Jennifer Lang

Background: Human induced pluripotent stem cells (hiPSCs) are an important model for cardiovascular research, drug discovery, and translational research applications. Commonly used methods to direct iPSCs to cardiac myocytes can be technically demanding. Prior studies have shown that both VEGF and endothelial cells promote differentiation of stem cells to cardiac myocytes. Furthermore, DMEM/F12 with 10% fetal calf serum (DMEM-FCS) has been shown to induce cardiac myocytes in an embryoid body (EB) system. The objective of this study was to determine if differentiation of hiPSCs using conditions that support endothelial cell differentiation would promote cardiac myocyte colony formation. Methods: Two hiPSC lines derived using non-genome integrating methods were maintained on Matrigel-coated surfaces under serum free conditions in mTeSR1 medium. We performed a comparison of monolayer myocyte differentiation efficiency using DMEM-FCS and endothelial cell medium (EC). Cells were maintained in iPSC medium (mTeSR1) as a negative control. The number of beating colonies derived under each growth condition was determined using phase microscopy at 4 weeks. Cardiac myocyte commitment was characterized using an α-MHC-GFP reporter vector and electrophysiologic action potentials on isolated beating colonies. Results: Differentiation of human iPSCs in EC medium induced substantial numbers of beating colonies 4 weeks after differentiation (2.29 ± 0.3 beating colonies/cm2 culture area, n=42). Unlike EB models of myocyte differentiation, no beating clusters were observed in our monolayer system with DMEM-FCS medium (n=14) (p<0.01). As expected, mTESR1 (n=12) did not induce any cardiac myocytes. All beating cell colonies expressed GFP driven by the cardiac specific α-MHC promoter. Electrophysiological studies confirmed the presence of action potentials with ventricular phenotypes. Conclusions: Differentiation of human iPSCs under monolayer conditions that support endothelial cells facilitates efficient induction of functional human cardiac myocytes. Our findings simplify the differentiation of iPSCs to cardiac myocytes, making research with human iPSCs more accessible to a broad range of cardiovascular investigators.

Monocytes are critical mediators of the inflammatory response following myocardial infarction (MI) and ischemia-reperfusion injury. They are involved in both initiation and resolution of inflammation and play an integral role in cardiac repair. The antagonistic nature of their function is dependent on their subset heterogeneity and biphasic response following injury. New advancements in single-cell transcriptomics and mass cytometry have allowed us to identify smaller, transcriptionally distinct clusters that may have functional relevance in disease and homeostasis. Additionally, recent insights into the spatiotemporal dynamics of monocytes following ischemic injury and their subsequent interactions with the endothelium and other immune cells reveal a complex interplay between monocytes and the cardiac milieu. In this review, we highlight recent findings on monocyte functional heterogeneity, present new mechanistic insight into monocyte recruitment and fate specification following M...

We hypothesized that in the window of therapeutic extracellular vesicle (EV) administration, inflammatory M1 macrophages are likely the primary target of cardiosphere-derived cell (CDC)-derived EVs. The effect of CDC-EVs on this population, however, is currently unknown. In this study, we demonstrate that CDC-derived EVs polarize M1 macrophages to a proangiogenic phenotype dependent on arginase 1 upregulation. These results provide insight into an immunomodulatory mechanism of CDC-EVs in a more physiologically relevant model of post-myocardial infarction (post-MI) macrophage polarization.

Research has shown that treating the heart with stem cell populations, including cardiosphere-derived cells (CDCs), post myocardial infarction stimulates regeneration, angiogenesis, and functional improvement. While this treatment has shown promise in early stage clinical trials, there remains a gap in the ability to efficiently deliver tissue-specific agents directly to the heart while avoiding nonspecific delivery to other organs. Our aim was to develop an efficient delivery system that can target cardiomyocytes and transport drugs, siRNA, and/or miRNA to aid in the treatment of cardiovascular diseases. Methods: Lamp-2b was cloned with cDNA from C2C12 cells and ligated downstream of the CMV promoter in a lentiviral transfer plasmid. Primers designed to encode a cardiomyocyte targeting peptide were used to introduce the targeting ligand between XhoI and BspEI at the N terminus of Lamp-2b forming the final vector (LV-CMP). We subsequently generated CMP lentivirus by triple transfect...

Atherosclerosis causing heart attack and stroke is the leading cause of death in the modern world. Therapy for end-stage atherosclerotic disease using CD34(+) hematopoietic cells has shown promise in human clinical trials, and the in vivo function of hematopoietic and progenitor cells in atherogenesis is becoming apparent. Inflammation plays a central role in the pathogenesis of atherosclerosis. Cholesterol is a modifiable risk factor in atherosclerosis, but in many patients cholesterol levels are only mildly elevated. Those with high cholesterol levels often have elevated circulating monocyte and neutrophil counts. How cholesterol affects inflammatory cell levels was not well understood. Recent findings have provided new insight into the interaction among hematopoietic stem cells, cholesterol, and atherosclerosis. In mice, high cholesterol levels or inactivation of cholesterol efflux transporters have multiple effects on hematopoietic stem cells (HSPCs), including promoting their m...