The directed differentiation of human cardiomyocytes (CMs) from pluripotent cells provides an invaluable model for understanding mechanisms of cell fate determination and offers considerable promise in cardiac regenerative medicine. Here, we utilize a human embryonic stem cell suspension bank, produced according to a good manufacturing practice, to generate CMs using a fully defined and small molecule-based differentiation strategy. Primitive and cardiac mesoderm purification was used to remove non-committing and multi-lineage populations and this significantly aided the identification of key transcription factors, lncRNAs, and essential signaling pathways that define cardiomyogenesis. Global methylation profiles reflect CM development and we report on CM exon DNA methylation "memories" persisting beyond transcription repression and marking the expression history of numerous developmentally regulated genes, especially transcription factors.

DNA methylation is a quintessential epigenetic mechanism. Widely considered a stable regulator of gene silencing, it represents a form of “molecular braille,” chemically printed on DNA to regulate its structure and the expression of genetic information. However, there was a time when methyl groups simply existed in cells, mysteriously speckled across the cytosine building blocks of DNA. Why was the code of life chemically modified, apparently by “no accident of enzyme action” (Wyatt 1951)? If all cells in a body share the same genome sequence, how do they adopt unique functions and maintain stable developmental states? Do cells remember? In this historical perspective, I review epigenetic history and principles and the tools, key scientists, and concepts that brought us the synthesis and discovery of prokaryotic and eukaryotic methylated DNA. Drawing heavily on Gerard Wyatt’s observation of asymmetric levels of methylated DNA across species, as well as to a pair of visionary 1975 DNA methylation papers, 5-methylcytosine is connected to DNA methylating enzymes in bacteria, the maintenance of stable cellular states over development, and to the regulation of gene expression through protein-DNA binding. These works have not only shaped our views on heritability and gene regulation but also remind us that core epigenetic concepts emerged from the intrinsic requirement for epigenetic mechanisms to exist. Driven by observations across prokaryotic and eukaryotic worlds, epigenetic systems function to access and interpret genetic information across all forms of life. Collectively, these works offer many guiding principles for our epigenetic understanding for today, and for the next generation of epigenetic inquiry in a postgenomics world.

Therapeutic interventions to replenish lost cardiomyocytes and recover myocardium functions following ischemic myocardial infarction (MI) remain major goals in the cardiac regeneration field. Clinical trials harnessing autologous or allogeneic cell therapy approaches from both cardiac and noncardiac cells sources, thus far, demonstrate marginal improvement. Moreover, complications such as arrythmias and graft rejections associated with cellular or organ-based therapies continue to prevail. Extracellular vesicles, on the other hand, are cell-derived, nano-sized, cargo-containing biomolecules that have emerged as potent alternatives to cell-based cardiac regeneration/replacement therapy. Recent studies demonstrate that most stem-cell-derived extracellular vesicles (Stem-EVs) are nonimmunogenic and carry cardioprotective therapeutic cargos. Moreover, administration of multiple Stem-EV types in animal models of acute MI results in reduced inflammation, apoptosis, smaller infarct size and improved cardiac functionality. With recent developments, engineered Stem-EVs with enhanced cardiac targeting, prolonged circulation and recombinant therapeutic cargos may tilt the cardiac regeneration field toward these novel cell-free biologics. Here we provide a brief overview of current approaches to repair and replenish damaged cardiomyocytes following MI via cell therapy and in vivo reprogramming, and we delve deeply into the therapeutic potentials of Stem-EVs in cardiac repair and regeneration.

STAT3 deficiency (STAT3^–/–) in donor T cells prevents graft-versus-host disease (GVHD), but the impact on graft-versus-leukemia (GVL) activity and mechanisms of GVHD prevention remains unclear. Here, using murine models of GVHD, we show that STAT3^–/– donor T cells induced only mild reversible acute GVHD while preserving GVL effects against nonsusceptible acute lymphoblastic leukemia (ALL) cells in a donor T cell dose–dependent manner. GVHD prevention depended on programmed death ligand 1/programmed cell death protein 1 (PD-L1/PD-1) signaling. In GVHD target tissues, STAT3 deficiency amplified PD-L1/PD-1 inhibition of glutathione (GSH)/Myc pathways that regulate metabolic reprogramming in activated T cells, with decreased glycolytic and mitochondrial ATP production and increased mitochondrial ROS production and dysfunction, leading to tissue-specific deletion of host-reactive T cells and prevention of GVHD. Mitochondrial STAT3 deficiency alone did not reduce GSH expression or prevent GVHD. In lymphoid tissues, the lack of host-tissue PD-L1 interaction with PD-1 reduced the inhibition of the GSH/Myc pathway despite reduced GSH production caused by STAT3 deficiency and allowed donor T cell functions that mediate GVL activity. Therefore, STAT3 deficiency in donor T cells augments PD-1 signaling–mediated inhibition of GSH/Myc pathways and augments dysfunction of T cells in GVHD target tissues while sparing T cells in lymphoid tissues, leading to prevention of GVHD while preserving GVL effects.

Therapeutic plasma exchange (TPE) is a blood purification technique which functions to remove pathological plasma constituents such as autoantibodies, inflammatory cytokines, immune complexes, and extracellular vesicles (EVs) that contribute to a range of disease states. In this review, we examine current and emerging indications for TPE across cardiovascular, metabolic, neurological, inflammatory, and oncological diseases. We cover emerging preclinical animal models and new applications, emphasizing the roles of cellular signaling and EV biology in mediating plasma functions, and discuss unique therapeutic “windows of opportunity” offered by TPE. We conclude that TPE is underutilized in both preventative and precision medicine, and that next generation TPE therapies will involve personalized plasma biomarker and modulation feedback, with synergistic plasma infusion therapies to mitigate age associated disease and promote tissue rejuvenation.

During gestation, maternal (F0), embryonic (F1), and migrating primordial germ cell (F2) genomes can be simultaneously exposed to environmental influences. Accumulating evidence suggests that operating epi- or above the genetic DNA sequence, covalent DNA methylation (DNAme) can be recorded onto DNA in response to environmental insults, some sites which escape normal germline erasure. These appear to intrinsically regulate future disease propensity, even transgenerationally. Thus, an organism’s genome can undergo epigenetic adjustment based on environmental influences experienced by prior generations. During the earliest stages of mammalian development, the three-dimensional presentation of the genome is dramatically changed, and DNAme is removed genome wide. Why, then, do some pathological DNAme patterns appear to be heritable? Are these correctable? In the following sections, I review concepts of transgenerational epigenetics and recent work towards programming transgenerational DNAme. A framework for editing heritable DNAme and challenges are discussed, and ethics in human research is introduced.