The direct conversion, or transdifferentiation, of non-cardiac cells into cardiomyocytes by forced expression of transcription factors and microRNAs provides promising approaches for cardiac regeneration. However, genetic manipulations raise safety concerns and are thus not desirable in most clinical applications. The discovery of full chemically induced pluripotent stem cells suggest the possibility of replacing transcription factors with chemical cocktails. Here, we report the generation of automatically beating cardiomyocyte-like cells from mouse fibroblasts using only chemical cocktails. These chemical-induced cardiomyocyte-like cells (CiCMs) express cardiomyocyte-specific markers, exhibit sarcomeric organization, and possess typical cardiac calcium flux and electrophysiological features. Genetic lineage tracing confirms the fibroblast origin of these CiCMs. Further studies show the generation of CiCMs passes through a cardiac progenitor stage instead of a pluripotent stage. Bypassing the use of viral-derived factors, this proof of concept study lays a foundation for in vivo cardiac transdifferentiation with pharmacological agents and possibly safer treatment of heart failure.

Although extending the duration of ambulatory electrocardiographic monitoring beyond 24 to 48 hours can improve the detection of arrhythmias, lead-based (Holter) monitors might be limited by patient compliance and other factors. We, therefore, evaluated compliance, analyzable signal time, interval to arrhythmia detection, and diagnostic yield of the Zio Patch, a novel leadless, electrocardiographic monitoring device in 26,751 consecutive patients. The mean wear time was 7.6 ± 3.6 days, and the median analyzable time was 99% of the total wear time. Among the patients with detected arrhythmias (60.3% of all patients), 29.9% had their first arrhythmia and 51.1% had their first symptom-triggered arrhythmia occur after the initial 48-hour period. Compared with the first 48 hours of monitoring, the overall diagnostic yield was greater when data from the entire Zio Patch wear duration were included for any arrhythmia (62.2% vs 43.9%, p <0.0001) and for any symptomatic arrhythmia (9.7% vs 4.4%, p <0.0001). For paroxysmal atrial fibrillation (AF), the mean interval to the first detection of AF was inversely proportional to the total AF burden, with an increasing proportion occurring after 48 hours (11.2%, 10.5%, 20.8%, and 38.0% for an AF burden of 51% to 75%, 26% to 50%, 1% to 25%, and <1%, respectively). In conclusion, extended monitoring with the Zio Patch for ≤14 days is feasible, with high patient compliance, a high analyzable signal time, and an incremental diagnostic yield beyond 48 hours for all arrhythmia types. These findings could have significant implications for device selection, monitoring duration, and care pathways for arrhythmia evaluation and AF surveillance.

Objectives To evaluate the association of digoxin with mortality in atrial fibrillation. Background Despite endorsement of digoxin in clinical practice guidelines, there exist limited data on its safety in atrial fibrillation and flutter (AF). Methods Using complete data from the US Department of Veterans Administration (VA) Health Care System, we identified patients with newly-diagnosed, non-valvular AF seen within 90 days in an outpatient setting between VA fiscal years 2004-2008. We used multivariate and propensity-matched Cox proportional hazards to evaluate the association of digoxin use to death. Residual confounding was assessed by sensitivity analysis. Results Of 122,465 patients with 353,168 person-years of follow-up (age 72.1±10.3 years, 98.4% males), 28,679 (23.4%) patients received digoxin. Cumulative mortality rates were higher for digoxin-treated patients than for untreated patients (95 vs. 67 per 1,000 person-years; P<0.001). Digoxin use was independently associated with mortality after multivariate adjustment (HR: 1.26, 95%CI: 1.23-1.29, P<0.001) and propensity matching (HR: 1.21, 95%CI: 1.17-1.25, P<0.001), even after adjustment for drug adherence. The risk of death was not modified by age, sex, heart failure, kidney function, or concomitant use of beta blockers, amiodarone, or warfarin. Conclusion Digoxin was associated with increased risk of death in patients with newly-diagnosed AF, independent of drug adherence, kidney function, cardiovascular comorbidities, and concomitant therapies. These findings challenge current cardiovascular society recommendations on use of digoxin in AF.

Somatic cells can be reprogrammed into induced pluripotent stem cells (iPSCs) by defined factors. The low efficiency of reprogramming and genomic integration of oncogenes and viral vectors limited the potential application of iPSCs. Here we report that Lithium (Li), a drug used to treat mood disorders, greatly enhances iPSC generation from both mouse embryonic fibroblast and human umbilical vein endothelial cells. Li facilitates iPSC generation with one (Oct4) or two factors (OS or OK). The effect of Li on promoting reprogramming only partially depends on its major target GSK3β. Unlike other GSK3β inhibitors, Li not only increases the expression of Nanog, but also enhances the transcriptional activity of Nanog. We also found that Li exerts its effect by promoting epigenetic modifications via downregulation of LSD1, a H3K4-specific histone demethylase. Knocking down LSD1 partially mimics Li's effect in enhancing reprogramming. Our results not only provide a straightforward method to improve the iPSC generation efficiency, but also identified a histone demethylase as a critical modulator for somatic cell reprogramming.

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Primary hepatocytes cultured in vitro are a powerful tool to study the functions of hepatocytes and to evaluate the metabolism and toxicity of new drugs. However, in vitro culture of hepatocytes has proven to be very difficult. Ordinary culture conditions lead to dedifferentiation of hepatocytes, resulting in rapid change in cell morphology and significant reduction in specific cell functions. In the current study, we show that hepatocyte dedifferentiation is a rapid process under 21% O2 conditions. Hepatocytes cultured in 21% O2 undergo epithelial-to-mesenchymal transition (EMT), obtain fibroblast-like morphology, and show decreased hepatic functions. In contrast, 5% O2 is very effective in maintaining the epithelial morphology and many functions of the primary hepatocytes cultured in vitro for up to five days. These functions include albumin production, glycogen storage, LDL-uptake and CYP450-mediated drug metabolism. Furthermore, we find that 5% O2 can relieve the production of reactive oxygen species (ROS) and decrease the level of DNA damage in primary cultured hepatocytes. In addition, we also show that blocking the ERK and GSK-3β pathways can inhibit the dedifferentiation of hepatocytes to a certain extent. Lowering the oxygen tension in cell culture is easily achievable, we believe it could be combined with other methods, such as the use of small molecule cocktails and 3D culture, to maintain proliferation and functions of primary hepatocytes in vitro.

Environmental stress-mediated adaptation plays essential roles in the evolution of life. Cellular adaptation mechanisms usually involve the regulation of chromatin structure, transcription, mRNA stability and translation, which eventually lead to efficient changes in gene expression. Global epigenetic change is also involved in the reprogramming of somatic cells into induced pluripotent stem (iPS) cells by defined factors. Here we report that environmental stress such as hyperosmosis not only facilitates four factor-mediated reprogramming, but also enhances two or one factor-induced iPS cell generation. Hyperosmosis-induced p38 activation plays a critical role in this process. Constitutive active p38 mimics the positive effect of hyperosmosis, while dominant negative p38 and p38 inhibitor block the effect of hyperosmosis. Further study indicates stress-mediated p38 activation may promote reprogramming by reducing the global DNA methylation level and enhancing the expression of pluripotency genes. Our results demonstrate how simple environmental stress like hyperosmosis helps to alter the fate of cells via intracellular signaling and epigenetic modulation.