Epicardially secreted fibronectin drives cardiomyocyte maturation in 3D-engineered heart tissues.

Ischemic heart failure is due to irreversible loss of cardiomyocytes. Preclinical studies showed that human pluripotent stem cell (hPSC)-derived cardiomyocytes could remuscularize infarcted hearts and improve cardiac function. However, these cardiomyocytes remained immature. Incorporating hPSC-derived epicardial cells has been shown to improve cardiomyocyte maturation, but the exact mechanisms are unknown. We posited epicardial fibronectin (FN1) as a mediator of epicardial-cardiomyocyte crosstalk and assessed its role in driving hPSC-derived cardiomyocyte maturation in 3D-engineered heart tissues (3D-EHTs). We found that the loss of FN1 with peptide inhibition F(pUR4), CRISPR-Cas9-mediated FN1 knockout, or tetracycline-inducible FN1 knockdown in 3D-EHTs resulted in immature cardiomyocytes with decreased contractile function, and inefficient Ca2+ handling. Conversely, when we supplemented 3D-EHTs with recombinant human FN1, we could recover hPSC-derived cardiomyocyte maturation. Finally, our RNA-sequencing analyses found FN1 within a wider paracrine network of epicardial-cardiomyocyte crosstalk, thus solidifying FN1 as a key driver of hPSC-derived cardiomyocyte maturation in 3D-EHTs.

A distractions capture tool for cardiac surgery and lung transplantation: impact on outcomes.

OBJECTIVES: Surgical distractions are associated with worse patient outcomes. Lung transplantation and cardiac surgery's multi-disciplinary nature, and their inherent complexities render them more vulnerable to distractions. We aim to use a novel distractions capture tool to evaluate the severity of distractions during cardiac surgery (CS) and lung transplantation (LTx) and assess its impact on post-operative complications. METHODS: A prospective 'blinded' study was undertaken by direct observation of distractions during CS and LTx. Events were identified using the Imperial College Error Capture tool (ICECAP). Number and severity of distractions were correlated with post-operative outcomes (ICU & hospital stay, bleeding and anastomotic complications). RESULTS: In LTx, we observed 2059 distractions within 287 h across 41 surgeries. In CS, we observed 1089 distractions within 192 h across 62 surgeries. Surgeons were consciously aware of 19.2% (LTx) and 21.3% (CS) of recorded events. Distractions consisted of procedure-independent pressures (61% LTx vs 56% CS), equipment problems (15% LTx vs 23%CS), communication (12% LTx vs 12% CS), technical problems or patient safety concerns (12% LTx vs 9% CS). In CS, 91% of procedure-independent pressures were non-operative distractions whilst LTx recorded 83%. Staff absences at a critical moment of surgery were recorded at 9% (LTx) and 7% (CS). The number and severity of distractions correlated with bleeding (CS p < 0.001, LTx p < 0.01), prolonged ICU stay (CS p = 0.002, LTx p = 0.002), hospital stay (CS p < 0.001) and anastomotic complications(LTx p < 0.03). CONCLUSIONS: ICECAP as a novel surgical distractions capture tool was effective & applicable to both elective cardiac and urgent transplant surgeries. Surgeons were unaware of a large number of distractions & interruptions. Distractions were associated with longer ICU stay and higher rate of bleeding.

SARS-CoV-2 Infects Human Pluripotent Stem Cell-Derived Cardiomyocytes, Impairing Electrical and Mechanical Function.

COVID-19 patients often develop severe cardiovascular complications, but it remains unclear if these are caused directly by viral infection or are secondary to a systemic response. Here, we examine the cardiac tropism of SARS-CoV-2 in human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) and smooth muscle cells (hPSC-SMCs). We find that that SARS-CoV-2 selectively infects hPSC-CMs through the viral receptor ACE2, whereas in hPSC-SMCs there is minimal viral entry or replication. After entry into cardiomyocytes, SARS-CoV-2 is assembled in lysosome-like vesicles and egresses via bulk exocytosis. The viral transcripts become a large fraction of cellular mRNA while host gene expression shifts from oxidative to glycolytic metabolism and upregulates chromatin modification and RNA splicing pathways. Most importantly, viral infection of hPSC-CMs progressively impairs both their electrophysiological and contractile function, and causes widespread cell death. These data support the hypothesis that COVID-19-related cardiac symptoms can result from a direct cardiotoxic effect of SARS-CoV-2.

Epicardial cells derived from human embryonic stem cells augment cardiomyocyte-driven heart regeneration.

The epicardium and its derivatives provide trophic and structural support for the developing and adult heart. Here we tested the ability of human embryonic stem cell (hESC)-derived epicardium to augment the structure and function of engineered heart tissue in vitro and to improve efficacy of hESC-cardiomyocyte grafts in infarcted athymic rat hearts. Epicardial cells markedly enhanced the contractility, myofibril structure and calcium handling of human engineered heart tissues, while reducing passive stiffness compared with mesenchymal stromal cells. Transplanted epicardial cells formed persistent fibroblast grafts in infarcted hearts. Cotransplantation of hESC-derived epicardial cells and cardiomyocytes doubled graft cardiomyocyte proliferation rates in vivo, resulting in 2.6-fold greater cardiac graft size and simultaneously augmenting graft and host vascularization. Notably, cotransplantation improved systolic function compared with hearts receiving either cardiomyocytes alone, epicardial cells alone or vehicle. The ability of epicardial cells to enhance cardiac graft size and function makes them a promising adjuvant therapeutic for cardiac repair.

Cardiac surgery improves survival in advanced left ventricular dysfunction: multivariate analysis of a consecutive series of 4491 patients over an 18-year period.

OBJECTIVES: Risks of cardiac surgery in patients with poor [ejection fraction (EF) ≤ 30%] and very poor left ventricular (LV) function (EF ≤ 20%) may be considered high due to increased mortality. We examine our results in this cohort of patients. METHODS: Data were prospectively collected and retrospectively analysed from 4491 consecutive patients referred for cardiac surgery over 18 years (July 1993-June 2012). Univariate predictors of in-hospital postoperative mortality were analysed by the appropriate tests. Variables with P < 0.1 were entered into multivariable logistic-regression model to identify predictors of in-hospital postoperative mortality, with data presented as odds ratios; P < 0.05 was statistically significant. Data on long-term survival and cardiac-specific mortality were obtained from the UK Office for National Statistics; the date of last follow-up was 13 October 2013 for the alive patients. Univariate predictors influencing cardiac death were determined by log-rank method. Variables with P < 0.1 were entered into multivariable Cox regression model to determine independent predictors of long-term survival, with data presented as hazard ratios; P < 0.05 was statistically significant. RESULTS: Cardiac surgery was performed on 3890 consecutive patients (74.7% male, age 68.7 ± 8.1 years); 601 patients did not undergo surgery. Postoperative hospital mortality was 2.9% (n = 112/3890). Predictors of postoperative hospital mortality included age ≥ 70 years, female sex, hypertension, LVEF < 50%, neurological dysfunction, previous cardiac surgery, early time period 1993-1997, emergency procedures and triple procedures. All patients were followed until the date of last follow-up or date of death, with a median follow-up of 8.1 ± 7.6 years and a total follow-up of 33 208 years. There were 533 (13.7%) postoperative early and late deaths from cardiac causes. Predictors of long-term survival free from cardiac death included LVEF > 50%. Predictors of postoperative cardiac deaths in the long-term follow-up included older age, diabetes, neurological dysfunction, LVEF < 50%, non-coronary artery bypass surgery, early time period of surgery (1993-1997) and redo-cardiac surgery. CONCLUSIONS: Cardiac surgery provides long-term survival benefit in all subsets of LV function, including advanced LV dysfunction.

Allogeneic blood transfusion in bilateral lung transplantation: impact on early function and mortality.

OBJECTIVES: Blood transfusion is associated with higher morbidity and mortality after general cardiothoracic surgery but its impact within the transplant population is unclear. We investigated the profile of blood product transfusion in the bilateral lung transplant population and its impact on function and mortality. METHODS: Three hundred and eleven adult patients who underwent bilateral lung transplant between 2003 and 2013 were retrospectively reviewed. Patients were stratified according to pretransplant diagnoses and amount of blood products transfused within 24 h of transplant. All-cause mortality at the 1-year follow-up was analysed using a Cox proportional hazards regression model. RESULTS: One hundred and seventy-four male patients and 137 female patients (mean age = 41.4 ± 14.0 years) underwent bilateral lung transplant using cardiopulmonary bypass for cystic fibrosis (48.9%), fibrotic lung disease (12.2%), emphysema (27.0%), bronchiectasis (5.8%), pulmonary hypertension (1.3%) and others (4.5%). The median number of red blood cells in the first 24 h was 3 (0-40) units, fresh frozen plasma (FFP) = 2 (0-26) units and platelets = 1 (0-7) units. The unadjusted all-cause mortality at the 1-year follow-up did not appear to be different between patient subgroups stratified by the median number of units of red blood cells (P = 0.827) or FFP transfused (P = 0.456). However, 1-year mortality was adversely affected when more than the median number of units of platelets was transfused (P = 0.010). Upon adjustment for confounding variables, 1-year mortality was noted to be greater among patients transfused more than the median unit of platelets (adjusted hazard ratios: 2.3, 95% confidence interval: 1.15-4.61, P = 0.019) and those with longer bypass times (P = 0.046). No significant difference in the number of units transfused was noted when patients were stratified by pretransplant diagnosis. Predicted lung function at 3 and 6 months was not significantly affected by greater blood product use. CONCLUSIONS: Unlike general cardiothoracic surgery, blood transfusion had no effect on all-cause mortality, whereas a greater administration of platelets was observed to be associated with higher adjusted 1-year mortality. Transfusion rates were not significantly influenced by pretransplant diagnoses. Interestingly, lung function at 3 and 6 months was similar for patients who received more blood product transfusion.

Lung Transplant With Cardiopulmonary Bypass: Impact of Blood Transfusion on Rejection, Function, and Late Mortality.

BACKGROUND: Allogeneic blood transfusion has been associated with immune modulation in other solid organ transplants. Within cardiothoracic surgery, allogeneic blood transfusion is associated with greater postoperative morbidity and mortality. We investigated the impact of allogeneic blood transfusion on rejection, function, and late mortality within lung transplantation. METHODS: A retrospective review was made of 311 adult patients who underwent bilateral lung transplantation with cardiopulmonary bypass from 2003 to 2013. Patients were stratified based on the amount of blood products transfused within 24 hours of transplantation. Kaplan-Meier methods and multivariate Cox proportional hazards models were used for time to first rejection/death and all-cause mortality analyses. RESULTS: In all, 174 men and 137 women (mean age 41.4 ± 14.0 years) utilized a median number of 3 units (range, 0 to 40) of red blood cells (RBC), 2 units (range, 0 to 26) of fresh frozen plasma (FFP), and 1 unit (range, 0 to 7) of platelets within the first 24 hours of transplantation. Time to first treated rejection/death was not statistically different whether patients were transfused with more or less than the median number of units of RBC (unadjusted p = 0.233, adjusted hazard ratio [HR] 1.02, 95% confidence interval [CI]: 0.75 to 1.40, p = 0.177), FFP (unadjusted p = 0.146, adjusted HR 1.29, 95% CI: 0.95 to 1.76, p = 0.108), or platelets (unadjusted p = 0.701, adjusted HR 0.74, 95% CI: 0.47 to 1.15, p = 0.177). Rate of rejection and number of rejection episodes per patient at 1 year after transplant were not statistically different. Forced expiratory volume in 1 second expressed as percentage of forced vital capacity at 3 and 6 months was similar for all groups. Unadjusted early all-cause mortality was not influenced by RBC (p = 0.162) or FFP (p = 0.298) but was significantly different with more platelets (p = 0.032). Adjusted 10-year mortality showed no significant differences for RBC (HR 1.12, 95% CI: 0.70 to 1.79, p = 0.645), FFP (HR 1.24, 95% CI: 0.78 to 1.97, p = 0.356), or platelets (HR 1.49, 95% CI: 0.84 to 2.64, p = 0.172.). CONCLUSIONS: All blood products administration regardless of amount transfused did not appear to affect early rejection outcomes or forced expiratory volume in 1 second expressed as percentage of forced vital capacity at 3 and 6 months. Use of RBC and FFP had no effect on survival. However, greater platelet usage appeared to adversely affect early but not late mortality.

Xenon mitigates isoflurane-induced neuronal apoptosis in the developing rodent brain.

BACKGROUND: Anesthetics, including isoflurane and nitrous oxide, an antagonist of the N-methyl-D-aspartate subtype of the glutamate receptor, have been demonstrated to induce apoptotic neurodegeneration when administered during neurodevelopment. Xenon, also an N-methyl-D-aspartate antagonist, not only lacks the characteristic toxicity produced by other N-methyl-D-aspartate antagonists, but also attenuates the neurotoxicity produced by this class of agent. Therefore, the current study sought to investigate xenon's putative protective properties against anesthetic-induced neuronal apoptosis. METHOD: Separate cohorts (n = 5 or 6 per group) of 7-day-old rats were randomly assigned and exposed to eight gas mixtures: air, 75% nitrous oxide, 75% xenon, 0.75% isoflurane, 0.75% isoflurane plus 35% or 75% nitrous oxide, 0.75% isoflurane plus 30% or 60% xenon for 6 h. Rats were killed, and cortical and hippocampal apoptosis was assessed using caspase-3 immunostaining. In separate cohorts, cortices were isolated for immunoblotting of caspase 3, caspase 8, caspase 9, and cytochrome c. Organotypic hippocampal slices of postnatal mice pups were derived and cultured for 24 h before similar gas exposures, as above, and subsequently processed for caspase-3 immunostaining. RESULTS: In vivo administration of isoflurane enhances neuronal apoptosis. When combined with isoflurane, nitrous oxide significantly increases whereas xenon significantly reduces apoptosis to a value no different from that of controls. In vitro studies corroborate the ability of xenon to attenuate isoflurane-induced apoptosis. Isoflurane enhanced expression of indicators of the intrinsic and common apoptotic pathways; this enhancement was increased by nitrous oxide but attenuated by xenon. CONCLUSIONS: The current study demonstrates that xenon prevents isoflurane-induced neonatal neuronal apoptosis.