Kevin Lai

Electrophysiological Properties of Pluripotent Human and Mouse Embryonic Stem Cells

Pluripotent embryonic stem cells (ESCs) possess promising potential for cell‐based therapies, but their electrophysiological properties have not been characterized. Here we describe the presence of ionic currents in mouse (m) and human (h) ESCs and their physiological function. In mESCs, tetraethylammonium (TEA)–sensitive depolarization‐activated delayed rectifier K+ currents (IKDR) (8.6 ± 0.9 pA/pF at +40 mV; IC50 = 1.2 ± 0.3 mM), which contained components sensitive to 4‐aminopyridine (4‐AP) (IC50 = 0.5 ± 0.1 mM) and 100 nM Ca2+‐activated K+ current (IKCa) blocker iberiotoxin (IBTX),were detected in 52.3% of undifferentiated cells.IKDR was similarly present in hESCs (∼100%) but with an approximately sixfold higher current density (47.5 ± 7.9 pA/pF at +40 mV). When assayed by bromodeoxyurindine incorporation, application of TEA, 4‐AP, or IBTX significantly reduced the proliferation of mESCs and hESCs in a dose‐dependent manner (p < .05). A hyperpolarization‐activated inward current (Ih) (−2.2 ± 0.4 pA/pF at −120 mV) was detected in 23% of mESCs but not hESCs. Neither Nav nor Cav currents were detected in mESCs and hESCs. Microarray and reverse transcription–polymerase chain reaction analyses identified several candidate genes for the ionic currents discovered. Collectively, our results indicate that pluripotent ESCs functionally express several specialized ion channels and further highlight similarities and differences between the two species. Practical considerations for the therapeutic use of ESCs are discussed.

Expression of Macrophage Migration Inhibitory Factor in Acute Ischemic Myocardial Injury

Macrophage migration inhibitory factor (MIF) is a key mediator in inflammatory or immune-mediated diseases, although its role in heart diseases is unknown. This study investigated the expression of MIF in the myocardium in the development of acute myocardial infarction (AMI). By use of immunohistochemistry, Western blotting, RT-PCR, and in situ hybridization, the gene and protein expression of MIF in the heart at 6 hr, 1 day, 3 days, 1 week, and 2 weeks after AMI was studied. In both normal and sham-operated rats, MIF mRNA and protein were expressed constitutively at low levels by the myocytes. By contrast, MIF mRNA was rapidly upregulated by the surviving myocytes in the infarcted region and, to a lesser extent, the non-infarcted region, accounting for a sevenfold increase at 6 hr after AMI (p<0.001). This was followed by a fourfold increase in MIF protein expression at day 1 after AMI (p<0.05). Macrophages were found accumulated in the infarcted region, being significant at day 1 (p<0.01) and progressive increased over the 2-week time course (p<0.01) in which MIF was found expressed in these cells. The results indicated that the infiltrating macrophages and myocytes were sources of MIF in the infarcted region. The latter cells became activated and involved in the amplification of inflammatory response in AMI. Therefore, upregulation of myocardial MIF may contribute to macrophage accumulation in the infarcted region and their pro-inflammatory role may participate in the myocyte damage seen in AMI.

Plasma Nitric Oxide Level in Heart Failure Secondary to Left Ventricular Diastolic Dysfunction

Nitric oxide (NO) is a free radical that is elevated in the plasma of patients with systolic heart failure. However, its relation to diastolic function is unknown. This study investigated the relation between the level of stable end-products of plasma NO (NOx level) and diastolic function in patients with heart failure. We performed echocardiographic Doppler studies in 76 patients (mean age of 66 +/- 10 years, 75% men) with congestive heart failure. Left ventricular (LV) diastolic dysfunction was classified as either a restrictive (RFP) or nonrestrictive filling pattern (non-RFP). Same day venous total nitrite plus nitrate levels were measured by chemiluminscence. Both patients with isolated diastolic heart failure (ejection fraction >50%) (77 +/- 9 micromol/L, n = 33) and systolic failure (ejection fraction < or = 50%) (115 +/- 17 micromol/L, n = 43) had significantly higher plasma NOx levels than controls (37 +/- 2 micromol/L, both p <0.001). RFP coexists mostly in patients with systolic heart failure (15 of 18), and these patients had a higher NOx level than patients with systolic failure and a non-RFP (n = 28) (163 +/- 35 vs 88 +/- 16 micromol/L, p <0.05). Patients who were not on oral nitrate drugs had insignificant lower plasma NOx levels than those on regular nitrate therapy, although it was still higher than controls. Plasma NOx level did not correlate with LV ejection fraction. Stepwise multiple regression analysis confirmed that the presence of RFP was the only independent predictor of NOx, and hence NO production. Plasma NOx level is elevated in patients with isolated diastolic heart failure. In addition, in patients with LV systolic failure, the severity of LV diastolic dysfunction determines the amount of NO production.

The decrement in circulating endothelial progenitor cells (EPCs) in type 2 diabetes is independent of the severity of the hypoadiponectemia.

Type 2 diabetes mellitus (DM) is associated with a decreased level of circulating endothelial progenitor cells (EPCs) and adiponectin. Experimental studies suggest a potential link between hypoadiponectinaemia and the depletion of the EPC level. This study investigated the relationships between adiponectin level and EPC in patients with type 2 DM.

Pre-Hospital Cardiac Arrest in Acute Coronary Syndromes: Insights from the Global Registry of Acute Coronary Events and the Canadian Registry of Acute Coronary Events

Objectives: Cardiac arrest in acute coronary syndromes (ACS) is associated with high morbidity and mortality. We examined the clinical characteristics, contemporary management patterns and outcomes of ACS patients with pre-hospital cardiac arrest. Methods: The Global Registry of Acute Coronary Events and the Canadian Registry of Acute Coronary Events enrolled 14,010 ACS patients in 1999-2008. We compared the clinical characteristics, in-hospital treatment and outcomes between patients with and without pre-hospital cardiac arrest. Results: Overall, 206 (1.4%) patients had cardiac arrest prior to hospital presentation. ACS patients with pre-hospital cardiac arrest were less frequently treated with aspirin, β-blocker, angiotensin-converting enzyme inhibitors, and statins within the first 24 h of presentation, but the use of cardiac procedures was similar compared to the group without cardiac arrest. Patients with pre-hospital cardiac arrest had significantly higher rates of in-hospital adverse events. Factors independently associated with pre-hospital cardiac arrest included male gender, current smoker status, tachycardia, higher Killip class and ST-segment deviation. Conclusion: ACS patients with pre-hospital cardiac arrest continue to have more in-hospital complications and higher mortality. Their use of evidence-based medical therapies was lower but the use of cardiac procedures was similar compared to the group without cardiac arrest. Better utilization of evidence-based therapies in these patients may translate into improved outcomes.

Relation Between Previous Angiotensin-Converting Enzyme Inhibitor Use and In-Hospital Outcomes in Acute Coronary Syndromes

Angiotensin-converting enzyme (ACE) inhibitor use in patients at high risk of coronary artery disease has been associated with a decrease in the risk of myocardial infarction (MI) and death. However, it is unclear whether chronic use of these agents modifies the course and outcome of an acute coronary syndrome (ACS). This study assessed the association between chronic use of ACE inhibitors and clinical outcomes in patients with ACS. From 1999 through 2008, 13,632 Canadian patients with ACS were identified in the Global Registry of Acute Coronary Events (GRACE), the expanded GRACE (GRACE(2)), and the Canadian Registry of Acute Coronary Events (CANRACE). Patients were stratified by previous use of an ACE inhibitor. Clinical characteristics, in-hospital treatment, and outcomes were compared between the 2 groups. Multivariable logistic regression analysis adjusting for GRACE risk score and other clinical factors was performed. Patients receiving an ACE inhibitor before the ACS had a higher prevalence of diabetes (40.6% vs 21.2%, p <0.001), previous MI (51.8% vs 23.3%, p <0.001), heart failure (18.0% vs 6.9%), and higher GRACE scores at presentation (133 vs 124, p <0.001). Multivariable analysis demonstrated no significant association between previous ACE inhibitor use and death (adjusted odds ratio [OR] 1.15, confidence interval [CI] 0.90 to 1.49, p = 0.27), in-hospital re-MI (adjusted OR 0.99, CI 0.78 to 1.25, p = 0.91), or the composite end point of death/re-MI (adjusted OR 1.01, CI 0.84 to 1.20, p = 0.94). In conclusion, previous use of an ACE inhibitor is not independently associated with improved in-hospital outcomes after an ACS.