The contribution of cell generation to physiological heart growth and maintenance in humans has been difficult to establish and has remained controversial. We report that the full complement of ...cardiomyocytes is established perinataly and remains stable over the human lifespan, whereas the numbers of both endothelial and mesenchymal cells increase substantially from birth to early adulthood. Analysis of the integration of nuclear bomb test-derived 14C revealed a high turnover rate of endothelial cells throughout life (>15% per year) and more limited renewal of mesenchymal cells (<4% per year in adulthood). Cardiomyocyte exchange is highest in early childhood and decreases gradually throughout life to <1% per year in adulthood, with similar turnover rates in the major subdivisions of the myocardium. We provide an integrated model of cell generation and turnover in the human heart.
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•The number of cardiomyocytes remains constant during the human lifespan•Endothelial and mesenchymal cells increase into adulthood and show high turnover•Cardiomyocyte turnover decreases exponentially with age and is <1% per year in adults•The cardiomyocyte turnover rate is equal in the main subdivisions of the human heart
A comprehensive analysis of cell generation and turnover in the human heart demonstrates that cardiomyocyte numbers are constant throughout the human lifespan, with a low turnover rate. Endothelial and mesenchymal cells are exchanged at a high rate, and their numbers increase into adulthood.
Despite progressive improvements over the decades, the rich temporally resolved data in an echocardiogram remain underutilized. Human assessments reduce the complex patterns of cardiac wall motion, ...to a small list of measurements of heart function. All modern echocardiography artificial intelligence (AI) systems are similarly limited by design - automating measurements of the same reductionist metrics rather than utilizing the embedded wealth of data. This underutilization is most evident where clinical decision making is guided by subjective assessments of disease acuity. Predicting the likelihood of developing post-operative right ventricular failure (RV failure) in the setting of mechanical circulatory support is one such example. Here we describe a video AI system trained to predict post-operative RV failure using the full spatiotemporal density of information in pre-operative echocardiography. We achieve an AUC of 0.729, and show that this ML system significantly outperforms a team of human experts at the same task on independent evaluation.
It has been difficult to establish whether we are limited to the heart muscle cells we are born with or if cardiomyocytes are generated also later in life. We have taken advantage of the integration ...of carbon-14, generated by nuclear bomb tests during the Cold War, into DNA to establish the age of cardiomyocytes in humans. We report that cardiomyocytes renew, with a gradual decrease from 1% turning over annually at the age of 25 to 0.45% at the age of 75. Fewer than 50% of cardiomyocytes are exchanged during a normal life span. The capacity to generate cardiomyocytes in the adult human heart suggests that it may be rational to work toward the development of therapeutic strategies aimed at stimulating this process in cardiac pathologies.
Aims Adult mammalian cardiomyocytes are traditionally viewed as being permanently withdrawn from the cell cycle. Whereas some groups have reported none, others have reported extensive mitosis in ...adult myocardium under steady-state conditions. Recently, a highly specific assay of 14C dating in humans has suggested a continuous generation of cardiomyocytes in the adult, albeit at a very low rate. Mice represent the most commonly used animal model for these studies, but their short lifespan makes them unsuitable for 14C studies. Herein, we investigate the cellular growth pattern for murine cardiomyocyte growth under steady-state conditions, addressed with new analytical and technical strategies, and we furthermore relate this to gene expression patterns. Methods and results The observed levels of DNA synthesis in early life were associated with cardiomyocyte proliferation. Mitosis was prolonged into early life, longer than the most conservative previous estimates. DNA synthesis in neonatal life was attributable to bi-nucleation, therefore suggesting that cardiomyocytes withdraw from the cell cycle shortly after birth. No cell cycle activity was observed in adult cardiomyocytes and significant polyploidy was observed in cardiomyocyte nuclei. Conclusion Gene analyses identified 32 genes whose expression was predicted to be particular to day 3–4 neonatal myocytes, compared with embryonic or adult cells. These cell cycle-associated genes are crucial to the understanding of the mechanisms of bi-nucleation and physiological cellular growth in the neonatal period.
Purpose
To evaluate the effect of the new heart transplant (HT) allocation system in left ventricular assist device (LVAD) supported patients listed as bridge to transplantation (BTT).
Methods
Adult ...patients who were listed for HT between October 18, 2016 and October 17, 2019, and were supported with an LVAD, enrolled in the UNOS database were included in this study. Patients were classified in the old or new system if they were listed or transplanted before or after October 18, 2018, respectively.
Results
A total of 3261 LVAD patients were listed for transplant. Of these, 2257 were classified in the old and 1004 in the new system. The cumulative incidence of death or removal from the transplant list due to worsening clinical status at 360‐days after listing was lower in the new system (4% vs. 7%, P = .011). LVAD Patients listed in the new system had a lower frequency of transplantation within 360‐days of listing (52% vs. 61%, P < .001). A total of 1843 LVAD patients were transplanted, 1004 patients in the old system and 839 patients in the new system. The post‐transplant survival at 360 days was similar between old and new systems (92.3% vs. 90%, P = .08). However, LVAD patients transplanted in the new system had lower frequency of the combined endpoint, freedom of death or re‐transplantation at 360 days (92.2% vs. 89.6%, P = .046).
Conclusion
The new HT allocation system has affected the LVAD‐BTT population significantly. On the waitlist, LVAD patients have a decreased cumulative frequency of transplantation and a concomitant decrease in death or delisting due to worsening status. In the new system, LVAD patients have a decreased survival free of re‐transplantation at 360 days post‐transplant.
Modulating signaling pathways including Wnt and Hippo can induce cardiomyocyte proliferation in vivo. Applying these signaling modulators to human induced pluripotent stem cell-derived cardiomyocytes ...(hiPSC-CMs) in vitro can expand CMs modestly (<5-fold). Here, we demonstrate massive expansion of hiPSC-CMs in vitro (i.e., 100- to 250-fold) by glycogen synthase kinase-3β (GSK-3β) inhibition using CHIR99021 and concurrent removal of cell-cell contact. We show that GSK-3β inhibition suppresses CM maturation, while contact removal prevents CMs from cell cycle exit. Remarkably, contact removal enabled 10 to 25 times greater expansion beyond GSK-3β inhibition alone. Mechanistically, persistent CM proliferation required both LEF/TCF activity and AKT phosphorylation but was independent from yes-associated protein (YAP) signaling. Engineered heart tissues from expanded hiPSC-CMs showed comparable contractility to those from unexpanded hiPSC-CMs, demonstrating uncompromised cellular functionality after expansion. In summary, we uncovered a molecular interplay that enables massive hiPSC-CM expansion for large-scale drug screening and tissue engineering applications.
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•GSK-3β inhibition-mediated hiPSC-cardiomyocyte proliferation is cell density dependent•GSK-3β inhibition with reduced cell-cell contact massively expands hiPSC-cardiomyocytes•LEF/TCF activity inhibits hiPSC-cardiomyocyte maturation without promoting cell cycling•Long-term expansion does not alter cardiomyocyte contractile function
Deriving a large number of hiPSC-cardiomyocytes would be beneficial for large-scale tissue engineering and drug screening applications. Buikema et al. show that GSK-3β inhibition combined with removal of cell-cell contact enables massive expansion of hiPSC-cardiomyocytes with comparable function to non-expanded cells.
Purpose
There is limited research on the use and outcomes of veno-arterial extracorporeal membrane oxygenation (VA-ECMO) treatment for massive pulmonary embolism (PE). This study compared VA-ECMO ...treatment for massive PE versus patients treated medically.
Materials and methods
Patients diagnosed with massive PE at one hospital system were reviewed. VA-ECMO and non-ECMO groups were compared by t test and Chi-square. Mortality risk factors were identified by logistic regression. Survival was assessed by Kaplan Meier and propensity matching of groups.
Results
Ninety-two patients were included (22 VA-ECMO and 70 non-ECMO). Age (OR 1.08, 95% CI 1.03–1.13), arterial SBP (OR 0.97, 95% CI 0.94–0.99), albumin (OR 0.3, 95% CI 0.1–0.8), and phosphorus (OR 2.0, 95% CI 1.4–3.17) were independently associated with 30-day mortality. Alkaline phosphate (OR 1.03, 95% CI 1.01–1.05) and SOFA score (OR 1.3, 95% CI 1.06–1.51) were associated with 1-year mortality. Propensity matching showed no difference in 30-day (59% VA-ECMO versus 72% non-ECMO, p = 0.363) or 1-year survival (50% VA-ECMO versus 64% non-ECMO, p = 0.355).
Conclusions
Patients treated with VA-ECMO for massive PE and medically treated patients have similar short- and long-term survival. Further research is needed to define clinical recommendations and benefits of intensive therapy such as VA-ECMO in this critically ill population.
Autophagy dysfunction in mouse atherosclerosis models has been associated with increased lipid accumulation, apoptosis and inflammation. Expression of cystatin C (CysC) is decreased in human ...atheroma, and CysC deficiency enhances atherosclerosis in mice. Here, we first investigated the association of autophagy and CysC expression levels with atheroma plaque severity in human atherosclerotic lesions. We found that autophagy proteins Atg5 and LC3β in advanced human carotid atherosclerotic lesions are decreased, while markers of dysfunctional autophagy p62/SQSTM1 and ubiquitin are increased together with elevated levels of lipid accumulation and apoptosis. The expressions of LC3β and Atg5 were positively associated with CysC expression. Second, we investigated whether CysC expression is involved in autophagy in atherosclerotic apoE‐deficient mice, demonstrating that CysC deficiency (CysC−/−) in these mice results in reduction of Atg5 and LC3β levels and induction of apoptosis. Third, macrophages isolated from CysC−/− mice displayed increased levels of p62/SQSTM1 and higher sensitivity to 7‐oxysterol‐mediated lysosomal membrane destabilization and apoptosis. Finally, CysC treatment minimized oxysterol‐mediated cellular lipid accumulation. We conclude that autophagy dysfunction is a characteristic of advanced human atherosclerotic lesions and is associated with reduced levels of CysC. The deficiency of CysC causes autophagy dysfunction and apoptosis in macrophages and apoE‐deficient mice. The results indicate that CysC plays an important regulatory role in combating cell death via the autophagic pathway in atherosclerosis.
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