In subclinical AF, apixaban reduced stroke or systemic embolism but increased major bleeding vs. aspirin at 3.5 y.

SOURCE CITATION: Healey JS, Lopes RD, Granger CB, et al; ARTESIA Investigators. Apixaban for stroke prevention in subclinical atrial fibrillation. N Engl J Med. 2024;390:107-117. 37952132.

The extracellular matrix protein agrin promotes heart regeneration in mice.

The adult mammalian heart is non-regenerative owing to the post-mitotic nature of cardiomyocytes. The neonatal mouse heart can regenerate, but only during the first week of life. Here we show that changes in the composition of the extracellular matrix during this week can affect cardiomyocyte growth and differentiation in mice. We identify agrin, a component of neonatal extracellular matrix, as required for the full regenerative capacity of neonatal mouse hearts. In vitro, recombinant agrin promotes the division of cardiomyocytes that are derived from mouse and human induced pluripotent stem cells through a mechanism that involves the disassembly of the dystrophin-glycoprotein complex, and Yap- and ERK-mediated signalling. In vivo, a single administration of agrin promotes cardiac regeneration in adult mice after myocardial infarction, although the degree of cardiomyocyte proliferation observed in this model suggests that there are additional therapeutic mechanisms. Together, our results uncover a new inducer of mammalian heart regeneration and highlight fundamental roles of the extracellular matrix in cardiac repair.

Left Internal Mammary Artery as an Endocrine Organ: Insights Into Graft Biology and Long-term Impact Following Coronary Artery Bypass Grafting.

The left internal mammary artery (LIMA) is considered the criterion standard vessel for use in coronary artery bypass grafting. In recent decades, countless studies have documented its superiority over other arterial and venous coronary artery bypass grafting conduits, although the full mechanisms for this superiority remain unknown. A growing body of literature has unveiled the importance of extracellular vesicles known as exosomes in cardiovascular signaling and various pathologic states. In this review, we briefly compare the clinical longevity of the LIMA relative to other conduits, explore the effects of varying grafting techniques on clinical and angiographic outcomes, and provide physiologic insights into graft function on a cellular and molecular level. Finally, we explore exosome signaling as it pertains to atherosclerosis in support of the LIMA as an "endocrine organ."

Exosome-Induced Vaginal Tissue Regeneration in a Porcine Mesh Exposure Model.

OBJECTIVES: The purpose of this study was to explore the utility of an injectable purified exosome product derived from human apheresis blood to (1) augment surgical closure of vaginal mesh exposures, and (2) serve as a stand-alone therapy for vaginal mesh exposure. METHODS: Sixteen polypropylene meshes (1×1-3×3 cm) were implanted in the vaginas of 7 Yorkshire-crossed pigs by urogynecologic surgeons (day 0). On day 7, group 1 underwent surgical intervention via vaginal tissue suture reclosure with (n=2 pigs, n=4 meshes) or without (n=2 pigs, n=4 meshes) exosome injection; group 2 underwent medical intervention with an exosome injection (n=3, n=8 meshes). One animal in group 2 was given oral 2'-deoxy-5-ethynyluridine to track cellular regeneration. Euthansia occurred at 5 weeks. RESULTS: Mesh exposures treated with surgical closure alone experienced reexposure of the mesh. Exosome treatment with or without surgical closure resulted in partial to full mesh exposure resolution up to 3×3 cm. Exosome-treated tissues had significantly thicker regenerated epithelial tissue (208 µm exosomes-only and 217 µm surgery+exosomes, versus 80 µm for surgery-only; P < 0.05); evaluation of 2'-deoxy-5-ethynyluridine confirmed de novo regeneration throughout the epithelium and underlying tissues. Capillary density was significantly higher in the surgery+exosomes group (P = 0.03). Surgery-only tissues had a higher inflammatory and fibrosis response as compared with exosome-treated tissues. CONCLUSIONS: In this pilot study, exosome treatment augmented healing in the setting of vaginal mesh exposure, reducing the incidence of mesh reexposure after suture closure and decreasing the area of mesh exposure through de novo tissue regeneration after exosome injection only. Further study of varied local tissue conditions and mesh configurations is warranted.

Impact of Repeat Dosing and Mesh Exposure Chronicity on Exosome-Induced Vaginal Tissue Regeneration in a Porcine Mesh Exposure Model.

OBJECTIVE: The aim of the study was to compare vaginal wound healing after exosome injection in a porcine mesh exposure model with (1) single versus multiple dose regimens and (2) acute versus subacute exposure. METHODS: Six 80-kg Yorkshire-crossed swine each had 2 polypropylene meshes implanted to create the vaginal mesh exposure model. Animals were divided into 3 groups based on number and timing of exosome injection: (1) single purified exosome product (PEP) injection (acute-single), (2) weekly PEP injections (acute-weekly, 4 total injections), and (3) delayed single injection (subacute-single). Acute and subacute injections occurred 1 and 8 weeks after mesh implantation, respectively. EdU, a thymidine analog, was given twice weekly after the first injection to track tissue regeneration. Euthanasia and tissue analysis occurred 4 weeks after the first injection. ImageJ was used to quantify epithelial thickness, cellular proliferation, and capillary density. Statistical analysis was performed using analysis of variance and post hoc Tukey test. RESULTS: Acute-single PEP injection tissues mirrored pilot study results, validating replication of protocol. Within the acute groups, weekly dosing resulted in 1.5× higher epithelial thickness (nonsignificant), 1.8× higher epithelial proliferation (P < 0.05), and 1.5× higher regenerated capillary density (P < 0.05) compared with single injection. Regarding chronicity of the exposure, the subacute group showed 1.7× higher epithelial proliferation (nonsignificant) and similar capillary density and epithelial thickness as compared with the acute group. CONCLUSIONS: Exosome redosing resulted in significantly greater epithelial proliferation with significantly higher regenerated capillary density, leading to a trend toward thicker epithelium. Subacute exposure exhibited similar regeneration to acute exposure despite a delayed injection timeline. These results contribute to a growing body of preclinical research demonstrating utility of exosomes in pelvic floor disorders.

Percutaneous Axillary Intra-aortic Balloon Pump Insertion Technique as Bridge to Advanced Heart Failure Therapy.

In patients with advanced heart failure (HF), temporary mechanical circulator support (TMCS) is used to improve hemodynamics, via left ventricular unloading, and end-organ function as a bridge to definitive therapy. While listed for cardiac transplantation, use of TMCS may be prolonged, preventing adequate mobility. Here, we describe the technique for placement of a percutaneous axillary intra-aortic balloon pump (IABP) using single-site arterial access to facilitate ambulation and subsequent safe removal without surgery or a closure device. Retrospective review of the experience with this approach at a single institution between September 2017 and February 2020 documented feasibility and safety. Baseline demographics, hemodynamic data, and clinical outcomes were collected. Thirty-eight patients had a total of 56 IABPs placed. There were no significant access site or cerebrovascular complications. One fifth of IABPs (21.4%) had balloon failure or migration, requiring placement of a new device, though no patients had significant complications from balloon failure. The majority (81.6%) of patients in the cohort on axillary IABP support were ambulatory and ultimately received the intended therapy (63.2% transplant, 13.2% durable left ventricular assist device, 5.3% other cardiac surgery). Percutaneous, axillary IABP is feasible and associated with an acceptable complication rate as a bridge to definitive therapy.

Migratory Polyarthralgias and Skin Rash: Rat Bite Fever with a Positive Anti-Cyclic Citrullinated Peptide.

Rat bite fever is a rare, underdiagnosed disease caused by Streptobacillus moniliformis in the United States, and is typically characterized by leukocytosis, elevated C-reactive protein, migratory polyarthralgias, and pustular skin rash. Rat bite fever is frequently misdiagnosed as either a viral illness or a rheumatologic disease and carries a high mortality risk if untreated. We report the first case of rat bite fever associated with positive anti-cyclic citrullinated peptide. The patient initially presented with low back pain and developed a pustular rash as well as severe asymmetric polyarthralgias. Blood cultures turned positive for S. moniliformis and the patient completed a 4-week course of antibiotics for presumed septic arthritis.

Cardiopatch platform enables maturation and scale-up of human pluripotent stem cell-derived engineered heart tissues.

Despite increased use of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) for drug development and disease modeling studies, methods to generate large, functional heart tissues for human therapy are lacking. Here we present a "Cardiopatch" platform for 3D culture and maturation of hiPSC-CMs that after 5 weeks of differentiation show robust electromechanical coupling, consistent H-zones, I-bands, and evidence for T-tubules and M-bands. Cardiopatch maturation markers and functional output increase during culture, approaching values of adult myocardium. Cardiopatches can be scaled up to clinically relevant dimensions, while preserving spatially uniform properties with high conduction velocities and contractile stresses. Within window chambers in nude mice, cardiopatches undergo vascularization by host vessels and continue to fire Ca2+ transients. When implanted onto rat hearts, cardiopatches robustly engraft, maintain pre-implantation electrical function, and do not increase the incidence of arrhythmias. These studies provide enabling technology for future use of hiPSC-CM tissues in human heart repair.

Rapid fusion between mesenchymal stem cells and cardiomyocytes yields electrically active, non-contractile hybrid cells.

Cardiac cell therapies involving bone marrow-derived human mesenchymal stem cells (hMSCs) have shown promising results, although their mechanisms of action are still poorly understood. Here, we investigated direct interactions between hMSCs and cardiomyocytes in vitro. Using a genetic Ca(2+) indicator gCaMP3 to efficiently label hMSCs in co-cultures with neonatal rat ventricular myocytes (NRVMs), we determined that 25-40% of hMSCs (from 4 independent donors) acquired periodic Ca(2+) transients and cardiac markers through spontaneous fusion with NRVMs. Sharp electrode and voltage-clamp recordings in fused cells showed action potential properties and Ca(2+) current amplitudes in between those of non-fused hMSCs and NRVMs. Time-lapse video-microscopy revealed the first direct evidence of active fusion between hMSCs and NRVMs within several hours of co-culture. Application of blebbistatin, nifedipine or verapamil caused complete and reversible inhibition of fusion, suggesting potential roles for actomyosin bridging and Ca(2+) channels in the fusion process. Immunostaining for Cx43, Ki67, and sarcomeric α-actinin showed that fused cells remain strongly coupled to surrounding NRVMs, but downregulate sarcomeric structures over time, acquiring a non-proliferative and non-contractile phenotype. Overall, these results describe the phenotype and mechanisms of hybrid cell formation via fusion of hMSCs and cardiomyocytes with potential implications for cardiac cell therapy.

Human Cardiac Tissue Engineering: From Pluripotent Stem Cells to Heart Repair.

Engineered cardiac tissues hold great promise for use in drug and toxicology screening, in vitro studies of human physiology and disease, and as transplantable tissue grafts for myocardial repair. In this review, we discuss recent progress in cell-based therapy and functional tissue engineering using pluripotent stem cell-derived cardiomyocytes and we describe methods for delivery of cells into the injured heart. While significant hurdles remain, notable advances have been made in the methods to derive large numbers of pure human cardiomyocytes, mature their phenotype, and produce and implant functional cardiac tissues, bringing the field a step closer to widespread in vitro and in vivo applications.

Tissue-engineered cardiac patch for advanced functional maturation of human ESC-derived cardiomyocytes.

Human embryonic stem cell-derived cardiomyocytes (hESC-CMs) provide a promising source for cell therapy and drug screening. Several high-yield protocols exist for hESC-CM production; however, methods to significantly advance hESC-CM maturation are still lacking. Building on our previous experience with mouse ESC-CMs, we investigated the effects of 3-dimensional (3D) tissue-engineered culture environment and cardiomyocyte purity on structural and functional maturation of hESC-CMs. 2D monolayer and 3D fibrin-based cardiac patch cultures were generated using dissociated cells from differentiated Hes2 embryoid bodies containing varying percentage (48-90%) of CD172a (SIRPA)-positive cardiomyocytes. hESC-CMs within the patch were aligned uniformly by locally controlling the direction of passive tension. Compared to hESC-CMs in age (2 weeks) and purity (48-65%) matched 2D monolayers, hESC-CMs in 3D patches exhibited significantly higher conduction velocities (CVs), longer sarcomeres (2.09 ± 0.02 vs. 1.77 ± 0.01 µm), and enhanced expression of genes involved in cardiac contractile function, including cTnT, αMHC, CASQ2 and SERCA2. The CVs in cardiac patches increased with cardiomyocyte purity, reaching 25.1 cm/s in patches constructed with 90% hESC-CMs. Maximum contractile force amplitudes and active stresses of cardiac patches averaged to 3.0 ± 1.1 mN and 11.8 ± 4.5 mN/mm(2), respectively. Moreover, contractile force per input cardiomyocyte averaged to 5.7 ± 1.1 nN/cell and showed a negative correlation with hESC-CM purity. Finally, patches exhibited significant positive inotropy with isoproterenol administration (1.7 ± 0.3-fold force increase, EC50 = 95.1 nm). These results demonstrate highly advanced levels of hESC-CM maturation after 2 weeks of 3D cardiac patch culture and carry important implications for future drug development and cell therapy studies.

In situ visualization and dynamics of newly synthesized proteins in rat hippocampal neurons.

Protein translation has been implicated in different forms of synaptic plasticity, but direct in situ visualization of new proteins is limited to one or two proteins at a time. Here we describe a metabolic labeling approach based on incorporation of noncanonical amino acids into proteins followed by chemoselective fluorescence tagging by means of 'click chemistry'. After a brief incubation with azidohomoalanine or homopropargylglycine, a robust fluorescent signal was detected in somata and dendrites. Pulse-chase application of azidohomoalanine and homopropargylglycine allowed visualization of proteins synthesized in two sequential time periods. This technique can be used to detect changes in protein synthesis and to evaluate the fate of proteins synthesized in different cellular compartments. Moreover, using strain-promoted cycloaddition, we explored the dynamics of newly synthesized membrane proteins using single-particle tracking and quantum dots. The newly synthesized proteins showed a broad range of diffusive behaviors, as would be expected for a pool of labeled proteins that is heterogeneous.