[Show abstract][Hide abstract] ABSTRACT: Improving the limited ability of the heart to regenerate after infarction is crucial. Researchers now demonstrate that delivery of follistatin-like 1 (FSTL1) into injured hearts via collagen patches stimulates cardiomyocyte proliferation and cardiac functional recovery. These findings highlight the epicardium as a source of novel regenerative factors and biomimetic nanomaterials in cardiac translational medicine.
Trends in Molecular Medicine 11/2015; DOI:10.1016/j.molmed.2015.10.006 · 9.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Significance:
Recent advances in the generation of cardiomyocytes (CMs) from human pluripotent stem cells (hPSCs) and the development of novel cell therapy strategies using hPSC-CMs (e.g., cardiac patches) in conjunction with promising preclinical and clinical studies, have raised new hopes for patients with end-stage cardiovascular disease, which remains the leading cause of morbidity and mortality globally. In this study, a simplified, scalable, robust, and integrated differentiation platform was developed to generate clinical grade hPSC-CMs as cell aggregates under chemically defined culture conditions. This approach resulted in approximately 100% beating CM spheroids with virtually pure (∼90%) functional cardiomyocytes in 10 days from multiple hPSC lines. This universal and robust bioprocessing platform can provide sufficient numbers of hPSC-CMs for companies developing regenerative medicine technologies to rescue, replace, and help repair damaged heart tissues and for pharmaceutical companies developing advanced biologics and drugs for regeneration of lost heart tissue using high-throughput technologies. It is believed that this technology can expedite clinical progress in these areas to achieve a meaningful impact on improving clinical outcomes, cost of care, and quality of life for those patients disabled and experiencing heart disease.
STEM CELLS TRANSLATIONAL MEDICINE 10/2015; DOI:10.5966/sctm.2014-0275 · 5.71 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Gene ontology (GO) enrichment is commonly used for inferring biological meaning from systems biology experiments. However, determining differential GO and pathway enrichment between DNA-binding experiments or using the GO structure to classify experiments has received little attention.
Herein, we present a bioinformatics tool, CompGO, for identifying Differentially Enriched Gene Ontologies, called DiEGOs, and pathways, through the use of a z-score derivation of log odds ratios, and visualizing these differences at GO and pathway level. Through public experimental data focused on the cardiac transcription factor NKX2-5, we illustrate the problems associated with comparing GO enrichments between experiments using a simple overlap approach.
We have developed an R/Bioconductor package, CompGO, which implements a new statistic normally used in epidemiological studies for performing comparative GO analyses and visualizing comparisons from . BED data containing genomic coordinates as well as gene lists as inputs. We justify the statistic through inclusion of experimental data and compare to the commonly used overlap method. CompGO is freely available as a R/Bioconductor package enabling easy integration into existing pipelines and is available at: http://www.bioconductor.org/packages/release/bioc/html/CompGO.html packages/release/bioc/html/CompGO.html.
[Show abstract][Hide abstract] ABSTRACT: To model cardiac gene regulatory networks in health and disease we used DamID to establish robust target gene sets for the cardiac homeodomain factor NKX2-5 and two congenital heart disease-associated mutants carrying a crippled homeodomain, which normally functions as DNA- and protein-binding interface. Despite compromised direct DNA-binding, NKX2-5 mutants retained partial functionality and bound hundreds of targets, including NKX2-5 wild type targets and unique sets of 'off-targets'. NKX2-5∆HD, which lacks the entire homeodomain, could still dimerise with wild type NKX2-5 and its cofactors, including newly-discovered cofactors of the ETS family, through the conserved tyrosine-rich domain (YRD). NKX2-5∆HD off-targets showed overrepresentation of many binding motifs, including ETS motifs, the majority co-occupied by ETS proteins as determined by DamID. Off-targets of an NKX2-5 YRD mutant were not enriched in ETS targets. Our study reveals off-target binding and transcriptional activity for NKX2-5 mutations driven in part by cofactor interactions, suggesting a novel type of gain-of-function in congenital heart disease.
[Show abstract][Hide abstract] ABSTRACT: The murine neonatal heart can regenerate after injury through cardiomyocyte (CM) proliferation, although this capacity markedly diminishes after the first week of life. Neuregulin-1 (NRG1) administration has been proposed as a strategy to promote cardiac regeneration. Here, using loss- and gain-of-function genetic tools, we explore the role of the NRG1 co-receptor ERBB2 in cardiac regeneration. NRG1-induced CM proliferation diminished one week after birth owing to a reduction in ERBB2 expression. CM-specific Erbb2 knockout revealed that ERBB2 is required for CM proliferation at embryonic/neonatal stages. Induction of a constitutively active ERBB2 (caERBB2) in neonatal, juvenile and adult CMs resulted in cardiomegaly, characterized by extensive CM hypertrophy, dedifferentiation and proliferation, differentially mediated by ERK, AKT and GSK3β/β-catenin signalling pathways. Transient induction of caERBB2 following myocardial infarction triggered CM dedifferentiation and proliferation followed by redifferentiation and regeneration. Thus, ERBB2 is both necessary for CM proliferation and sufficient to reactivate postnatal CM proliferative and regenerative potentials.
[Show abstract][Hide abstract] ABSTRACT: Congenital heart disease places a significant burden on the individual, family and community despite significant advances in our understanding of aetiology and treatment. Early research in ischaemic heart disease has paved the way for stem cell technology and bioengineering, which promises to improve both structural and functional aspects of disease. Stem cell therapy has demonstrated significant improvements in cardiac function in adults with ischaemic heart disease. This finding, together with promising case studies in the paediatric setting, demonstrates the potential for this treatment in congenital heart disease. Furthermore, induced pluripotent stems cell technology, provides a unique opportunity to address aetiological, as well as therapeutic, aspects of disease.
Journal of Clinical Medicine 04/2015; 4(4):768-781. DOI:10.3390/jcm4040768
[Show abstract][Hide abstract] ABSTRACT: Mutations in the giant sarcomeric protein titin (TTN) are a major cause for inherited forms of dilated cardiomyopathy (DCM). We have previously developed a mouse model that imitates a TTN truncation mutation we found in a large pedigree with DCM. While heterozygous
knock-in mice do not display signs of heart failure under sedentary conditions, they recapitulate the human phenotype when exposed to the pharmacological stressor angiotensin II or isoproterenol. In this study we investigated the effects of pressure overload by transverse aortic constriction (TAC) in heterozygous (Het)
knock-in mice. Two weeks after TAC, Het mice developed marked impairment of left ventricular ejection fraction
, while wild-type (WT) TAC mice did not. Het mice also trended toward increased ventricular end diastolic pressure and volume compared to WT littermates. We found an increase in histologically diffuse cardiac fibrosis in Het compared to WT in TAC mice. This study shows that a pattern of DCM can be induced by TAC-mediated pressure overload in a TTN-truncated mouse model. This model enlarges our arsenal of cardiac disease models, adding a valuable tool to understand cardiac pathophysiological remodeling processes and to develop therapeutic approaches to combat heart failure.
[Show abstract][Hide abstract] ABSTRACT: Animal genomes contain a code for construction of the body plan from a fertilized egg. Understanding how genome information is deciphered to create the complex multilayered regulatory systems that drive organismal development, and which become altered in disease, is one of the greatest challenges in the biological sciences. The development of methods that effectively represent and communicate the complexity inherent in gene regulatory networks remains a major barrier. This review introduces the philosophy of systems biology and discusses recent progress in understanding the development of the heart at a systems biology level.
Cold Spring Harbor Perspectives in Medicine 10/2014; 4(11). DOI:10.1101/cshperspect.a013839 · 9.47 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mammalian hearts carry a number of primitive stem cell-like populations, although the magnitude of their contribution to tissue homeostasis and repair remains controversial. Recent CRE recombinase-based lineage tracing experiments suggest only a minor contribution to the formation of new cardiomyocytes from such cells, albeit one that might be augmented therapeutically. As the field explores clinical translation of cardiac stem cells, it will be important to understand the biology of these cells in great detail. In this review we document the various reported stem and progenitor cell populations in mammalian hearts and discuss the current state of knowledge on their origins and lineage capabilities.
Stem Cell Research 10/2014; 13(3). DOI:10.1016/j.scr.2014.09.008 · 3.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mammalian embryos develop in a low oxygen environment. The transcription factor hypoxia inducible factor 1a (HIF1α) is a key element in the cellular response to hypoxia. Complete deletion of Hif1α from the mouse conceptus causes extensive placental, vascular and heart defects, resulting in embryonic lethality. However the precise role of Hif1α in each of these organ systems remains unknown. To further investigate, we conditionally-deleted Hif1α from mesoderm, vasculature and heart individually. Surprisingly, deletion from these tissues did not recapitulate the same severe heart phenotype or embryonic lethality. Placental insufficiency, such as occurs in the complete Hif1α null, results in elevated cellular hypoxia in mouse embryos. We hypothesized that subjecting the Hif1α conditional null embryos to increased hypoxic stress might exacerbate the effects of tissue-specific Hif1α deletion. We tested this hypothesis using a model system mimicking placental insufficiency. We found that the majority of embryos lacking Hif1α in the heart died when exposed to non-physiological hypoxia. This was a heart-specific phenomenon, as HIF1α protein accumulated predominantly in the myocardium of hypoxia-stressed embryos. Our study demonstrates the vulnerability of the heart to lowered oxygen levels, and that under such conditions of non-physiological hypoxia the embryo absolutely requires Hif1α to continue normal development. Importantly, these findings extend our understanding of the roles of Hif1α in cardiovascular development.
[Show abstract][Hide abstract] ABSTRACT: Donation after circulatory death (DCD) offers a potential additional source of cardiac allografts. We used a porcine asphyxia model to evaluate viability of DCD hearts subjected to warm ischemic times (WIT) of 20–40 min prior to flushing with Celsior (C) solution. We then assessed potential benefits of supplementing C with erythropoietin, glyceryl trinitrate and zoniporide (Cs), a combination that we have shown previously to activate ischemic postconditioning pathways. Hearts flushed with C/Cs were assessed for functional, biochemical and metabolic recovery on an ex vivo working heart apparatus. Hearts exposed to 20-min WIT showed full recovery of functional and metabolic profiles compared with control hearts (no WIT). Hearts subjected to 30- or 40-min WIT prior to C solution showed partial and no recovery, respectively. Hearts exposed to 30-min WIT and Cs solution displayed complete recovery, while hearts exposed to 40-min WIT and Cs solution demonstrated partial recovery. We conclude that DCD hearts flushed with C solution demonstrate complete recovery up to 20-min WIT after which there is rapid loss of viability. Cs extends the limit of WIT tolerability to 30 min. DCD hearts with ≤30-min WIT may be suitable for transplantation and warrant assessment in a transplant model.
American Journal of Transplantation 07/2014; 14(8). DOI:10.1111/ajt.12782 · 5.68 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Risk for schizophrenia is likely to involve gene × environment interactions. Neuregulin 1 (NRG1) is a schizophrenia risk gene, hence any interaction with environmental adversity, such as maternal infection, may provide further insights into the basis of the disease. This study examined the individual and combined effects of prenatal immune activation with Poly I:C and disruption of the schizophrenia risk gene NRG1 on the expression of behavioural phenotypes related to schizophrenia. NRG1 heterozygous (NRG1 HET) mutant breeding pairs were time-mated. Pregnant dams received a single injection (5 mg/kg i.p.) of Poly I:C or vehicle on gestation day 9 (GD9). Offspring were then cross-fostered to vehicle-treated or PolyI:C-treated dams. Expression of schizophrenia-related behavioural endophenotypes was assessed at adolescence and in adulthood. Combining NRG1 disruption and prenatal environmental insult (Poly I:C) caused developmental stage-specific deficits in social behaviour, spatial working memory and PPI. However, combining Poly I:C and cross-fostering produced a number of behavioural deficits in the open field, social behaviour and PPI. This became more complex by combining NRG1 deletion with both Poly I:C exposure and cross-fostering, which had a robust effect on PPI. These findings suggest that concepts of gene × environment interaction in risk for schizophrenia should be elaborated to multiple interactions that involve individual genes interacting with diverse biological and psychosocial environmental factors over early life, to differentially influence particular domains of psychopathology, sometimes over specific stages of development.