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Background Current strategies to inhibit androgen receptor (AR) are circumvented in castration-resistant prostate cancer (CRPC). Cyclin-dependent kinase 7 (CDK7) promotes AR signalling, in addition to established roles in cell cycle and global transcription, providing a rationale for its therapeutic targeting in CRPC. Methods The antitumour activity of CT7001, an orally bioavailable CDK7 inhibitor, was investigated across CRPC models in vitro and in xenograft models in vivo. Cell-based assays and transcriptomic analyses of treated xenografts were employed to investigate the mechanisms driving CT7001 activity, alone and in combination with the antiandrogen enzalutamide. Results CT7001 selectively engages with CDK7 in prostate cancer cells, causing inhibition of proliferation and cell cycle arrest. Activation of p53, induction of apoptosis, and suppression of transcription mediated by full-length and constitutively active AR splice variants contribute to antitumour efficacy in vitro. Oral administration of CT7001 represses growth of CRPC xenografts and significantly augments growth inhibition achieved by enzalutamide. Transcriptome analyses of treated xenografts indicate cell cycle and AR inhibition as the mode of action of CT7001 in vivo. Conclusions This study supports CDK7 inhibition as a strategy to target deregulated cell proliferation and demonstrates CT7001 is a promising CRPC therapeutic, alone or in combination with AR-targeting compounds.

Patients and animal models of arterial hypertension are characterized by structural and functional abnormalities of the coronary microcirculation. Using a translational approach, we ascertained whether antihypertensive treatment can reverse microvascular remodelling and improve myocardial perfusion.In 20 hypertensive patients with left ventricular hypertrophy, blood pressure, left ventricular mass index and myocardial blood flow were measured at baseline and after 6 months of treatment with perindopril + indapamide. In spontaneously hypertensive rats, blood pressure, coronary flow and histomorphometry of intramural coronary arterioles were measured after 8 weeks of treatment with placebo or perindopril + indapamide.In patients, treatment decreased blood pressure (161 ± 10/96 ± 5 to 136 ± 12/81 ± 6 mmHg; P0.0001) and left ventricular mass index (93 ± 16 to 85 ± 17 g/m; P0.01) while increasing baseline (0.69 ± 0.13 to 0.88 ± 0.36 ml/min per g; P0.05) and hyperaemic myocardial blood flow (1.42 ± 0.32 to 1.94 ± 0.99 ml/min per g; P0.05). In rats treated with perindopril + indapamide (n = 11), blood pressure was 93 ± 18/55 ± 18 mmHg compared to 215 ± 18/161 ± 17 mmHg in placebo (n = 6; P0.001), baseline flow was unchanged whilst hyperaemic coronary flow was 19.89 ± 3.50 vs. 12.15 ± 0.99 ml/min per g, respectively (P0.01). The medial area of intramural arterioles was 1613 ± 409 with perindopril + indapamide and 8118 ± 901 μm with placebo (P0.001).In patients with arterial hypertension and left ventricular hypertrophy, perindopril + indapamide reduced blood pressure and left ventricular mass index and improved resting and hyperaemic myocardial blood flow. Data in rats provide evidence that the improvement in coronary flow observed after treatment is due to reverse remodelling of intramural coronary arterioles and improved microvascular function.

Aims Whole body and myocardial insulin resistance are features of non-insulin-dependent diabetes mellitus (NIDDM) and left-ventricular dysfunction (LVD). We determined whether abnormalities of insulin receptor substrate-1 (IRS1), IRS1-associated PI3K (IRS1-PI3K), and glucose transporter 4 (GLUT4) contribute to tissue-specific insulin resistance. Methods and results We collected skeletal muscle ( n = 27) and myocardial biopsies ( n = 24) from control patients ( n = 7), patients with NIDDM ( n = 9) and patients with LVD ( n = 8), who were characterized by euglycaemic–hyperinsulinaemic clamp and positron emission tomography. Comparative studies were carried out in three mouse models. We demonstrate an unrecognized reduction of IRS1 in skeletal muscle of LVD patients and an unexpected increase in cardiac IRS1-PI3K activity in NIDDM and LVD patients. In NIDDM, there was a concomitant reduction in sarcolemmal GLUT4, whereas in patients with LVD sarcolemmal GLUT4 was increased. We confirm activation of IRS1-PI3K and reduction in sarcolemmal GLUT4 in the insulin resistant ob/ob mouse heart where we also demonstrate perturbation of GLUT4 docking and fusion. A direct relationship between PI3K and GLUT4 was demonstrated in mice expressing activated PI3K in the heart and increased GLUT4 at the sarcolemma was confirmed in a mouse model of LVD. Conclusion Our data show that the mechanisms of myocardial insulin resistance are different between NIDDM and LVD.

Cell transplantation is an emerging therapy for treating post-infarction heart failure. Although the paracrine effect has been proposed to be an important mechanism for the therapeutic benefits, details remain largely unknown. This study compared various aspects of the paracrine effect after transplantation of either bone marrow mononuclear cells (BMC) or skeletal myoblasts (SMB) into the post-infarction chronically failing heart. Three weeks after left coronary artery ligation, adult rats received intramyocardial injection of either BMC, SMB or PBS only. Echocardiography demonstrated that injection of either cell type improved cardiac function compared to PBS injection. Interestingly, BMC injection markedly improved neovascularization in the border areas surrounding infarcts, while SMB injection decreased fibrosis in both the border and remote areas. Injection of either cell type similarly reduced hypertrophy of cardiomyocytes as assessed by cell-size planimetry using isolated cardiomyocytes. Quantitative RT-PCR revealed that, among 15 candidate mediators of paracrine effects studied, Fgf2 and Hgf were upregulated only after BMC injection, while Mmp2 and Timp4 were modulated after SMB injection. Additional investigations of signalling pathways relevant to heart failure by western blotting showed that p38 and STAT3 were temporarily activated after BMC injection, in contrast, ERK1/2 and JNK were activated after SMB injection. There was no difference in activation of Akt, PKD or Smad3 among groups. These data suggest that paracrine effects observed after cell transplantation in post-infarction heart failure were noticeably different between cell types in terms of mediators, signal transductions and consequent effects.

Side population cells have been found in various types of adult tissue including heart and are presumed to be tissue-specific stem/progenitor cells. In the present study, we confirmed the presence of cardiac side population (cSP) cells, which showed both the Hoechst 33342 efflux ability and ABCG2 expression, in adult murine heart. Flow cytometric analysis showed that more than half of cSP cells expressed the endothelial marker VE-cadherin or the smooth muscle markers, alpha-smooth muscle actin and desmin. In addition, immunohistochemical analysis demonstrated that ABCG2(+) cells were mainly localized within vascular walls. Quantitative RT-PCR analysis demonstrated that VE-cadherin(-) cSP cells progressively expressed Nkx2.5 and cardiac troponin T with time in culture. VE-cadherin(-) cSP cells also expressed mesodermal-mesenchymal-associated markers and differentiated into osteocytes and adipocytes. These results highlight the heterogeneic nature of cSP cells, consisting of vascular endothelial cells, smooth muscle cells, and mesenchymal stem/progenitor cells including potential cardiomyogenic cells.

One of the major issues in myocardial gene therapy is poor transfection efficiency. The herpes simplex virus protein VP22 is known to facilitate intercellular protein transport. Not only VP22 but also VP22-linked protein are exported from the cytoplasm of cells, in which it is synthesised endogenously, and transferred to surrounding cells, where it is translocated into the nuclei. However, the feasibility and efficiency of the intercellular trafficking properties of VP22-linked protein in the myocardium has not been clarified. Rat hearts were transfected by direct intramyocardial injection of naked plasmid vectors encoding either lacZ or VP22-linked lacZ. At day 5 following transfection, similar numbers of cardiomyocytes surrounding the injection sites showed beta-galactosidase (beta-gal) expression in the cytoplasm in both groups. In addition to this, following transfection of VP22-linked lacZ, most of the cardiomyocytes adjacent to the cytoplasmic-positive cells demonstrated nuclear-localised beta-gal expression. The number of these nuclear-positive cardiomyocytes, which are thought to be secondary protein-transported cells, was 4.3-fold greater than that of primary transfected, cytoplasmic-positive cells. Western blot analysis demonstrated that the amount of targeted protein expression is 2.9-fold greater following VP22-lacZ transfection (VP22-linked beta-gal; approximately 40 kDa bigger than wild-type beta-gal) compared with lacZ transfection (wild-type beta-gal). This data highlights the efficiency of the VP22-mediated intercellular protein delivery in the myocardium following in vivo gene transfection and suggests that the VP22-mediated effect is useful in enhancing the efficacy of myocardial gene therapy.

Active and passive exposure to cigarette smoke (CS) increases the risk of, and has deleterious effects in, ischaemic heart disease. Exposure to CS increases infarct size in experimental models of coronary occlusion and reperfusion. Among many possible mechanisms for these deleterious effects in intact animals and humans three have more substantial evidence: 1) functional alterations of endothelial cells, neutrophils and platelets; 2) impaired mitochondrial function and energy metabolism caused by toxins in CS, including oxidative free radicals; 3) increased arterial stiffness and vulnerability of the atherosclerotic plaque. In addition to the various pro-mitogenic, carcinogenic and apoptotic pathways thought to be affected and upregulated by CS, a direct necrotic action on cardiomyocytes is also believed to exist. Many, if not all, of these alterations are caused by oxidative stress, either as a direct consequence of inhalation of free radicals, or by induction from the vast range of chemicals present in both the gas and solid phase of tobacco smoke. Here, some of the proposed mechanisms will be reviewed and their impact on the cardiomyocytes and peripheral vasculature discussed.

Background— Arrhythmia occurrence is a variable but serious concern of cell therapy for treating heart failure. Using a rat postinfarction chronic heart failure model, we compared skeletal myoblast (SMB) with bone marrow cell (BMC) injection to highlight donor cell-specific, late-phase arrhythmogenesis and the underlying factors. Methods and Results— SMBs or BMCs derived from male GFP-transgenic rats, or PBS were injected intramyocardially into female rat hearts 3 weeks after coronary artery occlusion. At 28 days after injection, echocardiography showed that the left ventricular ejection fraction was significantly improved in both the SMB and BMC groups, compared to PBS control despite poor graft survival as assessed by PCR for the male-specific gene. Radio-telemetry analysis revealed that the SMB group displayed a higher occurrence of ventricular premature contractions with an elongation of the QRS complex and the hearts were more susceptible to isopreterenol-induced ventricular tachycardia compared to the BMC and PBS groups. Western blot and immunoconfocal analysis showed that the gap junction protein, connexin43, was widely and persistently decreased in the SMB group compared to the other groups. IL-1β was shown to be upregulated in hearts after SMB injection, and in vitro experiments demonstrated that exposure to IL-1β caused a decrease in connexin43 and intercellular communication in cultured cardiomyocytes. Conclusions— Although cell therapy was capable of improving function of the postinfarction chronically failing heart, there was late-phase arrhythmogenicity specific to donor cell type. Global downregulation of connexin43 in the host myocardium was indicated to be an important factor underlying late-phase arrhythmogenicity after SMB transplantation.

We thank Dr Ly for his interest in our article.1 We, too, strongly believe that cell therapy as a treatment for heart failure requires further laboratory research to ensure its future success. It is likely that not only the injection site, but also the number and volume of injections and the number of cells injected, will influence therapeutic benefit …

Background— Therapeutic efficacy of bone marrow (BM) cell injection for treating ischemic chronic heart failure has not been established. In addition, experimental data are lacking on arrhythmia occurrence after BM cell injection. We hypothesized that therapeutic efficacy and arrhythmia occurrence induced by BM cell injection may be affected by the cell delivery route. Methods and Results— Three weeks after left coronary artery ligation, wild-type female rats were injected with 1×10 7 mononuclear BM cells derived from green fluorescent protein–transgenic male rats through either a direct intramyocardial or a retrograde intracoronary route. Both intramyocardial and intracoronary injection of BM cells demonstrated similar improvement in left ventricular ejection fraction measured by echocardiography and a similar graft size analyzed by real-time polymerase chain reaction for the Y chromosome–specific Sry gene. Noticeably, intramyocardial injection of BM cells induced frequent ventricular premature contractions (108±73 per hour at 7 days after BM cell injection), including multiform, consecutive ventricular premature contractions and ventricular tachycardia for the initial 14 days; intracoronary injection of BM cells and intramyocardial injection of phosphate-buffered saline rarely induced arrhythmias. Immunohistochemistry demonstrated that intramyocardial BM cell injection formed distinct cell clusters containing donor-derived cells and accumulated host-derived inflammatory cells in the infarct border zone, whereas intracoronary BM cell injection provided more homogeneous donor cell dissemination with less inflammation and without disrupting the native myocardial structure. Conclusions— BM cell injection is able to improve cardiac function in ischemic chronic heart failure but has a risk of arrhythmia occurrence when the intramyocardial route is used. Such arrhythmias may be prevented by using the intracoronary route.

Background— Antibody therapy to inhibit either P-selectin or intercellular adhesion molecule-1 (ICAM-1) has been reported to provide myocardial protection against leukocyte-mediated reperfusion injury. Because these molecules play different roles in the leukocyte-endothelial interaction, co-inhibition of both may achieve further enhanced cardioprotection. In addition, the therapeutic efficacy of such antibody therapy may be affected by the delivery route used. Retrograde intracoronary infusion will offer an effective, direct access to the postcapillary venules, where the target event (leukocyte–endothelial interaction) takes place. We investigated the feasibility and efficiency of the combined antibody therapy targeting both P-selection and ICAM-1 via the retrograde intracoronary route to attenuate myocardial ischemia-reperfusion injury. Methods and Results— Lewis rats underwent 30-minute left coronary artery occlusion. Just before reperfusion, anti-P-selectin monoclonal antibody (150 μg/kg), anti-ICAM-1 monoclonal antibody (200 μg/kg), both antibodies together, or control antibody were retrogradely infused into the left cardiac vein. At 24 hours after reperfusion, administration of either anti-P-selectin or anti-ICAM-1 antibody significantly ( P Conclusions— Combined antibody therapy inhibiting both P-selectin and ICAM-1 via the retrograde intracoronary route could be a promising new strategy for myocardial protection against ischemia-reperfusion injury.

Cell transplantation of skeletal myoblasts (SMs) is one possible treatment for repairing cardiac tissue after myocardial injury. However, inappropriate electrical coupling between grafted SMs and host cardiomyocytes may be responsible for the arrhythmias observed in clinical trials of SM transplantation. Whether functional gap junctions occur between the two cell types remains controversial. We have studied the ability of SMs to electrically couple with isolated adult rat cardiomyocytes (CMs) and assessed whether connexin43 (Cx43) overexpression enhanced gap junctional conductance (Gj). C2C12 myoblast lines overexpressing Cx43 were generated by gene transfection and clonal selection. CMs were cocultured with either SMs overexpressing Cx43 (CM-SM(Cx43)) or control SMs (CM-SM(WT)) in vitro. Gj between pairs of SMs and CMs was quantified with dual whole cell patch clamping. Formation of Gj occurred between 22% of CM-SM(WT) pairs (n=73) and 48% of CM-SM(Cx43) pairs (n=71, P0.001). The Gj of CM-SM(Cx43) pairs (29.7+/-4.3 nS, n=21) was greater than that of CM-SM(WT) pairs (14.8+/-2.0 nS, n=12, P0.05). The overexpression of Cx43 in SMs increased the formation of electrical communication and the steady-state conductance between SMs and CMs. Enhanced gap junctional conductance may be useful to promote the integration of transplanted SMs into the myocardium.

Background— Intracoronary infusion for cell transplantation has potential advantages in disseminating cells globally into the myocardium with less injury over direct intramuscular injection. Arterial route, however, has a risk of coronary embolism and a limitation in cell delivery into ischemic or infarcted areas. We assessed the efficiency of retrograde intracoronary cell implantation into infarcted hearts using a novel rat model. Methods and Results— After left coronary artery ligation in rat, a catheter was inserted into the left cardiac vein, which drains the left ventricular free wall. Through this, 1×10 6 skeletal muscle precursor cells expressing nuclear β-galactosidase were infused retrogradely into the vein. In situ staining demonstrated that β-galactosidase–expressing donor cells had disseminated throughout the left ventricular free wall, including both infarcted and surrounding border areas, at 10 minutes after infusion. At 28 days, in contrast, positively stained multinuclear myotubes were found in border zones, whereas no positive cells were seen in infarcted areas. Measurement of β-galactosidase enzyme activity estimated that 29.8±6.9% of total infused cells were retained within the myocardium at 10 minutes and that this number decreased to 23.7±8.1% at 3 days but rapidly increased thereafter, reaching a plateau at 90.2±17.1% by 14 days. Echocardiography and Langendorff perfusion demonstrated that cell implantation improved cardiac function and dimensions by 28 days, compared with both sham-treated and phosphate-buffered saline-infused infarcted hearts, and this was associated with decreased collagen deposition. Conclusion— Retrograde intracoronary cell transplantation could provide an effective cell delivery into infarcted hearts and could be a useful strategy for treating myocardial infarction.

Background— Poor survival of grafted cells is a major factor hindering the therapeutic effect of cell transplantation; however, the causes of cell death remain unclear. We hypothesized that interleukin-1β (IL-1β) might play a role in the acute inflammatory response and graft death after cell transplantation and that inhibition of IL-1β might improve graft survival. Methods and Results— 14 C-labeled male skeletal muscle precursor cells were implanted into female mouse hearts by direct intramuscular injection. The amount of 14 C-label provides an estimate of the surviving cell number, whereas the amount of male-specific Smc y gene measured by polymerase chain reaction indicates the total (surviving+proliferated) number of donor-derived cells. At 10 minutes after implantation, 44.8±2.4% of the grafted cells survived and this steadily decreased to 14.6±1.1% by 24 hours, and to 7.9±0.6% by 72 hours (n=6 in each point). Proliferation of the surviving cells, which began after 24 hours, resulted in an increase in the total cell number from 15.5±0.8% at 24 hours to 24.4±1.6% at 72 hours. Acute inflammation was prominent at 24 hours and was reduced by 72 hours, in parallel with IL-1β expression. Administration of anti-IL-1β antibody improved graft survival at both 24 (25.6±1.6%) and 72 hours (14.8±1.1%) and resulted in a 2-fold increase in the total cell number at 72 hours (45.8±2.4%). The effects of IL-1β inhibition corresponded with a reduced inflammatory response. Conclusion— IL-1β is involved in acute inflammation and graft death after direct intramyocardial cell transplantation. Targeted inhibition of IL-1β may be a useful strategy to improve graft survival.

Survival and proliferation of skeletal myoblasts within the cardiac environment are crucial to the therapeutic efficacy of myoblast transplantation to the heart. We have analyzed the early dynamics of myoblasts implanted into the myocardium and investigated the mechanisms underlying graft attrition. At 10 min after implantation of [14C]thymidine-labeled male myoblasts into female mice hearts, 14C measurement showed that 39.2 +/- 3.0% of the grafted cells survived, and this steadily decreased to 16.0 +/- 1.7% by 24 h and to 7.4 +/- 0.9% by 72 h. PCR of male-specific Smcy gene calculated that the total (surviving plus proliferated) number of donor-derived cells was 18.3 +/- 1.6 and 23.3 +/- 1.3% at 24 and 72 h, respectively, indicating that proliferation of the surviving cells began after 24 h. Acute inflammation became prominent by 24 h and was reduced by 72 h as indicated by myeloperoxidase activity and histological findings. Multiplex RT-PCR revealed corresponding changes in IL-1beta, TGF-beta, IL-6, and TNF-alpha expression. Treatment with CuZn-superoxide dismutase attenuated the initial rapid death and resulted in enhanced cell numbers afterward, giving a twofold increased total number at 72 h compared with the nontreatment. This effect was associated with reduced inflammatory response, suggesting a causative role for superoxide in the initial rapid graft death and subsequent inflammation. These data describe the early dynamics of myoblasts implanted into the myocardium and suggest that initial oxidative stress and following inflammatory response may be important mechanisms contributing to acute graft attrition, both of which could be potential therapeutic targets to improve the efficiency of cell transplantation to the heart.