular endothelial growth factor (VEGF) in ASCs and SPIOASCs. The VEGF protein in the conditioned medium was significantly higher in hypoxic ASCs and SPIOASCs than in normoxic ASCs and SPIOASCs. The capillary density and left ventricular contractile function in the infarcted myocardium were significantly higher 4 weeks after implantation with hypoxic ASCs and SPIOASCs than with normoxic ASCs and SPIOASCs. Improvement in the capillary density and left ventricle function didn't differ between hypoxic ASCs-transplanted rats and hypoxic SPIOASCs-transplanted rats. Hypoxic culture enhanced the angiogenic efficiency of ASCs. It was concluded that implantation of hypoxic ASCs or SPIOASCs promotes therapeutic angiogenesis and cardiac function recovery in the infarcted myocardium. SPIO labeling does not impact the beneficial effect of hypoxic ASCs.

The effects of activin A on the migration of human breast cancer cells and neutrophils and their migratory interaction.

Activin A belongs to the superfamily of transforming growth factor beta (TGFß) and is a critical regulatory cytokine in breast cancer and inflammation. However, the role of activin A in migration of breast cancer cells and immune cells was not well characterized. Here, a microfluidic device was used to examine the effect of activin A on the migration of human breast cancer cell line MDA-MB-231 cells and human blood neutrophils as well as their migratory interaction. We found that activin A promoted the basal migration but impaired epidermal growth factor (EGF)-induced migration of breast cancer cells. By contrast, activin A reduced neutrophil chemotaxis and transendothelial migration to N-Formyl-Met-Leu-Phe (fMLP). Finally, activin A promoted neutrophil chemotaxis to the supernatant from breast cancer cell culture. Collectively, our study revealed the different roles of activin A in regulating the migration of breast cancer cells and neutrophils and their migratory interaction. These findings suggested the potential of activin A as a therapeutic target for inflammation and breast cancers.

Preservation of Myocardial Perfusion and Function by Keeping Hypertrophied Heart Empty and Beating for Valve Surgery: An In Vivo MR Study of Pig Hearts.

Objectives. Normothermic hyperkalemic cardioplegia arrest (NHCA) may not effectively preserve hypertrophied myocardium during open-heart surgery. Normothermic normokalemic beating perfusion (NNBP), keeping hearts empty-beating, was utilized as an alternative to evaluate its cardioprotective role. Materials and Methods. Twelve hypertrophied pig hearts at 58.6 ± 7.2 days after ascending aorta banding underwent NNBP and NHCA, respectively. Near infrared myocardial perfusion imaging with indocyanine green (ICG) was conducted to assess myocardial perfusion. Left ventricular (LV) contractile function was assessed by cine MRI. TUNEL staining and western blotting for caspase-3 cleavage and cardiac troponin I (cTnI) degradation were conducted in LV tissue samples. Results. Ascending aortic diameter was reduced by 52.7% ± 0.4% at approximately fifty-eight days after banding. LV wall thickness was significantly higher in aorta banding than in sham operation. Myocardial blood flow reflected by maximum ICG absorbance value was markedly higher in NNBP than in NHCA. The amount of apoptotic cardiomyocyte was significantly lower in NNBP than in NHCA. NNBP alleviated caspase-3 cleavage and cTnI degradation associated with NHCA. NNBP displayed a substantially increased postoperative ejection fraction relative to NHCA. Conclusions. NNBP was better than NHCA in enhancing myocardial perfusion, inhibiting cardiomyocyte apoptosis, and preserving LV contractile function for hypertrophied hearts.

Corrigendum to "Preservation of Myocardial Perfusion and Function by Keeping Hypertrophied Heart Empty and Beating for Valve Surgery: An In Vivo MR Study of Pig Hearts".

[This corrects the article DOI: 10.1155/2017/4107587.].

Impact of Reperfusion Calcium and pH on the Resuscitation of Hearts Donated After Circulatory Death.

BACKGROUND: Hearts donated after circulatory death may represent an additional donor source. The influx of sodium and calcium ions across the sarcolemma play a central role in the pathogenesis of ischemia-reperfusion injury; however, this process may be inhibited if the initial reperfusion solution is rendered hypocalcemic and acidic. We sought to determine the calcium concentration and pH of the initial reperfusion solution that yielded optimal functional recovery of hearts donated after circulatory death during ex vivo heart perfusion. METHODS: Pigs were anesthetized, mechanical ventilation was discontinued, and a 15-minute standoff period was observed after circulatory arrest. Hearts were reperfused with a normothermic cardioplegia of varying calcium concentrations (part 1 [50 µmol/L, n = 4; 220 µmol/L, n = 9; 500 µmol/L, n = 4; and 1,250 µmol/L, n = 5]) and pH (part 2 [7.9, n = 5; 7.4, n = 9; 6.9, n = 8; and 6.4, n = 6]). Myocardial function was then assessed in a physiologic working model 1 hour after initiation of normothermic ex vivo heart perfusion. RESULTS: The calcium concentration and pH of the cardioplegic solution affected the development of myocardial edema (part 1: 50 µmol/L = 5.8% ± 0.9%; 220 µmol/L = 4.3% ± 0.4%; 500 µmol/L = 7.0% ± 0.6%; and 1,250 µmol/L = 6.6% ± 0.8% weight gain, p = 0.015; part 2: 7.9 = 3.6% ± 0.4%, 7.4 = 4.3% ± 0.4%, 6.9 = 3.7% ± 0.6%, and 6.4 = 6.4% ± 1.3% weight gain, p = 0.056) and the recovery of myocardial function (cardiac index part 1: 50 µmol/L = 2.6 ± 0.6; 220 µmol/L = 6.0 ± 0.8; 500 µmol/L = 2.3 ± 0.5; and 1,250 µmol/L = 1.9 ± 0.6 mL · m-1 · g-1, p < 0.001; part 2: 7.9 = 1.5 ± 0.7; 7.4 = 6.0 ± 0.8; 6.9 = 8.4 ± 1.8; and 6.4 = 3.1 ± 0.8 mL · m-1 · g-1, p = 0.003) during ex vivo heart perfusion. CONCLUSIONS: Initial reperfusion of hearts donated after circulatory death with a hypocalcemic and moderately acidic cardioplegia minimizes edema and optimizes functional recovery during subsequent ex vivo heart perfusion.

Externally Applied Static Magnetic Field Enhances Cardiac Retention and Functional Benefit of Magnetically Iron-Labeled Adipose-Derived Stem Cells in Infarcted Hearts.

: Although adipose-derived stem cells (ASCs) hold the promise of effective therapy for myocardial infarction, low cardiac retention of implanted ASCs has hindered their therapeutic efficiency. We investigated whether an externally applied static magnetic field (SMF) enhances cardiac localization of "magnetic" cells and promotes heart function recovery when ASCs are preloaded with superparamagnetic iron oxide (SPIO) nanoparticles. The influence of SMF (0.1 Tesla) on the biological activities of SPIO-labeled ASCs (SPIOASCs) was investigated first. Fifty-six female rats with myocardial infarction underwent intramyocardial injection of cell culture medium (CCM) or male SPIOASCs with or without the subcutaneous implantable magnet (CCM-magnet or SPIOASC-magnet). Four weeks later, endothelial differentiation, angiogenic cytokine secretion, angiogenesis, cardiomyocyte apoptosis, cell retention, and cardiac performance were examined. The 0.1-Tsela SMF did not adversely affect the viability, proliferation, angiogenic cytokine secretion, and DNA integrity of SPIOASCs. The implanted SPIOASCs could differentiate into endothelial cell, incorporate into newly formed vessels, and secrete multiple angiogenic cytokines. Four weeks after cell transplantation, the number of cardiac SPIOASCs was significantly increased, vascular density was markedly enlarged, fewer apoptotic cardiomyocytes were present, and heart contractile function was substantially improved in the SPIOASC-magnet treated rats in comparison with the SPIOASC-treated rats. The SPIOASCs could differentiate into endothelial cells, incorporate into vessels, promote angiogenesis, and inhibit ischemic cardiomyocyte apoptosis. An externally applied SMF offered a secure environment for biological properties of SPIOASCs, increased the cardiac retention of implanted magnetic SPIOASCs, and further enhanced heart function recovery after myocardial infarction. SIGNIFICANCE: This pilot proof-of-concept study suggests that a 0.1-Tesla static magnetic field does not adversely affect the viability, proliferation, angiogenic cytokine secretion, or DNA integrity of the superparamagnetic iron oxide-labeled adipose-derived stem cells (SPIOASCs). Implantation of adipose-derived stem cells promotes myocardial neovascularization and inhibits ischemic cardiomyocyte apoptosis through endothelial differentiation, incorporation into vessels, and paracrine factor secretion. An externally applied static magnetic field enhanced myocardial retention of intramyocardially injected "magnetic" SPIOASCs and promoted cardiac function recovery after myocardial infarction. With further preclinical optimization, this approach may improve the outcome of current stem cell therapy for ischemic myocardial infarction.

Adipose-derived stem cells from both visceral and subcutaneous fat deposits significantly improve contractile function of infarcted rat hearts.

Adipose-derived stem cells (ASCs) from subcutaneous and visceral adipose tissues have been studied individually. No studies have compared their abilities in treatment of heart failure. This study was designed to evaluate whether ASCs from the two sources could provide a long-term improvement of cardiac function in infarcted hearts. Rat subcutaneous and visceral adipose tissues were excised for isolation of ASCs. Morphology, yield, proliferation, surface markers, differentiation, and cytokine secretion of the subcutaneous ASCs (S-ASCs) and visceral ASCs (V-ASCs) were analyzed. Then a rat model of myocardial infarction (MI) was established by a coronary occlusion. Seven days after occlusion, S-ASCs (n = 22), V-ASCs (n = 22), and Dulbecco's modified Eagle medium (DMEM, n = 20) were injected into the infarct rim, respectively. Cardiac function was then monitored with MRI for up to 6 months. The hearts were then removed for histological assessments. The yield of V-ASCs per gram of the visceral adipose depot was significantly greater than that of S-ASCs in 1 g of the subcutaneous adipose depot. On the other hand, the S-ASCs showed a greater proliferation rate and colony-forming unit relative to the V-ASCs. In addition, the infarcted hearts treated with either S-ASCs or V-ASCs showed a significantly greater left ventricular ejection fraction (LVEF) than those treated with DMEM at 4 weeks and 6 months following the cell/DMEM transplantation. Moreover, the infarct sizes of both S-ASC- and V-ASC-treated hearts were significantly smaller than that in the DMEM-treated hearts. MRI showed the implanted ASCs at the end of 6 months of recovery. Despite the differences in cell yield, proliferation, and colony formation capacity, both S-ASCs and V-ASCs provide a long-lasting improvement of cardiac contractile function in infarcted hearts. We conclude that the subcutaneous and visceral adipose tissues are equally effective cell sources for cell therapy of heart failure.

Temporal dystrophic remodeling within the intrinsic cardiac nervous system of the streptozotocin-induced diabetic rat model.

INTRODUCTION: The pathogenesis of heart failure (HF) in diabetic individuals, called "diabetic cardiomyopathy", is only partially understood. Alterations in the cardiac autonomic nervous system due to oxidative stress have been implicated. The intrinsic cardiac nervous system (ICNS) is an important regulatory pathway of cardiac autonomic function, however, little is known about the alterations that occur in the ICNS in diabetes. We sought to characterize morphologic changes and the role of oxidative stress within the ICNS of diabetic hearts. Cultured ICNS neuronal cells from the hearts of 3- and 6-month old type 1 diabetic streptozotocin (STZ)-induced diabetic Sprague-Dawley rats and age-matched controls were examined. Confocal microscopy analysis for protein gene product 9.5 (PGP 9.5) and amino acid adducts of (E)-4-hydroxy-2-nonenal (4-HNE) using immunofluorescence was undertaken. Cell morphology was then analyzed in a blinded fashion for features of neuronal dystrophy and the presence of 4-HNE adducts. RESULTS: At 3-months, diabetic ICNS neuronal cells exhibited 30% more neurite swellings per area (p = 0.01), and had a higher proportion with dystrophic appearance (88.1% vs. 50.5%; p = <0.0001), as compared to control neurons. At 6-months, diabetic ICNS neurons exhibited more features of dystrophy as compared to controls (74.3% vs. 62.2%; p = 0.0448), with 50% more neurite branching (p = 0.0015) and 50% less neurite outgrowth (p = <0.001). Analysis of 4-HNE adducts in ICNS neurons of 6-month diabetic rats demonstrated twice the amount of reactive oxygen species (ROS) as compared to controls (p = <0.001). CONCLUSION: Neuronal dystrophy occurs in the ICNS neurons of STZ-induced diabetic rats, and accumulates temporally within the disease process. In addition, findings implicate an increase in ROS within the neuronal processes of ICNS neurons of diabetic rats suggesting an association between oxidative stress and the development of dystrophy in cardiac autonomic neurons.

Human mesenchymal stem cells express a myofibroblastic phenotype in vitro: comparison to human cardiac myofibroblasts.

Cardiac fibrosis accompanies a variety of myocardial disorders, and is induced by myofibroblasts. These cells may be composed of a heterogeneous population of parent cells, including interstitial fibroblasts and circulating progenitor cells. Direct comparison of human bone marrow-derived mesenchymal stem cells (BM-MSCs) and cardiac myofibroblasts (CMyfbs) has not been previously reported. We hypothesized that BM-MSCs readily adopt a myofibroblastic phenotype in culture. Human primary BM-MSCs and human CMyfbs were isolated from patients undergoing open heart surgery and expanded under standard culture conditions. We assessed and compared their phenotypic and functional characteristics by examining their gene expression profile, their ability to contract collagen gels and synthesize collagen type I. In addition, we examined the role of non-muscle myosin II (NMMII) in modulating MSC myogenic function using NMMII siRNA knockdown and blebbistatin, a specific small molecule inhibitor of NMMII. We report that, while human BM-MSCs retain pluripotency, they adopt a myofibroblastic phenotype in culture and stain positive for the myofibroblast markers α-SMA, vimentin, NMMIIB, ED-A fibronectin, and collagen type 1 at each passage. In addition, they contract collagen gels in response to TGF-ß1 and synthesize collagen similar to human CMyfbs. Moreover, inhibition of NMMII activity with blebbistatin completely attenuates gel contractility without affecting cell viability. Thus, human BM-MSCs share and exhibit similar physiological and functional characteristics as human CMyfbs in vitro, and their propensity to adopt a myofibroblast phenotype in culture may contribute to cardiac fibrosis.

Assessment of three techniques for delivering stem cells to the heart using PET and MR imaging.

BACKGROUND: Stem cell therapy has a promising potential for the curing of various degenerative diseases, including congestive heart failure (CHF). In this study, we determined the efficacy of different delivery methods for stem cell administration to the heart for the treatment of CHF. Both positron emission tomography (PET) and magnetic resonance imaging (MRI) were utilized to assess the distribution of delivered stem cells. METHODS: Adipose-derived stem cells of male rats were labeled with super-paramagnetic iron oxide (SPIO) and 18 F-fluorodeoxyglucose (FDG). The left anterior descending coronary artery (LAD) of the female rats was occluded to induce acute ischemic myocardial injury. Immediately after the LAD occlusion, the double-labeled stem cells were injected into the ischemic myocardium (n = 5), left ventricle (n = 5), or tail vein (n = 4). In another group of animals (n = 3), the stem cells were injected directly into the infarct rim 1 week after the LAD occlusion. Whole-body PET images and MR images were acquired to determine biodistribution of the stem cells. After the imaging, the animals were euthanized and retention of the stem cells in the vital organs was determined by measuring the cDNA specific to the Y chromosome. RESULTS: PET images showed that retention of the stem cells in the ischemic myocardium was dependent on the cell delivery method. The tail vein injection resulted in the least cell retention in the heart (1.2% ± 0.6% of total injected cells). Left ventricle injection led to 3.5% ± 0.9% cell retention and direct myocardial injection resulted in the highest rate of cell retention (14% ± 4%) in the heart. In the animals treated 1 week after the LAD occlusion, rate of cell retention in the heart was only 4.5% ±1.1%, suggesting that tissue injury has a negative impact on cell homing. In addition, there was a good agreement between the results obtained through PET-MR imaging and histochemical measurements. CONCLUSION: PET-MR imaging is a reliable technique for noninvasive tracking of implanted stem cells in vivo. Direct injection of stem cells into the myocardium is the most effective way for cell transplantation to the heart in heart failure models.

A cardioprotective preservation strategy employing ex vivo heart perfusion facilitates successful transplant of donor hearts after cardiocirculatory death.

BACKGROUND: Ex vivo heart perfusion (EVHP) has been proposed as a means to facilitate the resuscitation of donor hearts after cardiocirculatory death (DCD) and increase the donor pool. However, the current approach to clinical EVHP may exacerbate myocardial injury and impair function after transplant. Therefore, we sought to determine if a cardioprotective EVHP strategy that eliminates myocardial exposure to hypothermic hyperkalemia cardioplegia and minimizes cold ischemia could facilitate successful DCD heart transplantation. METHODS: Anesthetized pigs sustained a hypoxic cardiac arrest and a 15-minute warm ischemic standoff period. Strategy 1 hearts (S1, n = 9) underwent initial reperfusion with a cold hyperkalemic cardioplegia, normothermic EVHP, and transplantation after a cold hyperkalemic cardioplegic arrest (current EVHP strategy). Strategy 2 hearts (S2, n = 8) underwent initial reperfusion with a tepid adenosine-lidocaine cardioplegia, normothermic EVHP, and transplantation with continuous myocardial perfusion (cardioprotective EVHP strategy). RESULTS: At completion of EVHP, S2 hearts exhibited less weight gain (9.7 ± 6.7 [S2] vs 21.2 ± 6.7 [S1] g/hour, p = 0.008) and less troponin-I release into the coronary sinus effluent (4.2 ± 1.3 [S2] vs 6.3 ± 1.5 [S1] ng/ml; p = 0.014). Mass spectrometry analysis of oxidized pleural in post-transplant myocardium revealed less oxidative stress in S2 hearts. At 30 minutes after wean from cardiopulmonary bypass, post-transplant systolic (pre-load recruitable stroke work: 33.5 ± 1.3 [S2] vs 19.7 ± 10.9 [S1], p = 0.043) and diastolic (isovolumic relaxation constant: 42.9 ± 6.7 [S2] vs 65.2 ± 21.1 [S1], p = 0.020) function were superior in S2 hearts. CONCLUSION: In this experimental model of DCD, an EVHP strategy using initial reperfusion with a tepid adenosine-lidocaine cardioplegia and continuous myocardial perfusion minimizes myocardial injury and improves short-term post-transplant function compared with the current EVHP strategy using cold hyperkalemic cardioplegia before organ procurement and transplantation.

Clusters of superparamagnetic iron oxide nanoparticles encapsulated in a hydrogel: a particle architecture generating a synergistic enhancement of the T2 relaxation.

Clusters of iron oxide nanoparticles encapsulated in a pH-responsive hydrogel are synthesized and studied for their ability to alter the T(2)-relaxivity of protons. Encapsulation of the clusters with the hydrophilic coating is shown to enhance the transverse relaxation rate by up to 85% compared to clusters with no coating. With the use of pH-sensitive hydrogel, difficulties inherent in comparing particle samples are eliminated and a clear increase in relaxivity as the coating swells is demonstrated. Agreement with Monte Carlo simulations indicates that the lower diffusivity of water inside the coating and near the particle surface leads to the enhancement. This demonstration of a surface-active particle structure opens new possibilities in using similar structures for nanoparticle-based diagnostics using magnetic resonance imaging.

Can stunned hearts be resuscitated? Evaluation of aspartate/glutamate secondary blood cardioplegia using magnetic resonance spectroscopy.

Objectives: Reperfusion of ischemic hearts with warm, substrate-enriched, blood cardioplegia may alleviate post-ischemic metabolic and functional derangements. This study investigates this possibility using (31)P magnetic resonance (MR) spectroscopy. Methods: Fifteen blood-perfused Langendorff pig hearts were subjected to 30 min of total, normothermic ischemia. Control hearts (n=8) were reperfused with blood for 40 min. Experimental hearts (n=7) received 20 min of aspartate/glutamate (asp/glu) enriched blood cardioplegic solution, followed by 20 min of normal blood. (31)P MR spectroscopy was used to observe cellular energetics and intracellular pH (pHi) throughout the experiments. Left-ventricular function and myocardial oxygen consumption were evaluated before and after ischemia. Results: MR spectra showed no improvement in the rate or extent of high-energy phosphate recovery with asp/glu cardioplegia, but showed a transient increase in pHi during cardioplegic reperfusion (p<0.05). This, however, did not affect post-ischemic recovery of high energy metabolites, myocardial function or oxygen consumption. Conclusions: This study raises questions regarding the potential beneficial effects of asp/glu enriched secondary cardioplegic solution on functional or metabolic status of stunned pig hearts. Extrapolation of these results to humans should be viewed with caution. Keywords: Magnetic resonance; Pig heart; Aspartate; Glutamate; Cardioplegia; Myocardial stunning.

Adipose-derived stem cells are an effective cell candidate for treatment of heart failure: an MR imaging study of rat hearts.

This study assessed the potential therapeutic efficacy of adipose-derived stem cells (ASCs) on infarcted hearts. Myocardial infarction was induced in rat hearts by occlusion of the left anterior descending artery (LAD). One week after LAD occlusion, the rats were divided into three groups and subjected to transplantation of ASCs or transplantation of cell culture medium (CCM) or remained untreated. During a 1-mo recovery period, magnetic resonance imaging showed that the ASC-treated hearts had a significantly greater left ventricular (LV) ejection fraction and LV wall thickening than did the CCM-treated and untreated hearts. The capillary density in infarct border zone was significantly higher in the ASC-treated hearts than in the CCM-treated and untreated hearts. However, only 0.5% of the ASCs recovered from the ASC-treated hearts were stained positive for cardiac-specific fibril proteins. It was also found that ASCs under a normal culture condition secreted three cardiac protective growth factors: vascular endothelial growth factor, hepatocyte growth factor, and insulin-like growth factor-1. Results of this study suggest that ASCs were able to improve cardiac function of infarcted rat hearts. Paracrine effect may be the mechanism underlying the improved cardiac function and increased capillary density.

Superparamagnetic iron oxide does not affect the viability and function of adipose-derived stem cells, and superparamagnetic iron oxide-enhanced magnetic resonance imaging identifies viable cells.

The objectives of this study were (1) to determine whether superparamagnetic iron oxide (SPIO) affects viability, transdifferentiation potential and cell-factor secretion of adipose-derived stem cells (ASCs); and (2) to determine whether SPIO-enhanced magnetic resonance (MR) imaging highlights living stem cells. Rat ASCs were incubated in SPIO-containing cell culture medium for 2 days. The SPIO-treated ASCs were then subjected to adipogenic, osteogenic and myogenic transdifferentiation. Expression of vascular endothelial growth factor, hepatocyte growth factor and insulin-like growth factor 1 by the SPIO-treated ASCs was measured using reverse transcription polymerase chain reaction. Cell viability was assessed using trypan blue stain. For in vivo experiments, SPIO-labeled ASCs were injected into 10 rat hearts. The hearts were monitored using MRI. We found that survival rate of the ASCs cultured in the SPIO-containing medium was very high (97-99%). The SPIO-treated ASCs continued to express specific markers for the three types of transdifferentiation. Expression of the cell factors by the ASCs was not affected by SPIO. Signal voids on MR images were associated with the living SPIO-labeled ASCs in the rat hearts. We conclude that SPIO does not affect viability, transdifferentiation potential or cell-factor secretion of ASCs. MRI mainly highlights living SPIO-labeled stem cells.

Alternate antegrade/retrograde perfusion: an effective technique to preserve hypertrophied hearts during valvular surgery.

OBJECTIVE: Continuous antegrade perfusion (AP) may interfere with surgical precision. Continuous retrograde perfusion (RP), on the other hand, cannot sustain the empty-beating hypertrophied hearts. Therefore, alternate antegrade/retrograde perfusion (A(A/R)P) may be a rational technique to preserve the hypertrophied hearts. This study is to determine whether A(A/R)P could maintain myocardial energy metabolism, oxygenation, and contractile function of the empty-beating hypertrophied hearts. METHODS: Sixteen hypertrophied pig hearts were divided into four groups (n=4 per group). Group I and II underwent an 80-min A(A/R)P (four 10-min APs and four 10-min RPs), followed by a 20-min reperfusion. Group III and IV were subjected to an 80-min AP and 20-min reperfusion and used as a control. Energy metabolism was evaluated in group I and III using magnetic resonance spectroscopy. Myocardial oxygenation (MO) was assessed in group II and IV using near infrared spectroscopic imaging. RESULTS: During 80-min A(A/R)P, four episodes of RP resulted in a significant decrease in myocardial phosphocreatine (PCr) and MO. The subsequent AP, however, resulted in complete recovery of the parameters. Moreover, myocardial adenosine triphosphate (ATP) remained at a normal level throughout the 80-min A(A/R)P. As expected, hearts in groups III and IV showed normal level of myocardial PCr, ATP, and MO throughout protocol. Finally, hearts in all four groups showed similar contractile function during reperfusion. CONCLUSIONS: A(A/R)P with four 10-min intervals of AP and RP sustained normal myocardial energy metabolism, oxygenation, and contractile function of empty-beating hypertrophied hearts. We conclude that A(A/R)P is an effective technique for preservation of empty-beating hypertrophied hearts during valvular surgery.

The effects of simultaneous antegrade/retrograde cardioplegia on cellular volumes and energy metabolism.

BACKGROUND AND AIM OF THE STUDY: Simultaneous antegrade/retrograde cardioplegia (SARC) has been employed frequently during cardiac surgery to preserve the jeopardized myocardium. However, retrograde perfusion of SARC may interfere with myocardial drainage and disrupt myocardial fluid homeostasis, which may affect the myocardial energy metabolism and contractile function. The study was, therefore, designed to assess the effects of SARC on myocardial fluid homeostasis, cellular volumes, and energy metabolism. METHODS: Eight isolated pig hearts were subjected to a protocol consisting of a 20-minute control perfusion, 120-minute SARC, and 20-minute reperfusion. The myocardial water content was monitored using near-infrared spectroscopy. Phosphorus-31 magnetic resonance ((31)P MR) spectroscopy was used to monitor the volumes of both intracellular and extracellular compartments and assess myocardial energy metabolism. RESULTS: The near-infrared spectra showed that the 120-min SARC resulted in a 60 +/- 12% increase in the myocardial water content. (31)P MR spectra showed a 36 +/- 4% increase in the intracellular compartment and a 54 +/- 8% increase in the extracellular compartment during SARC relative to their initial volumes measured during control perfusion (100%). However, the myocardial energy metabolites (adenosine triphosphate [ATP] and phosphocreatine [PCr]) remained unchanged during the 120-minute SARC. Moreover, during reperfusion, the hearts showed an almost complete recovery in the left ventricular-developed pressure. CONCLUSIONS: A prolonged SARC resulted in water accumulation in both extracellular and intracellular compartments in the normal myocardium. Although its detrimental effect on tissue fluid homeostasis did not jeopardize the myocardial energy metabolism, a prolonged use of SARC should be avoided, particularly in the diseased hearts.