Number of Stent Retriever Passes Associated with Clinical Outcome After Mechanical Thrombectomy in Acute Ischemic Stroke.

OBJECTIVE: To evaluate the association between the number of stent retriever (SR) passes and clinical outcome after mechanical thrombectomy (MT) in patients with acute ischemic stroke(AIS). METHODS: We retrospectively analyze data collected from consecutive patients with large vessel occlusion (LVO) in anterior circulation treated with MT. Baseline characteristics, number of SR passes, symptomatic intracranial hemorrhage (sICH), clinical outcome measured by modified Rankin Scale (mRS) at 90 days after MT were collected. Multivariate logistic regression analysis was performed to assess the association between number of SR passes and patients' clinical outcome. RESULTS: 134 patients with LVO achieved successful reperfusion (mTICI 2B/3) were enrolled. Univariate analysis showed that patients with favorable outcomes were less likely to need more than three passes of SR (9.8%vs39.7%, p = 0.001). In a multivariable analysis, baseline NIHSS score (OR 0.922, 95%CI 0.859∼0.990, p = 0.025), more than three passes of SR (OR 0.284, 95%CI0.091∼0.882, p = 0.030) and symptomatic intracranial hemorrhage (OR 0.116,95%CI0.021∼0.650, p = 0.014) each independently predicted poor outcome after MT at 90 days. CONCLUSION: The need for more than three passes of SR may be used as an independent predictor of poor outcome after MT in patients with acute ischemic stroke at 90 days.

The Value of the Score for the Targeting of Atrial Fibrillation (STAF) Screening in Acute Stroke Patients.

BACKGROUND AND PURPOSE: Recently, the score for the targeting of atrial fibrillation (STAF) was introduced to identify the risk of atrial fibrillation (AF) in stroke patients. In this study, we aim to evaluate the usefulness of the STAF score for AF screening in acute stroke patients. METHODS: Patients with acute ischemic stroke who were admitted to our stroke unit were prospectively enrolled from March 2011 to March 2013. Baseline National Institutes of Health Stroke Scale (NIHSS), left atrial dilatation, and vascular etiology were assessed to calculate the STAF score. Logistic regression analysis was used to examine the relationship between AF and STAF factors. Univariate analysis of AF and age, history of coronary heart disease and rheumatic heart disease, NIHSS, left atrial dilatation, and vascular etiology was performed. RESULTS: A total of 472 patients were enrolled in our analysis. AF was documented in 78 (16.53%) patients, of which 50% were paroxysmal. Multivariable analysis demonstrated that age, NIHSS, left atrial dilatation, and the absence of vascular etiology can each function as independent predictors for AF. In addition, all AF patients with a STAF ≥5 show a sensitivity of 76.92% and a specificity of 78.68%. The area under the receiver operating characteristic for all AF patients was .842 versus .763 for the paroxysmal AF (pAF) patients. In addition, a sensitivity of 81% (95% CI 73-92) and a ROC of .829 were for new-AF. CONCLUSIONS: The value of the STAF system for predicting the risk of pAF and new-AF in stroke patients is relatively limited.

Calcium and cyclic nucleotides affect TNF-alpha-induced stem cell migration.

The purpose of this study was to study the effect of calcium, cyclic AMP (cAMP) and cyclic GMP (cGMP) on embryonic stem cell (ESC) motility during TNF-alpha-induced chemotaxis. ESCs were monitored using a chemotaxis chamber, with different concentrations of calcium or cAMP or cGMP added to the medium. Changes in intracellular calcium ([Ca(2+)](i)) were measured with the fluorescent dye fura-2/AM. We combined migratory parameters in a mathematical model and described it as "mobility". After adding calcium, a dose-dependant increase in cell speed was found. Cyclic AMP increased mobility as well as the [Ca(2+)](i). In contrast, adding dbcGMP resulted in a significant decrease in the mobility of the ESCs. During migration ESCs showed an increase in [Ca(2+)](i). Furthermore, TNF-alpha dramatically increased the movement as well as the directionality of ESCs. These results demonstrate that ESCs are highly motile and respond to different concentrations of calcium in a dose-related manner.

Clozapine-induced myocarditis: role of catecholamines in a murine model.

Clozapine, an atypical antipsychotic, is very effective in the treatment of resistant schizophrenia. However, cardiotoxicity of clozapine, particularly in young patients, has raised concerns about its safety. Increased catecholamines have been postulated to trigger an inflammatory response resulting in myocarditis, dilated cardiomyopathy, and death, although this has not yet been thoroughly studied. Here, we used the mouse to study whether clozapine administration could cause adverse myocarditis associated with an increase in catecholamines. Male Balb/C mice, age ~6 weeks, were administered 5, 10 or 25 mg/kg clozapine daily for 7 and 14 days; one group was administered 25 mg/kg clozapine plus 2 mg/kg propranolol for 14 days. Saline-treated mice served as controls. Heart sections were stained with hematoxylin and eosin for histopathological examination. Plasma catecholamines were measured with HPLC. Myocardial TNF-alpha concentrations were determined by ELISA. Histopathology of clozapine-treated mice showed a significant dose-related increase in myocardial inflammation that correlated with plasma catecholamine levels and release of TNF-alpha. Propranolol significantly attenuated these effects. A hypercatecholaminergic state induced by clozapine could explain the occurrence of myocarditis in some patients. Our data suggest that a beta-adrenergic blocking agent may be effective in reducing the incidence and severity of clozapine-induced myocarditis.

Excess placental soluble fms-like tyrosine kinase 1 (sFlt1) may contribute to endothelial dysfunction, hypertension, and proteinuria in preeclampsia.

Preeclampsia, a syndrome affecting 5% of pregnancies, causes substantial maternal and fetal morbidity and mortality. The pathophysiology of preeclampsia remains largely unknown. It has been hypothesized that placental ischemia is an early event, leading to placental production of a soluble factor or factors that cause maternal endothelial dysfunction, resulting in the clinical findings of hypertension, proteinuria, and edema. Here, we confirm that placental soluble fms-like tyrosine kinase 1 (sFlt1), an antagonist of VEGF and placental growth factor (PlGF), is upregulated in preeclampsia, leading to increased systemic levels of sFlt1 that fall after delivery. We demonstrate that increased circulating sFlt1 in patients with preeclampsia is associated with decreased circulating levels of free VEGF and PlGF, resulting in endothelial dysfunction in vitro that can be rescued by exogenous VEGF and PlGF. Additionally, VEGF and PlGF cause microvascular relaxation of rat renal arterioles in vitro that is blocked by sFlt1. Finally, administration of sFlt1 to pregnant rats induces hypertension, proteinuria, and glomerular endotheliosis, the classic lesion of preeclampsia. These observations suggest that excess circulating sFlt1 contributes to the pathogenesis of preeclampsia.

Antiapoptotic effect of implanted embryonic stem cell-derived early-differentiated cells in aging rats after myocardial infarction.

This study tested whether implanted embryonic stem cell-derived early-differentiated cells (EDCs) lead to improvement in cardiac function by preventing cardiac apoptosis in aging rats after myocardial infarction. Cardiac apoptosis after transplantation of EDCs was assessed in situ by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling reaction (TUNEL) staining as well as by measurements of protein levels of cleaved caspases 3, Bax, and Bcl-2. Our results indicate that cell transplantation improved cardiac function at 6-months observation. The frequency of apoptotic cells in the peri-infarcted myocardium 3 days after cell transplantation was significantly decreased in the cell transplantation group. EDC therapy decreased the protein levels of cleaved caspase 3 and Bax, and increased the level of Bcl-2 in comparison to myocardial infarction control. Additionally, the number of apoptotic cells decreased significantly in cardiomyocytes precocultured with EDCs. This study demonstrates that functional improvement of EDC transplantation may at least in part be related to a reduction in cardiomyocyte apoptosis.

Stem cell therapy in the aging hearts of Fisher 344 rats: synergistic effects on myogenesis and angiogenesis.

OBJECTIVE: Advanced age is a major risk factor for ventricular dysfunction and reduction of cardiac reserve. Finding novel approaches to prevent and attenuate heart dysfunction associated with advanced age is a major therapeutic challenge. The present study was designed to test whether engrafted embryonic stem cells could improve myocardial function in aging hearts. METHODS: Cultured mouse embryonic stem cells used for cell therapy were transfected with green fluorescent protein. Aging rats in the cell-treated group received intramyocardial injection of embryonic stem cells. Hemodynamic measurement, myocyte counting, and evaluation of blood flow were performed 6 weeks after cell transplantation. RESULTS: Embryonic stem cell therapy partially improved cardiac reserve, as reflected by the in vivo response to isoproterenol (INN: isoprenaline) stimulation in aging hearts 6 weeks after cell implantation. The functional benefits from engrafted embryonic stem cells were associated with increased myocyte numbers and enhanced left ventricular blood perfusion in the aging heart. The characteristic phenotype of engrafted embryonic stem cells was identified in the transplanted heart on the basis of green fluorescent protein-positive spots that were further demonstrated to differentiate into cardiac tissue with positive staining for cardiac alpha-myosin heavy chain. CONCLUSIONS: Regenerating cardiomyocytes and increasing regional blood perfusion in the aging heart after embryonic stem cell transplantation synergistically resulted in improvement of cardiac function. Embryonic stem cell transplantation might hold significant clinical potential in attenuating the progressive decrease of cardiac function associated with advanced aging.

Long-term improvement of cardiac function in rats after infarction by transplantation of embryonic stem cells.

OBJECTIVE: This study was designed to investigate the feasibility of and potential functional improvement with embryonic stem cell transplantation in rats 32 weeks after myocardial infarction. METHODS: Before cell transplantation, cultured embryonic stem cells were transfected with the complementary DNA of green fluorescent protein to identify engrafted cells in myocardium. Myocardial infarction was induced by ligation of the left coronary artery. Either 3 x 10(5) mouse embryonic stem cells or an equivalent volume of cell-free medium was injected into injured myocardium within 20 minutes after induction of myocardial infarction. RESULTS: Embryonic stem cell transplantation significantly increased the survival rate in rats undergoing myocardial infarction during the experimental period of 32 weeks. Hemodynamic and echocardiographic data showed that embryonic stem cell transplantation significantly improved ventricular function relative to the myocardial infarction plus medium control group. Tissue positive for green fluorescent protein was found in the injured myocardium with cell transplantation. The proportion of myocardium positively immunostained by antibodies against alpha-myosin heavy chain and cardiac troponin I was greater in the infarcted area with embryonic stem cell transplantation than in the injured myocardium with medium injection. Single green fluorescent protein-positive cells with a rod shape and clear striations were observed in cardiomyocytes isolated from infarcted hearts with embryonic stem cell transplantation. In addition, the number of blood vessels in injured myocardium was greater in the cell-transplanted myocardial infarction group than in the medium-injected myocardial infarction group. CONCLUSIONS: Engrafted embryonic stem cells differentiated into cardiomyocytes in injured myocardium, caused an angiogenetic effect, and subsequently improved cardiac function during the 32-week observation period.

Transplantation of embryonic stem cells improves cardiac function in postinfarcted rats.

Massive loss of cardiac myocytes after myocardial infarction (MI) is a common cause of heart failure. The present study was designed to investigate the improvement of cardiac function in MI rats after embryonic stem (ES) cell transplantation. MI in rats was induced by ligation of the left anterior descending coronary artery. Cultured ES cells used for cell transplantation were transfected with the marker green fluorescent protein (GFP). Animals in the treated group received intramyocardial injection of ES cells in injured myocardium. Compared with the MI control group injected with an equivalent volume of the cell-free medium, cardiac function in ES cell-implanted MI animals was significantly improved 6 wk after cell transplantation. The characteristic phenotype of engrafted ES cells was identified in implanted myocardium by strong positive staining to sarcomeric alpha-actin, cardiac alpha-myosin heavy chain, and troponin I. GFP-positive cells in myocardium sectioned from MI hearts confirmed the survival and differentiation of engrafted cells. In addition, single cells isolated from cell-transplanted MI hearts showed rod-shaped GFP-positive myocytes with typical striations. The present data demonstrate that ES cell transplantation is a feasible and novel approach to improve ventricular function in infarcted failing hearts.

VEGF enhances functional improvement of postinfarcted hearts by transplantation of ESC-differentiated cells.

Despite considerable advances in medicine, the incidence of heart failure remains high in patients after myocardial infarction (MI). This study investigated the effects of engrafted early-differentiated cells (EDCs) from mouse embryonic stem cells, with or without transfection of vascular endothelial growth factor (VEGF) cDNA (phVEGF(165)), on cardiac function in postinfarcted mice. EDCs were transfected with green fluorescent protein (GFP) cDNA and transplanted into infarcted myocardium. Compared with the MI mice receiving cell-free medium, cardiac function was significantly improved in the MI mice 6 wk after transplantation of EDCs. Moreover, improvement of heart function was significantly greater in the mice implanted with EDCs overexpressing VEGF (EDCs-VEGF) than with EDCs alone. Frozen sections of infarcted myocardium with EDCs or EDCs-VEGF transplantation showed GFP-positive tissue. The area with positive immunostaining for cardiac troponin I and alpha-myosin heavy chain was larger in injured myocardium with EDCs or EDCs-VEGF transplantation than with medium injection. Transplantation of EDCs or EDCs-VEGF significantly increased the number of blood vessels in the MI area. However, the density of capillaries was significantly higher in the EDCs-VEGF animals than in the EDC mice. Double staining for GFP and connexin-43 was positive in injured myocardium with EDC transplantation. Our data demonstrate that engrafted EDCs or EDCs-VEGF regenerated cardiac tissue and significantly improved cardiac function in postinfarcted hearts. The novel EDCs-VEGF synergistic approach may have an important impact on future cell therapy for patients experiencing MI or heart failure.

Immunosuppression and xenotransplantation of cells for cardiac repair.

The death of highly vulnerable cardiomyocytes during ischemia leads to cardiac dysfunction, including heart failure. Due to limited proliferation of adult mammalian cardiomyocytes, the dead myocardium is replaced by noncontractile fibrotic tissue. Introducing exogenous cells to participate in the regeneration of infarcted myocardium has thus been proposed as a novel therapeutic approach. In view of the availability of various xenogeneic cells and fewer ethical and political concerns that surround human embryonic stem cells and fetal cardiomyocytes, cellular xenotransplantation may be a potential alternative approach for cardiac repair in humans. However, one of the most daunting challenges of xenotransplantation is immunorejection. This article summarizes the progress in cellular xenotransplantation for cardiac repair in experimental settings and the current understanding of possible immune responses following the engraftment of xenogeneic cells. The public attitude towards xenotransplantation is reportedly more favorable to receiving cells or tissues than a whole organ, but many scientific obstacles need to be overcome before the utilization of xenogeneic cells for cardiac repair in patients with heart disease becomes applicable to clinical practice.

Significant improvement of heart function by cotransplantation of human mesenchymal stem cells and fetal cardiomyocytes in postinfarcted pigs.

BACKGROUND: Viable cardiomyocytes after myocardial infarction (MI) are unable to repair the necrotic myocardium due to their limited capability of regeneration. The present study investigated whether intramyocardial transplantation of human mesenchymal stem cells (hMSCs) or cotransplantation of hMSCs plus human fetal cardiomyocytes (hFCs; 1:1) reconstituted impaired myocardium and improved cardiac function in MI pigs. METHODS AND RESULTS: Cultured hMSCs were transfected with green fluorescent protein (GFP). Six weeks after MI induction and cell transplantation, cardiac function was significantly improved in MI pigs transplanted with hMSCs alone. However, the improvement was even markedly greater in MI pigs cotransplanted with hMSCs plus hFCs. Histological examination demonstrated that transplantation of hMSCs alone or hMSCs plus hFCs formed GFP-positive engrafts in infarcted myocardium. In addition, immunostaining for cardiac alpha-myosin heavy chain and troponin I showed positive stains in infarcted regions transplanted with hMSCs alone or hMSCs plus hFCs. CONCLUSIONS: Our data demonstrate that transplantation of hMSCs alone improved cardiac function in MI pigs with a markedly greater improvement from cotransplantation of hMSCs plus hFCs. This improvement might result from myocardial regeneration and angiogenesis in injured hearts by engrafted cells.

Dantrolene: effects on abnormal intracellular Ca(2+) handling and inotropy in postinfarcted rat myocardium.

The present study was designed to investigate the effects of dantrolene on intracellular Ca(2+) ([Ca(2+)](i)) handling and inotropy in rat infarcted myocardium. Dantrolene-treated rats with myocardial infarction were placed into two different dosage groups. The infarcted control group received placebo only. Isometric contractility and intracellular Ca(2+) transients were recorded simultaneously in isolated papillary muscles. Diastolic [Ca(2+)](i) was significantly lower in muscle preparations from infarcted rats receiving dantrolene compared to the placebo control group. Additionally, treatment with dantrolene in infarcted rats significantly improved the inotropic response to 10(-4) M isoproterenol. The protein levels of the sarcoplasmic reticulum Ca(2+) ATPase were increased in infarcted rat hearts with dantrolene treatment. We conclude that dantrolene improved the inotropic response to beta-adrenoceptor stimulation in rat postinfarcted myocardium, which is related to improved intracellular Ca(2+) handling, and lowered diastolic Ca(2+) concentration.

Mibefradil improves beta-adrenergic responsiveness and intracellular Ca(2+) handling in hypertrophied rat myocardium.

The present study investigated the effects of mibefradil, a novel T-type channel blocker, on ventricular function and intracellular Ca(2+) handling in normal and hypertrophied rat myocardium. Ca(2+) transient was measured with the bioluminescent protein, aequorin. Mibefradil (2 microM) produced nonsignificant changes in isometric contraction and peak systolic intracellular Ca(2+) concentration ([Ca(2+)](i)) in normal rat myocardium. Hypertrophied papillary muscles isolated from aortic-banded rats 10 weeks after operation demonstrated a prolonged duration of isometric contraction, as well as decreased amplitudes of developed tension and peak Ca(2+) transient compared with the sham-operated group. Additionally, diastolic [Ca(2+)](i) increased in hypertrophied rat myocardium. The positive inotropic effect of isoproterenol stimulation was blunted in hypertrophied muscles despite a large increase in Ca(2+) transient amplitude. Afterglimmers and corresponding aftercontractions were provoked with isoproterenol (10(-5) and 10(-4) M) stimulation in 4 out of 16 hypertrophied muscles, but were eliminated in the presence of mibefradil (2 microM). In addition, hypertrophied muscles in the presence of mibefradil had a significant improvement of contractile response to isoproterenol stimulation and a reduced diastolic [Ca(2+)](I), although a mild decrease of peak Ca(2+)-transient was also shown. However, verapamil (2 microM) did not restore the inotropic and Ca(2+) modulating effects of isoproterenol in hypertrophied myocardium. Mibefradil partly restores the positive inotropic response to beta-adrenergic stimulation in hypertrophied myocardium from aortic-banded rats, an effect that might be useful in hypertrophied myocardium with impaired [Ca(2+)](i) homeostasis.

Genistein attenuates postischemic depressed myocardial function by increasing myofilament Ca2+ sensitivity in rat myocardium.

The present study investigated whether genistein, a broad-spectrum tyrosine kinase inhibitor, could increase the myofilament Ca(2+) sensitivity and partially reverse postischemic depressed myocardial function. Left ventricular papillary muscles were isolated from adult Wistar rats and loaded with the Ca2+ indicator, aequorin. The use of fluorocarbon immersion with hypoxia simulated a model of ischemia. Myofilament responsiveness to Ca2+ was evaluated from force-[Ca2+]i relationship recorded during tetani in papillary muscles. Protein levels of troponin I (TnI) were measured in postischemic papillary muscles with the Western blot technique. Isometric contraction was depressed during the period of ischemia and remained low after 60 min of reoxygenation without a corresponding significant change of peak [Ca2+]i in the control group (n = 7). In contrast, the depression of isometric contraction was ameliorated during ischemia in muscle preparations in the presence of genistein (2 micro M; n = 8), and postischemic depressed myocardial contractility partially recovered after a 60-min reperfusion. The myofilament Ca2+ responsiveness was significantly increased in papillary muscles in the presence of genistein. Protein levels of TnI were reduced in postischemic papillary muscles, whereas genistein partially restored decreased protein levels of TnI. Our results reveal that genistein produces an effective attenuation of postischemic depressed myocardial function and improves myofibrillar Ca2+ responsiveness in rat myocardium.

Targeted deletion of Puma attenuates cardiomyocyte death and improves cardiac function during ischemia-reperfusion.

The p53-upregulated modulator of apoptosis (Puma), a BH3-only member of the Bcl-2 protein family, is required for p53-dependent and -independent forms of apoptosis and has been implicated in the pathomechanism of several diseases, including cancer, acquired immunodeficiency syndrome, and ischemic brain disease. The role of Puma in cardiomyocyte death, however, has not been analyzed. On the basis of the ability of Puma to integrate diverse cell death stimuli, we hypothesized that Puma might be critical for cardiomyocyte death upon ischemia-reperfusion (I/R) of the heart. Here we show that hypoxia-reoxygenation of isolated cardiomyocytes led to an increase in Puma mRNA and protein levels. Moreover, if Puma was delivered by an adenoviral construct, cardiomyocytes died by apoptosis. Under ATP-depleted conditions, however, Puma overexpression primarily induced necrosis, suggesting that Puma is involved in the development of both types of cell death. Consistent with these findings, targeted deletion of Puma in a mouse model attenuated both apoptosis and necrosis. When the Langendorff ex vivo I/R model was used, infarcts were approximately 50% smaller in Puma(-/-) than in wild-type mice. As a result, after I/R, cardiac function was significantly better preserved in Puma(-/-) mice than in their wild-type littermates. Our study thus establishes Puma as an essential mediator of cardiomyocyte death upon I/R injury and offers a novel therapeutic target to limit cell loss in ischemic heart disease.

Vascular endothelial growth factor promotes cardiomyocyte differentiation of embryonic stem cells.

Embryonic stem cells (ESCs) overexpressing the vascular endothelial growth factor (VEGF) improve cardiac function in mouse models of myocardial ischemia and infarction by mechanisms that are poorly understood. Here we studied the effects of VEGF on cardiomyocyte differentiation of mouse ESCs in vitro. We used flow cytometry to determine the expression of alpha-myosin heavy chain (alpha-MHC), cardiac troponin I (cTn-I), and Nkx2.5 in differentiated ESCs. VEGF (20 ng/ml) significantly enhanced alpha-MHC, cTn-I, and Nkx2.5 expression in differentiated ESCs. Western blot analysis confirmed these findings. We found that VEGF receptor FMS-like tyrosine kinase-1 (Flt-1) and fetal liver kinase-1 (Flk-1) expression increased during ESC differentiation. Antibodies against Flk-1 totally blocked and against Flt-1 partially blocked VEGF-induced NKx2.5-positive-stained cells. The ERK inhibitor PD-098059 abolished VEGF-induced cardiomyocyte differentiation of ESCs. Our results suggest that VEGF promotes cardiomyocyte differentiation predominantly by ERK-mediated Flk-1 activation and, to a lesser extent, by Flt-1 activation. These findings may be of significance for stem cell and growth factor therapies to regenerate failing cardiomyocytes.

Homing of intravenously infused embryonic stem cell-derived cells to injured hearts after myocardial infarction.

OBJECTIVE: The present study was designed to test whether intravenously infused embryonic stem cell-derived cells could translocate to injured myocardium after myocardial infarction and improve cardiac function. METHODS: Cultured embryonic stem cell-derived cells were transfected with green fluorescent protein. Embryonic stem cell-derived cells were administered through the tail vein (approximately 10(7) cells in 1 mL of medium for each rat) every other day for 6 days in 45 rats after myocardial infarction. Six weeks after myocardial infarction and cell infusion, cardiac function, blood flow, and the numeric density of arterioles were measured to test the benefits of cell therapy. An in vitro Transwell assay was performed to evaluate the embryonic stem cell migration. RESULTS: Ventricular function, regional blood flow, and arteriole density were significantly increased in rats receiving intravenously infused embryonic stem cell-derived cells compared with control rats after myocardial infarction. Histologic analysis demonstrated that infused embryonic stem cell-derived cells formed green fluorescent protein-positive grafts in infarcted myocardium. Additionally, positive immunostaining for cardiac troponin I was found in hearts after myocardial infarction receiving embryonic stem cell-derived cell infusion that corresponded to the green fluorescent protein-positive staining. The Transwell migration assay indicated that cultured neonatal rat cardiomyocytes with overexpression of tumor necrosis factor alpha induced greater migration of embryonic stem cells compared with cardiomyocytes without tumor necrosis factor alpha expression. CONCLUSIONS: Our data demonstrate that intravenously infused embryonic stem cell-derived cells homed to the infarcted heart, improved cardiac function, and enhanced regional blood flow at 6 weeks after myocardial infarction. The in vitro migration assay suggested that such a homing mechanism could be associated with locally released cytokines, such as tumor necrosis factor alpha, that are upregulated in the setting of acute myocardial infarction and heart failure.

Successful implantation of intravenously administered stem cells correlates with severity of inflammation in murine myocarditis.

The present study was designed to determine whether cardiac inflammation is important for the successful homing of stem cells to the heart after intravenous injection in a murine myocarditis model. Male Bagg albino/c mice were infected with encephalomyocarditis virus (EMCV) to produce myocarditis. Subgroups of mice received single injections by tail vein of embryonic stem cells (ESCs) transfected with green fluorescent protein (GFP) as a marker at days 3, 14, or 60 after infection; other subgroups without stem cell injections were killed at each of these time points to assess the degree of inflammation present. The surviving mice were killed at day 90 after virus infection and hemodynamics, gross pathology, histology, and inflammatory cytokine production in the hearts were measured. Our results indicate that myocardial inflammation was most severe and cytokine production highest at day 14 after EMCV inoculation, and in particular, was strongly positive for interleukin 6. Mice receiving intravenous ESC injections on day 14 after EMCV inoculation showed the largest number of GFP-positive cells at the time of death and the greatest functional improvement compared to uninfected controls without inflammation. We conclude that factors released from myocardium during inflammation are important for enhancing the homing, migration, and implantation of systemically infused stem cells.