Direct Cardiac Reprogramming: Progress and Promise.

The human adult heart lacks a robust endogenous repair mechanism to fully restore cardiac function after insult; thus, the ability to regenerate and repair the injured myocardium remains a top priority in treating heart failure. The ability to efficiently generate a large number of functioning cardiomyocytes capable of functional integration within the injured heart has been difficult. However, the ability to directly convert fibroblasts into cardiomyocyte-like cells both in vitro and in vivo offers great promise in overcoming this problem. In this review, we describe the insights and progress that have been gained from the investigation of direct cardiac reprogramming. We focus on the use of key transcription factors and cardiogenic genes as well as on the use of other biological molecules such as small molecules, cytokines, noncoding RNAs, and epigenetic modifiers to improve the efficiency of cardiac reprogramming. Finally, we discuss the development of safer reprogramming approaches for future clinical application

Cardiac manifestations of PRKAG2 mutation.

BACKGROUND:The Protein Kinase AMP-Activated Non-Catalytic Subunit Gamma 2 (PRKAG2) cardiac syndrome is characterized by glycogen accumulation in the cardiac tissue. The disease presents clinically with hypertrophic cardiomyopathy (HCM), and it is often associated with conduction abnormalities. CASE PRESENTATION:A 23 year-old female with history of Wolff-Parkinson-White (WPW) and HCM presented for evaluation after an episode of Non-ST Elevation Myocardial Infarction (NSTEMI). The patient was found to have severe coronary bridging on angiography and underwent an unroofing of the left anterior descending artery (LAD). Due to the constellation of symptoms, the patient underwent genetic testing and a cardiac muscle biopsy. Genetic testing was significant for an Arg302Gln mutation in the PRKAG2 gene. Cardiac tissue biopsy revealed significant myocyte hypertrophy and large vacuoles with glycogen stores. CONCLUSION:The pathologic and genetics findings of our patient are consistent with PRKAG2 syndrome. Patients presenting with conduction abnormalities and suspected HCM should be considered for genetic testing to identify possible underlying genetic etiologies

Endogenous Wnt signalling in human embryonic stem cells generates an equilibrium of distinct lineage-specified progenitors.

The pluripotent nature of human embryonic stem cells (hESCs) makes them convenient for deriving therapeutically relevant cells. Here we show using Wnt reporter hESC lines that the cells are heterogeneous with respect to endogenous Wnt signalling activity. Moreover, the level of Wnt signalling activity in individual cells correlates with differences in clonogenic potential and lineage-specific differentiation propensity. The addition of Wnt protein or, conversely, a small-molecule Wnt inhibitor (IWP2) reduces heterogeneity, allowing stable expansion of Wnt(high) or Wnt(low) hESC populations, respectively. On differentiation, the Wnt(high) hESCs predominantly form endodermal and cardiac cells, whereas the Wnt(low) hESCs generate primarily neuroectodermal cells. Thus, heterogeneity with respect to endogenous Wnt signalling underlies much of the inefficiency in directing hESCs towards specific cell types. The relatively uniform differentiation potential of the Wnt(high) and Wnt(low) hESCs leads to faster and more efficient derivation of targeted cell types from these populations

Giant cell myocarditis masquerading as orbital myositis with a rapid, fulminant course necessitating mechanical support and heart transplantation.

Giant cell myocarditis (GCM), a rapidly progressive inflammation of the myocardium, is associated with fulminant heart failure, refractory ventricular arrhythmias, and conduction system abnormalities. Few case reports have noted orbital myositis as the initial clinical presentation. Our case demonstrates a unique presentation of GCM with only ocular symptoms, which unlike prior studies, rapidly progressed to heart failure, tachyarrhythmias, and conduction disease. Our case necessitated quick recognition and treatment with mechanical support making this the first known case of GCM with successful placement of biventricular assist devices and ultimately with heart transplantation

Translational aspects of cardiac cell therapy.

Cell therapy has been intensely studied for over a decade as a potential treatment for ischaemic heart disease. While initial trials using skeletal myoblasts, bone marrow cells and peripheral blood stem cells showed promise in improving cardiac function, benefits were found to be short-lived likely related to limited survival and engraftment of the delivered cells. The discovery of putative cardiac 'progenitor' cells as well as the creation of induced pluripotent stem cells has led to the delivery of cells potentially capable of electromechanical integration into existing tissue. An alternative strategy involving either direct reprogramming of endogenous cardiac fibroblasts or stimulation of resident cardiomyocytes to regenerate new myocytes can potentially overcome the limitations of exogenous cell delivery. Complimentary approaches utilizing combination cell therapy and bioengineering techniques may be necessary to provide the proper milieu for clinically significant regeneration. Clinical trials employing bone marrow cells, mesenchymal stem cells and cardiac progenitor cells have demonstrated safety of catheter based cell delivery, with suggestion of limited improvement in ventricular function and reduction in infarct size. Ongoing trials are investigating potential benefits to outcome such as morbidity and mortality. These and future trials will clarify the optimal cell types and delivery conditions for therapeutic effect

Light-Sheet Imaging to Elucidate Cardiovascular Injury and Repair

Purpose of Review: Real-time 3-dimensional (3-D) imaging of cardiovascular injury and regeneration remains challenging. We introduced a multi-scale imaging strategy that uses light-sheet illumination to enable applications of cardiovascular injury and repair in models ranging from zebrafish to rodent hearts. Recent Findings: Light-sheet imaging enables rapid data acquisition with high spatiotemporal resolution and with minimal photo-bleaching or photo-toxicity. We demonstrated the capacity of this novel light-sheet approach for scanning a region of interest with specific fluorescence contrast, thereby providing axial and temporal resolution at the cellular level without stitching image columns or pivoting illumination beams during one-time imaging. This cutting-edge imaging technique allows for elucidating the differentiation of stem cells in cardiac regeneration, providing an entry point to discover novel micro-circulation phenomenon with clinical significance for injury and repair. Summary: These findings demonstrate the multi-scale applications of this novel light-sheet imaging strategy to advance research in cardiovascular development and regeneration

Cardiac Fibrosis Is Associated With Decreased Circulating Levels of Full-Length CILP in Heart Failure.

Cardiac fibrosis is a pathological process associated with various forms of heart failure. This study identified latent transforming growth factor-β binding protein 2, cartilage oligomeric matrix protein, and cartilage intermediate layer protein 1 as potential biomarkers for cardiac fibrosis. All 3 encoded proteins showed increased expression in fibroblasts after transforming growth factor-β stimulation in vitro and localized specifically to fibrotic regions in vivo. Of the 3, only the full-length cartilage intermediate layer protein 1 showed a significant decrease in circulating levels in patients with heart failure compared with healthy volunteers. Further studies on these 3 proteins will lead to a better understanding of their biomarker potential for cardiac fibrosis

Light-Sheet Imaging to Elucidate Cardiovascular Injury and Repair

Purpose of Review: Real-time 3-dimensional (3-D) imaging of cardiovascular injury and regeneration remains challenging. We introduced a multi-scale imaging strategy that uses light-sheet illumination to enable applications of cardiovascular injury and repair in models ranging from zebrafish to rodent hearts. Recent Findings: Light-sheet imaging enables rapid data acquisition with high spatiotemporal resolution and with minimal photo-bleaching or photo-toxicity. We demonstrated the capacity of this novel light-sheet approach for scanning a region of interest with specific fluorescence contrast, thereby providing axial and temporal resolution at the cellular level without stitching image columns or pivoting illumination beams during one-time imaging. This cutting-edge imaging technique allows for elucidating the differentiation of stem cells in cardiac regeneration, providing an entry point to discover novel micro-circulation phenomenon with clinical significance for injury and repair. Summary: These findings demonstrate the multi-scale applications of this novel light-sheet imaging strategy to advance research in cardiovascular development and regeneration