Roberto Bolli

Cardiomyocyte Regeneration: A Consensus Statement

Cell therapy is an exciting option for repairing the injured heart, one that has attracted considerable interest over the past 15 years. Consensus exists that the injection/infusion or tissue-based implantation of various cell types may exert therapeutic effects,1–3 and there is general agreement that additional molecular, translational, and clinical studies are required to define the optimal cell source, method of delivery, and underlying mechanism(s) of action.nnOne of the remaining questions in this field pertains to cardiomyocyte turnover under normal and diseased conditions and its contribution to the beneficial effects of cell therapy. Although results published in the literature have not been consistent, we believe that the time is ripe to formulate a consensus for many of the pertinent questions.nnIt is important to emphasize that the focus of this consensus statement is on cardiomyocyte renewal; it is not on cell therapy in general. Although we touch on some aspects of therapeutic strategies based on delivery of exogenous cells, our intent here is to define areas of agreement and areas requiring further elucidation related to the regenerative potential of the myocardium itself.nnWe have included references to the scientific literature throughout the document. Although it is impossible for us to include all publications in this expansive field, representative studies that corroborate statements herein have been cited.nn1. Definition of cardiomyocyte renewal.n In this consensus statement, the term cardiomyocyte renewal is defined as the ability to replace lost cardiomyocytes by new ones. It is distinct from the turnover of cardiac proteins or the generation of polyploid cardiomyocytes (ie, those harboring >2 sets of chromosomes), either by nuclear division giving rise to multinucleation or by duplication of DNA without nuclear division resulting in polyploid nuclei.nn2. Naturally occurring cardiomyocyte renewal and proliferation.n 1. During normal mammalian developmentn 1. Growth of the heart during …

Guidelines for experimental models of myocardial ischemia and infarction

Myocardial infarction is a prevalent major cardiovascular event that arises from myocardial ischemia with or without reperfusion, and basic and translational research is needed to better understand its underlying mechanisms and consequences for cardiac structure and function. Ischemia underlies a broad range of clinical scenarios ranging from angina to hibernation to permanent occlusion, and while reperfusion is mandatory for salvage from ischemic injury, reperfusion also inflicts injury on its own. In this consensus statement, we present recommendations for animal models of myocardial ischemia and infarction. With increasing awareness of the need for rigor and reproducibility in designing and performing scientific research to ensure validation of results, the goal of this review is to provide best practice information regarding myocardial ischemia-reperfusion and infarction models. Listen to this article’s corresponding podcast at ajpheart.podbean.com/e/guidelines-for-experimental-models-of-myocardial-ischemia-and-infarction/.

Overcoming the Roadblocks to Cardiac Cell Therapy Using Tissue Engineering

Transplantations of various stem cells or their progeny have repeatedly improved cardiac performance in animal models of myocardial injury; however, the benefits observed in clinical trials have been generally less consistent. Some of the recognized challenges are poor engraftment of implanted cells and, in the case of human cardiomyocytes, functional immaturity and lack of electrical integration, leading to limited contribution to the hearts contractile activity and increased arrhythmogenic risks. Advances in tissue and genetic engineering techniques are expected to improve the survival and integration of transplanted cells, and to support structural, functional, and bioenergetic recovery of thexa0recipient hearts. Specifically, application of a prefabricated cardiac tissue patch to prevent dilation and to improvexa0pumping efficiency of the infarcted heart offers a promising strategy for making stem cell therapy a clinicalxa0reality.

Translational research in cardiovascular repair a call for a paradigm shift

The international consortium TACTICS (Transnational Alliance for Regenerative Therapies in Cardiovascular Syndromes) has recently addressed key priorities in the field of cell-based therapy for cardiac repair, identifying the efficacy of translational research as one of the main challenges to ultimately improve the quality of life of patients with ischemic disease. Much of the controversy and confusion surrounding cardiac regenerative therapy stems from insufficient rigor in the conduct of preclinical studies, and there is an increasing recognition of a number of problems that undermine its quality that may contribute to translational failure. Here, we introduce well defined stages for preclinical research, and put forth proposals that should promote more rigorous preclinical work, in an effort to improve its quality and translatability. To augment the utility of preclinical research and its translation, it is necessary to (1) improve the quality of preclinical research, (2) promote collaborative efforts, and (3) enhance the sharing of knowledge and protocols. In particular, confirmatory (stage III) preclinical studies should be considered as a preamble to clinical studies and therefore must adhere to their standards of quality (including internal validity, standardization of protocols, and multicenter design). To increase transparency and minimize bias, these studies should be prospectively registered in an independent, open database. Ultimately, these recommendations should be implemented in the daily routine of investigators and in the policies of institutions, journals, and funding agencies.

Circulating Biomarkers to Identify Responders in Cardiac Cell therapy

Bone marrow mononuclear cell (BM-MNC) therapy in ST-elevation acute myocardial infarction (STEMI) has no biological inclusion criteria. Here, we analyzed 63 biomarkers and cytokines in baseline plasma samples from 77 STEMI patients treated with BM-MNCs in the TIME and Late-TIME trials as well as 61 STEMI patients treated with placebo. Response to cell therapy was defined by changes in left ventricular ejection fraction, systolic/diastolic volumes, and wall motion indexes. We investigated the clinical value of circulating proteins in outcome prediction using significance testing, partial least squares discriminant analysis, and receiver operating characteristic (ROC) analysis. Responders had higher biomarker levels (76–94% elevated) than non-responders. Several biomarkers had values that differed significantly (Pu2009<u20090.05) between responders and non-responders including stem cell factor, platelet-derived growth factor, and interleukin-15. We then used these lead candidates for ROC analysis and found multiple biomarkers with values areas under the curve >0.70 including interleukin 15. These biomarkers were not involved in the placebo-treated subjects suggesting that they may have predictive power. We conclude that plasma profiling after STEMI may help identify patients with a greater likelihood of response to cell-based treatment. Prospective trials are needed to assess the predictive value of the circulating biomarkers.

Repeated Administrations of Cardiac Progenitor Cells Are Superior to a Single Administration of an Equivalent Cumulative Dose

Background We have recently found that 3 repeated doses (12×106 each) of c‐kitPOS cardiac progenitor cells (CPCs) were markedly more effective than a single dose of 12×106 cells in alleviating postinfarction left ventricular dysfunction and remodeling. However, since the single‐dose group received only one third of the total number of CPCs given to the multiple‐dose group, it is unknown whether the superior therapeutic efficacy was caused by repeated treatments per se or by administration of a higher total number of CPCs. This issue has major clinical implications because multiple cell injections in patients pose significant challenges, which would be obviated by using 1 large injection. Accordingly, we determined whether the beneficial effects of 3 repeated CPC doses can be recapitulated by 1 large dose containing the same total number of cells. Methods and Results Rats with a 30‐day‐old myocardial infarction received 3 echo‐guided intraventricular infusions, 35 days apart, of vehicle‐vehicle‐vehicle, 36×106 CPCs‐vehicle‐vehicle, or 3 equal doses of 12×106 CPCs. Infusion of a single, large dose of CPCs (36×106 cells) produced an initial improvement in left ventricular function, but no further improvement was observed after the second and third infusions (both vehicle). In contrast, each of the 3 doses of CPCs (12×106) caused a progressive improvement in left ventricular function, the cumulative magnitude of which was greater than with a single dose. Unlike the single dose, repeated doses reduced collagen content and immune cell infiltration. Conclusions Three repeated doses of CPCs are superior to 1 dose even though the total number of cells infused is the same, possibly because of greater antifibrotic and anti‐inflammatory actions.

Global Overview of the Transnational Alliance for Regenerative Therapies in Cardiovascular Syndromes (TACTICS) Recommendations: A Comprehensive Series of Challenges and Priorities of Cardiovascular Regenerative Medicine

Cardiovascular regenerative medicine (CRM) has been defined as an innovative research field that includes all diagnostic and therapeutic strategies aimed at restoring cardiovascular health by enhancing the innate regenerative response of cardiac and vascular tissues.1 The TACTICS (Transnational Alliance for Regenerative Therapies in Cardiovascular Syndromes) was created in 2015 with the vision of advancing CRM through synergy of basic discoveries and translational clinical efforts in the fight against cardiovascular failure and has grown to include >100 research groups worldwide.2 This unprecedented initiative stated as specific missions the redefinition of CRM and advanced therapy regenerative products, the establishment of discovery and development priorities for the next decade, and the attainment and dissemination of a consensual strategy to reinforce the field increasing its credibility.nnThe first milestone of TACTICS has been achieved with the publication of a Global Consensus Document.1 However, given the amplitude and relevance of its different chapters, a more detailed description of all of them has been deemed necessary, following the same scheme of the Global Consensus Document and, therefore, discussing the main topics and priorities of the CRM field.nnThis is the final aim of this Cardiovascular Regenerative and Reparative Medicine Circulation Research review series. In this first chapter, the following ones are presented and summarized in the form of and index of consecutive articles, which will cover biological fundamentals, preclinical models, and all clinical research-related issues. These articles will be regularly and subsequently published in this journal, on behalf of the TACTICS Consortium (Figure).nnnnFigure. nSchematic representation of all articles included in this Review series . TACTICS indicates Transnational Alliance for Regenerative Therapies in Cardiovascular Syndromes.nnnnThe hypothesis of CRM being able to revolutionize cardiovascular clinical practice has been based on the mainly positive and overall consistent results of preclinical research. However, the lack …

Histone Deacetylase 1 Depletion Activates Human Cardiac Mesenchymal Stromal Cell Proangiogenic Paracrine Signaling Through a Mechanism Requiring Enhanced Basic Fibroblast Growth Factor Synthesis and Secretion

Background Cardiac mesenchymal cell (CMC) administration improves cardiac function in animal models of heart failure. Although the precise mechanisms remain unclear, transdifferentiation and paracrine signaling are suggested to underlie their cardiac reparative effects. We have shown that histone deacetylase 1 (HDAC1) inhibition enhances CMC cardiomyogenic lineage commitment. Here, we investigated the impact of HDAC1 on CMC cytokine secretion and associated paracrine‐mediated activities on endothelial cell function. Methods and Results CMCs were transduced with shRNA constructs targeting HDAC1 (shHDAC1) or nontarget (shNT) control. Cytokine arrays were used to assess the expression of secreted proteins in conditioned medium (CM) from shHDAC1 or shNT‐transduced CMCs. In vitro functional assays for cell proliferation, protection from oxidative stress, cell migration, and tube formation were performed on human endothelial cells incubated with CM from the various treatment conditions. CM from shHDAC1‐transduced CMCs contained more cytokines involved in cell growth/differentiation and more efficiently promoted endothelial cell proliferation and tube formation compared with CM from shNT. After evaluating key cytokines previously implicated in cell‐therapy–mediated cardiac repair, we found that basic fibroblast growth factor was significantly upregulated in shHDAC1‐transduced CMCs. Furthermore, shRNA‐mediated knockdown of basic fibroblast growth factor in HDAC1‐depleted CMCs inhibited the effects of shHDAC1 CM in promoting endothelial proliferation and tube formation—indicating that HDAC1 depletion activates CMC proangiogenic paracrine signaling in a basic fibroblast growth factor–dependent manner. Conclusions These results reveal a hitherto unknown role for HDAC1 in the modulation of CMC cytokine secretion and implicate the targeted inhibition of HDAC1 in CMCs as a means to enhance paracrine‐mediated neovascularization in cardiac cell therapy applications.