Anwar J. Siddiqui

Human embryonic stem cells are immunogenic in allogeneic and xenogeneic settings

Recent studies have suggested that human embryonic stem cells (HESC) are immune-privileged and may thereby circumvent rejection. The expression of immunologically active molecules was studied by DNA microarray analysis and by flow cytometry. HESC were transplanted into immunologically competent mice and traced by fluorescence in-situ hybridization (FISH) and immunohistochemistry. The ability of HESC to directly and indirectly induce immune responses in CD4+ T-cells from naive and transplanted mice was studied. Their ability to induce immune responses of human CD4+ T-cells, when cultured in the presence of dendritic cells (DC) syngeneic to responder T-cells, was also analysed. HESC demonstrated expression of HLA class I and HLA class II genes, but the cell surface expression of HLA class II molecules was low even after incubation with IFNgamma. In wild-type mice, HESC could be demonstrated by FISH until 3 days after transplantation and were surrounded by heavy infiltrates of T-cells and macrophages. HESC induced a similar immune response as human fibroblast cells (HFib) on naive and immunized T-cells, both directly and in the presence of syngeneic DC. A similar response was observed in the allogeneic setting. It is concluded that HESC are immunologically inert and do not inhibit immune responses during direct or indirect antigen presentation, and they were acutely rejected in a xenogeneic setting.

Human mesenchymal stem cells do not differentiate into cardiomyocytes in a cardiac ischemic xenomodel

AIM. As the capability of human mesenchymal stem cells (hMSC) to engraft, differentiate and improve myocardial function cannot be studied in humans, exploration was performed in a xenomodel. METHODS. The rats were divided into three groups depending on the type of rats used (Rowett nude (RNU) or Fischer rats +/− immunosuppression). Different groups were treated with intramyocardial injection of hMSC (1–2 million) either directly or three days after ligation of the left anterior descending artery (LAD). Myocardial function was investigated by echocardiography. The hMSC were identified with fluorescence in situ hybridization and myocardial differentiation was assessed by immunohistochemistry. RESULTS. When hMSC were injected directly after LAD ligation they could be identified in half (8/16) of the RNU rats (without immunosuppression) at 4 weeks. When injected 3 days after LAD ligation in immunosuppressed RNU rats they were identified in all (6/6) rats at 6 weeks. The surviving hMSC showed signs of differentiation into fibroblasts. No cardiomyocyte differentiation was observed. There was no difference in myocardial function in treated animals compared to controls. CONCLUSIONS. The hMSC survived in this xenomodel up to 6 weeks. However, hMSC required implantation into immunoincompetent animals as well as immunosuppression to survive, indicating that these cells are otherwise rejected. Furthermore, these cells did not differentiate into cardiomyocytes nor did they improve heart function in this xenomodel.

Modulation of ephrinB2 leads to increased angiogenesis in ischemic myocardium and endothelial cell proliferation

Eph/ephrin signaling is pivotal in prenatal angiogenesis while its potential role in postnatal angiogenesis largely remains to be explored. Therefore its putative angiogenic and therapeutic effects were explored in endothelium and in myocardial ischemia. In culture of human aortic endothelial cells the fusion protein ephrinB2-Fc induced cell proliferation (p<0.0005) and in the murine aortic ring model ephrinB2-Fc induced increased sprouting (p<0.05). Myocardial infarction was induced by ligation of the left anterior descending artery in mouse. During the following 2 weeks mRNA of the receptor/ligand pair EphB4/ephrinB2 was expressed dichotomously (p<0.05) and other Eph/ephrin pairs were expressed to a lesser degree. Twenty-four hours after intraperitoneal administration of ephrinB2-Fc it was detected in abundance throughout the myocardium along capillaries, showing signs of increased mitosis. After 4 weeks the capillary density was increased 28% in the periinfarcted area (p<0.05) to a level not different from healthy regions of the heart where no change was observed. These results implicate that EphB4/ephrinB2 is an important signaling pathway in ischemic heart disease and its modulation may induce therapeutic angiogenesis.

Depressed expression of angiogenic growth factors in the subacute phase of myocardial ischemia: a mechanism behind the remodeling plateau?

Background and aimsTo investigate whether, in the subacute phase of acute myocardial infarction, in the peri-infarcted area the expressions of the vascular endothelial growth factor (VEGF-A) and angiopoietin (Ang) ligand receptors are depressed, and whether overexpression of these angiogens counteracts a downregulation of myocardial function. MethodsAcute myocardial infarction was induced by left anterior descending artery ligation and overexpression through injection of human VEGF-A165 and Ang-1 plasmids. The capillary and arteriolar densities, Akt-1 phosphorylation and citrate synthase activity were measured concurrent with the expression of VEGF-A, VEGFR1 and R2, Ang-1, Ang-2 and Tie-2. ResultsOne day after AMI, VEGR-2 was unchanged but all other measured factors in the two families were upregulated. After day 2, the Ang-2 expression increased but other measured factors decreased. After gene transfer, the vascular supply, Akt phosphorylation and citrate synthase activity were higher in the peri-infarcted area, where also the endogenous angiogenic growth factor expressions were increased. ConclusionA rapid decrease in angiogenic stimulating factors occurs in the subacute phase of AMI and is related to a progressive decrease in myocardial contraction. A negative consequence of such a circuit is a successive reduction in the vascular supply and contractility in areas with reduced perfusion. These negative adaptations can be counteracted by angiogen overexpression.

Rosuvastatin Inhibits TIMP-2 and Promotes Myocardial Angiogenesis

Background: Angiogenesis is usually driven by inflammation. Matrix metalloproteinases MMP-3 and MMP-9 and tissue inhibitors of metalloproteinases TIMP-1 and TIMP-2 are implicated in vascular remodeling. TIMP-2 exhibits antiangiogenic properties. Statins show benefits that are additional to lipid lowering including pro- and antiangiogenic properties. Atherosclerotic lesions in the coronary arteries have been well studied, but less is known about the fine terminal branches of the myocardial vasculature. Methods: To examine this, we studied rosuvastatin (RSV) treatment in ApoE knockout (ApoE-/-) mice fed a high cholesterol (HC) diet. Hearts from ApoE-/- mice on a normal diet, HC diet and HC diet with RSV were harvested to determine MMP-3, MMP-9, TIMP-1, TIMP-2, vascular endothelial growth factor (VEGF)-A and estrogen receptor-α (ER-α) mRNA. Results: RSV inhibited TIMP-1 and TIMP-2 expression and enhanced myocardial VEGF-A and ER-α expression, independently of plasma lipid level changes, but had no effect on MMP-3 and MMP-9 expression. Conclusions: These modulations of TIMPs, VEGF and ER-α expression induced by RSV may act as local stimulating factors for arteriolar growth in the myocardium.

Age-adjusted D-dimer cut-off leads to more efficient diagnosis of venous thromboembolism in the emergency department: a comparison of four assays

Essentials Age‐adjusted D‐dimer cut‐offs decrease the false positives in the elderly. Four D‐dimer assays were compared in venous thromboembolism outpatients in an emergency ward. Age‐adjusted cut‐off resulted in improved specificity with maintained sensitivity for all assays. There was a substantial decrease in false positive results, especially in the older population.

Percutaneous coronary intervention versus conservative treatment for non ST-segment elevation myocardial infarction in patients above 80 years of age

BACKGROUND There is a paucity of data if there is a benefit for patients above 80 years of age with non-ST-segment elevation myocardial infarction (NSTEMI) to undergo percutaneous coronary intervention (PCI). OBJECTIVES To investigate the association between PCI or conservative treatment and outcomes in NSTEMI patients above 80 years of age. METHODS From the SWEDEHEART register were included 13,854 patients above 80 years of age with NSTEMI during 2011-2014 in Sweden. Cox regression was used to calculate hazard ratios (HR) with 95% confidence intervals (CI) for the association between PCI compared with conservative treatment for the outcome all-cause mortality. RESULTS In total 4158 (30%) patients underwent PCI, and 9696 (70%) were treated conservatively. The mean age was 86 (±4) years. During a mean 2.2 (±1.4) years there were 6458 (47%) deaths, where of 1078 (26%) in PCI treated, and 5380 (56%) in conservatively treated patients. Treatment with PCI compared with conservative treatment was associated with a 40% lower risk of death (adjusted HR 0.60, 95% CI 0.55-0.66). Similarly, patients in the PCI group had a 60% lower 30-day, and 51% lower 1-year all-cause mortality, respectively (adjusted HR 0.40, 95% CI 0.25-0.63, and HR, 0.49 95% CI 0.42-0.57, respectively). There were no differences in risk of bleedings (1.4% versus 1.3%). CONCLUSIONS PCI compared with conservative treatment was associated with a lower mortality in patients above 80 years of age with NSTEMI without an increased risk of bleedings. PCI may be considered as the treatment of choice for elderly with NSTEMI.

PERCUTANEOUS CORONARY INTERVENTION (PCI) HAS BETTER PROGNOSIS THAN CONSERVATIVE TREATMENT IN PATIENT OVER 80 YEARS DURING NON ST-ELEVATION MYOCARDIAL INFARCTION (NSTEMI)

Background: Percutaneous coronary intervention (PCI) in patients over 80 years with non ST elevated myocardial infarction (NSTEMI) has poorly investigated. We sought to investigate whether NSTEMI patients over 80 years has better prognosis by PCI than conservative approach. Methods: Total 17,935