Cardiopulmonary resuscitation (CPR) is a first-line therapy for sudden cardiac arrest, while extracorporeal membrane oxygenation (ECMO) has traditionally been used as a means of countering circulatory failure. However, new advances dictate that CPR and ECMO could be complementary for support after cardiac arrest. This review details the emerging science, technology, and clinical application that are enabling the new paradigm of these iconic circulatory support modalities in the setting of cardiac arrest. Cardiac arrest is defined as the loss of mechanical activity of the heart, leading to the sudden loss of forward blood flow. This causes a marked reduction or elimination of perfusion to vital organs, which can rapidly lead to death if circulation is not restored. There are over 350,000 out-of-hospital and over 205,000 in-hospital cardiac arrest events each year in the United States,A major guiding principle of resuscitation is that increasing the amount of forward blood flow generated during resuscitation increases chance of survival.14Extracorporeal membrane oxygenation (ECMO) is a form of mechanical circulatory support that combines an extracorporeal blood pump with an oxygenator. The ECMO technique has traditionally been deployed for a variety of cardiopulmonary conditions and, more recently, sudden cardiac arrest.15There are two common configurations of ECMO which enable customization of support for each patient. In general, for respiratory support during which oxygenation is affected, such as with severe refractory acute respiratory distress syndrome, veno-venous ECMO (VV-ECMO) can be used to remove deoxygenated blood from the venous system, pass it through an oxygenator, then return the oxygenated blood into the circulation via the venous system. However, in cases of cardiac failure during which oxygenated blood is not adequately circulated throughout the body, additional support can be obtained through veno-arterial ECMO (VA-ECMO) . With VAAt present, initiation and management of ECMO can be cumbersome, as it requires a skilled and experienced provider to cannulate, as well as systemic anticoagulation therapy, and a perfusionist dedicated to bedside management. When applied for refractory cardiac failure, ECMO results in approximately 60% survival in pediatric patients and around 40% in adults.17Recent studies have identified ECMO as a reasonable alternative to traditional CPR in the setting of cardiac arrest, when appropriate resources are available. The use of VA-ECMO in patients who suddenly experience a loss of pulse due to compromised cardiac mechanical activity is known as extracorporeal CPR (E-CPR).n=48) versus 28 minutes when resuscitation was unsuccessful (n= 40).23Extracorporeal membrane oxygenation (ECMO) can be used in sudden cardiac arrest to restore blood flow when the heart has little or no intrinsic mechanical activity. When applied for sudden cardiac arrest, ECMO can double survival rates relative to CPR, even after 50 minutes of arrest.post hoc analysis of data from a prospective observational cohort, 48 OHCA patients were propensity-matched, with intact survival being significantly higher in the E-CPR group than in the C-CPR group.31Evidence generally supports the use of E-CPR when compared to C-CPR. However, the evidence varies. One systematic review of 25 observational studies concluded that due to low quality of evidence across studies there was no clear advantage to E-CPR over manual or mechanical CPR,Studies comparing the effectiveness of E-CPR for OHCA versus IHCA are inconclusive. A systematic review of 15 OHCA studies and 7 IHCA studies concluded that evidence did not support or refute the use of E-CPR for either group.34A systematic review of refractory OHCA found a survival rate of 22%, and 13% had satisfactory neurologic recovery,30Patient selection, time course of resuscitation, and patient age are likely determinants of E-CPR outcomes. A potential neurologic outcome improvement of 20% was demonstrated when patients were chosen based on being ≤65 years old, were witnessed having arrest and received bystander CPR, had no major comorbidities, and ECMO was initiated within 1 hour of arrest.41The identification and validation of prognostic markers of E-CPR outcomes would be valuable to inform patient selection. However, one review specifies that prognostic markers are not available for OHCA E-CPR,30While mechanical circulatory support with ECMO continues to be a promising therapy to improve resuscitation efforts, current systems are resource-intensive and have substantial morbidity which limits more widespread use. A perfusionist is required in ECMO to prime, de-bubble, and manage the system, and this is generally not available in an emergency. Surgeons, who may also not be immediately available, are needed to place the large-bore cannula that enables venous withdrawal and allows adequate flow without venous collapse in adults. In addition, the large cannula size increases vascular complications, especially limb ischemia and bleeding around the insertion site.At this time, guidelines for training and continuation of ECMO specialists suggest that physicians “successfully complete institutional training requirements for clinical specialists.”From 2006 to 2011 there was a 433% increase in ECMO use in adults in the United States.There are many gaps in knowledge that, if filled, could dramatically enhance the future success of ECMO, particularly when applied for cardiac arrest.2) are all actively monitored. Changes in these parameters can be indicative of both intrinsic and extrinsic issues of the circuit. For example, in the setting of a stable RPM, a flow rate drop may be reflective of decreased preload  or increased afterload .46The goal of VA-ECMO is to provide adequate perfusion to achieve hemodynamic stability and return and maintain oxygenation of vital organs. There are various hemodynamic parameters that must be considered when assessing ECMO flow. To reach adequate arterial oxygenation, ECMO flows generally need to reach >60% of normal cardiac output. This is achieved through the use of various types of blood pumps that provide pressure to drive blood through the circuit. As such, the revolutions per minute (RPM), flow (L/min), inflow and outflow pressures, and mixed venous oxygen saturation  is another surrogate marker of perfusion that is carefully monitored in all patients with hemodynamic compromise. The MAP can be roughly approximated as a function of diastolic and systolic pressures, or alternatively as a surrogate of cardiac output, central venous pressure, and systemic vascular resistance. In VA-ECMO, MAP is determined by a combination of native cardiac function and circuit pump output, which can occur with or without pulsatility depending on the relative driving force. Therefore, flow is adjusted based on multiple parameters including MAP, intrinsic cardiac function, systemic vascular resistance, or need for additional support with inotropic agents or other mechanical circulatory support devices.2) and lactate level as they directly correlate with tissue perfusion. Ideal settings will balance oxygen delivery and absorption, as reflected by a venous oxygen saturation >70% and serum lactate level less than 2.2 mmol/L or those trending towards normal. If SvO2 and lactate do not recover within a reasonable time period while on ECMO, it is possible that either ECMO may not be indicated (i.e. high output septic shock) or there is poor delivery of oxygen, which may require increased flows or transfusion.47Veno-arterial ECMO flows begin at 30 mL/kg/minute of ideal body weight with a desired central venous oxygen saturation >70%. However, in general, target perfusion for adults is 60 mL/kg/min.While hemodynamic and physiologic indicators of perfusion are essential for ECMO management strategies, there are substantial limitations. First, these indicators are based on population averages and therefore may not be sufficient for an individual patient. Second, these indicators are specific to whole-body physiology and thus do not represent what a specific organ requires versus what it is receiving. Finally, oxygen and blood flow delivery demands may shift based on many factors such as patient alertness and blood shunting to the gut if the patient is able to eat while on ECMO. While the latter is not relevant to ECMO applied for sudden cardiac arrest, all these limitations stem from not knowing tissue-level, organ-specific, real-time perfusion demand versus supply.Extracorporeal membrane oxygenation (ECMO) has profound implications for central arterial and left ventricular (LV) dynamics. As VA-ECMO displaces blood from a large venous reservoir to the arterial circulation, the patient’s volume status and intrinsic ventricular function are important components that impact LV volume. For example, if the patient has reduced preload , then, with ECMO initiation, the left ventricle will have a reduction in preload and relatively diminished LV volume. However, because VA-ECMO is often utilized in cardiogenic shock where there may be concomitant congestion, additional pressurization of the arterial system will increase systemic blood pressure. If the native LV function is preserved, LV systolic pressures will increase and overcome the LV afterload leading to an ejection of blood through the aortic valve. Additionally, if LV contractility is adequate, increases in flow and LV systolic pressure will not come at the expense of the LV diastolic pressure. However, if the native LV function is compromised, both LV systolic and diastolic pressures will increase with a concurrent reduction in stroke volume as the left ventricle fails to pump effectively against increased afterload imposed by an extracorporeal pump and pressurized arterial tree. This increase in LV afterload increases LV and left atrial wall stress, myocardial oxygen consumption, and may worsen pulmonary congestion, acute lung injury, and pulmonary hemorrhage, thereby worsening cardiopulmonary function and initiating a vicious cycle of mechanically driven injury.50LV venting to assist the ailing left ventricle in the setting of ECMO. Such strategies involve inotropic support, passive venting with atrial septostomy, central or peripheral surgical venting, trans-septal inflow catheters or cannulas, intra-aortic balloon pump, and Impella trans-aortic axial flow pumps . A recent systematic review found that LV venting, especially if done early (<12 hours after initiation of ECMO), appears to be associated with increased success of weaning and reduced short-term mortality.51In an attempt to mitigate increased LV diastolic pressures and LV volume, there have been several proposed methods for what has been termed Left ventricular volume also depends on the level of ECMO flow. In a previously validated model of the cardiovascular system that generated pressure–volume loops and Starling curves, the addition of VA-ECMO did not affect LV contractile function but, in the setting of a failing heart, increased afterload.While it is appreciated that ECMO flows often lead to overloading of the left ventricle to the point of limiting or even preventing ejection, there are many unknown aspects of this relationship. For example, it is not known which strategy is best for venting or what volume of LV distension requires venting. Also, the influence that time and the volume–time profile have on the detrimental manifestations of low native ejection is not known.Understanding arterial and ventricular dynamics during ECMO is important because overloading of the ventricle leads to depressed ejection, which may in turn result in blood stagnation and microemboli56Bleeding and clotting are the two most common VA-ECMO complications, with significant clot formation within the circuit or oxygenator occurring in approximately 10% of adult cases.To make a significant impact on cardiac arrest resuscitation outcomes, there is the obvious need for collaborative efforts between clinicians, engineers, and scientists to bridge physiologic and medical gaps. Improvements to ECMO technology has tremendous potential to bridge these gaps and further optimize ECMO as an E-CPR strategy for cardiac arrest resuscitation. Potential concepts for technology improvements are included here.As with other blood-wetted circulatory support technologies such as ventricular assist devices, ECMO systems are innately prone to complications such as thrombosis, hemolysis, and percutaneous site infection. Therefore, advances made in blood-wetted biomaterials and hemodynamically favorable geometric designs can benefit prospective ECMO circuits.A general strategy to limit thrombosis and enhance overall hemocompatibility in blood-wetted devices involves minimizing artificial surface area. Less surface area means fewer possible niduses for clot formation. In the context of ECMO, the largest artificial surface area is associated with the oxygenator, which is likely not available for minimization because oxygen diffusion also depends on surface area. Previous attempts to miniaturize the ECMO oxygenator experienced difficulties in one preclinical study.62Beyond reducing surface area, the blood-wetted surfaces have a role in thrombosis. Current ECMO circuits commonly utilize standard PVC tubingAnother approach to limit thrombosis and hemolysis entails pump design via computational fluid dynamics (CFD), which is an advanced computational technique that enables the three-dimensional prediction of flow field characteristics  around both stationary and moving solid structures. Using CFD enables continuous flow axial and centrifugal blood pumps to be designed and optimized so that zones of stasis and profiles of shear stress and shear rate that activate platelets and cause hemolysis are avoided.73It is also important to minimize the volume required to prime the ECMO circuit. Saline priming dilutes red blood cell concentration, and thus higher flows are necessary to provide the same perfusion than with less priming volume. Higher flows cause more blood damage via relatively increased shear rates and shear stress, therefore promoting thrombosis and hemolysis. Studies on flow velocity have also shown that high ECMO flow can lead to high wall shear stress and hypertension, ultimately leading to vascular complications and acute limb ischemia.74Another technology that may prove highly valuable to ECMO optimization is magnetic resonance imaging (MRI) because it is capable of evaluating cerebral blood flow and cerebral rate of oxygen consumption in real time. Specifically, brain blood flow can be measured directly,81When applied for resuscitation purposes, ECMO is often initiated after C-CPR, and in this manner the two therapies are complementary. Additional opportunities exist to optimize patient outcomes via synergistic therapies. Two additional examples of synergy involving ECMO are included here.The ECMO outcomes for sudden cardiac arrest may be improved with simultaneous therapeutic hypothermia. Beyond ECMO, therapeutic hypothermia is one of the few treatments that enhances cardiac and neurological function and survival outcomes. However, it takes hours to reach the targeted temperature even though a drop of only a few degrees is sought (commonly from 37°C to 34–36°C). If active cooling is delayed by just 20 minutes, survival benefit is lost, suggesting that an important therapeutic window exists during CPR for affecting sudden cardiac arrest outcome.The CHEER trial is a single-center, prospective, observational study for selected patients with refractory IHCA and OHCA. Patients in this study received mechanical CPR, E-CPR, and rapid intravenous administration of 30 mL/kg of ice-cold saline to induce intra-arrest therapeutic hypothermia. In that study, survival to hospital discharge was 60% in patients with refractory IHCA and 45% for OHCA.84In a porcine model of ventricular fibrillation arrest with ECMO, 2-hour therapeutic hypothermia during E-CPR offers an equal resuscitation success rate, but did not preserve post-arrest cardiac function nor reduce the magnitude of myocardial injury, compared to normothermic E-CPR.30In addition to improvement of cardiac arrest resuscitation outcomes, there is potential to address the organ shortage in the transplantation community.33There are abundant opportunities to improve future sudden cardiac arrest outcomes via progress in research and technology of ECMO, and through the synergy of CPR, ECMO, and therapeutic hypothermia. These advances will ultimately result in ECMO being more commonly utilized for sudden cardiac arrest at a larger distribution of clinical sites by a more broadly trained pool of providers. Organ transplant recipients may also benefit from expanded ECMO application that includes sudden cardiac arrest.


Dietary and lifestyle modifications remain the primary effective therapeutic interventions, although long-term efficacy is limited by poor adoption or adherence. Advances in the development and validation of non-invasive biomarkers and imaging modalities will facilitate diagnosis for affected children and adolescents and facilitate long-term natural history studies and the development of therapeutic interventions.Nonalcoholic fatty liver disease (NAFLD) represents a spectrum of disease that can range from isolated macrovesicular hepatocellular steatosis to nonalcoholic steatohepatitis (NASH) with or without fibrosis to cirrhosis. The prevalence of NAFLD has increased over several decades, mirroring the global obesity pandemic. NAFLD currently represents the most common etiology of chronic liver disease in children and adolescents worldwide. Disease presentation in childhood strongly suggests that these children may have unique susceptibilities and more severe long-term consequences. Emerging data demonstrate that the pathogenesis of early-onset NAFLD is secondary to a complex interplay involving genetic, metabolic, environmental, and microbiological factors. Such influences may begin Over the last decade, it has become a leading indication for liver transplantation in adults3, mandating the need for early recognition and treatment.Nonalcoholic fatty liver disease (NAFLD) represents a clinical spectrum of liver abnormalities resulting from excessive fat accumulation within hepatocytes. These abnormalities may range from simple steatosis to nonalcoholic steatohepatitis (NASH) with evident inflammation and cell injury. In some, NASH progresses to advanced fibrosis, cirrhosis, or increased risk for hepatocellular carcinoma. The prevalence of NAFLD has increased over the last several decades in tandem with the rise in obesity globally. Currently, NAFLD represents the most common etiology of chronic liver disease in children and adolescents, affecting nearly 10% of the pediatric population in some parts of the developed world4. Emerging data support the idea that individuals whose NAFLD is diagnosed in childhood have an increased risk of morbidity and mortality in adulthood5. These findings show that affected children may be afflicted with a more aggressive disease phenotype. It follows that, when NAFLD presents earlier, these children are at risk for a more advanced liver disease entering adulthood. Also, they may be at heightened risk for other comorbidities related to metabolic syndrome, including cardiovascular disease.Earlier-onset NASH may result from a distinct underlying pathogenesis, which is demonstrable by differences in certain features relating to histopathology, evident in a subset of prepubertal childrenin utero and perinatal stressors such as premature birth may predispose pediatric patients to NAFLD6. Recently, our understanding of NAFLD has improved significantly with advances in diagnosis, etiopathogenesis, genetic predispositions, and intervention.Some unique pediatric histologic features include a more pronounced fat accumulation, increased portal inflammation and fibrosis, and a less pronounced lobular inflammation and ballooning degeneration. Earlier presentation of disease, along with discrepant features of histology, suggests that children and adults may differ in regard to pathophysiology, and children may display enhanced genetic and environmental vulnerability. Some1. When autopsy studies from Poland, Turkey, and the United States are considered, the worldwide prevalence of NAFLD ranges from 4.2 to 9.6% and increases to 38% in those with obesity9. Hispanic children, particularly of Mexican descent, have the highest incidence of NAFLD when body mass index (BMI) z-score, gender, and age are controlled for, whereas black children, who have the lowest reported incidence, seem to be relatively protected from the accumulation of hepatic fat (HF)10. There is a male predominance in pediatric studies and the problem is most often detected in the early pubertal period11.The prevalence of pediatric NAFLD is difficult to ascertain since most studies use indirect indicators of hepatic steatosis. Furthermore, the definitive diagnosis of NASH requires a histologic diagnosis via liver biopsy, which is not feasible in population-based studies. With indirect measures, including ultrasound-based imaging or elevated serum aminotransaminase values, the prevalence of NAFLD has been reported as 7% among children and adolescents in the general population and upwards of 34% among obese childrenIt is important to recognize that current prevalence studies likely do not reflect the true prevalence of disease given the lack of uniform screening methodologies and consistency in diagnostic criteria. Data on the prevalence of NASH, as opposed to NAFLD without NASH, require autopsy-based studies of liver histology in children and adolescents dying from non-medical causes.13.The clinical spectrum of NAFLD results from specific lipotoxicity (or lipotoxicities) with or without augmented oxidative stress that is found in connection with chronic excess of hepatic lipids. Hepatocellular steatosis in some provides the substrate for invoking hepatic inflammation that predisposes patients to cell injury, apoptosis, stellate cell activation, and production of excess matrix. Why certain individuals develop progressive disease whereas others are less affected remains less clear. Although the majority of children with NAFLD are obese, not all children with obesity develop NAFLD. NAFLD can occur, albeit much less often, in lean individuals. In these cases, further evaluation is especially crucial to assess for alternative etiologies. Several conditions, such as Wilson’s disease, appear similar to NAFLD and may have available therapies15. In an epidemiologic study, increased fructose intake was associated with NAFLD in adolescents with obesity16. Fructose promotes increased visceral adiposity, decreased insulin sensitivity, and increased hepaticde novo lipogenesis which potentiates intrahepatic fat accumulation18. Visceral obesity and insulin resistance are important risk factors for pediatric NAFLD19. Increasingly, sedentary lifestyles and diminished attention to healthier diets are the primary drivers for the increase in obesity prevalence.Clear risk factors for NAFLD include male gender, obesity, and increased waist circumference21. Data regarding the effect of treatment with continuous positive airway pressure therapy on NAFLD are mixed. Long-term prospective studies of a larger scale are necessary, particularly in the pediatric population22.The reported incidence of obstructive sleep apnea (OSA) in pediatric NAFLD is 40 to 60%. Several studies have suggested that chronic intermittent hypoxia secondary to OSA and excess production of reactive oxygen species may contribute to the progression of pediatric NAFLD and increased fibrosis independently of BMIet al. demonstrated that NAFLD was significantly more common in siblings (59%) and parents (78%) of children with NAFLD when compared with siblings (17%) and parents (37%) of BMI-matched children without NAFLD23.NAFLD appears to have a strong heritable component based on ethnic differences in prevalence and clustering within families independently of adiposity. SchwimmerPNPLA3), transmembrane 6 superfamily member 2, and glucokinase regulatory protein (GCKR) are associated with the risk of NAFLD in children28.Genetic polymorphisms of patatin-like phospholipase domain–containing protein 3  via the portal vein29.There has been an increased recognition regarding the role of gut microbiota and an association with the development and progression of NAFLD. Patients with NASH appear to have intestinal microbiota enriched in alcohol-producing bacteria, such as30. NAFLD and increased disease severity were also associated with an increased abundance of genes encoding for pro-inflammatory bacterial products30. Alterations in the intestinal microbiome may contribute to the pathogenesis of NAFLD and should be further evaluated as markers of disease and severity.In a recent study of children with obesity or NAFLD, the intestinal microbiomes of children with NAFLD were found to have a decreased α-diversity and increased variation in β-diversity, otherwise known as dysbiosis, when compared with obese children without NAFLD32.Many aspects of the mother–child dyad have been examined to identify potentially modifiable risk factors for infant and maternal NAFLD. Maternal obesity, antepartum hyperglycemia, gestational diabetes, excessive weight gain during pregnancy, cesarean section, early-life exposure to antibiotics, and the absence of breastfeeding have all been associated with increased risk for obesity in offspring and the development of NAFLD34. SeeAltered intestinal microbiomes in the infants of obese mothers result in altered bile acid metabolism, increased short-chain fatty acids, and increased intestinal permeability with bacterial translocation. Dysbiosis also has implications for the bone marrow with recruitment of poorly functioning macrophages. Hepatic inflammation secondary to the translocated bacteria, or their endotoxins which stimulate hepatocyte TLRs triggering a pro-inflammatory cascade, is inadequately controlled because of these hyporesponsive macrophages. A secondary hit, such as that found in Western diets, results in hepatic steatosis and obesity11 and the North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition (NASPGHAN)14 published independent guidelines for the screening, diagnosis, and management of pediatric NAFLD.There is a current discrepancy in recommendations between societal guidelines in regard to the utility of screening for pediatric NAFLD. In 2017, both the American Association for the Study of Liver Diseases (AASLD)14. These recommendations are based on expert opinion, whereas AASLD Guidelines do not recommend such screening in adults or children; this is due to a lack of established evidence related to current benefits associated with screening, particularly in the current environment where pharmacologic interventions remain unapproved11. The guidelines purport that since lifestyle modification aimed at weight loss, improved diet, and exercise remains the standard recommendation for all overweight children and adults, a diagnosis of NAFLD will not alter management. This essentially calls into question the utility of screening in the absence of alternative treatment. However, clinicians should consider that confirmation of an existing comorbidity, such as NAFLD, in pediatric obesity may have a role in improving adherence to lifestyle modifications.NASPGHAN recommends screening for obese children beginning at ages 9 to 11 years as well as overweight children with additional risk factors, including insulin resistance, dyslipidemia, or a family history of NAFLD or cryptogenic cirrhosis. Screening consists of serum alanine aminotransferase (ALT) measurement, using the upper limit of normal (ULN) of 22 U/L for girls and 26 U/L for boys. Patients with an ALT value persistently greater than twice the ULN for at least three months should undergo further evaluation and work-up35. They stated that liver biopsy is required for a definitive diagnosis of NAFLD or NASH but is not proposed in screening. In agreement with AASLD pediatric guidelines, liver biopsy should be performed to exclude other diseases, if advanced disease is suspected, before pharmacologic or surgical treatment, and in clinical research trials35.In 2015, the European Society for Pediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) Hepatology Committee published a position paper regarding the role of liver biopsyAlthough percutaneous liver biopsy remains the clinical and research standard for the diagnosis of NASH and for assessing histologic improvement during treatment, several imaging modalities have demonstrated promise as surrogate markers of certain features relating to histologic improvement.36.Vibration-controlled transient elastography (VCTE) is an ultrasound-based modality that measures liver stiffness as an estimate of fibrosis. This technique is widely available at point of care, requires minimal training, and provides rapid and reproducible results. VCTE has demonstrated sufficient accuracy for predicting the presence and stability of fibrosis in children with biopsy-proven NAFLD and other chronic liver diseases37.Shear wave elastography (SWE) is another ultrasound-based technique that can be used with a conventional ultrasound machine, thereby allowing elastography and anatomical evaluation to be performed in the same sitting. Small cohort studies suggest that SWE is reasonably accurate in distinguishing high- from low-grade fibrosis with cutoff values similar to those reported for adults. This technique requires further validation15. This surrogate requires further validation with larger sample sizes at independent sites.Acoustic radiation force impulse (ARFI) is an ultrasound-based technique that estimates liver fibrosis by assessing tissue stiffness through the evaluation of wave-propagation speed. An ARFI cutoff value of less than 2 m/s reportedly can distinguish between mild and severe fibrosis with 100% sensitivity in children40. Utility appears to be optimal for patients with the highest and lowest degrees of steatosis, and the diagnostic accuracy regarding the mild to moderate range of HF content needs to be improved38. There are insufficient data to relate changes in MRI fat fraction to changes in important NASH features, including inflammation and cell injury. MRI-estimated steatosis may be obfuscated by fibrosis stage. Magnetic resonance elastography offers a potential approach and has been reported to detect advanced fibrosis in pediatric patients, including severely obese patients, with an accuracy of 90% or more41. Barriers to routine use include cost, lack of universal availability, and lack of child cooperation.Although magnetic resonance imaging (MRI) has not been adequately validated as a surrogate marker of histologic improvement in children with NAFLD, emerging data are promisingMaintaining a healthy lifestyle is the cornerstone of NAFLD prevention. Pediatric health-care providers must regularly assess BMI z-scores. This assessment will allow for an allotment of time during routine health-care visits to discuss appropriate diet, exercise, and family involvement in maintaining weight within an appropriate range. This often requires that obstacles to implementing advice be identified with the help of other ancillary providers, including dietitians, social workers, exercise physiologists, psychologists, and educators.32. These potentially modifiable risk factors may present an opportunity for early disease prevention. Controlling antepartum hyperglycemia, preventing gestational diabetes, and avoiding excessive weight gain during pregnancy may lead to a decrease in childhood obesity and NAFLD. The promotion of prolonged breastfeeding may also provide long-term benefit for both mother and child32. Further studies are needed to evaluate the long-term benefit of such interventions.As previously mentioned, growing evidence suggests that perinatal factors and aspects of the maternal–infant dyad play a contributory role in the development of obesity and the metabolic syndrome, including its hepatic component, NAFLD43. Fibrosis measures currently accepted by the US Food and Drug Administration (FDA) require histologic assessment obtained via liver biopsy, which is not always feasible in pediatric studies, especially in those controlled with a placebo arm. In children, NAFLD comorbidities  are also important comorbidities to treat in order to improve future outcomes.End-points for treatment studies vary substantially. Commonly pursued and easily measured goals are a decrease in HF fraction and a decrease in or resolution of inflammation and cell injury  or fibrosis, which are difficult to measure without liver biopsy. This is more difficult in pediatric populations in particular. A sustained decrease in serum ALT from baseline  is commonly used as a surrogate marker for earlier stages studies relating to histologic improvement and response to treatment14. Hypocaloric, low-carbohydrate diets and low-fat diets provide similar reductions in intrahepatic fat content as long as weight loss is achieved45. In a randomized clinical study of adolescent boys with NAFLD, a home-delivered diet that was low in free sugars resulted in significant improvement (as assessed by MRI) in hepatic steatosis compared with usual diet46.Lifestyle modification, encompassing dietary modifications and a focus on increased physical activity, constitutes first-line treatment for NAFLD48. Barriers to behavioral change may relate to socioeconomic barriers, including access to affordable healthy food and safe recreational areas and culture-specific beliefs relating health to increased weight.Though proven effective, this treatment modality has inherent barriers. As patients with NAFLD often do not exhibit physical symptoms, they frequently lack the motivation required to alter contributory habits and fail to implement prescribed lifestyle changes. Studies confirm that long-term efficacy of diet and lifestyle management in decelerating weight gain has limited success because of inadequate complianceGiven the inherent difficulties of sustained lifestyle modification, alternative bariatric surgical approaches, including Roux-en-Y gastric bypass (RYGB), laparoscopic adjustable gastric banding, and laparoscopic sleeve gastrectomy (LSG), have been explored, although data are limited to adolescents.49. The authors concluded that bariatric intervention in pediatric patients with morbid obesity results in sustained and clinically significant weight loss and improved NASH but has the potential for serious complications. Therefore, current data are not sufficient to recommend widespread use for weight loss in adolescents without other major comorbidities. As long as appropriate long-term follow-up is provided, RYGB may be considered an effective option for adolescents with extreme obesity associated with other concerning morbidities49.In 2015, the ESPGHAN Hepatology Committee published a position paper regarding the role of bariatric intervention in severely obese children and adolescents with or without NASHet al. conducted a prospective, multicenter observational study and examined outcomes among obese adolescents with biopsy-proven NAFLD who underwent LSG50. One year after intervention, 20 patients who underwent LSG lost 21.5% of their baseline body weight compared with patients who underwent lifestyle intervention with a decrease from baseline of 1.7%. Six of the six surgical subjects with fibrosis stage 2 were reported to have fibrosis resolution. The authors reported significant improvements in hypertension, hyperlipidemia, and OSA in those undergoing LSG50.Manco42. Other proposed therapies include probiotics, insulin sensitizers, and anti-inflammatory, lipid-lowering, and anti-fibrotic agents. Current data are insufficient to support the use of these other agents in pediatric patients. A composite of completed and current pediatric treatment trials is listed inAt present, there are no FDA-approved pharmacologic agents for the treatment of NAFLD in children or adults. Evidence suggests that d-alpha tocopherol provided at 800 IU orally daily significantly resolves NASH in some patients (both children and adults) with biopsy-proven NASH. Long-term safety remains to be established51. Though widely available, these surrogates have not demonstrated sufficient relation with histology. Continued development of age-validated non-invasive biomarkers and imaging will facilitate future study conduct and monitoring of therapeutic response.One of the primary challenges in pediatric NAFLD has been the variability in clinical trial designs with relatively small sample sizes, heterogeneity of populations, and length of treatments. The absence of validated or accepted non-invasive markers to assess for disease diagnosis or response remains a significant barrier to clinical trial designs and monitoring. Treatment end-points vary across studies. ALT and ultrasound are frequently used as primary outcome surrogates in lieu of liver biopsy given the mandates for trial participation benefits related to clinical research in minorsin utero. Lifestyle modifications involving physical activity and dietary changes remain the only practical therapeutic intervention now available, albeit long-term efficacy is limited by poor adherence. Advancements in non-invasive biomarkers and imaging techniques offer promise in assessing the presence and changes in steatosis and fibrosis. Further validation will facilitate longitudinal, natural history, and therapeutic efficacy studies.Pediatric NAFLD has emerged as the leading cause of chronic liver disease in children and adolescents worldwide. The pathogenesis of early-onset NAFLD is secondary to a complex interplay involving distinct genetic, metabolic, environmental, and microbiological factors which may begin


Recently revised public health guidelines acknowledge the health benefits of regular intermittent bouts of vigorous intensity incidental physical activity done as part of daily living, such as carrying shopping bags, walking uphill, and stair climbing. Despite this recognition and the advantages such lifestyle physical activity has over continuous vigorous intensity structured exercise, a scoping review we conducted revealed that current research in this area is, at best, rudimentary. Key gaps include the absence of an empirically-derived dose specification , lack of acceptable measurement standards, limited understanding of acute and chronic (adaptive) effects of intermittent vigorous bouts on health, and paucity of essential information necessary to develop feasible and scalable interventions . To encourage collaboration and research agenda alignment among groups interested in this field, we propose a research framework to further understanding of vigorous intermittent lifestyle physical activity (VILPA). This framework comprises four pillars aimed at the development of: (a) an empirical definition of VILPA, (b) methods to reliably and accurately measure VILPA, (c) approaches to examine the short and long-term dose–response effects of VILPA, and (d) scalable and acceptable behavioural VILPA-promoting interventions.The online version of this article (10.1007/s40279-020-01368-8) contains supplementary material, which is available to authorized users. Physical inactivity, or insufficient physical activity (PA), is a major cause of non-communicable chronic disease responsible for at least 5 million premature deaths per year . Global any vigorous exercise for at least 15 continuous minutes a month [outside the leisure-time domain.Vigorous PA  PA encompasses activities of daily living that require little or no dedicated time commitment and are benefits . LifestyPrompted by changes in the 2018 US  PA guideAdopting a daily pattern of VILPA is theoretically akin to practicing popular exercise regimens that also emphasize non-continuous vigorous intensity exercise, such as high intensity interval training (HIIT). HIIT is a structured exercise approach that improves key cardiometabolic health markers, particularly cardiorespiratory fitness (CRF) . HoweverInformed by a systematic scoping review conducted to map the emerging research area of VILPA and identify critical research gaps, the aim of this Leading Article is to highlight future research directions on this topic across four pillars: (a) an empirical definition of VILPA, (b) methods to reliably and accurately measure VILPA, (c) approaches to examine the short and long-term dose–response effects of VILPA, and (d) scalable and acceptable behavioural VILPA-promoting interventions.We searched three databases  to identify any peer-reviewed literature  relevant to VILPA. As no standardized terminology exists to describe what is herein referred to as VILPA, we used terms that reflect roughly the same concept as VILPA, such as “high intensity incidental PA” , “exercino health value to intermittent bouts of lifestyle PA, regardless of intensity [absence of evidence (to support a minimum bout duration of 10 min) rather than direct evidence of the health enhancing properties of shorter and intermittent bouts. With the exception of certain HIIT protocols involving very short exercise bursts , the minimum specification of a “short bout” of health enhancing PA in still unknown, particularly in the context of everyday life and outside the realm of purposeful exercise. A recent systematic review [Until recently, major authorities, including the WHO , recommentensity . The 201ntensity , 30 and ntensity  PA guidec review  concludec review .One of the first requirements for advancing the VILPA research agenda is to empirically and operationally define what future studies should consider a “VILPA bout” in terms of minimum time needed to reach absolute and relative vigorous intensity during activities of daily living. The relative intensity aspect of such a definition will likely be age-specific to incorporate functional status and relative fitness. Examples of future research needs include studies to determine the minimal duration required for common lifestyle physical activities  performed to reach vigorous intensity defined objectively  or subjectively  . To maxiObservational cohort studies with questionnaire-based PA measures account for most evidence used in PA guidelines development globally , 22, 32.Measuring capacity of accelerometers varies by accelerometer placement. For example, waist-mounted accelerometers can collect frequency, duration, and mode information as well as speed of pace-based indicators of intensity, but cannot capture intensity modulation due to changes in surface gradient . Additionally, the existence of a dozen different waist-mounted accelerometry standards (cut-off points) to define vigorous PA  is challIn summary, there is no established and validated method to capture frequency and duration of VILPA bouts in free-living conditions. Laboratory-derived VILPA measurement could be the first step, followed by their cross-validation within and between observational cohorts which are heterogenous with regards to cardiorespiratory fitness and other physiological markers known to respond to vigorous PA. Devices such as the Actiheart, which is validated against electrocardiogram (ECG) in both laboratory  and in fRecent proof-of concept trials in young adults suggested that as few as three 20-s VILPA-mimicking stair climbing bouts at > 85% of maximal heart rate (termed “exercise snacks”) on 3 days per week have measurable effects on cardiorespiratory fitness and aerobic power improvement in young adults within only 6 weeks , 41. SucFuture research would be significantly enhanced by studies that examine a broader range of VILPA activities. Depending on type of dwelling/workplace and geographical location, stair climbing and walking on a gradient could offer opportunities to attain a vigorous intensity stimulus for many. Modulation of intensity by walking pace , and/or Once acceptable device-based VILPA measurement standards are in place, large scale observational studies linked with surrogate  and long-term  outcomes will be an essential link to better understand the health effects of VILPA. Proof of concept trials with longer duration interventions would establish long-term efficacy for improving health outcomes, paving the way for better evidence-based behavioural interventions.The majority of PA interventions are developed with a view to increasing continuous moderate to vigorous PA (MVPA). VILPA could be examined both as a stand-alone, and complementary to continuous MVPA, interventions. First, VILPA could be applied across a number of settings , and adapted for various physical, social and cultural contexts, and thus may have wider reach across different population groups. Assuming its theoretical feasibility advantage in some parts of the population Fig.  will be Technology-based PA approaches, such as wearable technologies  and smartphone apps, are prolific in both number and usage. Current offerings do not adequately address VILPA. For example, many apps offer guided planned exercise workouts , or the ability to track workouts ; workout-based PA is undertaken during leisure time, and typically in sustained bouts. Somewhat closer to VILPA are the short workout apps , however, these are still planned and structured. More in line with the incidental nature of VILPA are consumer wearable technologies and step-counting apps. Yet these products typically emphasise overall volume of activity  rather than accumulation of PA through intermittent bouts, and increase light-to-moderate rather than vigorous activity . Many chAdditional considerations apply to VILPA interventions aimed at older populations. The suitability and acceptability of incorporating VILPA in daily living would need to be evaluated with healthy older adults prior to focusing on clinical or at-risk populations of older adults. Assessment of risk also needs to be considered, including cardiovascular, respiratory and musculoskeletal. This would also allow the identification of acceptable strategies for facilitating VILPA without alarming older adults about potential health risks due to the physiological cues/responses linked with this exercise intensity  , 51. ExtQuick bursts of activity that do not require specific equipment/preparation/time investments may be particularly attractive to older adults, especially those who care for grandchildren where opportunities for VILPA may include carrying a child or playing with children . Ensurinindicative research priorities across the proposed four pillars of the VILPA framework. Recent progress with PA measurement capacities, mHealth tools, and changes in PA guidelines provide new opportunities to develop targeted interventions focusing on VILPA to improve population health. A key premise of the proposed research framework is that VILPA is a complementary and not a competing approach to traditional continuous MVPA, which is already well embedded in current PA guidelines and has been researched for several decades. Depending on the population and context, future interventions could test both stand-alone VILPA or VILPA combined with other more established PA approaches. An important outcome of such research efforts would be to provide members of the public, practitioners, and policy makers with new evidence to capitalize on this potentially feasible health-enhancing form of PA. We hope that the proposed framework will encourage research in this field, contribute to the alignment of research agendas of different research groups, and promote international multidisciplinary collaboration.We have provided an overview of the key issues and knowledge gaps to assist future research into defining, measuring and understanding the health effects of VILPA as an emerging strategy to achieve public health recommendations. Table Supplementary file1 (DOCX 35 kb)Supplementary file2 (DOCX 123 kb)Below is the link to the electronic supplementary material.


Pre-metastatic niches provide favorable conditions for tumor cells to disseminate, home to and grow in otherwise unfamiliar and distal microenvironments. Tumor-derived extracellular vesicles are now recognized as carriers of key messengers secreted by primary tumors, signals that induce the formation of pre-metastatic niches. Recent evidence suggests that tumor cells can disseminate from the very earliest stages of primary tumor development. However, once they reach distal sites, tumor cells can persist in a dormant state for long periods of time until their growth is reactivated and they produce metastatic lesions. In this new scenario, the question arises as to whether extracellular vesicles could influence the formation of these metastatic niches with dormant tumor cells? (here defined as “sleepy niches”). If so, what are the molecular mechanisms involved? In this perspective-review article, we discuss the possible influence of extracellular vesicles in early metastatic dissemination and whether they might play a role in tumor cell dormancy. In addition, we comment whether extracellular vesicle-mediated signals may be involved in tumor cell awakening, considering the possibility that extracellular vesicles might serve as biomarkers to detect early metastasis and/or minimal residual disease (MRD) monitoring. There is evidence suggesting that tumor cells disseminate from the very beginning of primary tumor formation . DissemiInterestingly, extracellular vesicles (EVs) have emerged as important messengers in cell-cell communication , althougMetastatic lesions preferentially develop in specific anatomical locations , suggestThe ability of different organs to support DTC growth can be classified as dormancy-permissive or dormancy-restrictive . It has Alternatively, dormant tumor cells acquire stem cell-like properties and they overexpress pluripotential and self-renewal genes in dormant niches . For exa+ T cells induce tumor cell dormancy and indeed, spontaneous metastases can be controlled and maintained in a dormant state by the wild-type (WT) immune system in mouse models, with no application of any anti-cancer treatment  which can indirectly contribute to tumor dormancy by stabilizing the endothelium  cells , the cytOther innate immune cells like macrophages are responsible for the survival of dormant breast cancer cells just after their extravasation into the lung. Aberrant expression of vascular cell adhesion molecule-1 (VCAM-1) was seen to favor the interaction of extravasated breast cancer cells with metastasis associated macrophages, an interaction that activates Akt via Ezrin, and that eventually offers metastatic cells protection against cytokine induced apoptosis . However+ T cell immune evasion, since MHC-I remains intact in tumor cells implanted into immunodeficient or T cell immunodepleted mice  in immunogenic niches might also favor the dormant niche. Interestingly, bone marrow is one of the best characterized dormant niches and it represents an important reservoir for Tregs . Since min vivo model of breast cancer dissemination  and small EVs (sEVs) , wherebyin vitro. The in vivo experiments lack from verification of cell death after engraftment of metastatic breast cancer cells treated with MSC-derived exosomes. Further in vivo data and cell death analysis is needed to understand the relevance of these findings. Controversially, MSC EVs were only seen to suppress the metastatic potential of parental MDA-MB-231 cells but not that of metastatic MDA-231 organ tropic models , with a concomitant reduction of cancer cell proliferation  derived exosomes contribute to breast cancer cell homing, survival and dormancy when studied in an feration . Exosomeferation .in vitro; (2) the dose of exosomes and the models used  are not always clearly defined; and (3) these studies are restricted to a limited number of cell models and immunodeficient mouse models, which limits the interpretation of the results. Further data in vivo and in immunocompetent models will help to understand if stroma-secreted EVs are involved in regulating tumor cell dormancy.Taking all these data together, if stromal-derived EVs influence tumor cell dormancy is a matter of current debate. We have reviewed the information in the literature and draw any conclusion would be premature at this time. Works showed that stromal cell-derived EVs may affect some characteristics of tumor cells such as proliferation, further data is needed to support their role in DTC dormacy . Severalin vivo setting, analyzing the involvement of EVs in this process is very challenging. The development of models to properly demonstrate the influence of endothelial cell- and immune cell-derived EVs will be necessary to demonstrate their relevance, and their role in vivo must be compared with that of soluble and intrinsic factors.Similarly, while endothelial cells play a central role regulating tumor cell stemness, there is very little data suggesting that EVs secreted by endothelial cells are involved in tumor cell dormancy. In fact, endothelial cell-derived EVs have been implicated in tumor cell awakening rather than dormancy . As an exception to this statement, it was recently described that endothelial cells in the bone marrow supply miR-126 to chronic myelogenous leukemia stem cells to support quiescence, which correlates with poor prognosis. MiR-126 is highly expressed in normal HSCs and hematopoietic progenitor cells and restrains cell-cycle progression during hematopoiesis. However, in leukemic cells, miR-126 is down-regulated through a BCR-ABL-dependent mechanism. EVs from the surrounding bone marrow endothelial cells has been described as the main source to compensate the downregulation, this way allowing the reinduction of quiescence in a percentage of the leukemic cells, contributing to self-renewal, engraftment and perpetuation of the disease . NeverthVery little is known about the role of EVs derived from immune cells in directly controlling tumor cell dormancy. There is no data in the literature linking T Cell or NK-cell derived EVs to this phenomenon. EVs derived from specific sub-populations of immune cells could have different outcomes at dormant niches. Exosomes derived from M2 macrophages reduce proliferation and limit cell cycle progression in bladder cancer models, while M1 macrophages appear to be involved in tumor cell awakening , as will+ EVs and reinforce immunosuppression in niches. However, there is no data yet supporting this hypothesis in a metastatic setting.Interestingly, tumor-secreted EVs may contribute to immunosuppression by favoring DTC survival. Several tumor types release EVs that carry PD-L1 on their surface, mostly in the form of exosomes, and these may suppress the activity of CD8 T cells and facilitate tumor growth. Indeed, PD-L1 expression in the plasma of patients with several tumor types is correlated with a worse patient outcome and weaker immune responses . TherefoA particular challenge when considering metastasis is to understand which signals are involved in the outgrowth of quiescent DTCs . Multiplin vitro, whereas tumor-derived EVs may contribute to tumor progression and could be involved in tumor cell awakening , IL-8/CXCL8, vascular endothelial cell growth factor (VEGF) and monocyte-chemotactic protein-1 (MCP-1)  . Similarin vitro . Elsewhein vitro . Overallin vitro . The secin vitro . Analyziakeners”  as opposakeners” .Similarly, there is growing evidence that leukemic cells can modulate the EVs in their host bone marrow microenvironment to survive and expand. AML-derived EVs suppress normal hematopoiesis by inhibiting protein synthesis and they induce long-term hematopoietic stem cell quiescence through the internalization of miR-1246  or by inIt has been proposed that the primary tumor is involved in the preparation of secondary organs for the arrival and growth of tumor cells, known as the pre-metastatic niche (PMN) . During There is evidence that endothelial cell-derived EVs influence tumor cells and for example, human brain microvascular endothelial-derived exosomes are thought to favor lung cancer tumor cell survival and resistance to apoptosis by increasing the levels of S100A16 . In a moTumor-derived EVs also contribute to tumor angiogenesis and the disruption of the endothelial vascular barrier. Cell-to-cell communication between cancer cells and endothelial cells via EVs, is one of the most relevant mechanisms promoting vascular leakiness, angiogenesis and vascular remodeling reported in the literature . Tumor-dAnother hallmark of PMN formation that may be also relevant to tumor cell awakening is ECM remodeling . Fibrone+ macrophages, which eventually enhance metastasis , while diminishing the numbers of CD8 T cells and NK cells, skewing the microenvironment toward an immunosuppressive state and promoting metastasis  or circulating tumor-derived factors, in particular, circulating tumor DNA (ctDNA) . The qua cancers . Another cancers . Further cancers . ComplemDue to their heterogeneous content , their ubiquitous production by body cells and detection in most biological fluids, circulating EVs could be useful for specific or multiplatform analyses to provide an accurate evaluation of cancer disease at early time points, during progression, therapy and post-treatment facilitating the detection of MRD and relapse anticipation .Each technique has its own pros and cons. For example, CTCs have been mainly used to understand the biology of early metastatic spread and resistance to established therapies, they require higher amount of plasma and specific equipment for isolation and detection . ctDNA aIn the particular case of dormancy, distinguish circulating dormant cells could represent an arduous task due to the limited number of these cell populations. Similarly, defining the EV signatures related to “dormant” and “awakened” tumor cells is far from their use in the clinic. Since miRNAs in circulating EVs have diagnostic and/or prognostic potential for many cancer types, this may be a potential way to identify novel biomarkers. In exosomes isolated from plasma/serum of cancer patients, miR17-92a and miR-19a are correlated with increased colon cancer recurrence or a worse prognosis . ExosomaSimilarly, defining an EV signature related to DTC awakening could potentially be of interest. While CTCs have been used successfully in the last years to detect early metastatic cell awakening, there are several limitations in sensitivity that must be solved in the case of EVs to play a relevant role in this scenario . Due to One of the main advantages of using liquid biopsies to detect awaked DTCs is that can be identified in pre-symptomatic patients after surgery, opening the possibility of using them as an early marker and screening tool of MRD. In addition, non-invasive liquid biopsies confer the advantage and the opportunity to follow patients during and after treatment, providing an accurate and real time read-out of tumor development with a minimal risk to patients. CTCs and ctDNA have demonstrated their use for MRD detection in plasma . In addiDefining the signals released by the awakened DTCs could define novel biomarkers that help to identify MRD. However, liquid biopsies to determine dormancy have several limitations. First, since DTCs remain at low numbers within niches, the representation of their EVs in the bloodstream could be confused with EVs released from normal tissues. Second, it is not clear whether all tumor sub-clones at different metastatic locations will secrete and distribute EVs equally into the bloodstream, or if this might be influenced by other factors, such as the extravasation properties of the tissues they have colonized. Third, there is heterogeneity in the dormant niches within tissues in terms of how their surrounding cell microenvironment promotes the quiescence or reawakening of DTCs. Fourth, works shown in this section come from patients that had already reactivation of the residual disease and disruption of dormancy. In order to detect signals of tumor reawakening by liquid biopsy a strong effort should be made to design new protocols and collect samples  in a routinely basis  after surgery to follow up disease reactivation.Thus, it is important to expand the dormant EV signatures to stromal EVs rather than just limiting these to tumor-derived dormant EVs. Moreover, optimized protocols for EV isolation and cargo analysis are required, including the use of novel biofluids or combined sources .in vitro. Thus, it is necessary to overcome this limitation and demonstrate their relevance in vivo. In addition, metastasis in human patients has traditionally been addressed once the secondary lesion has been detected, meaning that dormancy had already been disrupted. Hence, human data concerning DTC awakening is very scarce . Another main question to be solved is whether dormant niches may be influenced by naïve stroma-derived EVs or alternatively if dormant niches may be influenced by stroma-derived EVs after being primed by exosomes from primary tumors or primed by the first arriving DTCs.Regarding the involvement of endothelial cell-derived EVs in DTC awakening, works do not clarify if these interactions are happening during early or late DTC dissemination. The clinical context is also hard to depict for these interactions. How it is possible that EVs may be relevant years after tumor resection? Is pre-metastatic niche once created able to lasts for years, even decades? Can tumor cells be influenced by endothelial cell-derived EVs in this setting? or Can DTC secrete enough EVs to trigger their own awakening? Are external factors involved  formation)? While both awakening and PMN formation involve tumor cells and their microenvironment, the molecular mechanisms involved in DTC awakening and the involvement of EVs have yet to be formerly demonstrated.Another crucial issue that remains to be demonstrated is the potential to detect tumor cell awakening-derived EVs in liquid biopsies. The identification of biomarkers to detect patients with an active disease due to DTC awakening could have a major impact in the clinic. While this is plausible, several limitations must be overcome, and as such, it will be necessary to identify biomarkers secreted by “awakened” DTC that can be assessed and to confirm that they can be detected in liquid biopsies. Similarly, their correlation with disease outcome must be defined.Thus, it is still early to determine the true potential of liquid biopsies to detect tumor cell awakening or their derived EVs. Similarly, defining the relevance of EVs derived both from tumor and stromal cells in tumor cell awakening and therapy resistance would help establish their relevance in the clinical setting.HP developed the idea and wrote the manuscript. AH-B wrote the manuscript and designed the figures. LN wrote the manuscript. All authors contributed to the article and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Antimicrobial resistance is a growing global health concern. Antimicrobial stewardship (AMS) curbs resistance rates by encouraging rational antimicrobial use. However, data on antimicrobial stewardship in developing countries is scarce. The objective of this study was to characterize antimicrobial use at the University Teaching Hospital (UTH) in Lusaka, Zambia as a guiding step in the development of an AMS program. This was a cross-sectional, observational study evaluating antimicrobial appropriateness and consumption in non-critically ill adult medicine patients admitted to UTH. Appropriateness was defined as a composite measure based upon daily chart review. Sixty percent (88/146) of all adult patients admitted to the general wards had at least one antimicrobial ordered and were included in this study. The most commonly treated infectious diseases were tuberculosis, pneumonia, and septicemia. Treatment of drug sensitive tuberculosis is standardized in a four-drug combination pill of rifampicin, isoniazid, pyrazinamide and ethambutol, therefore appropriateness of therapy was not further evaluated. The most common antimicrobials ordered were cefotaxime (n = 45), ceftriaxone (n = 28), and metronidazole (n = 14). Overall, 67% of antimicrobial orders were inappropriately prescribed to some extent, largely driven by incorrect dose or frequency in patients with renal dysfunction. Antimicrobial prescribing among hospitalized patients at UTH is common and there is room for optimization of a majority of antimicrobial orders. Availability of certain antimicrobials must be taken into consideration during AMS program development. In 2015, the World Health Organization (WHO) officially recognized the growing problem of worldwide antimicrobial resistance, leading to the development of a global action plan to increase awareness and surveillance, improve antimicrobial prescribing practices, and reduce the incidence of infections.) and penicillin-resistance in Streptococcus pneumoniae, although poorly reported, was 26.7%.[Although antimicrobial treatment selection is largely driven by the limited formulary and availability of many antimicrobials in resource-limited areas, the results of this study highlight discrepancies that exist between clinical practice, Zambian infectious diseases guidelines, and national guidelines from more developed parts of the world.–19 For eas 26.7%. UnfortunOur study highlights the critical need for epidemiological surveillance of microbial resistance in Africa, which could then guide clinical decision-making and AMS programs. The global implementation of AMS programs is necessary to combat the rise of multi-drug resistant (MDR) organisms and related morbidity and mortality. Limited data is available describing the characterization of antimicrobial use and AMS program implementation in resource-limited areas. More specifically, to the best of our knowledge, no literature exists regarding antimicrobial stewardship efforts in Zambia.However, AMS efforts in South Africa have been successful. Groote Schuur Hospital, an academic teaching hospital in Cape Town, South Africa, demonstrated a 19.6% reduction in antimicrobial consumption and 35% reduction in antibiotic costs without increasing mortality or readmission rates after introducing a dedicated antibiotic prescription chart and weekly antibiotic stewardship ward rounds. A larger study described the implementation of AMS programs across 47 South African hospitals targeting appropriate culture obtainment, duration of therapy, overprescribing, and concurrent double coverage and found a significant reduction in mean antibiotic defined daily doses per 100 patient-days of 18.34 from pre-implementation to post-implementation AMS program. Many emeSeveral limitations to this study exist, including the small sample size and short study duration. UTH utilizes paper medical charts which do not always contain complete and up-to-date information. Specifically, antimicrobial indication, clinical signs and symptoms of suspected infection, and anticipated duration of therapy are generally not clearly defined in patient charts, making it difficult to extrapolate all of the necessary data for this study. Once a documentation form was filled out completely, it was often removed from patient charts, making them unavailable to the medical staff. It is possible that data from some patients receiving antimicrobials were not included due to misplaced medical charts. However, this number is likely sufficiently small that it would not impact the outcomes of this study. Additionally, due to limited resources at UTH, laboratory results and certain antimicrobials were not always available, requiring patients and/or their family members to purchase antimicrobials from private pharmacies if they could afford to do so. While few cultures were obtained, susceptibilities for the speciated cultures were not collected, so presence of resistant organisms could not be evaluated. The pharmacy dispensing records provided a good estimate of antimicrobial consumption for the three-month period evaluated, however antimicrobials purchased by patients from outside pharmacies were not captured.Based on the results of this study, antimicrobial-use guidelines will be developed by an interdisciplinary team to help guide clinicians to make the most appropriate antimicrobial decisions according to likely source of infection and individual patient characteristics  in accordance with antimicrobial availability and local resistance patterns. The guidelines will also emphasize obtaining appropriate cultures prior to administration of empiric antimicrobials and narrowing antimicrobial treatment based on susceptibilities. Additionally, providers will be educated on these guidelines and the importance of infection control throughout the implementation of the AMS program.Multiple structural and logistical barriers to implementation of an AMS program at UTH remain. Utilizing paper medical charts may lead to misplaced or outdated documentation and results, making it difficult for AMS team members to identify and execute interventions. Due to limited laboratory resources, routine labs and culture data are not obtained on a routine basis and results may be delayed. Laboratory equipment should be operational and correctly calibrated as to accurately identify organisms and resistance patterns. Availability of certain antimicrobials (i.e. vancomycin and cefepime) fluctuates in the hospital, or may not be available at all in Zambia, and therefore, must be taken into consideration during AMS guideline development. Some antimicrobials are not part of the essential medication list and will not be supplied by the government. Following the implementation of an AMS program at UTH, future research includes post-implementation AMS program antimicrobial use, patient outcomes, and impact on resistance patterns.Implementation of AMS programs are essential to reducing emergence of MDR organisms and improving patient outcomes. These results offer insight into antimicrobial use in a resource-limited setting currently lacking an AMS program.S1 Table(DOCX)Click here for additional data file.S1 Dataset(XLSX)Click here for additional data file.


While numerous therapies are highly efficacious in early-stage breast cancers and in particular subsets of breast cancers, therapeutic resistance and metastasis unfortunately arise in many patients. In many cases, tumors that are resistant to standard of care therapies, as well as tumors that have metastasized, are treatable but incurable with existing clinical strategies. Both therapy resistance and metastasis are multi-step processes during which tumor cells must overcome diverse environmental and selective hurdles. Mechanisms by which tumor cells achieve this are numerous and include acquisition of invasive and migratory capabilities, cell-intrinsic genetic and/or epigenetic adaptations, clonal selection, immune evasion, interactions with stromal cells, entering a state of dormancy or senescence, and maintaining self-renewal capacity. To overcome therapy resistance and metastasis in breast cancer, the ability to effectively model each of these mechanisms in the laboratory is essential. Herein we review historic and the current state-of-the-art laboratory model systems and experimental approaches used to investigate breast cancer metastasis and resistance to standard of care therapeutics. While each model system has inherent limitations, they have provided invaluable insights, many of which have translated into regimens undergoing clinical evaluation. We will discuss the limitations and advantages of a variety of model systems that have been used to investigate breast cancer metastasis and therapy resistance and outline potential strategies to improve experimental modeling to further our knowledge of these processes, which will be crucial for the continued development of effective breast cancer treatments. Breast cancer is the most commonly diagnosed cancer in women and results in 40,000 deaths in the United States annually. The presence of hormone receptors (HR), specifically estrogen receptor (ER) and progesterone receptor (PR), together with expression and amplification of the human epidermal growth factor receptor type 2 (HER2), help to broadly classify breast cancer into three main clinical subtypes: ER/PR+, HER2+, or triple negative (TNBC). The histological classification of breast cancer by HR status largely dictates treatment decisions today. However, the molecular stratification of breast cancer, discovered almost 20 years ago by cDNA microarray of breast tumors, further unmasked intrinsic subtypes of breast cancer. These molecular portraits of breast cancer, now based on a 50-gene classifier (PAM50) , 2, helpMetastatic breast cancer accounts for the vast majority of breast cancer related deaths. However, our understanding of this process is still largely evolving. Further complicating this multistep process is the inherent heterogeneity present within a patient’s tumor (intra-tumor heterogeneity) and the fact that the intrinsic classification of breast cancer shapes both the timing and location of metastatic relapse. For instance, while HR+ breast cancers tend to home to the bone and lymph nodes, TNBCs exhibit a preference for visceral organs like the lungs, liver, and brain. HER2+ breast cancers tend to metastasize to the brain after averting HER2-targeted therapies. Additionally, the timing of metastatic presentation also differs by breast cancer subtype, with HR+ tumors typically recurring later than TNBCs after initial presentation and treatment of the primary disease. The predilection of subtypes to home to specific locations in the body, the subtype-dependent variation in recurrence windows, as well as how particular subpopulations of tumor cells within these cancers accomplish metastatic steps remain imperative questions to answer in order to mitigate breast cancer mortality.in vitro and in vivo models over several decades has helped illuminate the metastatic process. Considerable work remains to improve such models in order to gain molecular insights into metastasis and therapeutic resistance, the primary culprits of cancer-related deaths.Despite considerable appreciation for the subtype-specific differences in timing and location of metastatic disease, knowledge is lacking on how to accurately predict a tumor’s metastatic fitness as well as the specific biological mechanisms instructing the stage-specific steps of the metastatic cascade. The development of Metastasis is a multistep process that requires the successful dissemination of tumor cells from the primary site, vascular entry (intravasation) and transit to a distant site, exit (extravasation) from the vasculature into the secondary site, and finally seeding and colonization in the secondary organ site. Importantly, the accomplishment of only one phase of the metastatic cascade by the tumor cell does not necessarily predict successful fulfillment of metastasis as a whole. Thus, experimental models and interpretation of the mechanisms derived from these models is imperative in order to differentiate successful from unsuccessful metastasis and the consequential events dictating a tumor cell’s fitness to evade, spread, and thrive a distant site from the breast. The multistep nature of metastasis and the heterogeneity exhibited within breast cancer warrants the continued use and development of laboratory models to accurately reflect this complicated process in order to discover therapeutic interventions. To date, a compilation of experimental models has shed light on mechanisms surrounding invasion and dissemination, tumor cell dormancy, organ tropism, and microenvironment interactions , clonal dynamics (enrichment and/or depletion of genomic subclones through Darwinian selection), epigenetic adaptations , and acquisition or maintenance of cancer stem-like cell (CSC) features. While some genomic mechanisms of therapy resistance have been appreciated for decades, models to study epigenetic-mediated mechanisms of resistance have been developed more recently. As an added layer of complexity, many non-genomic resistance mechanisms have been found to be reversible, such as drug tolerant or persister cell states. Thus, elucidating the temporal nature of resistance mechanisms is of utmost importance to effectively identify appropriate therapeutic windows. Laboratory models to investigate these complex mechanisms will be discussed below  has enabled demonstration that they functionally drive metastasis through aberrant ESR1 signaling (i.e. epigenetic) mechanisms that can be modeled in the laboratory, such as tumor cell-microenvironmental interactions. The continued mystery surrounding multiple facets of breast cancer metastasis and the need to develop therapies around this advanced stage of disease requires a renewed approach by investigators to develop and use models with increased physiological relevance, whether in vitro or in vivo. Specifically, how experimental models accurately reflect early versus late recurrences, distinguish metastatic risk among patients, and provide an accurate approximation of the metastatic process that can be extrapolated to patients remain imperative questions to answer. The model platforms, as well as the advantages and disadvantages of various systems, will be summarized in the current section , PDXs, or primary cells directly from patients for in vitro studies has the potential to significantly enhance our understanding of metastasis.in vitro assay in a two-dimensional (2D) space that measures the ability of a monolayer of tumor cells to fill a “wounded” area created experimentally by introducing a scratch through the cell sheet. Often these assays are applied to studies that query the function of a particular gene in the regulation of migration properties. The application of live-cell microscopy can provide a level of quantitation that enables the establishment of cell migration kinetics over time. Despite the relative ease of the 2D invasion assay, the scalable nature of the method, and the relative flexibility of the system with multiple cell inputs, these 2D cell models differ considerably from in vivo models. Namely, their spatial organization, cell interactions, and intercellular signaling can differ substantially from the physiologically complex three-dimensional (3D) space of a tumor. Indeed, drug screening outcomes in 2D systems often fail to accurately recapitulate the in vivo setting , glycosaminoglycans, and proteogIycans. In particular, the deposition, remodeling, and crosslinking of ECM within the primary tumor regulates both mechanical and biochemical cues for the cancer cells, and “stiffer” tumors often exhibit poorer prognosis (+) basal epithelial program orchestrates collective leader-follower cell behaviors during tumor cell invasion in 3D Type 1 Collagen  identified the importance of the microvascular niche in distinguishing states of tumor cell dormancy versus emergence based on thrombospondin-1 and TGF-β availability , which model the full extent of the metastatic cascade. In the case of PDXs and human cell lines, the majority of these injection studies are conducted in immunodeficient mice, precluding analysis of the immune system. Despite this limited snapshot of the metastatic process, the application of such an approach by Fidler and colleagues sparked the landmark discovery that only subpopulations of cells possess metastatic abilities, and these could be clonally selected to derive lines with enhanced metastatic seeding to a particular organ .Importantly, experimental models of metastasis are largely dictated by the site of injection and inherent tropism of the tumor cells. Although these studies rely heavily on the lodging of tumor cells into the first capillary bed encountered downstream of the location of vascular delivery, mechanisms of Paget’s seed-and-soil hypothesis have been pursued to identify factors involved in organ-specific metastasis . For insA major advantage of orthotopic models of breast cancer metastasis, in which breast cancer cells are engrafted into the mammary glands of mice, is that they capture all steps of the metastatic cascade. These models enable direct comparison of primary tumors, circulating tumor cells (CTCs), and metastases matched within the same animal. Importantly, some models metastasize to multiple secondary sites, enabling comparisons of tumor cells growing in distinct secondary organ microenvironments. Numerous breast cancer cell lines have been orthotopically xenografted into mice for CTC and metastasis studies , 38, 39.Ideally, PDXs should reflect the full range of cellular heterogeneity and disease progression across breast cancers. The PDX consortium, a shared effort comprised of several academic institutions, has amassed 537 PDX lines representing 500 patients . An openin vivo imaging constructs (e.g. bioluminescent markers), allowing in vivo and ex vivo detection of metastatic lesions from multiple secondary organs of the mouse  LTR promoter, among several other promoters  58), , 58), thTP53-null syngeneic transplant model of mammary tumorigenesis comprises a biobank of tumors that reflect heterogeneity of human breast cancers at the molecular and histological levels  in improving patient outcomes has only amplified a growing interest the application of such therapies to breast cancer . Syngenein vivo . As mentin vivo . Such moin vivo . Other min vivo . Separatpartment . At prespartment . Future e.g. tamoxifen), selective estrogen degraders  or aromatase inhibitors  acquired either permanently or reversibly, and either clonally or sub-clonally, following treatment, or 2) pre-existing clonally or sub-clonally prior to treatment. Acquired or pre-existing resistance can be mediated by genomic events , transcriptional programs, epigenetic modification of chromatin, post-transcriptional regulation of RNA and/or protein levels, and metabolic rewiring. Reversible resistance is often referred to as drug-tolerance or adaptation of “persister” cell phenotypes. These molecular changes can ultimately mediate resistance by enhancing efflux or breakdown of drugs, blocking drug uptake, inhibiting drug-mediated apoptosis, adaptive programs of repair and survival, or protection of CSC features. Tumor cell extrinsic mechanisms driving resistance such as immune system escape, have also been identified. Furthermore, tumor cell dormancy has been found to contribute to therapy resistance, especially in the ER+ subtype with characteristically late-arising metastatic/therapy resistant relapses. In contrast, TNBCs typically exhibit relapses on the scale of only a few years after diagnosis . Here wein vivo systems, they have provided valuable insights about the biology of breast cancer resistance. While systematic analyses of SOC therapy resistance mechanisms across a multitude of models within each major breast cancer subtype are yet incomplete, some studies have provided snapshots of these mechanisms in defined contexts as described below  cell subpopulation in basal-like breast cancer cell lines after acute treatment with therapies such as MEK or BRAF inhibitors revealed that epigenetic plasticity, rather than Darwinian selection, was associated with resistance. This study demonstrated that targeting this epigenetic plasticity with a BET inhibitor abrogated the DTP state and cell survival . Acute tTreatment of TNBC cell lines with SOC chemotherapy was found to result in adaptation of a polyploid “giant cell” phenotype, a morphological feature that has been observed in chemotherapy-treated human breast tumors . These rin vivo using cell line xenografts and PDXs, enabling preclinical trials demonstrating novel therapeutic combinations to treat NF1-low ER+ breast tumors  in driving breast tumorigenesis, resistance, and metastasis. These cells can be distinguished from the non-TIC population based on cell surface marker expression  and havee tumors .in vitro models have also been observed in biopsies obtained directly from patients. Development of anti-CSC therapies is a major topic of current investigation in the field and is expected to perturb both therapy resistance and metastasis.Subsets of breast CSCs, termed the “side population”, have been identified that have high expression of drug efflux proteins and are resistant to chemotherapeutics due to their ability to expel drugs from within the cells. This population has been observed in breast cancer cell lines . Breast in vitro and tumors derived from orthotopic xenotransplantation into mice has revealed a high degree of concordance  discovery-based approaches in which SOC agents are administered to PDXs, then tumors are sampled longitudinally to identify mechanisms of resistance, and 2) preclinical testing approaches monitoring the efficacy of experimental agents or combinations with SOC.in vivo and, combined with transcriptomic profiling, revealed targeted therapy options that were translated into preclinical trials in PDXs  genetics. In particular, these tumors exhibited a hypersensitivity to platinum drugs and PARP inhibitors, yet like patients, GEMMs succumbed to acquired resistance  of dormant ER+ breast cancer cells  1K22CA241113-01 to GE and 5K22CA207463 to KR, and Susan G. Komen CCR18548284 to KR. The content is solely the responsibility of the authors and does not necessarily represent the official views of NIH, Susan G. Komen, or CPRIT.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


District health managers (DHMs) operate and manage most public health care facilities in the health systems of many low- and middle-income countries (LMICs). They must turn national health policies and human, material, and financial resources into accessible high-quality health services  in a specific context , but bilateral development partners who are responsible for capacity-building initiatives in LMICs often disregard country policies and plans (United Nations Enhancing A systemic and participatory approach to strengthening management capacity may be more time-consuming than traditional competency development interventions, as it requires building relationships and a level of trust that facilitates effective partnerships with local stakeholders. Moreover, contextual and organizational factors like policies, structures, and resource availability that undermine a DHM’s ability and willingness to carry out their duties are more complex to address compared with individual competencies (Brinkerhoff Targeting competencies alone is insufficient to develop sustained improvements in management capacity. Since DHMs’ capacity is determined by a complex interaction of individual, organizational, and contextual factors, future capacity-strengthening initiatives should take on a systemic approach that utilizes tools to encourage systemic thinking, and encourages close collaboration with relevant local stakeholders (Heerdegen et al.


A deeper understanding of the molecular mechanisms underlying the development and progression of cardiovascular diseases represents a major goal in cardiovascular medicine. Mitochondrial dysfunction has emerged as major player in the development of cardiovascular diseases, with potential therapeutic implications. Mitochondrial dysfunction encompasses mitochondrial complex disruption, mitochondrial uncoupling, and cristae remodeling and swelling, which in turn cause ROS accumulation, energy stress, and cell death.This Research Topic is a collection of original and state-of-the art review articles discussing and extending our current knowledge about molecular mechanisms responsible for mitochondrial dysfunction in cardiovascular diseases. Many aspects of mitochondrial biology and therapies targeting damaged mitochondria have been highlighted.Kaludercic and Di Lisa in their review article. Mitochondrial ROS are generated from multiple sources in cardiomyocytes during diabetes by a feed-forward/amplification mechanism, which further exacerbates oxidative stress and causes contractile dysfunction. The authors reviewed current therapies aimed at reducing ROS and improving cardiac function in diabetic patients. While some systemic antioxidants failed to exert cardiac protection in clinical trials, mitochondrial-targeted antioxidants such as MitoTEMPO were shown to be cardioprotective in preclinical models of diabetic cardiomyopathy.One of the main feature of mitochondrial dysfunction observed in several cardiovascular diseases is the exaggerated generation of mitochondrial ROS , which rMaejima provided a detailed overview about the mitochondrial-mediated mechanisms underlying the beneficial effects of SGLT2 inhibitors in heart failure. SGLT2 inhibitors increase ketone bodies, which represent a suitable source of energy in failing hearts, and also improve sodium metabolism and mitochondrial dynamics. However, further studies are needed to identify other targets modulated by SGLT2 inhibitors, since SGLT2 does not appear to be expressed in human and rodent cardiomyocytes, at least in unstressed conditions. A modulation of mitochondrial dynamics may contribute to the beneficial effects of this class of drugs on mitochondrial function in response to metabolic derangements (Sodium glucose cotransporter 2 (SGLT2) inhibitors also appear to be promising drugs to reduce cardiovascular events in diabetic patients. In this regard, Machiraju et al. demonstrated that SS-31, a mitochondrial targeted antioxidant, also known as elamipretide or Bendavia, rescues mitochondrial fragmentation, oxidative stress, and improves mitochondrial fusion in skin fibroblasts extracted from DCMA patients. However, the therapeutic potential of SS-31 in improving cardiac function in patients with DCMA should be assessed in further studies.Targeting mitochondria, and in particular mitochondrial ROS, has also emerged as a potential therapy for patients with dilated cardiomyopathy with ataxia syndrome (DCMA), a rare genetic disorder caused by a mutation of DNAJ Heat Shock Protein Family (Hsp40) Member C19 (DNAJC19), a protein localized in the inner mitochondrial membrane. Thomas et al. found decreased levels of Parkin protein in the heart of obese mice. Parkin is a ubiquitin E3 ligase, which represents a canonical regulator of mitophagy and proteasome degradation. The authors also observed a modest increase of infarct size in obese mice undergoing ischemia/reperfusion (IR) ex-vivo and a cardiac accumulation of ubiquitinated mitochondrial proteins at baseline and in response to IR in obese animals. This study suggested that mitophagy may be impaired in the context of obesity because of Parkin downregulation, thereby predisposing the heart to develop increased injury in response to stress. However, a direct assessment of mitophagy was not performed in this study and further work is necessary to clarify the impact of metabolic alterations on Parkin-dependent and independent mitophagy in the heart.Mitochondrial health is facilitated by specific quality control mechanisms, such as mitophagy, a cargo-specific form of autophagy selective for elimination of damaged mitochondria . DamagedLiang and Gustafsson. The authors reviewed relevant literature supporting the concept that autophagy declines with aging, leading to age-related cardiovascular diseases, due to alterations in cellular energy metabolism and adaption to stress. Either genetic or pharmacological activation of mitophagy appears to attenuate aging-related abnormalities, whereas its inhibition seems to accelerate them  is activated by means of accumulation of ATF5, which translocates to the nucleus and stimulates the upregulation of an adaptive gene response aimed at the restoration of mitochondrial protein folding and proteostasis. Previous work showed that stimulation of mtUPR improves mitochondrial function and reduces cardiac damage in response to I/R injury and pressure overload. The elucidation of the integration points between mitochondrial and endoplasmic reticulum proteostasis represents an important aspect to be clarified in future studies.Aside from mitophagy and mitochondrial dynamics, mitochondrial proteostasis is also emerging as an important mechanism regulating mitochondrial quality control in the heart, as described in the paper by Murabito et al. Doxorubicin, a well-known drug belonging to the anthracycline class, directly binds cardiolipin and accumulates into mitochondria, causing disruption of electron transport chain complexes, thereby contributing to ROS accumulation. The latter triggers several adverse events, such as mitochondrial uncoupling, oxidative stress, apoptosis, ferroptosis, and impairment of calcium metabolism, which then lead to cardiomyopathy development. In addition, mitochondrial dynamics and autophagy are impaired by doxorubicin treatment, further aggravating mitochondrial damage. Different therapeutic strategies have been suggested to reduce anthracycline-induced mitochondrial dysfunction and cardiotoxicity. These include mitochondria-targeted antioxidants, autophagy activators, or inhibitors of mitochondrial fatty acid beta-oxidation. However, the signaling pathways involved in the perpetuation of mitochondrial damage in response to doxorubicin treatment still need to be clarified. The elucidation of this aspect will be very important for the discovery of new therapeutic targets for the prevention of doxorubicin-induced cardiotoxicity and for the identification of subjects with potentially higher susceptibility to develop cardiac injury after chemotherapy.Mitochondria are also massively damaged by anthracycline-based chemotherapy, and mitochondrial dysfunction contributes to the development anthracycline-induced cardiotoxicity, as reviewed by Oka et al. A dysregulation of PGC-1α signaling during heart failure occurs at transcriptional and post-transcriptional level, contributing to the development of cardiac dysfunction, due to alterations of multiple mechanisms, particularly those involved in mitochondrial metabolism.Mitochondrial biogenesis is also critical for the regulation of mitochondrial turnover and function in cardiovascular pathophysiology . The traMohammed et al. Epigenetic changes impair mitochondrial function, resulting in a decrease in mitochondrial metabolites  used as cofactors by components involved in chromatin modifications. The latter further exacerbates epigenetic remodeling. Among epigenetic modulators, HDAC inhibitors or SIRT1-3 activators were shown to preserve mitochondrial function in different cardiovascular diseases by reducing epigenetic remodeling.Perturbations of epigenetic mechanisms regulating mitochondrial function also contribute to cardiovascular diseases, as reviewed by In conclusion, this Research Topic highlights that alterations in different mechanisms regulating mitochondrial quality control and function directly contribute to the development of cardiovascular diseases. Mitochondrial dysfunction determines an impairment of energy production, which is detrimental for heart function. In addition, mitochondrial damage triggers cell death pathways. Although the reduction of mitochondrial ROS appears to be a valid approach to reduce mitochondrial dysfunction, an improvement of mitochondrial quality control and epigenetic mechanisms may also represent an efficacious strategy in future clinical applications.All authors listed have made a substantial, direct and intellectual contribution to the work, and approved it for publication.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.