[Ethics of stem cell therapy for heart failure]. / Terapia con células madre e insuficiencia cardiaca: aspectos éticos.

Heart failure is one of the first diseases in which stem cells were used for regenerative medicine. Since 2001, many publications have shown that stem cell therapy has the potential to mitigate heart diseases, but there is no solid scientific evidence to fully support its clinical application at present. The future of regenerative medicine requires validated clinical trials with standardized platforms and transdisciplinary efforts to enable the development of safe and effective regenerative therapies to protect patients and to promote the ethical application of this new and highly promising therapy. Doctors and scientists have a responsibility to discuss with patients the current reality of regenerative therapies. They also have a responsibility to discourage the indiscriminate and commercial use of these therapies, which are sometimes based on false hopes, since their inappropriate use can harm vulnerable patients as well as research efforts. Although regenerative medicine may be the medicine of the future and might bring the hope of cure for chronic diseases, it is not yet ready for its wide clinical application.

Musclin is an activity-stimulated myokine that enhances physical endurance.

Exercise remains the most effective way to promote physical and metabolic wellbeing, but molecular mechanisms underlying exercise tolerance and its plasticity are only partially understood. In this study we identify musclin-a peptide with high homology to natriuretic peptides (NP)-as an exercise-responsive myokine that acts to enhance exercise capacity in mice. We use human primary myoblast culture and in vivo murine models to establish that the activity-related production of musclin is driven by Ca(2+)-dependent activation of Akt1 and the release of musclin-encoding gene (Ostn) transcription from forkhead box O1 transcription factor inhibition. Disruption of Ostn and elimination of musclin secretion in mice results in reduced exercise tolerance that can be rescued by treatment with recombinant musclin. Reduced exercise capacity in mice with disrupted musclin signaling is associated with a trend toward lower levels of plasma atrial NP (ANP) and significantly smaller levels of cyclic guanosine monophosphate (cGMP) and peroxisome proliferator-activated receptor gamma coactivator 1-α in skeletal muscles after exposure to exercise. Furthermore, in agreement with the established musclin ability to interact with NP clearance receptors, but not with NP guanyl cyclase-coupled signaling receptors, we demonstrate that musclin enhances cGMP production in cultured myoblasts only when applied together with ANP. Elimination of the activity-related musclin-dependent boost of ANP/cGMP signaling results in significantly lower maximum aerobic capacity, mitochondrial protein content, respiratory complex protein expression, and succinate dehydrogenase activity in skeletal muscles. Together, these data indicate that musclin enhances physical endurance by promoting mitochondrial biogenesis.

Calreticulin secures calcium-dependent nuclear pore competency required for cardiogenesis.

Calreticulin deficiency causes myocardial developmental defects that culminate in an embryonic lethal phenotype. Recent studies have linked loss of this calcium binding chaperone to failure in myofibrillogenesis through an as yet undefined mechanism. The purpose of the present study was to identify cellular processes corrupted by calreticulin deficiency that precipitate dysregulation of cardiac myofibrillogenesis related to acquisition of cardiac phenotype. In an embryonic stem cell knockout model, calreticulin deficit (crt(-/-)) compromised nucleocytoplasmic transport of nuclear localization signal-dependent and independent pathways, disrupting nuclear import of the cardiac transcription factor MEF2C. The expression of nucleoporins and associated nuclear transport proteins in derived crt(-/-) cardiomyocytes revealed an abnormal nuclear pore complex (NPC) configuration. Altered protein content in crt(-/-) cells resulted in remodeled NPC architecture that caused decreased pore diameter and diminished probability of central channel occupancy versus wild type counterparts. Ionophore treatment of impaired calcium handling in crt(-/-) cells corrected nuclear pore microarchitecture and rescued nuclear import resulting in normalized myofibrillogenesis. Thus, calreticulin deficiency alters nuclear pore function and structure, impeding myofibrillogenesis in nascent cardiomyocytes through a calcium dependent mechanism. This essential role of calreticulin in nucleocytoplasmic communication competency ties its regulatory action with proficiency of cardiac myofibrillogenesis essential for proper cardiac development.

Transcriptome from circulating cells suggests dysregulated pathways associated with long-term recurrent events following first-time myocardial infarction.

BACKGROUND: Whole-genome gene expression analysis has been successfully utilized to diagnose, prognosticate, and identify potential therapeutic targets for high-risk cardiovascular diseases. However, the feasibility of this approach to identify outcome-related genes and dysregulated pathways following first-time myocardial infarction (AMI) remains unknown and may offer a novel strategy to detect affected expressome networks that predict long-term outcome. METHODS AND RESULTS: Whole-genome expression microarray on blood samples from normal cardiac function controls (n=21) and first-time AMI patients (n=31) within 48-hours post-MI revealed expected differential gene expression profiles enriched for inflammation and immune-response pathways. To determine molecular signatures at the time of AMI associated with long-term outcomes, transcriptional profiles from sub-groups of AMI patients with (n=5) or without (n=22) any recurrent events over an 18-month follow-up were compared. This analysis identified 559 differentially-expressed genes. Bioinformatic analysis of this differential gene-set for associated pathways revealed 1) increasing disease severity in AMI patients is associated with a decreased expression of genes involved in the developmental epithelial-to-mesenchymal transition pathway, and 2) modulation of cholesterol transport genes that include ABCA1, CETP, APOA1, and LDLR is associated with clinical outcome. CONCLUSION: Differentially regulated genes and modulated pathways were identified that were associated with recurrent cardiovascular outcomes in first-time AMI patients. This cell-based approach for risk stratification in AMI could represent a novel, non-invasive platform to anticipate modifiable pathways and therapeutic targets to optimize long-term outcome for AMI patients and warrants further study to determine the role of metabolic remodeling and regenerative processes required for optimal outcomes.

Disease-causing mitochondrial heteroplasmy segregated within induced pluripotent stem cell clones derived from a patient with MELAS.

Mitochondrial diseases display pathological phenotypes according to the mixture of mutant versus wild-type mitochondrial DNA (mtDNA), known as heteroplasmy. We herein examined the impact of nuclear reprogramming and clonal isolation of induced pluripotent stem cells (iPSC) on mitochondrial heteroplasmy. Patient-derived dermal fibroblasts with a prototypical mitochondrial deficiency diagnosed as mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) demonstrated mitochondrial dysfunction with reduced oxidative reserve due to heteroplasmy at position G13513A in the ND5 subunit of complex I. Bioengineered iPSC clones acquired pluripotency with multilineage differentiation capacity and demonstrated reduction in mitochondrial density and oxygen consumption distinguishing them from the somatic source. Consistent with the cellular mosaicism of the original patient-derived fibroblasts, the MELAS-iPSC clones contained a similar range of mtDNA heteroplasmy of the disease-causing mutation with identical profiles in the remaining mtDNA. High-heteroplasmy iPSC clones were used to demonstrate that extended stem cell passaging was sufficient to purge mutant mtDNA, resulting in isogenic iPSC subclones with various degrees of disease-causing genotypes. On comparative differentiation of iPSC clones, improved cardiogenic yield was associated with iPSC clones containing lower heteroplasmy compared with isogenic clones with high heteroplasmy. Thus, mtDNA heteroplasmic segregation within patient-derived stem cell lines enables direct comparison of genotype/phenotype relationships in progenitor cells and lineage-restricted progeny, and indicates that cell fate decisions are regulated as a function of mtDNA mutation load. The novel nuclear reprogramming-based model system introduces a disease-in-a-dish tool to examine the impact of mutant genotypes for MELAS patients in bioengineered tissues and a cellular probe for molecular features of individual mitochondrial diseases.

Cardiac rehabilitation services in low- and middle-income countries: a scoping review.

BACKGROUND: Despite the decreasing rate of cardiovascular disease-related mortality in developed nations, low- and middle-income countries (LMICs) are experiencing an increase. Cardiac rehabilitation (CR) successfully addresses this burden; however, the availability and nature of CR service delivery in LMICs are not well known. OBJECTIVE: This scoping review examined the (1) presence and accessibility of CR services, (2) structure of CR services, and (3) effects of CR on patient outcomes in LMICs. METHODS: Search criteria consisted of (1) nations considered to be low- or middle-income according to World Bank criteria, (2) CR, defined as programs including exercise and education, and (3) adults with cardiovascular diseases. Literature was identified through searching (a) the MEDLINE and EMBASE electronic databases, (b) proceedings from international cardiac conferences, (c) the grey literature and (d) through consulting experts in the field. RESULTS: Thirty peer-reviewed publications were identified. Grey literature, including Web sites for individual CR programs, revealed that CR is available in 32 (22.1%) LMICs. The most comprehensive data on accessibility stem from Latin America and the Caribbean, where 56% of institutions with cardiac catheterization facilities offered CR. Literature showed that some programs offered exercise, dietary advice, education, and psychological support, to assist patients to resume work and other activities of daily living. Fifteen peer-reviewed studies reported on CR outcomes, most of which were positive. CONCLUSION: Although patients similarly benefit from CR, few programs are available in LMICs. Policies need to be implemented to increase provision of tailored CR models at the global and national level, with evaluation.

Induced pluripotent stem cell intervention rescues ventricular wall motion disparity, achieving biological cardiac resynchronization post-infarction.

Dyssynchronous myocardial motion aggravates cardiac pump function. Cardiac resynchronization using pacing devices is a standard-of-care in the management of heart failure. Post-infarction, however, scar tissue formation impedes the efficacy of device-based therapy. The present study tests a regenerative approach aimed at targeting the origin of abnormal motion to prevent dyssynchronous organ failure. Induced pluripotent stem (iPS) cells harbour a reparative potential, and were here bioengineered from somatic fibroblasts reprogrammed with the stemness factors OCT3/4, SOX2, KLF4, and c-MYC. In a murine infarction model, within 30 min of coronary ligation, iPS cells were delivered to mapped infarcted areas. Focal deformation and dysfunction underlying progressive heart failure was resolved prospectively using speckle-tracking imaging. Tracked at high temporal and spatial resolution, regional iPS cell transplantation restored, within 10 days post-infarction, the contractility of targeted infarcted foci and nullified conduction delay in adjacent non-infarcted regions. Local iPS cell therapy, but not delivery of parental fibroblasts or vehicle, prevented or normalized abnormal strain patterns correcting the decrease in peak strain, disparity of time-to-peak strain, and pathological systolic stretch. Focal benefit of iPS cell intervention translated into improved left ventricular conduction and contractility, reduced scar, and reversal of structural remodelling, protecting from organ decompensation. Thus, in ischaemic cardiomyopathy, targeted iPS cell transplantation synchronized failing ventricles, offering a regenerative strategy to achieve biological resynchronization.

Cardiopoietic programming of embryonic stem cells for tumor-free heart repair.

Embryonic stem cells have the distinct potential for tissue regeneration, including cardiac repair. Their propensity for multilineage differentiation carries, however, the liability of neoplastic growth, impeding therapeutic application. Here, the tumorigenic threat associated with embryonic stem cell transplantation was suppressed by cardiac-restricted transgenic expression of the reprogramming cytokine TNF-alpha, enhancing the cardiogenic competence of recipient heart. The in vivo aptitude of TNF-alpha to promote cardiac differentiation was recapitulated in embryoid bodies in vitro. The procardiogenic action required an intact endoderm and was mediated by secreted cardio-inductive signals. Resolved TNF-alpha-induced endoderm-derived factors, combined in a cocktail, secured guided differentiation of embryonic stem cells in monolayers produce cardiac progenitors termed cardiopoietic cells. Characterized by a down-regulation of oncogenic markers, up-regulation, and nuclear translocation of cardiac transcription factors, this predetermined population yielded functional cardiomyocyte progeny. Recruited cardiopoietic cells delivered in infarcted hearts generated cardiomyocytes that proliferated into scar tissue, integrating with host myocardium for tumor-free repair. Thus, cardiopoietic programming establishes a strategy to hone stem cell pluripotency, offering a tumor-resistant approach for regeneration.

Stem cell systems informatics for advanced clinical biodiagnostics: tracing molecular signatures from bench to bedside.

Development of innovative high throughput technologies has enabled a variety of molecular landscapes to be interrogated with an unprecedented degree of detail. Emergence of next generation nucleotide sequencing methods, advanced proteomic techniques, and metabolic profiling approaches continue to produce a wealth of biological data that captures molecular frameworks underlying phenotype. The advent of these novel technologies has significant translational applications, as investigators can now explore molecular underpinnings of developmental states with a high degree of resolution. Application of these leading-edge techniques to patient samples has been successfully used to unmask nuanced molecular details of disease vs healthy tissue, which may provide novel targets for palliative intervention. To enhance such approaches, concomitant development of algorithms to reprogram differentiated cells in order to recapitulate pluripotent capacity offers a distinct advantage to advancing diagnostic methodology. Bioinformatic deconvolution of several "-omic" layers extracted from reprogrammed patient cells, could, in principle, provide a means by which the evolution of individual pathology can be developmentally monitored. Significant logistic challenges face current implementation of this novel paradigm of patient treatment and care, however, several of these limitations have been successfully addressed through continuous development of cutting edge in silico archiving and processing methods. Comprehensive elucidation of genomic, transcriptomic, proteomic, and metabolomic networks that define normal and pathological states, in combination with reprogrammed patient cells are thus poised to become high value resources in modern diagnosis and prognosis of patient disease.

Validity of cardiovascular risk prediction models in Latin America and among Hispanics in the United States of America: a systematic review.

OBJECTIVE: To assess the use and validity of prediction models to estimate the risk of cardiovascular disease (CVD) in Latin America and among Hispanic populations in the United States of America. METHODS: This was a systematic review of three databases: Ovid MEDLINE (1 January 1950-15 April 2010), LILACS (1 January 1988-15 April 2010), and EMBASE (1 January 1988-15 April 2010). MeSH search terms and domains were related to CVD, prediction rules, Latin America (including the Caribbean), and Hispanics in the United States. Database searches were supplemented by correspondence with experts in the field. RESULTS: A total of 1 655 abstracts were identified, of which five cohorts with a total of 13 142 subjects met inclusion criteria. A Mexican cohort showed that the predicted/observed event-rate ratio for coronary heart disease (CHD) according to the Framingham risk score (FRS) was 1.68 (95% CI, 1.26-2.11); incident myocardial infarction, 1.36 (95% CI, 0.90-1.83); and CHD death, 1.21 (95% CI, 0.43-2.00). In Ecuador, a prediction model for CVD and total deaths in hypertensive patients had an area under the curve (AUC) of 0.79 (95% CI, 0.72-0.86), while the World Health Organization method had an AUC of 0.74 (95% CI, 0.67-0.82). A study predicting mortality risk in people with Chagas' disease had an AUC of 0.81 (95% CI, 0.72-0.90). Among a United State s cohort that included Hispanics, FRS overestimated CVD risk for Hispanics with an AUC of 0.69. Another study in the United States that assessed FRS factors predicting CVD death among Mexican-Americans had an AUC of 0.78. CONCLUSIONS: The evidence regarding CVD risk prediction rules in Latin America or among Hispanics in the United States is modest at best. It is likely that the FRS overestimates CVD risk in Hispanics when not properly recalibrated.

[Current status of cardiac rehabilitation in Chile]. / Situación actual de la rehabilitación cardiaca en Chile.

BACKGROUND: Cardiac rehabilitation (CR) programs play an important role in the control and prevention of new cardiac events. AIM: A survey was performed to evaluate the current situation of CR programs in Chile. MATERIAL AND METHODS: A questionnaire evaluating the structure of rehabilitation centers, characteristics of the rehabilitation programs and patients, management of risk factors, reimbursement methods, human resources and potential barriers for an efficient rehabilitation, was mailed to centers dedicated to CR in Chile. RESULTS: Eight centers were contacted and seven responded. Coronary heart disease is the most common underlying disease of attended patients and CR is carried out mainly during phases II and III. All CR centers perform an initial assessment, stratify patients, plan and provide tips on physical activity and nutrition. Only three centers provide help to quit smoking. Lipid profile and blood sugar are assessed in 62% of centers. Most practitioners involved are cardiologists, nurses, physiotherapists and nutritionists, all trained in cardiopulmonary resuscitation. The main barrier for their development is the lack of patient referral from practitioners. CONCLUSIONS: Despite the recognized value of CR in the care of patients after a cardiac event, this study reveals the need for further development of such programs and improvement of patient referrals.

Decoded calreticulin-deficient embryonic stem cell transcriptome resolves latent cardiophenotype.

Genomic perturbations that challenge normal signaling at the pluripotent stage may trigger unforeseen ontogenic aberrancies. Anticipatory systems biology identification of transcriptome landscapes that underlie latent phenotypes would offer molecular diagnosis before the onset of symptoms. The purpose of this study was to assess the impact of calreticulin-deficient embryonic stem cell transcriptomes on molecular functions and physiological systems. Bioinformatic surveillance of calreticulin-null stem cells, a monogenic insult model, diagnosed a disruption in transcriptome dynamics, which re-prioritized essential cellular functions. Calreticulin-calibrated signaling axes were uncovered, and network-wide cartography of undifferentiated stem cell transcripts suggested cardiac manifestations. Calreticulin-deficient stem cell-derived cardiac cells verified disorganized sarcomerogenesis, mitochondrial paucity, and cytoarchitectural aberrations to validate calreticulin-dependent network forecasts. Furthermore, magnetic resonance imaging and histopathology detected a ventricular septal defect, revealing organogenic manifestation of calreticulin deletion. Thus, bioinformatic deciphering of a primordial calreticulin-deficient transcriptome decoded at the pluripotent stem cell stage a reconfigured multifunctional molecular registry to anticipate predifferentiation susceptibility toward abnormal cardiophenotype.

Early aging-associated phenotypes in Bub3/Rae1 haploinsufficient mice.

Aging is a highly complex biological process that is believed to involve multiple mechanisms. Mice that have small amounts of the mitotic checkpoint protein BubR1 age much faster than normal mice, but whether other mitotic checkpoint genes function to prevent the early onset of aging is unknown. In this study, we show that several aging-associated phenotypes appear early in mice that are double haploinsufficient for the mitotic checkpoint genes Bub3 and Rae1 but not in mice that are single haploinsufficient for these genes. Mouse embryonic fibroblasts (MEFs) from Bub3/Rae1 haploinsufficient mice undergo premature senescence and accumulate high levels of p19, p53, p21, and p16, whereas MEFs from single haploinsufficient mice do not. Furthermore, although BubR1 hypomorphic mice have less aneuploidy than Bub3/Rae1 haploinsufficient mice, they age much faster. Our findings suggest that early onset of aging-associated phenotypes in mice with mitotic checkpoint gene defects is linked to cellular senescence and activation of the p53 and p16 pathways rather than to aneuploidy.

iPS programmed without c-MYC yield proficient cardiogenesis for functional heart chimerism.

RATIONALE: Induced pluripotent stem cells (iPS) allow derivation of pluripotent progenitors from somatic sources. Originally, iPS were induced by a stemness-related gene set that included the c-MYC oncogene. OBJECTIVE: Here, we determined from embryo to adult the cardiogenic proficiency of iPS programmed without c-MYC, a cardiogenicity-associated transcription factor. METHODS AND RESULTS: Transgenic expression of 3 human stemness factors SOX2, OCT4, and KLF4 here reset murine fibroblasts to the pluripotent ground state. Transduction without c-MYC reversed cellular ultrastructure into a primitive archetype and induced stem cell markers generating 3-germ layers, all qualifiers of acquired pluripotency. Three-factor induced iPS (3F-iPS) clones reproducibly demonstrated cardiac differentiation properties characterized by vigorous beating activity of embryoid bodies and robust expression of cardiac Mef2c, alpha-actinin, connexin43, MLC2a, and troponin I. In vitro isolated iPS-derived cardiomyocytes demonstrated functional excitation-contraction coupling. Chimerism with 3F-iPS derived by morula-stage diploid aggregation was sustained during prenatal heart organogenesis and contributed in vivo to normal cardiac structure and overall performance in adult tumor-free offspring. CONCLUSIONS: Thus, 3F-iPS bioengineered without c-MYC achieve highest stringency criteria for bona fide cardiogenesis enabling reprogrammed fibroblasts to yield de novo heart tissue compatible with native counterpart throughout embryological development and into adulthood.

Impact of Musculoskeletal Limitations on Cardiac Rehabilitation Participation.

Background: To help clarify a potential barrier to cardiac rehabilitation (CR) participation we sought to examine the association between musculoskeletal limitations (MSLs) and CR enrollment and participation. Methods: Consecutive CR eligible individuals hospitalized for a cardiac event (myocardial infarction, percutaneous coronary intervention, and/or coronary artery bypass graft) between the months of November 2007 and May 2008, were asked to complete a mailed survey within 2 weeks after hospital discharge, assessing demographic factors, Patient Health Questionnaire (PHQ-9), participation in CR and MSLs through a validated MSLs screening tool. CR enrollment rates were compared between patients with and without MSLs. Results: Three hundred and twenty-one (37%) of patients contacted responded to our survey, including 228 males (71%), with a mean age 68 ± 10.8 years, of whom 98% were Caucasian. Eighty-two percent of responders reported a musculoskeletal disorder at the time of hospital discharge. Arthritis was the most frequent diagnosis (45%). Muscle or joint pain sufficient to limit the ability to do moderate exercise was reported in 52% of the respondents. Problems with balance affected 37%, of whom 45% reported a fall within the previous year. No significant difference in CR enrollment was observed in respondents with and without MSLs [OR = 0.98, 95% CI (0.88-1.09), p = 0.750]. Similar results were found when severity and number of MSLs were taken into account. However, we found that when compared to those without MSLs, the presence of MSLs was associated with lower CR participation (OR = 0.80, 95%, CI: 0.65-0.97, p = 0.0252). Conclusion: Despite a high prevalence of MSLs among CR-eligible patients, we found no association between MSLs and CR enrollment. However, patients with MSLs attended significantly fewer CR sessions as compared to patients without them. CR programs should consider providing additional support and interventions to patients with MSLs in order to optimize their adherence to prescribed CR sessions.

Repair of acute myocardial infarction by human stemness factors induced pluripotent stem cells.

BACKGROUND: Nuclear reprogramming provides an emerging strategy to produce embryo-independent pluripotent stem cells from somatic tissue. Induced pluripotent stem cells (iPS) demonstrate aptitude for de novo cardiac differentiation, yet their potential for heart disease therapy has not been tested. METHODS AND RESULTS: In this study, fibroblasts transduced with human stemness factors OCT3/4, SOX2, KLF4, and c-MYC converted into an embryonic stem cell-like phenotype and demonstrated the ability to spontaneously assimilate into preimplantation host morula via diploid aggregation, unique to bona fide pluripotent cells. In utero, iPS-derived chimera executed differentiation programs to construct normal heart parenchyma patterning. Within infarcted hearts in the adult, intramyocardial delivery of iPS yielded progeny that properly engrafted without disrupting cytoarchitecture in immunocompetent recipients. In contrast to parental nonreparative fibroblasts, iPS treatment restored postischemic contractile performance, ventricular wall thickness, and electric stability while achieving in situ regeneration of cardiac, smooth muscle, and endothelial tissue. CONCLUSIONS: Fibroblasts reprogrammed by human stemness factors thus acquire the potential to repair acute myocardial infarction, establishing iPS in the treatment of heart disease.

Current status of cardiac rehabilitation in Latin America and the Caribbean.

BACKGROUND: The prevalence of coronary artery disease (CAD) in Latin America is increasing and contributes importantly to the global burden of cardiovascular diseases. Advanced resources for the diagnosis and treatment of CAD are available in most of the region. However, preventive approaches such as cardiovascular rehabilitation programs (CVRP) may not be widely implemented. METHODS: We carried out a telephone-based survey to hospitals sampled in a random and population-weighted fashion from a list of 202 centers with cardiac catheterization laboratories in Mexico, Central and South America, and the Caribbean. We collected information of availability of cardiac procedures and imaging techniques and also extensive data about the presence, characteristics, and quality measures of CVRP. RESULTS: A total of 98 centers were contacted, and a complete survey was provided by 59 centers (60%) from 13 countries. Cardiovascular rehabilitation programs were available in only 56% of centers. There were no differences between centers with and without CVRP regarding type of hospital, availability of cardiac surgery, and annual volume of patients with myocardial infarction. Among centers with CVRP, 70% offered all phases of CVRP. The lack of CVRP was attributed to lack of qualified personnel in 41% of centers, financial constraints in 33%, and lack of physical space in 13%. All centers without CVRP performed cardiac surgery and percutaneous interventions. CONCLUSIONS: Despite the presence of state-of-the-art technology for the diagnosis and treatment of CAD, availability of CVRP, a less expensive yet effective tool for the treatment of CAD, appears to be limited in Latin America and the Caribbean.

Embryonic stem cell therapy of heart failure in genetic cardiomyopathy.

Pathogenic causes underlying nonischemic cardiomyopathies are increasingly being resolved, yet repair therapies for these commonly heritable forms of heart failure are lacking. A case in point is human dilated cardiomyopathy 10 (CMD10; Online Mendelian Inheritance in Man #608569), a progressive organ dysfunction syndrome refractory to conventional therapies and linked to mutations in cardiac ATP-sensitive K(+) (K(ATP)) channel subunits. Embryonic stem cell therapy demonstrates benefit in ischemic heart disease, but the reparative capacity of this allogeneic regenerative cell source has not been tested in inherited cardiomyopathy. Here, in a Kir6.2-knockout model lacking functional K(ATP) channels, we recapitulated under the imposed stress of pressure overload the gene-environment substrate of CMD10. Salient features of the human malignant heart failure phenotype were reproduced, including compromised contractility, ventricular dilatation, and poor survival. Embryonic stem cells were delivered through the epicardial route into the left ventricular wall of cardiomyopathic stressed Kir6.2-null mutants. At 1 month of therapy, transplantation of 200,000 cells per heart achieved teratoma-free reversal of systolic dysfunction and electrical synchronization and halted maladaptive remodeling, thereby preventing end-stage organ failure. Tracked using the lacZ reporter transgene, stem cells engrafted into host heart. Beyond formation of cardiac tissue positive for Kir6.2, transplantation induced cell cycle activation and halved fibrotic zones, normalizing sarcomeric and gap junction organization within remuscularized hearts. Improved systemic function induced by stem cell therapy translated into increased stamina, absence of anasarca, and benefit to overall survivorship. Embryonic stem cells thus achieve functional repair in nonischemic genetic cardiomyopathy, expanding indications to the therapy of heritable heart failure. Disclosure of potential conflicts of interest is found at the end of this article.

Calreticulin reveals a critical Ca(2+) checkpoint in cardiac myofibrillogenesis.

Calreticulin (crt) is an ubiquitously expressed and multifunctional Ca(2+)-binding protein that regulates diverse vital cell functions, including Ca(2+) storage in the ER and protein folding. Calreticulin deficiency in mice is lethal in utero due to defects in heart development and function. Herein, we used crt(-/-) embryonic stem (ES) cells differentiated in vitro into cardiac cells to investigate the molecular mechanisms underlying heart failure of knockout embryos. After 8 d of differentiation, beating areas were prominent in ES-derived wild-type (wt) embryoid bodies (EBs), but not in ES-derived crt(-/-) EBs, despite normal expression levels of cardiac transcription factors. Crt(-/-) EBs exhibited a severe decrease in expression and a lack of phosphorylation of ventricular myosin light chain 2 (MLC2v), resulting in an impaired organization of myofibrils. Crt(-/-) phenotype could be recreated in wt cells by chelating extracellular or cytoplasmic Ca(2+) with EGTA or BAPTA, or by inhibiting Ca(2+)/calmodulin-dependent kinases (CaMKs). An imposed ionomycin-triggered cystolic-free Ca(2+) concentration ([Ca(2+)](c)) elevation restored the expression, phosphorylation, and insertion of MLC2v into sarcomeric structures and in turn the myofibrillogenesis. The transcription factor myocyte enhancer factor C2 failed to accumulate into nuclei of crt(-/-) cardiac cells in the absence of ionomycin-triggered [Ca(2+)](c) increase. We conclude that the absence of calreticulin interferes with myofibril formation. Most importantly, calreticulin deficiency revealed the importance of a Ca(2+)-dependent checkpoint critical for early events during cardiac myofibrillogenesis.

Guided stem cell cardiopoiesis: discovery and translation.

Over 1000 patients have participated worldwide in clinical trials exploring the therapeutic value of bone marrow-derived cells in ischemic heart disease. Meta-analysis evaluation of this global effort indicates that adult stem cell therapy is in general safe, but yields a rather modest level of improvement in cardiac function and structural remodeling in the setting of acute myocardial infarction or chronic heart failure. Although promising, the potential of translating adult stem cell-based therapy from bench to bedside has yet to be fully realized. Inter-trial and inter-patient variability contribute to disparity in the regenerative potential of transplanted stem cells with unpredictable efficacy on follow-up. Strategies that mimic the natural embryonic program for uniform recruitment of cardiogenic progenitors from adult sources are currently tested to secure consistent outcome. Guided cardiopoiesis has been implemented with mesenchymal stem cells obtained from bone marrow of healthy volunteers, using a cocktail of secreted proteins that recapitulate components of the endodermal secretome critical for cardiogenic induction of embryonic mesoderm. With appropriate validation of this newly derived cardiopoietic phenotype, the next generation of trials should achieve demonstrable benefit across patient populations.