Complement C1q activates canonical Wnt signaling and promotes aging-related phenotypes.

Wnt signaling plays critical roles in development of various organs and pathogenesis of many diseases, and augmented Wnt signaling has recently been implicated in mammalian aging and aging-related phenotypes. We here report that complement C1q activates canonical Wnt signaling and promotes aging-associated decline in tissue regeneration. Serum C1q concentration is increased with aging, and Wnt signaling activity is augmented during aging in the serum and in multiple tissues of wild-type mice, but not in those of C1qa-deficient mice. C1q activates canonical Wnt signaling by binding to Frizzled receptors and subsequently inducing C1s-dependent cleavage of the ectodomain of Wnt coreceptor low-density lipoprotein receptor-related protein 6. Skeletal muscle regeneration in young mice is inhibited by exogenous C1q treatment, whereas aging-associated impairment of muscle regeneration is restored by C1s inhibition or C1qa gene disruption. Our findings therefore suggest the unexpected role of complement C1q in Wnt signal transduction and modulation of mammalian aging.

Prognostic Effect of Incidental Pulmonary Embolism on Long-Term Mortality in Cancer Patients.

BACKGROUND: The effect of incidental pulmonary embolism (PE) on long-term prognosis in cancer patients is unclear. This study assessed the characteristics of cancer and venous thromboembolism (VTE) and the effect of incidental PE identified by oncologists on long-term survival of patients with cancer.Methods and Results:This single-center, retrospective, cohort study used hospital-based cancer registry data from the Osaka International Cancer Institute linked with electronic medical records and administrative data from Japan's Diagnosis Procedure Combination Per-diem Payment System. Overall, 15,689 cancer patients underwent contrast-enhanced thoracic computed tomography during 2010-2018. After excluding patients with missing data, symptomatic patients, or patients with suspected PE, 174 with incidental PE (PE+ group) and 13,197 with no PE (PE- group) were identified. The total incidence of incidental PE was 1.3%. No deaths from thrombotic events were identified in the PE+ group. Both groups were adjusted for cancer- and VTE-related characteristics using inverse probability weighting. After adjusting for immortal time bias in the PE+ group, Kaplan-Meier analysis revealed that all-cause mortality was higher in the PE+ group (hazard ratio, 2.26; 95% confidence interval, 1.53-3.33). A Cox proportional hazard model revealed that metastatic cancer and a history of curative treatment were significant prognostic factors, whereas central PE and residual proximal deep vein thrombosis were not. CONCLUSIONS: Incidental PE in cancer patients indicates poorer prognosis. Cancer-related but not thrombosis-related factors determine prognosis.

Multicentre cohort study of the impact of percutaneous coronary intervention on patients with concurrent cancer and ischaemic heart disease.

BACKGROUND: The incidence of concurrent cancer and ischaemic heart disease (IHD) is increasing; however, the long-term patient prognoses remain unclear. METHODS: Five-year all-cause mortality data pertaining to patients in the Osaka Cancer Registry, who were diagnosed with colorectal, lung, prostate, and gastric cancers between 2010 and 2015, were retrieved and analysed together with linked patient administrative data. Patient characteristics (cancer type, stage, and treatment; coronary risk factors; medications; and time from cancer diagnosis to index admission for percutaneous coronary intervention [PCI] or IHD diagnosis) were adjusted for propensity score matching. Three groups were identified: patients who underwent PCI within 3 years of cancer diagnosis (n = 564, PCI + group), patients diagnosed with IHD within 3 years of cancer diagnosis who did not undergo PCI (n = 3058, PCI-/IHD + group), and patients without IHD (n = 27,392, PCI-/IHD- group). Kaplan-Meier analysis was used for comparisons. RESULTS: After propensity score matching, the PCI + group had better prognosis (n = 489 in both groups, hazard ratio 0.64, 95% confidence interval 0.51-0.81, P < 0.001) than the PCI-/IHD + group. PCI + patients (n = 282) had significantly higher mortality than those without IHD (n = 280 in each group, hazard ratio 2.88, 95% confidence interval 1.90-4.38, P < 0.001). CONCLUSIONS: PCI might improve the long-term prognosis in cancer patients with IHD. However, these patients could have significantly worse long-term prognosis than cancer patients without IHD. Since the present study has some limitations, further research will be needed on this important topic in cardio-oncology.

Serial Changes in Cardiac Strain and Contractility After Hematopoietic Stem Cell Transplantation in Patients with Hematologic Malignancies.

Hematopoietic stem cell transplantation (HSCT) is occasionally associated with cardiac dysfunction during long-term follow-up. Global longitudinal strain (GLS) has emerged as an early predictor of cardiotoxicity associated with cancer therapy; however, the serial changes in GLS before and after HSCT have not been elucidated. To clarify the association between HSCT and GLS, we investigated serial changes in GLS before and after HSCT. We evaluated cardiac function before and 1, 3, and 6 months after HSCT in 38 consecutive HSCT patients enrolled in this study. Overall, GLS and left ventricular (LV) ejection fraction (EF) temporally decreased 1 month post-HSCT. LVEF completely recovered to baseline at 3 months after HSCT, whereas GLS partially recovered 6 months after HSCT. Except for five patients who died within 6 months, GLS values in the low EF group (LVEF ≤ 55% at 6 months post-HSCT, n = 6) were significantly and consistently lower than those in the normal EF group (LVEF > 55% at 6 months post-HSCT, n = 27) at any time during follow-up. These findings suggest that GLS before HSCT might be associated with a decrease in LVEF after HSCT in patients with hematologic malignancies. Further prospective and long-term data will be important for understanding the management of HSCT-associated cardiac dysfunction.

Pressure Overload Impairs Cardiac Function in Long-Chain Fatty Acid Transporter CD36-Knockout Mice.

CD36 is one of the important transporters of long-chain fatty acids (LCFAs) in the myocardium. We previously reported that CD36-deficient patients demonstrate a marked reduction of myocardial uptake of LCFA, while myocardial glucose uptake shows a compensatory increase, and are often accompanied by cardiomyopathy. However, the molecular mechanisms and functional role of CD36 in the myocardium remain unknown.The current study aimed to explore the pathophysiological role of CD36 in the heart. Methods: Using wild type (WT) and knockout (KO) mice, we generated pressure overload by transverse aortic constriction (TAC) and analyzed cardiac functions by echocardiography. To assess cardiac hypertrophy and fibrosis, histological and molecular analyses and measurement of ATP concentration in mouse hearts were performed.By applying TAC, the survival rate was significantly lower in KO than that in WT mice. After TAC, KO mice showed significantly higher heart weight-to-tibial length ratio and larger cross-sectional area of cardiomyocytes than those of WT. Although left ventricular (LV) wall thickness in the KO mice was similar to that in the WT mice, the KO mice showed a significant enlargement of LV cavity and reduced LV fractional shortening compared to the WT mice with TAC. A tendency for decreased myocardial ATP concentration was observed in the KO mice compared to the WT mice after TAC operation.These data suggest that the LCFA transporter CD36 is required for the maintenance of energy provision, systolic function, and myocardial structure.

Aortic Dissection and Cardiac Dysfunction Emerged Coincidentally During the Long-Term Treatment with Angiogenesis Inhibitors for Metastatic Renal Cell Carcinoma.

Angiogenesis inhibitors, such as sorafenib and axitinib, which target vascular endothelial growth factor (VEGF) signaling, are widely used for renal cell carcinoma, including metastasis. In this study, we report a case of cardiovascular adverse events of aortic dissection and cardiac dysfunction during treatment with sorafenib and axitinib for metastatic renal cell carcinoma. A 66-year-old man had been administered sorafenib for 2 years after nephrectomy due to renal cell carcinoma. To control the progression of metastatic lung tumor, axitinib was started after sorafenib for four years. During the treatment, angiotensin II type 1 receptor blockers and Ca antagonists were used to strictly control the axitinib-induced hypertension and proteinuria. Aortic dissection and cardiac dysfunction occurred coincidentally. Considering the critical role of VEGF signaling in the homeostasis of the cardiovascular system, we speculated that the long-term use of axitinib and sorafenib directly influenced the initiation of aortic dissection and cardiac dysfunction. Although the precise mechanisms underlying the aortic dissection and cardiac dysfunction induced by angiogenesis inhibition are still elusive, onco-cardiologists and oncologists should pay careful attention to cardiovascular toxicity and complications in patients with cancer, particularly patients undergoing long-term cancer treatment.

An EP4 Receptor Agonist Inhibits Cardiac Fibrosis Through Activation of PKA Signaling in Hypertrophied Heart.

Cardiac fibrosis is a pathological feature of myocardium of failing heart and plays causative roles in arrhythmia and cardiac dysfunction, but its regulatory mechanisms remain largely elusive. In this study, we investigated the effects of the novel EP4 receptor agonist ONO-0260164 on cardiac fibrosis in hypertrophied heart and explored the regulatory mechanisms in cardiac fibroblasts.In a mouse model of cardiac hypertrophy generated by transverse aortic constriction (TAC), ONO-0260164 treatment significantly prevented systolic dysfunction and progression of myocardial fibrosis at 5 weeks after TAC. In cultured neonatal rat cardiac fibroblasts, transforming growth factor-ß1 (TGF-ß1) induced upregulation of collagen type 1, alpha 1 (Col1a1) and type 3, alpha 1 (Col3a1), which was inhibited by ONO-0260164 treatment. ONO-0260164 activated protein kinase A (PKA) in the presence of TGF-ß1 in the cardiac fibroblasts. PKA activation suppressed an increase in collagen expression induced by TGF-ß1, indicating the important inhibitory roles of PKA activation in TGF-ß1mediated collagen induction.We have demonstrated for the first time the antifibrotic effects of the novel EP4 agonist ONO-0260164 in vivo and in vitro, and the important role of PKA activation in the effects.

Novel molecular mechanisms and regeneration therapy for heart failure.

Heart failure (HF) is one of the leading causes of mortality in the world. Various molecular mechanisms have been proposed for HF, but its precise mechanisms are still largely unknown. In this review, summarizing the "President's Distinguished Lecture Award" of XX World Congress of International Society for Heart Research 2010 in Kyoto, Japan, we introduce recent our studies on HF, including 1) p53-induced suppression of Hif-1-induced angiogenesis as a novel mechanism of HF, 2) angiogenesis as a potential therapeutic strategy for HF, and 3) IGFBP-4 as a novel factor for cardiomyogenesis by inhibiting canonical Wnt signaling.

Angiogenesis and cardiac hypertrophy: maintenance of cardiac function and causative roles in heart failure.

Cardiac hypertrophy is an adaptive response to physiological and pathological overload. In response to the overload, individual cardiac myocytes become mechanically stretched and activate intracellular hypertrophic signaling pathways to re-use embryonic transcription factors and to increase the synthesis of various proteins, such as structural and contractile proteins. These hypertrophic responses increase oxygen demand and promote myocardial angiogenesis to dissolve the hypoxic situation and to maintain cardiac contractile function; thus, these responses suggest crosstalk between cardiac myocytes and microvasculature. However, sustained pathological overload induces maladaptation and cardiac remodeling, resulting in heart failure. In recent years, specific understanding has increased with regard to the molecular processes and cell-cell interactions that coordinate myocardial growth and angiogenesis. In this review, we summarize recent advances in understanding the regulatory mechanisms of coordinated myocardial growth and angiogenesis in the pathophysiology of cardiac hypertrophy and heart failure.

Calpain-dependent cleavage of N-cadherin is involved in the progression of post-myocardial infarction remodeling.

Enzymatic proteolysis by calpains, Ca(2+)-dependent intracellular cysteine proteases, has been implicated in pathological processes such as cellular degeneration or death. Here, we investigated the role of calpain activation in the hearts subjected to myocardial infarction. We produced myocardial infarction in Cast(-/-) mice deficient for calpastatin, the specific endogenous inhibitory protein for calpains, and Cast(+/+) mice. The activity of cardiac calpains in Cast(+/+) mice was not elevated within 1 day but showed a gradual elevation after 7 days following myocardial infarction, which was further pronounced in Cast(-/-) mice. Although the prevalence of cardiomyocyte death was indistinguishable between Cast(-/-) and Cast(+/+) mice, Cast(-/-) mice exhibited profound contractile dysfunction and chamber dilatation and showed a significant reduction in survival rate after myocardial infarction as compared with Cast(+/+) mice. Notably, immunofluorescence revealed that at 28 days after myocardial infarction, calpains were activated in cardiomyocytes exclusively at the border zone and that Cast(-/-) mice showed higher intensity and a broader extent of calpain activation at the border zone than Cast(+/+) mice. In the border zone of Cast(-/-) mice, pronounced activation of calpains was associated with a decrease in N-cadherin expression and up-regulation of molecular markers for cardiac hypertrophy and fibrosis. In cultured rat neonatal cardiomyocytes, calpain activation by treatment with ionomycin induced cleavage of N-cadherin and decreased expression levels of ß-catenin and connexin 43, which was attenuated by calpain inhibitor. These results thus demonstrate that activation of calpains disassembles cell-cell adhesion at intercalated discs by degrading N-cadherin and thereby promotes left ventricular remodeling after myocardial infarction.

Pirfenidone exhibits cardioprotective effects by regulating myocardial fibrosis and vascular permeability in pressure-overloaded hearts.

Although cardiac fibrosis causes heart failure, its molecular mechanisms remain elusive. In this study, we investigated the mechanisms of cardiac fibrosis and examined the effects of the antifibrotic drug pirfenidone (PFD) on chronic heart failure. To understand the responsible mechanisms, we generated an in vivo pressure-overloaded heart failure model via transverse aortic constriction (TAC) and examined the effects of PFD on chronic-phase cardiac fibrosis and function. In the vehicle group, contractile dysfunction and left ventricle fibrosis progressed further from 4 to 8 wk after TAC but were prevented by PFD treatment beginning 4 wk after TAC. We isolated cardiac fibroblasts and vascular endothelial cells from the left ventricles of adult male mice and investigated the cell-type-specific effects of PFD. Transforming growth factor-ß induced upregulated collagen 1 expression via p38 phosphorylation and downregulated claudin 5 (Cldn5) expression in cardiac fibroblasts and endothelial cells, respectively; both processes were inhibited by PFD. Moreover, PFD inhibited changes in the collagen 1 and Cldn5 expression levels, resulting in reduced fibrosis and serum albumin leakage into the interstitial space during the chronic phase in TAC hearts. In conclusion, PFD inhibited cardiac fibrosis by suppressing both collagen expression and the increased vascular permeability induced by pressure overload.

A Predictive Model for Cancer-Associated Thrombosis in Japanese Cancer Patients: Findings from the J-Khorana Registry.

Background Although the close relationship between cancer and venous thromboembolism (VTE) has been identified, risk stratification for VTE in Japanese patients with cancer remains unclear. Objectives This study aimed to validate the Khorana VTE risk assessment score (KRS) for VTE diagnosis and establish an optimal predictive model for VTE in Japanese patients with cancer. Methods A total of 7,955 Japanese patients with cancer were subdivided into low- (0), intermediate- (1-2), and high-score (3) groups according to the KRS. Using 37 explanatory variables, a total of 2,833 patients with cancer were divided into derivation and validation cohorts (5:5). A risk model for Japanese participants was developed using the derivation cohort data. Results The prevalence of VTE in low-, intermediate-, and high-score patients was 1.2, 2.5, and 4.3%, respectively. Logistic regression analysis demonstrated that cancer stage (III-IV) and KRS ≥ 2 were independent and significant predictors of VTE onset. The risk model for VTE assigned 1 point to body mass index ≥25 kg/m 2 and 2 points each to the prevalence of osteochondral cancer and D-dimer level ≥1.47 µg/mL. The areas under the curve of the risk model were 0.763 and 0.656 in the derivation and validation cohorts, respectively. Conclusion The KRS was useful in Japanese patients, and our new predictive model may be helpful for the diagnosis of VTE in Japanese patients with cancer.

Removal of radioactive Cs from gravel conglomerate using water containing air bubbles.

Remediation of sites contaminated with radioactive material such as Cs is important because of the risk posed to human health. Here, we report the effectiveness of water containing air bubbles with a diameter around 100 nm (nanobubbled water, NB water) for the removal of radioactive Cs. Laboratory experiments confirmed that NB water is more effective than purified water and as effective as water with neutral detergent in the removal of Cs-137 from gravel. Moreover, NB water retains its effectiveness even after storage for 7 d. Finally, NB water produced onsite from tap water was found to be effective for removal of radioactive Cs from gravel conglomerate in Fukushima, Japan.

Tenascin-C as a potential marker for immunohistopathology of doxorubicin-induced cardiomyopathy.

Aims: Doxorubicin is used in classical chemotherapy for several cancer types. Doxorubicin-induced cardiomyopathy (DOX-CM) is a critical issue among cancer patients. However, differentiating the diagnosis of DOX-CM from that of other cardiomyopathies is difficult. Therefore, in this study, we aimed to determine novel histopathological characteristics to diagnose DOX-CM. Methods and results: Twelve consecutive patients with DOX-CM who underwent cardiac histopathological examination in two medical centres were included. Twelve patients with dilated cardiomyopathy, who were matched with DOX-CM patients in terms of age, sex, and left ventricular ejection fraction, formed the control group. Another control group comprised five consecutive patients with cancer therapy-related cardiac dysfunction induced by tyrosine kinase inhibitors or vascular endothelial growth factor inhibitors were the controls. The positive area of tenascin-C, number of infiltrating macrophages, and presence of p62- and ubiquitin-positive cardiomyocytes were evaluated. Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) were used for in vitro investigation. The myocardium exhibited significantly greater tenascin-C-positive area and macrophage number in the DOX-CM group than in the control groups (P < 0.01). The tenascin-C-positive area correlated with the number of both CD68- and CD163-positive cells (r = 0.748 and r = 0.656, respectively). Immunostaining for p62 was positive in 10 (83%) patients with DOX-CM. Furthermore, western blotting analysis revealed significant increase in tenascin-C levels in hiPSC-CMs upon doxorubicin treatment (P < 0.05). Conclusion: The combined histopathological assessment for tenascin-C, macrophages, and p62/ubiquitin may serve as a novel tool for the diagnosis of DOX-CM. Doxorubicin may directly affect the expression of tenascin-C in the myocardium.

Advancing Cardio-Oncology in Asia.

Cardio-oncology is an emerging multi-disciplinary field, which aims to reduce morbidity and mortality of cancer patients by preventing and managing cancer treatment-related cardiovascular toxicities. With the exponential growth in cancer and cardiovascular diseases in Asia, there is an emerging need for cardio-oncology awareness among physicians and country-specific cardio-oncology initiatives. In this state-of-the-art review, we sought to describe the burden of cancer and cardiovascular disease in Asia, a region with rich cultural and socio-economic diversity. From describing the uniqueness and challenges (such as socio-economic disparity, ethnical and racial diversity, and limited training opportunities) in establishing cardio-oncology in Asia, and outlining ways to overcome any barriers, this article aims to help advance the field of cardio-oncology in Asia.

[Molecular and cellular mechanisms of organ fibrosis].

Extracellular matrix (ECM) is important component for the organ architecture and function, and dynamically regulated by fibroblasts in normal state. In pathological condition, abnormal ECM accumulation or fibrosis is induced by pathological stimulation and associated with organ dysfunction in liver, lung, kidney and heart. In the process of fibrosis, complex molecular mechanisms including renin-angiotensin-aldosterone system and transforming growth factor beta signaling play critical roles regulating fibroblast activation and ECM deposition. In addition to resident fibroblasts, it has been reported that other cell types originated from epithelial/endothelial mesenchymal transition, circulating fibrocytes, or pericytes also contribute to fibrosis. Detailed examination for molecular and cellular mechanisms of fibrosis can contribute to future therapy for organ failure.

Sinus Node Dysfunction Co-occurring with Immune Checkpoint Inhibitor-associated Myocarditis.

Immune checkpoint inhibitor (ICI)-induced myocarditis is a potentially life-threatening adverse event. We herein report a rare case of sick sinus syndrome (SSS) co-occurring with ICI-associated myocarditis. A 71-year-old woman with lung cancer undergoing pembrolizumab monotherapy was admitted owing to a fever, worsening kidney function, and sinus bradycardia. She was diagnosed with multi-organ immune-related adverse events, including myocarditis. Pulse steroid therapy was initiated immediately under the support of a temporary pacemaker, which resulted in the resolution of SSS in a few days. Biopsy specimens of the endomyocardium showed active myocarditis. Thus, we should be aware that SSS can co-occur with ICI-induced myocarditis.

A Case of Lung Cancer with Very-Late-Onset Immune Checkpoint Inhibitor-Related Myocarditis.

Immune checkpoint inhibitor (ICI)-related myocarditis has been reported to appear in the early phase after ICI initiation. Herein, we report the case of a 78-year-old man with non-small cell lung cancer. Pembrolizumab was introduced as first-line therapy. After 9 months, second-line therapy, including bevacizumab, was initiated. After another 7 months, echocardiography showed diffuse left ventricular dysfunction. Based on the histopathologic examination of the myocardium, the patient was diagnosed with ICI-related myocarditis. Initiation of prednisolone therapy improved cardiac function. This case of late-onset ICI-related myocarditis illustrates that endomyocardial biopsy can be useful in the differential diagnosis of cancer-related left ventricular dysfunction.

Il a été rapporté qu'une myocardite pouvait survenir peu après l'instauration d'un traitement par des inhibiteurs des points de contrôle immunitaire (ICI). Nous présentons le cas d'un homme de 78 ans atteint d'un cancer du poumon non à petites cellules. Le pembrolizumab a été administré comme traitement de première intention. Neuf mois plus tard, un traitement de deuxième intention par le bévacizumab a été instauré. Après sept autres mois, l'échocardiographie a montré une dysfonction ventriculaire gauche diffuse. À la suite des résultats de l'examen histopathologique du myocarde, une myocardite liée aux ICI a été diagnostiquée. L'instauration d'un traitement par la prednisolone a amélioré la fonction cardiaque du patient. Ce cas de myocardite tardive liée aux ICI montre l'utilité éventuelle de la biopsie de l'endomyocarde dans le diagnostic différentiel d'une dysfonction ventriculaire gauche liée au cancer.

Prevalence and characteristics of immune checkpoint inhibitor-related myocardial damage: A prospective observational study.

An increasing number of patients with cancer are being treated with immune checkpoint inhibitors. Consequently, the incidence of immune checkpoint inhibitor-related myocarditis has been increasing. Nonetheless, the diagnostic criteria for the immune checkpoint inhibitor-related myocarditis have not been sufficiently established. Therefore, the real-world incidence or prevalence of immune checkpoint inhibitor-related myocardial damage remains unknown. This was a single-center cohort study that included 100 patients admitted for immune checkpoint inhibitor therapy for any type of cancer. The patients underwent monthly measurement of cardiac troponin I and N-terminal pro-brain natriuretic peptide levels with electrocardiography. Additionally, echocardiography was performed every 3 months. Our protocol was continued until 6 months after the initiation of immune checkpoint inhibitors. We defined immune checkpoint inhibitor-related myocardial damage as an increase in cardiac troponin I levels by >0.026 ng/mL and/or a decrease in the left ventricular ejection fraction by >10% to <53% on echocardiography. The mean patient age was 64 years; 71% were men. The most commonly used immune checkpoint inhibitor was nivolumab (47%), followed by pembrolizumab (29%). Overall, 5% of patients received combination therapy. Among 100 patients, 10 (10%) were diagnosed with immune checkpoint inhibitor-related myocardial damage. Among them, five patients underwent endomyocardial biopsy. Of these patients, four were histopathologically observed to have lymphocyte infiltration in their myocardium. In conclusion, serial cardiac troponin I measurement during immune checkpoint inhibitor treatment could help detect early-phase myocardial damage. The prevalence of myocardial damage was much higher than previously expected.

STAT3/Pim-1 signaling pathway plays a crucial role in endothelial differentiation of cardiac resident Sca-1+ cells both in vitro and in vivo.

Cardiac stem cells potentially differentiate into cardiac cells, including cardiomyocytes and endothelial cells (ECs). Previously we demonstrated that STAT3 activation by IL-6 family cytokines, such as leukemia inhibitory factor (LIF), induces the endothelial differentiation of cardiac Sca-1+ cells. In this study, we addressed molecular mechanisms for EC differentiation of Sca-1+ cells. First, DNA array experiments were performed to search for the molecules induced by LIF. Among 134 genes that LIF upregulated by more than 4 fold, we focused on Pim-1 gene transcript, because Pim-1 is associated with the differentiation of some cell lineages. Real time RT-PCR analyses confirmed that LIF stimulation upregulated Pim-1 expression. Adenoviral transfection of dominant negative (dn) STAT3 inhibited LIF-mediated induction of Pim-1, while the overexpression of constitutively active STAT3 upregulated Pim-1 expression, suggesting that STAT3 activation is necessary and sufficient for Pim-1 induction. Moreover, in STAT3-deficient Sca-1+ cells, LIF failed to induce Pim-1 expression and EC differentiation. Importantly, the overexpression of dnPim-1 abrogated the induction of EC markers, indicating Pim kinase activity is indispensable for STAT3-mediated EC differentiation in vitro. Finally, Sca-1+ cells labeled with LacZ were transplanted into post-infarct myocardium and the transdifferentiation was estimated. The overexpression of wild-type STAT3 by adenovirus vector significantly promoted EC differentiation, while STAT3 gene ablation reduced the frequency of differentiating cells in post-infarct myocardium. Furthermore, transplanted Sca-1+ cells overexpressing dnPim-1 showed the reduced frequency of EC differentiation and capillary density. Collectively, Pim-1 kinase is upregulated by STAT3 activation in cardiac Sca-1+ cells and plays a pivotal role in EC differentiation both in vitro and in vivo.