Translational Research in Cardiovascular Repair

Metformin Preconditioning Augments Cardiac Perfusion and Performance in a Large Animal Model of Chronic Coronary Artery Disease

OBJECTIVE

To test the efficacy of metformin (MET) during the induction of coronary ischemia on myocardial performance in a large animal model of coronary artery disease (CAD) and metabolic syndrome (MS), with or without concomitant extracellular vesicular (EV) therapy.

BACKGROUND

Although surgical and endovascular revascularization are durably efficacious for many patients with CAD, up to one-third are poor candidates for standard therapies. For these patients, many of whom have comorbid MS, adjunctive strategies are needed. EV therapy has shown promise in this context, but its efficacy is attenuated by MS. We investigated whether MET pretreatment could ameliorate therapeutic decrements associated with MS.

METHODS

Yorkshire swine (n = 29) were provided a high-fat diet to induce MS, whereupon an ameroid constrictor was placed to induce CAD. Animals were initiated on 1000 mg oral MET or placebo; all then underwent repeat thoracotomy for intramyocardial injection of EVs or saline. Swine were maintained for 5 weeks before the acquisition of functional and perfusion data immediately before terminal myocardial harvest. Immunoblotting and immunofluorescence were performed on the most ischemic tissue from all groups.

RESULTS

Regardless of EV administration, animals that received MET exhibited significantly improved ejection fraction, cardiac index, and contractility at rest and during rapid myocardial pacing, improved perfusion to the most ischemic myocardial region at rest and during pacing, and markedly reduced apoptosis.

CONCLUSIONS

MET administration reduced apoptotic cell death, improved perfusion, and augmented both intrinsic and load-dependent myocardial performance in a highly translatable large animal model of chronic myocardial ischemia and MS.

Preclinical assessment for translation to humans: The PATH approach for assessing supporting evidence for early-phase trials and innovative care

Early-phase trials and innovative care draw support from basic science, preclinical studies, and clinical research. Such evidential diversity presents a challenge for traditional ways of synthesizing evidence. In what follows, we review the limitations of existing approaches for communicating supporting evidence for early-phase trials. We then offer a structured approach, PATH (preclinical assessment for translation to humans). PATH is grounded in the premise that the case for administering novel strategies to patients requires connecting the dots between nine mechanistic steps supporting a clinical claim. Using PATH entails first parsing supporting evidence, assessing the strength of evidence at each step, and then assessing the strength of a chain of evidence linking drug administration to clinical effect. While PATH requires further refinement, the approach reduces some of the opacity, arbitrariness, and biases in current ways of presenting and assessing scientific support for early-phase trials and innovative care.

A preclinical systematic review and meta-analysis assessing the effect of biological sex in lipopolysaccharide-induced acute lung injury

It is unclear what effect biological sex has on outcomes of acute lung injury (ALI). Clinical studies are confounded by their observational design. We addressed this knowledge gap with a preclinical systematic review of ALI animal studies. We searched MEDLINE and Embase for studies of intratracheal/intranasal/aerosolized lipopolysaccharide administration (the most common ALI model) that reported sex-stratified data. Screening and data extraction were conducted in duplicate. Our primary outcome was histological tissue injury and secondary outcomes included alveolar-capillary barrier alterations and inflammatory markers. We used a random-effects inverse variance meta-analysis, expressing data as standardized mean difference (SMD) with 95% confidence intervals (CIs). Risk of bias was assessed using the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE) tool. We identified six studies involving 132 animals across 11 independent experiments. A total of 41 outcomes were extracted, with the direction of effect suggesting greater severity in males than females in 26/41 outcomes (63%). One study reported on lung histology and found that male mice exhibited greater injury than females (SMD: 1.61, 95% CI: 0.53-2.69). Meta-analysis demonstrated significantly elevated albumin levels (SMD: 2.17, 95% CI: 0.63-3.70) and total cell counts (SMD: 0.80, 95% CI: 0.27-1.33) in bronchoalveolar lavage fluid from male mice compared with female mice. Most studies had an "unclear risk of bias." Our findings suggest sex-related differences in ALI severity. However, these conclusions are drawn from a small number of animals and studies. Further research is required to address the fundamental issue of biological sex differences in LPS-induced ALI.

Intracoronary Administration of Microencapsulated HGF in a Reperfused Myocardial Infarction Swine Model

Therapy microencapsulation allows minimally invasive, safe, and effective administration. Hepatocyte growth factor (HGF) has angiogenic, anti-inflammatory, anti-apoptotic, and anti-fibrotic properties. Our objective was to evaluate the cardiac safety and effectiveness of intracoronary (IC) administration of HGF-loaded extended release microspheres in an acute myocardial infarction (AMI) swine model. An IC infusion of 5 × 106 HGF-loaded microspheres (MS+HGF, n = 7), 5 × 106 placebo microspheres (MS, n = 7), or saline (SAL, n = 7) was performed two days after AMI. TIMI flow and Troponin I (TnI) values were assessed pre- and post-treatment. Cardiac function was evaluated with magnetic resonance imaging (cMR) before injection and at 10 weeks. Plasma cytokines were determined to evaluate the inflammatory profile and hearts were subjected to histopathological evaluation. Post-treatment coronary flow was impaired in five animals (MS+HGF and MS group) without significant increases in TnI. One animal (MS group) died during treatment. There were no significant differences between groups in cMR parameters at any time (p > 0.05). No statistically significant changes were found between groups neither in cytokines nor in histological analyses. The IC administration of 5 × 106 HGF-loaded-microspheres 48 h post-AMI did not improve cardiac function, nor did it decrease inflammation or cardiac fibrosis in this experimental setting.

NLRP3-Inflammasome Inhibition with IZD334 Does Not Reduce Cardiac Damage in a Pig Model of Myocardial Infarction

NLRP3-inflammasome-mediated signaling is thought to significantly contribute to the extent of myocardial damage after myocardial infarction (MI). The purpose of this study was to investigate the effects of the NLRP3-inflammasome inhibitor IZD334 on cardiac damage in a pig model of myocardial infarction. Prior to in vivo testing, in vitro, porcine peripheral blood mononuclear cells and whole blood were treated with increasing dosages of IZD334, a novel NLRP3-inflammasome inhibitor, and were stimulated with lipopolysaccharide (LPS) and adenosine triphosphate (ATP). After determination of the pharmacological profile in healthy pigs, thirty female Landrace pigs were subjected to 75 min of transluminal balloon occlusion of the LAD coronary artery and treated with placebo or IZD334 (1 mg/kg, 3 mg/kg, or 10 mg/kg once daily) in a blinded randomized fashion. In vitro, NLRP3-inflammasome stimulation showed the pronounced release of interleukin (IL)-1β that was attenuated by IZD334 (p < 0.001). In vivo, no differences were observed between groups in serological markers of inflammation nor myocardial IL-1β expression. After 7 days, the ejection fraction did not differ between groups, as assessed with MRI (placebo: 45.1 ± 8.7%, 1 mg/kg: 49.9 ± 6.1%, 3 mg/kg: 42.7 ± 3.8%, 10 mg/kg: 44.9 ± 6.4%, p = 0.26). Infarct size as a percentage of the area at risk was not reduced (placebo: 73.1 ± 3.0%, 1 mg/kg: 75.5 ± 7.3%, 3 mg/kg: 80.3 ± 3.9%, 10 mg/kg: 78.2 ± 8.0%, p = 0.21). In this pig MI model, we did not observe attenuation of the inflammatory response after NLRP3-inflammasome inhibition in vivo. Consecutively, no difference was observed in IS and cardiac function, while in vitro inhibition successfully reduced IL-1β release from stimulated porcine blood cells.

Monoamine oxidase A and organic cation transporter 3 coordinate intracellular β1AR signaling to calibrate cardiac contractile function

We have recently identified a pool of intracellular β1 adrenergic receptors (β1ARs) at the sarcoplasmic reticulum (SR) crucial for cardiac function. Here, we aim to characterize the integrative control of intracellular catecholamine for subcellular β1AR signaling and cardiac function. Using anchored Förster resonance energy transfer (FRET) biosensors and transgenic mice, we determined the regulation of compartmentalized β1AR-PKA signaling at the SR and plasma membrane (PM) microdomains by organic cation transporter 3 (OCT3) and monoamine oxidase A (MAO-A), two critical modulators of catecholamine uptake and homeostasis. Additionally, we examined local PKA substrate phosphorylation and excitation-contraction coupling in cardiomyocyte. Cardiac-specific deletion of MAO-A (MAO-A-CKO) elevates catecholamines and cAMP levels in the myocardium, baseline cardiac function, and adrenergic responses. Both MAO-A deletion and inhibitor (MAOi) selectively enhance the local β1AR-PKA activity at the SR but not PM, and augment phosphorylation of phospholamban, Ca2+ cycling, and myocyte contractile response. Overexpression of MAO-A suppresses the SR-β1AR-PKA activity and PKA phosphorylation. However, deletion or inhibition of OCT3 by corticosterone prevents the effects induced by MAOi and MAO-A deletion in cardiomyocytes. Deletion or inhibition of OCT3 also negates the effects of MAOi and MAO-A deficiency in cardiac function and adrenergic responses in vivo. Our data show that MAO-A and OCT3 act in concert to fine-tune the intracellular SR-β1AR-PKA signaling and cardiac fight-or-flight response. We reveal a drug contraindication between anti-inflammatory corticosterone and anti-depressant MAOi in modulating adrenergic regulation in the heart, providing novel perspectives of these drugs with cardiac implications.

Cardiovascular Diseases in the Digital Health Era: A Translational Approach from the Lab to the Clinic

Translational science has been introduced as the nexus among the scientific and the clinical field, which allows researchers to provide and demonstrate that the evidence-based research can connect the gaps present between basic and clinical levels. This type of research has played a major role in the field of cardiovascular diseases, where the main objective has been to identify and transfer potential treatments identified at preclinical stages into clinical practice. This transfer has been enhanced by the intromission of digital health solutions into both basic research and clinical scenarios. This review aimed to identify and summarize the most important translational advances in the last years in the cardiovascular field together with the potential challenges that still remain in basic research, clinical scenarios, and regulatory agencies.

Preregistration of animal research protocols: development and 3-year overview of preclinicaltrials.eu

Open, prospective registration of a study protocol can improve research rigour in a number of ways. Through preregistration, key features of the study’s methodology are recorded and maintained as a permanent record, enabling comparison of the completed study with what was planned. By recording the study hypothesis and planned outcomes a priori, preregistration creates transparency and can reduce the risk of several common biases, such as hypothesising after results are known and outcome switching or selective outcome reporting. Second, preregistration raises awareness of measures to reduce bias, such as randomisation and blinding. Third, preregistration provides a comprehensive listing of planned studies, which can prevent unnecessary duplication and reduce publication bias. Although commonly acknowledged and applied in clinical research since 2000, preregistration of animal studies is not yet the norm. In 2018 we launched the first dedicated, open, online register for animal study protocols: wwwpreclinicaltrialseu. Here, we provide insight in the development of preclinicaltrials.eu (PCT) and evaluate its use during the first 3 years after its launch. Furthermore, we elaborate on ongoing developments such as the rise of comparable registries, increasing support for preregistration in the Netherlands—which led to the funding of PCT by the Dutch government—and pilots of mandatory preregistration by several funding bodies. We show the international coverage of currently registered protocols but with the overall low number of (pre)registered protocols.

Declaration of common standards for the preregistration of animal research-speeding up the scientific progress

Preregistration of studies is a recognized tool in clinical research to improve the quality and reporting of all gained results. In preclinical research, preregistration could boost the translation of published results into clinical breakthroughs. When studies rely on animal testing or form the basis of clinical trials, maximizing the validity and reliability of research outcomes becomes in addition an ethical obligation. Nevertheless, the implementation of preregistration in animal research is still slow. However, research institutions, funders, and publishers start valuing preregistration, and thereby level the way for its broader acceptance in the future. A total of 3 public registries, the OSF registry, preclinicaltrials.eu, and animalstudyregistry.org already encourage the preregistration of research involving animals. Here, they jointly declare common standards to make preregistration a valuable tool for better science. Registries should meet the following criteria: public accessibility, transparency in their financial sources, tracking of changes, and warranty and sustainability of data. Furthermore, registration templates should cover a minimum set of mandatory information and studies have to be uniquely identifiable. Finally, preregistered studies should be linked to any published outcome. To ensure that preregistration becomes a powerful instrument, publishers, funders, and institutions should refer to registries that fulfill these minimum standards.

Combined meta-analysis of preclinical cell therapy studies shows overlapping effect modifiers for multiple diseases

Introduction

Cell therapy has been studied in many different research domains. Cellular replacement of damaged solid tissues is at an early stage of development, with much still to be understood. Systematic reviews and meta-analyses are widely used to aggregate data and find important patterns of results within research domains.

We set out to find common biological denominators affecting efficacy in preclinical cell therapy studies for renal, neurological and cardiac disease.

Methods

We used datasets of five previously published meta-analyses investigating cell therapy in preclinical models of chronic kidney disease, spinal cord injury, stroke and ischaemic heart disease. We transformed primary outcomes to ratios of means to permit direct comparison across disease areas. Prespecified variables of interest were species, immunosuppression, cell type, cell origin, dose, delivery and timing of the cell therapy.

Results

The five datasets from 506 publications yielded data from 13 638 animals. Animal size affects therapeutic efficacy in an inverse manner. Cell type influenced efficacy in multiple datasets differently, with no clear trend for specific cell types being superior. Immunosuppression showed a negative effect in spinal cord injury and a positive effect in cardiac ischaemic models. There was a dose–dependent relationship across the different models. Pretreatment seems to be superior compared with administration after the onset of disease.

Conclusions

Preclinical cell therapy studies are affected by multiple variables, including species, immunosuppression, dose and treatment timing. These data are important when designing preclinical studies before commencing clinical trials.

The epicardial delivery of cardiosphere derived cells or their extracellular vesicles is safe but of limited value in experimental infarction

The epicardial administration of therapeutics via the pericardial sac offers an attractive route, since it is minimally invasive and carries no risks of coronary embolization. The aim of this study was to assess viability, safety and effectiveness of cardiosphere-derived cells (CDCs), their extracellular vesicles (EVs) or placebo administered via a mini-thoracotomy 72 h after experimental infarction in swine. The epicardial administration was completed successfully in all cases in a surgery time (knife-to-skin) below 30 min. No significant differences between groups were found in cardiac function parameters evaluated using magnetic resonance imaging before therapy and at the end of the study, despite a trend towards improved function in CDC-treated animals. Moreover, infarct size at 10 weeks was smaller in treated animals, albeit not significantly. Arrhythmia inducibility did not differ between groups. Pathological examination showed no differences, nor were there any pericardial adhesions evidenced in any case 10 weeks after surgery. These results show that the epicardial delivery of CDCs or their EVs is safe and technically easy 3 days after experimental myocardial infarction in swine, but it does not appear to have any beneficial effect on cardiac function. Our results do not support clinical translation of these therapies as implemented in this work.

Pulmonary valve tissue engineering strategies in large animal models

In the last 25 years, numerous tissue engineered heart valve (TEHV) strategies have been studied in large animal models. To evaluate, qualify and summarize all available publications, we conducted a systematic review and meta-analysis. We identified 80 reports that studied TEHVs of synthetic or natural scaffolds in pulmonary position (n = 693 animals). We identified substantial heterogeneity in study designs, methods and outcomes. Most importantly, the quality assessment showed poor reporting in randomization and blinding strategies. Meta-analysis showed no differences in mortality and rate of valve regurgitation between different scaffolds or strategies. However, it revealed a higher transvalvular pressure gradient in synthetic scaffolds (11.6 mmHg; 95% CI, [7.31-15.89]) compared to natural scaffolds (4,67 mmHg; 95% CI, [3,94-5.39]; p = 0.003). These results should be interpreted with caution due to lack of a standardized control group, substantial study heterogeneity, and relatively low number of comparable studies in subgroup analyses. Based on this review, the most adequate scaffold model is still undefined. This review endorses that, to move the TEHV field forward and enable reliable comparisons, it is essential to define standardized methods and ways of reporting. This would greatly enhance the value of individual large animal studies.

A 3-year evaluation of preclinicaltrials.eu reveals room for improvement in preregistration of animal studies

In 2018, the first registry dedicated to preregistration of animal study protocols was launched. Despite international support, the overall number of (pre)registered protocols is still low, illustrating the need for pushing the preregistration agenda among researchers and policymakers.

Proteomic and Glyco(proteo)mic tools in the profiling of cardiac progenitors and pluripotent stem cell derived cardiomyocytes: Accelerating translation into therapy

Research in stem cells paved the way to an enormous amount of knowledge, increasing expectations on cardio regenerative therapeutic approaches in clinic. While the first generation of clinical trials using cell-based therapies in the heart were performed with bone marrow and adipose tissue derived mesenchymal stem cells, second generation cell therapies moved towards the use of cardiac-committed cell populations, including cardiac progenitor cells and pluripotent stem cell derived cardiomyocytes. Despite all these progresses, translating the aptitudes of R&D and pre-clinical data into effective clinical treatments is still highly challenging, partially due to the demanding regulatory and safety concerns but also because of the lack of knowledge on the regenerative mechanisms of action of these therapeutic products. Thus, the need of analytical methodologies that enable a complete characterization of such complex products and a deep understanding of their therapeutic effects, at the cell and molecular level, is imperative to overcome the hurdles of these advanced therapies. Omics technologies, such as proteomics and glyco(proteo)mics workflows based on state of the art mass-spectrometry, have prompted some major breakthroughs, providing novel data on cell biology and a detailed assessment of cell based-products applied in cardiac regeneration strategies. These advanced 'omics approaches, focused on the profiling of protein and glycan signatures are excelling the identification and characterization of cell populations under study, namely unveiling pluripotency and differentiation markers, as well as paracrine mechanisms and signaling cascades involved in cardiac repair. The leading knowledge generated is supporting a more rational therapy design and the rethinking of challenges in Advanced Therapy Medicinal Products development. Herein, we review the most recent methodologies used in the fields of proteomics, glycoproteomics and glycomics and discuss their impact on the study of cardiac progenitor cells and pluripotent stem cell derived cardiomyocytes biology. How these discoveries will impact the speed up of novel therapies for cardiovascular diseases is also addressed.

Intramyocardial Transplantation of Human iPS Cell-Derived Cardiac Spheroids Improves Cardiac Function in Heart Failure Animals

The severe shortage of donor hearts hampered the cardiac transplantation to patients with advanced heart failure. Therefore, cardiac regenerative therapies are eagerly awaited as a substitution. Human induced pluripotent stem cells (hiPSCs) are realistic cell source for regenerative cardiomyocytes. The hiPSC-derived cardiomyocytes are highly expected to help the recovery of heart. Avoidance of teratoma formation and large-scale culture of cardiomyocytes are definitely necessary for clinical setting. The combination of pure cardiac spheroids and gelatin hydrogel succeeded to recover reduced ejection fraction. The feasible transplantation strategy including transplantation device for regenerative cardiomyocytes are established in this study.

Echocardiography-guided percutaneous left ventricular intracavitary injection as a cell delivery approach in infarcted mice

In the field of cell therapy for heart disease, a new paradigm of repeated dosing of cells has recently emerged. However, the lack of a repeatable cell delivery method in preclinical studies in rodents is a major obstacle to investigating this paradigm. We have established and standardized a method of echocardiography-guided percutaneous left ventricular intracavitary injection (echo-guided LV injection) as a cell delivery approach in infarcted mice. Here, we describe the method in detail and address several important issues regarding it. First, by integrating anatomical and echocardiographic considerations, we have established strategies to determine a safe anatomical window for injection in infarcted mice. Second, we summarize our experience with this method (734 injections). The overall survival rate was 91.4%. Third, we examined the efficacy of this cell delivery approach. Compared with vehicle treatment, cardiac mesenchymal cells (CMCs) delivered via this method improved cardiac function assessed both echocardiographically and hemodynamically. Furthermore, repeated injections of CMCs via this method yielded greater cardiac function improvement than single-dose administration. Echo-guided LV injection is a feasible, reproducible, relatively less invasive and effective delivery method for cell therapy in murine models of heart disease. It is an important approach that could move the field of cell therapy forward, especially with regard to repeated cell administrations.

Damage-Associated Molecular Patterns in Myocardial Infarction and Heart Transplantation: The Road to Translational Success

In the setting of myocardial infarction (MI), ischemia reperfusion injury (IRI) occurs due to occlusion (ischemia) and subsequent re-establishment of blood flow (reperfusion) of a coronary artery. A similar phenomenon is observed in heart transplantation (HTx) when, after cold storage, the donor heart is connected to the recipient's circulation. Although reperfusion is essential for the survival of cardiomyocytes, it paradoxically leads to additional myocardial damage in experimental MI and HTx models. Damage (or danger)-associated molecular patterns (DAMPs) are endogenous molecules released after cellular damage or stress such as myocardial IRI. DAMPs activate pattern recognition receptors (PRRs), and set in motion a complex signaling cascade resulting in the release of cytokines and a profound inflammatory reaction. This inflammatory response is thought to function as a double-edged sword. Although it enables removal of cell debris and promotes wound healing, DAMP mediated signalling can also exacerbate the inflammatory state in a disproportional matter, thereby leading to additional tissue damage. Upon MI, this leads to expansion of the infarcted area and deterioration of cardiac function in preclinical models. Eventually this culminates in adverse myocardial remodeling; a process that leads to increased myocardial fibrosis, gradual further loss of cardiomyocytes, left ventricular dilation and heart failure. Upon HTx, DAMPs aggravate ischemic damage, which results in more pronounced reperfusion injury that impacts cardiac function and increases the occurrence of primary graft dysfunction and graft rejection via cytokine release, cardiac edema, enhanced myocardial/endothelial damage and allograft fibrosis. Therapies targeting DAMPs or PRRs have predominantly been investigated in experimental models and are potentially cardioprotective. To date, however, none of these interventions have reached the clinical arena. In this review we summarize the current evidence of involvement of DAMPs and PRRs in the inflammatory response after MI and HTx. Furthermore, we will discuss various current therapeutic approaches targeting this complex interplay and provide possible reasons why clinical translation still fails.

Insights into therapeutic products, preclinical research models, and clinical trials in cardiac regenerative and reparative medicine: where are we now and the way ahead. Current opinion paper of the ESC Working Group on Cardiovascular Regenerative and Reparative Medicine

Great expectations have been set around the clinical potential of regenerative and reparative medicine in the treatment of cardiovascular diseases [i.e. in particular, heart failure (HF)]. Initial excitement, spurred by encouraging preclinical data, resulted in a rapid translation into clinical research. The sobering outcome of the resulting clinical trials suggests that preclinical testing may have been insufficient to predict clinical outcome. A number of barriers for clinical translation include the inherent variability of the biological products and difficulties to develop potency and quality assays, insufficient rigour of the preclinical research and reproducibility of the results, manufacturing challenges, and scientific irregularities reported in the last years. The failure to achieve clinical success led to an increased scrutiny and scepticism as to the clinical readiness of stem cells and gene therapy products among clinicians, industry stakeholders, and funding bodies. The present impasse has attracted the attention of some of the most active research groups in the field, which were then summoned to analyse the position of the field and tasked to develop a strategy, to re-visit the undoubtedly promising future of cardiovascular regenerative and reparative medicine, based on lessons learned over the past two decades. During the scientific retreat of the ESC Working Group on Cardiovascular Regenerative and Reparative Medicine (CARE) in November 2018, the most relevant and timely research aspects in regenerative and/or reparative medicine were presented and critically discussed, with the aim to lay out a strategy for the future development of the field. We report herein the main ideas and conclusions of that meeting.

Systematic Review of Stem-Cell-Based Therapy of Burn Wounds: Lessons Learned from Animal and Clinical Studies

Treatment of severe burn wounds presents a daunting medical challenge, and novel approaches promoting healing and reducing scarring are highly desirable. The application of mesenchymal stem/stromal cells (MSCs) has been suggested as a novel treatment. In this paper, we present systematic reviews of pre-clinical and clinical studies of MSC therapy for second- or third-degree thermal burn wounds. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines, the PubMed and Embase databases were searched, and interventional studies of MSC therapy using rodent models (21 studies) or human burn patients (three studies) were included in the pre-clinical and clinical reviews, respectively, where both overall outcome and wound-healing-phase-specific methodologies and effects were assessed. The pre-clinical studies demonstrated a promising effect of the application of MSCs on several wound healing phases. The clinical studies also suggested that the MSC treatment was beneficial, particularly in the remodeling phase. However, the limited number of studies, their lack of homogeneity in study design, relatively high risk of bias, lack of reporting on mode of action (MOA), and discontinuity of evidence restrict the strength of these findings. This comprehensive review presents an overview of available methodologies to assess the MOA of MSC treatment for distinct wound healing phases. Furthermore, it includes a set of recommendations for the design of high-quality clinical studies that can determine the efficacy of MSCs as a therapy for burn wounds.

Effects of mesenchymal stromal cell-conditioned media on measures of lung structure and function: a systematic review and meta-analysis of preclinical studies

BACKGROUND

Lung disease is a leading cause of morbidity and mortality. A breach in the lung alveolar-epithelial barrier and impairment in lung function are hallmarks of acute and chronic pulmonary illness. This review is part two of our previous work. In part 1, we demonstrated that CdM is as effective as MSCs in modulating inflammation. Herein, we investigated the effects of mesenchymal stromal cell (MSC)-conditioned media (CdM) on (i) lung architecture/function in animal models mimicking human lung disease, and (ii) performed a head-to-head comparison of CdM to MSCs.

METHODS

Adhering to the animal Systematic Review Centre for Laboratory animal Experimentation protocol, we conducted a search of English articles in five medical databases. Two independent investigators collected information regarding lung: alveolarization, vasculogenesis, permeability, histologic injury, compliance, and measures of right ventricular hypertrophy and right pulmonary pressure. Meta-analysis was performed to generate random effect size using standardized mean difference with 95% confidence interval.

RESULTS

A total of 29 studies met inclusion. Lung diseases included bronchopulmonary dysplasia, asthma, pulmonary hypertension, acute respiratory distress syndrome, chronic obstructive pulmonary disease, and pulmonary fibrosis. CdM improved all measures of lung structure and function. Moreover, no statistical difference was observed in any of the lung measures between MSCs and CdM.

CONCLUSIONS

In this meta-analysis of animal models recapitulating human lung disease, CdM improved lung structure and function and had an effect size comparable to MSCs.

Renal protective effects of astragaloside IV, in diabetes mellitus kidney damage animal models: A systematic review, meta-analysis

Astragaloside IV (ASIV) is the essential active component of astragalus that has diverse biological activities. Previous research has suggested its potentially beneficial effects on diabetic nephropathies. However, its effects and protective mechanism remain unclear. In this study, we conducted a preclinical systematic review to evaluate the efficacy and potential mechanisms of ASIV in reducing kidney damage in diabetes mellitus (DM) models. Studies were searched from nine databases until January 2020. A random-effects model was used to calculate combined standardised mean difference estimates and 95 % confidence intervals. Risk of bias of studies was assessed using the Systematic Review Center for Laboratory Animal Experimentation risk of bias tool 10-item checklist. RevMan 5.3 software was used for statistical analysis. Twenty-three studies involving 562 animals were included in the meta-analysis. Studies quality scores ranged from 2 to 5. The ASIV group induced a marked decrease in serum creatinine (P < 0.00001), blood urea nitrogen (P < 0.00001), 24-h urine protein (P < 0.00001) and pathological score (P < 0.001) compared with the control group. The determined potential mechanisms of ASIV action were relieving oxidative stress, delaying renal fibrosis, anti-apoptosis and anti-inflammatory action. We conclude that ASIV exerts renal protective effects in animals with DM through multiple signalling pathways.

Publication rate in preclinical research: a plea for preregistration

OBJECTIVES

The ultimate goal of biomedical research is the development of new treatment options for patients. Animal models are used if questions cannot be addressed otherwise. Currently, it is widely believed that a large fraction of performed studies are never published, but there are no data that directly address this question.

METHODS

We have tracked a selection of animal study protocols approved in the University Medical Center Utrecht in the Netherlands, to assess whether these have led to a publication with a follow-up period of 7 years.

RESULTS

We found that 60% of all animal study protocols led to at least one publication (full text or abstract). A total of 5590 animals were used in these studies, of which 26% was reported in the resulting publications.

CONCLUSIONS

The data presented here underline the need for preclinical preregistration, in view of the risk of reporting and publication bias in preclinical research. We plea that all animal study protocols should be prospectively registered on an online, accessible platform to increase transparency and data sharing. To facilitate this, we have developed a platform dedicated to animal study protocol registration: www.preclinicaltrials.eu.

Development of Cardiac Regenerative Medicine Using Human iPS Cell-derived Cardiomyocytes

Heart failure is a life-threatening disease prevalent worldwide. Cardiac transplantation is the last resort for patients with severe heart failure, but donor shortages represent a critical issue. Cardiac regenerative therapy is beneficial, but it is currently unsuitable as a substitute for cardiac transplantation. Human induced pluripotent stem cells (hiPSCs) are excellent sources for the generation of terminally differentiated cells. The preparation of a large number of pure cardiomyocytes (CMs) is the major premise for translational studies. To control the quality of the generated CMs, an efficient differentiation method, purification strategy, and mass-scale culture must be developed. Metabolic purification and large-scale culture systems have been established, and pure hiPSC-derived CMs of clinical grade are now available for translational research. The most critical challenge in cell therapy is the engraftment of transplanted cells. To overcome the low engraftment ratio of single CMs, aggregations of CMs are developed as cardiac spheroids. A cardiac transplantation device with domed tips and lateral holes has been developed for the transplantation of cardiac spheroids. Large animal models are necessary as the next step in the process toward clinical application. The transplant device has successfully been used to inject cardiac spheroids uniformly into myocardial layers in swine, and this approach is progressing toward clinical use. Remaining issues include immunological rejection and arrhythmia, which will require further investigation to establish safe and effective transplantation. This review summarizes the present status and future challenges of cardiac regenerative therapies.

Safety and efficacy of cell therapies in pediatric heart disease: a systematic review and meta-analysis

BACKGROUND

Adult clinical trials have reported safety and the therapeutic potential of stem cells for cardiac disease. These observations have now translated to the pediatric arena. We conducted a meta-analysis to assess safety and efficacy of cell-based therapies in animal and human studies of pediatric heart disease.

METHODS AND RESULTS

A literature search was conducted to examine the effects of cell-based therapies on: (i) safety and (ii) cardiac function. In total, 18 pre-clinical and 13 human studies were included. Pre-clinical: right ventricular dysfunction was the most common animal model (80%). Cardiac-derived (28%) and umbilical cord blood (24%) cells were delivered intravenously (36%) or intramyocardially (35%). Mortality was similar between cell-based and control groups (OR 0.94; 95% CI 0.05, 17.41). Cell-based treatments preserved ejection fraction by 6.9% (p < 0.01), while intramyocardial at a dose of 1-10 M cells/kg optimized ejection fraction. Clinical: single ventricle physiology was the most common cardiac disease (n = 9). Cardiac tissue was a frequent cell source, dosed from 3.0 × 105 to 2.4 × 107 cells/kg. A decrease in adverse events occurred in the cell-based cohort (OR 0.17, p < 0.01). Administration of cell-based therapies improved ejection fraction (MD 4.84; 95% CI 1.62, 8.07; p < 0.01).

CONCLUSIONS

In this meta-analysis, cell-based therapies were safe and improved specific measures of cardiac function. Implications from this review may provide methodologic recommendations (source, dose, route, timing) for future clinical trials. Of note, many of the results described in this study pattern those seen in adult stem cell reviews and meta-analyses.

Unravelling the Biology of Adult Cardiac Stem Cell-Derived Exosomes to Foster Endogenous Cardiac Regeneration and Repair

Cardiac remuscularization has been the stated goal of the field of regenerative cardiology since its inception. Along with the refreshment of lost and dysfunctional cardiac muscle cells, the field of cell therapy has expanded in scope encompassing also the potential of the injected cells as cardioprotective and cardio-reparative agents for cardiovascular diseases. The latter has been the result of the findings that cell therapies so far tested in clinical trials exert their beneficial effects through paracrine mechanisms acting on the endogenous myocardial reparative/regenerative potential. The endogenous regenerative potential of the adult heart is still highly debated. While it has been widely accepted that adult cardiomyocytes (CMs) are renewed throughout life either in response to wear and tear and after injury, the rate and origin of this phenomenon are yet to be clarified. The adult heart harbors resident cardiac/stem progenitor cells (CSCs/CPCs), whose discovery and characterization were initially sufficient to explain CM renewal in response to physiological and pathological stresses, when also considering that adult CMs are terminally differentiated cells. The role of CSCs in CM formation in the adult heart has been however questioned by some recent genetic fate map studies, which have been proved to have serious limitations. Nevertheless, uncontested evidence shows that clonal CSCs are effective transplantable regenerative agents either for their direct myogenic differentiation and for their paracrine effects in the allogeneic setting. In particular, the paracrine potential of CSCs has been the focus of the recent investigation, whereby CSC-derived exosomes appear to harbor relevant regenerative and reparative signals underlying the beneficial effects of CSC transplantation. This review focuses on recent advances in our knowledge about the biological role of exosomes in heart tissue homeostasis and repair with the idea to use them as tools for new therapeutic biotechnologies for "cell-less" effective cardiac regeneration approaches.

N-cadherin overexpression enhances the reparative potency of human-induced pluripotent stem cell-derived cardiac myocytes in infarcted mouse hearts

AIMS

In regenerative medicine, cellular cardiomyoplasty is one of the promising options for treating myocardial infarction (MI); however, the efficacy of such treatment has shown to be limited due to poor survival and/or functional integration of implanted cells. Within the heart, the adhesion between cardiac myocytes (CMs) is mediated by N-cadherin (CDH2) and is critical for the heart to function as an electromechanical syncytium. In this study, we have investigated whether the reparative potency of human-induced pluripotent stem cell-derived cardiac myocytes (hiPSC-CMs) can be enhanced through CDH2 overexpression.

METHODS AND RESULTS

CDH2-hiPSC-CMs and control wild-type (WT)-hiPSC-CMs were cultured in myogenic differentiation medium for 28 days. Using a mouse MI model, the cell survival/engraftment rate, infarct size, and cardiac functions were evaluated post-MI, at Day 7 or Day 28. In vitro, conduction velocities were significantly greater in CDH2-hiPSC-CMs than in WT-hiPSC-CMs. While, in vivo, measurements of cardiac functions: left ventricular (LV) ejection fraction, reduction in infarct size, and the cell engraftment rate were significantly higher in CDH2-hiPSC-CMs treated MI group than in WT-hiPSC-CMs treated MI group. Mechanistically, paracrine activation of ERK signal transduction pathway by CDH2-hiPSC-CMs, significantly induced neo-vasculogenesis, resulting in a higher survival of implanted cells.

CONCLUSION

Collectively, these data suggest that CDH2 overexpression enhances not only the survival/engraftment of cultured CDH2-hiPSC-CMs, but also the functional integration of these cells, consequently, the augmentation of the reparative properties of implanted CDH2-hiPSC-CMs in the failing hearts.

Are all stem cells equal? Systematic review, evidence map, and meta-analyses of preclinical stem cell-based therapies for bronchopulmonary dysplasia

Regenerative stem cell-based therapies for bronchopulmonary dysplasia (BPD), the most common preterm birth complication, demonstrate promise in animals. Failure to objectively appraise available preclinical data and identify knowledge gaps could jeopardize clinical translation. We performed a systematic review and network meta-analysis (NMA) of preclinical studies testing cell-based therapies in experimental neonatal lung injury. Fifty-three studies assessing 15 different cell-based therapies were identified: 35 studied the effects of mesenchymal stromal cells (MSCs) almost exclusively in hyperoxic rodent models of BPD. Exploratory NMAs, for select outcomes, suggest that MSCs are the most effective therapy. Although a broad range of promising cell-based therapies has been assessed, few head-to-head comparisons and unclear risk of bias exists. Successful clinical translation of cell-based therapies demands robust preclinical experimental design with appropriately blinded, randomized, and statistically powered studies, based on biological plausibility for a given cell product, in standardized models and endpoints with transparent reporting.

Perspectives on Directions and Priorities for Future Preclinical Studies in Regenerative Medicine

The myocardium consists of numerous cell types embedded in organized layers of ECM (extracellular matrix) and requires an intricate network of blood and lymphatic vessels and nerves to provide nutrients and electrical coupling to the cells. Although much of the focus has been on cardiomyocytes, these cells make up <40% of cells within a healthy adult heart. Therefore, repairing or regenerating cardiac tissue by merely reconstituting cardiomyocytes is a simplistic and ineffective approach. In fact, when an injury occurs, cardiac tissue organization is disrupted at the level of the cells, the tissue architecture, and the coordinated interaction among the cells. Thus, reconstitution of a functional tissue must reestablish electrical and mechanical communication between cardiomyocytes and restore their surrounding environment. It is also essential to restore distinctive myocardial features, such as vascular patency and pump function. In this article, we review the current status, challenges, and future priorities in cardiac regenerative or reparative medicine. In the first part, we provide an overview of our current understanding of heart repair and comment on the main contributors and mechanisms involved in innate regeneration. A brief section is dedicated to the novel concept of rejuvenation or regeneration, which we think may impact future development in the field. The last section describes regenerative therapies, where the most advanced and disruptive strategies used for myocardial repair are discussed. Our recommendations for priority areas in studies of cardiac regeneration or repair are summarized in Tables 1 and 2 .

Mesenchymal stromal cell conditioned media for lung disease: a systematic review and meta-analysis of preclinical studies

BACKGROUND

Inflammation plays an important role in the pathogenesis of many lung diseases. Preclinical studies suggest that mesenchymal stromal cell (MSC) conditioned media (CdM) can attenuate inflammation. Our aim was threefold: (1) summarize the existing animal literature evaluating CdM as a therapeutic agent for pediatric/adult lung disease, (2) quantify the effects of CdM on inflammation, and (3) compare inflammatory effects of CdM to MSCs.

METHODS

Adhering to the Systematic Review Protocol for Animal Intervention Studies, a systematic search of English articles was performed in five databases. Meta-analysis and meta-regression were performed to generate random effect size using standardized mean difference (SMD).

RESULTS

A total of 10 studies met inclusion. Lung diseases included bronchopulmonary dysplasia, asthma, pulmonary hypertension, and acute respiratory distress syndrome. CdM decreased inflammatory cells (1.02 SMD, 95% CI 0.86, 1.18) and cytokines (0.71 SMD, 95% CI 0.59, 0.84). The strongest effect for inflammatory cells was in bronchopulmonary dysplasia (3.74 SMD, 95% CI 3.13, 4.36) while pulmonary hypertension had the greatest reduction in inflammatory cytokine expression (1.44 SMD, 95% CI 1.18, 1.71). Overall, CdM and MSCs had similar anti-inflammatory effects.

CONCLUSIONS

In this meta-analysis of animal models recapitulating lung disease, CdM improved inflammation and had an effect size comparable to MSCs. While these findings are encouraging, the risk of bias and heterogeneity limited the strength of our findings.

From the Lab to Patients: a Systematic Review and Meta-Analysis of Mesenchymal Stem Cell Therapy for Stroke

There may be the potential to improve stroke recovery with mesenchymal stem cells (MSCs); however, questions about the efficacy and safety of this treatment remain. To address these issues and inform future studies, we performed a preclinical and clinical systematic review of MSC therapy for subacute and chronic ischemic stroke. MEDLINE, Embase, the Cochrane Register of Controlled Trials, and PubMed were searched. For the clinical review, interventional and observational studies of MSC therapy in ischemic stroke patients were included. For the preclinical review, interventional studies of MSC therapy using in vivo animal models of subacute or chronic stroke were included. Measures of safety and efficacy were assessed. Eleven clinical and 76 preclinical studies were included. Preclinically, MSC therapy was associated with significant benefits for multiple measures of motor and neurological function. Clinically, MSC therapy appeared to be safe, with no increase in adverse events reported (with the exception of self-limited fever immediately following injection). However, the efficacy of treatment was less apparent, with significant heterogeneity in both study design and effect size being observed. Additionally, in the only randomized phase II study to date, efficacy of MSC therapy was not observed. Preclinically, MSC therapy demonstrated considerable efficacy. Although MSC therapy demonstrated safety in the clinical setting, efficacy has yet to be determined. Future studies will need to address the discordance in the continuity of evidence as MSC therapy has been translated from "bench-to-bedside".

Displacement analysis of myocardial mechanical deformation (DIAMOND) reveals segmental susceptibility to doxorubicin-induced injury and regeneration

Zebrafish are increasingly utilized to model cardiomyopathies and regeneration. Current methods evaluating cardiac function have known limitations, fail to reliably detect focal mechanics, and are not readily feasible in zebrafish. We developed a semiautomated, open-source method - displacement analysis of myocardial mechanical deformation (DIAMOND) - for quantitative assessment of 4D segmental cardiac function. We imaged transgenic embryonic zebrafish in vivo using a light-sheet fluorescence microscopy system with 4D cardiac motion synchronization. Our method permits the derivation of a transformation matrix to quantify the time-dependent 3D displacement of segmental myocardial mass centroids. Through treatment with doxorubicin, and by chemically and genetically manipulating the myocardial injury-activated Notch signaling pathway, we used DIAMOND to demonstrate that basal ventricular segments adjacent to the atrioventricular canal display the highest 3D displacement and are also the most susceptible to doxorubicin-induced injury. Thus, DIAMOND provides biomechanical insights into in vivo segmental cardiac function scalable to high-throughput research applications.

Stem cell-based therapies in neonatology: a new hope

Despite progress made in neonatal intensive care, complications of extreme preterm birth still contribute as the main cause of death to children below 5 years of age. Stem cell-based therapies-mesenchymal stromal cells in particular-offer a new hope in preventing and/or restoring organ damage in extreme preterm infants. Early phase clinical trials, fueled by promising preclinical studies on lung and brain injury, have begun. While the enthusiasm in the neonatal community is palpable, much more needs to be learnt about cell-based therapies. Maintaining the balance between temptation and a cautious, evidence-based approach will be critical for cell therapies to fulfil their promise in substantially improving the outcome of extreme preterm infants.

Therapeutic approaches for cardiac regeneration and repair

Ischaemic heart disease is a leading cause of death worldwide. Injury to the heart is followed by loss of the damaged cardiomyocytes, which are replaced with fibrotic scar tissue. Depletion of cardiomyocytes results in decreased cardiac contraction, which leads to pathological cardiac dilatation, additional cardiomyocyte loss, and mechanical dysfunction, culminating in heart failure. This sequential reaction is defined as cardiac remodelling. Many therapies have focused on preventing the progressive process of cardiac remodelling to heart failure. However, after patients have developed end-stage heart failure, intervention is limited to heart transplantation. One of the main reasons for the dramatic injurious effect of cardiomyocyte loss is that the adult human heart has minimal regenerative capacity. In the past 2 decades, several strategies to repair the injured heart and improve heart function have been pursued, including cellular and noncellular therapies. In this Review, we discuss current therapeutic approaches for cardiac repair and regeneration, describing outcomes, limitations, and future prospects of preclinical and clinical trials of heart regeneration. Substantial progress has been made towards understanding the cellular and molecular mechanisms regulating heart regeneration, offering the potential to control cardiac remodelling and redirect the adult heart to a regenerative state.

The Next Generation of Physician-Scientists: Adapting to Academic Cardiology in the 21st Century

More than 3 decades ago, Wyngaarden and Gill first warned of the challenges facing physician-scientists in their seminal papers "The Clinical Investigator as an Endangered Species" and "The End of the Physician-Scientist." In the years since these papers were published, there has been expansion of stage I-II preclinical research focusing on discovery and exploratory studies. Expansion has often come at the expense of physician-scientists whose traditional role has been to bridge the gap between early preclinical research (stage I-II) and clinical trials (stage IV). Consequently, a paradigm shift has occurred, and increasing pressure has been placed on physician-scientists to choose between clinical practice and fundamental research. This shift is particularly concerning in the field of cardiovascular medicine, where the ubiquitous nature and clinical significance of cardiovascular disease make the role of the translational scientist essential. The challenges facing academic cardiologists have then further been amplified by the necessity not only to maintain clinical competence but also to maintain competence in highly technical fields with rapidly advancing technology. Potential solutions to these problems include increasing support from postgraduate training programs, increased participation of trainees in physician-scientist development programs, and recognition of the pivotal role physician-scientists play in translational research by funding agencies. Although the physician-scientist remains an endangered species, multifaceted solutions with a focus on collaboration among institutions, training programs, and funding agencies have the potential to maximize efficiency in biomedical research and successfully translate scientific discoveries from bench to bedside.

Pharmacologic targeting of the diabetic stem cell mobilopathy

Diabetes is a chronic metabolic disease characterized by hyperglycemia and several associated biochemical abnormalities. Diabetes leads to multiorgan complications that collectively reduce life expectancy. Hematopoietic stem cells (HSCs) are nested within bone marrow (BM) niches whence they can be mobilized to the peripheral circulation. Clinically, this is done for HSC collection and autologous or allogenic transplantation. A great amount of data from basic and clinical studies support that diabetic patients are poor HSC mobilizers owing to BM remodeling. Dysfunction of the BM shares pathophysiological features and pathways with typical chronic diabetic complications that affect other issues (e.g. the retina and the kidney). From a clinical perspective, impaired HSC mobilization translates into the failure to collect a minimum number of CD34⁺ cells to achieve a safe engraftment after transplantation. Furthermore, blunted mobilization is associated with reduced steady-state levels of circulating HSCs, which have been consistently described in diabetic patients and associated with increased risk of adverse outcomes, including cardiovascular events and death. In this review, we discuss the most clinically relevant pharmacological options to overcome impaired HSC mobilization in diabetes. These therapeutic strategies may result in an improved outcome of diabetic patients undergoing HSC transplantation and restore circulating HSC levels, thereby protecting from adverse cardiovascular outcomes.

Sustained release of basic fibroblast growth factor using gelatin hydrogel improved left ventricular function through the alteration of collagen subtype in a rat chronic myocardial infarction model

OBJECTIVE

Chronic myocardial infarction (CMI) tends to be resistant to treatments possibly due to extensive solid fibrotic scar, hypoxia mediated by poorly vascularized environment, and/or inflammation and apoptosis. Here we aimed to testify the therapeutic effects of sustained release of basic fibroblast growth factor (bFGF) using gelatin hydrogel (GH) in a rat chronic MI model and to elucidate the therapeutic mechanism including the alteration of extracellular matrix component.

METHODS

CMI model rats are prepared by the permanent ligation of proximal left anterior descending coronary artery. After 4 weeks, GH sheets (GHSs) with bFGF (100 µg) (bFGF group) or with phosphate-buffered saline (Vehicle group) were implanted to the CMI models to evaluate the effect of bFGF-GHS on chronic scar tissue. Sham operation group was also prepared (n = 5 for each).

RESULTS

4 weeks after implantation, bFGF-GHS significantly improved cardiac contractile function (fractional shortening: 21.8 ± 1.1 vs 21.5 ± 1.3 vs 29.7 ± 1.8%; P < 0.001/fractional area change: 33.0 ± 1.4 vs 34.1 ± 2.3 vs 40.6 ± 1.8%; P < 0.001) (Sham vs Vehicle vs bFGF) accompanied with neovascularization. Immunohistochemical studies revealed that bFGF-GHS increased collagen III/I ratio indicating the alteration of solid scar tissue. Quantitative RT-PCR results showed a decrease of collagen I mRNA expression within border MI zone.

CONCLUSIONS

The implantation of bFGF-GHS altered the collagen subtype of the fibrotic scar more suitable for tissue repair. The treatment of sustained-release bFGF may be promising for ischemic heart disease through chronic pathology.

Role of Extracellular Matrix in Cardiac Cellular Therapies

The extracellular matrix (ECM) is an essential regulator of homeostasis at the cellular, tissue, and organ level. It is now very well known that ECM dynamic remodeling is indispensable not only for normal growth and development but also recovery from tissue injuries. Indeed, abnormal remodeling of the ECM plays a major role in many pathophysiological processes and contributes to many different pathologies including cardiovascular disorders. Recently, cellular therapies have emerged as a potential therapeutic strategy for restoration of lost cardiomyocytes or their rejuvenation after cardiac damage and injuries. Harnessing the biological properties of ECM could be a viable strategy to enhance the therapeutic effects of cellular therapies by improving the engraftment, integration, survival, and functional adaptation of newly transplanted cells in many different platforms. Conversely, transplanted cells could restore the functionality and original composition of damaged ECM by secreting and depositing new ECM or stimulating normal ECM production by cardiac tissue native cells. Although the ultimate role of cell therapy in treatment of cardiac disorders is still a matter of great debate, the potential utility of ECM in improving the therapeutic effect of transplanted cells and vice versa the potential role of cell therapy as a means to restore the structure and functionality of damaged ECM should be carefully considered in implementation of future clinical cardiovascular cell therapy trials.