Bioengineering approaches to mature induced pluripotent stem cell-derived atrial cardiomyocytes to model atrial fibrillation

Engineered cocultures of iPSC-derived atrial cardiomyocytes and atrial fibroblasts for modeling atrial fibrillation

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia treatable with antiarrhythmic drugs; however, patient responses remain highly variable. Human induced pluripotent stem cell-derived atrial cardiomyocytes (iPSC-aCMs) are useful for discovering precision therapeutics, but current platforms yield phenotypically immature cells and are not easily scalable for high-throughput screening. Here, primary adult atrial, but not ventricular, fibroblasts induced greater functional iPSC-aCM maturation, partly through connexin-40 and ephrin-B1 signaling. We developed a protein patterning process within multiwell plates to engineer patterned iPSC-aCM and atrial fibroblast coculture (PC) that significantly enhanced iPSC-aCM structural, electrical, contractile, and metabolic maturation for 6+ weeks compared to conventional mono-/coculture. PC displayed greater sensitivity for detecting drug efficacy than monoculture and enabled the modeling and pharmacological or gene editing treatment of an AF-like electrophysiological phenotype due to a mutated sodium channel. Overall, PC is useful for elucidating cell signaling in the atria, drug screening, and modeling AF.

Functional Activity of Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes on a Mouse Renal Subcapsular Xenograft Model

In the treatment of coronary heart disease, the most promising approach for replacing lost contractile elements involves obtaining cardiomyocytes through cardiac differentiation of pluripotent cells. The objective of this study is to develop a technology for creating a functional layer of cardiomyocytes derived from iPSCs, capable of generating rhythmic activity and synchronous contractions. To expedite the maturation of cardiomyocytes, a renal subcapsular transplantation model was employed in SCID mice. Following explantation, the formation of the cardiomyocyte contractile apparatus was assessed using fluorescence and electron microscopy, while the cytoplasmic oscillation of calcium ions was evaluated through visualization using the fluorescent calcium binding dye Fluo-8. The results demonstrate that transplanted human iPSC-derived cardiomyocyte cell layers, placed under the fibrous capsules of SCID mouse kidneys (for up to 6 weeks), initiate the development of an organized contractile apparatus and retain functional activity along with the ability to generate calcium ion oscillations even after removal from the body.

Novel method of differentiating human induced pluripotent stem cells to mature cardiomyocytes via Sfrp2

Current methods to generate cardiomyocytes from induced pluripotent stem cells (iPSc) utilize broad-spectrum pharmacological inhibitors. These methods give rise to cardiomyocytes which are typically immature. Since we have recently demonstrated that cardiomyogenesis in vitro and in vivo requires Sfrp2, we asked if Sfrp2 would drive differentiation of human iPSc into cardiomyocytes. Indeed, we found that Sfrp2 induced robust cardiac differentiation. Importantly, replacement of broad spectrum pharmacological inhibitors with Sfrp2 gave rise to mature cardiomyocytes as evidenced by their sarcomere structure, electrophysiological profiles, and ability to form gap junctions.

Healing the Broken Hearts: A Glimpse on Next Generation Therapeutics

Cardiovascular diseases are the leading cause of death worldwide, accounting for 32% of deaths globally and thus representing almost 18 million people according to WHO. Myocardial infarction, the most prevalent adult cardiovascular pathology, affects over half a million people in the USA according to the last records of the AHA. However, not only adult cardiovascular diseases are the most frequent diseases in adulthood, but congenital heart diseases also affect 0.8–1.2% of all births, accounting for mild developmental defects such as atrial septal defects to life-threatening pathologies such as tetralogy of Fallot or permanent common trunk that, if not surgically corrected in early postnatal days, they are incompatible with life. Therefore, both congenital and adult cardiovascular diseases represent an enormous social and economic burden that invariably demands continuous efforts to understand the causes of such cardiovascular defects and develop innovative strategies to correct and/or palliate them. In the next paragraphs, we aim to briefly account for our current understanding of the cellular bases of both congenital and adult cardiovascular diseases, providing a perspective of the plausible lines of action that might eventually result in increasing our understanding of cardiovascular diseases. This analysis will come out with the building blocks for designing novel and innovative therapeutic approaches to healing the broken hearts.

Mutant ANP induces mitochondrial and ion channel remodeling in a human iPSC-derived atrial fibrillation model

Human induced pluripotent stem cell–derived cardiomyocytes (iPSC-CMs) can model heritable arrhythmias to personalize therapies for individual patients. Although atrial fibrillation (AF) is a leading cause of cardiovascular morbidity and mortality, current platforms to generate iPSC-atrial (a) CMs are inadequate for modeling AF. We applied a combinatorial engineering approach, which integrated multiple physiological cues, including metabolic conditioning and electrical stimulation, to generate mature iPSC-aCMs. Using the patient’s own atrial tissue as a gold standard benchmark, we assessed the electrophysiological, structural, metabolic, and molecular maturation of iPSC-aCMs. Unbiased transcriptomic analysis and inference from gene regulatory networks identified key gene expression pathways and transcription factors mediating atrial development and maturation. Only mature iPSC-aCMs generated from patients with heritable AF carrying the non-ion channel gene (NPPA) mutation showed enhanced expression and function of a cardiac potassium channel and revealed mitochondrial electron transport chain dysfunction. Collectively, we propose that ion channel remodeling in conjunction with metabolic defects created an electrophysiological substrate for AF. Overall, our electro-metabolic approach generated mature human iPSC-aCMs that unmasked the underlying mechanism of the first non-ion channel gene, NPPA, that causes AF. Our maturation approach will allow for the investigation of the molecular underpinnings of heritable AF and the development of personalized therapies.