Cardiovascular Progenitor Research Articles

Id genes are essential for early heart formation.

Deciphering the fundamental mechanisms controlling cardiac specification is critical for our understanding of how heart formation is initiated during embryonic development and for applying stem cell biology to regenerative medicine and disease modeling. Using systematic and unbiased functional screening approaches, we discovered that the Id family of helix-loop-helix proteins is both necessary and sufficient to direct cardiac mesoderm formation in frog embryos and human embryonic stem cells. Mechanistically, Id proteins specify cardiac cell fate by repressing two inhibitors of cardiogenic mesoderm formation-Tcf3 and Foxa2-and activating inducers Evx1, Grrp1, and Mesp1. Most importantly, CRISPR/Cas9-mediated ablation of the entire Id (Id1-4) family in mouse embryos leads to failure of anterior cardiac progenitor specification and the development of heartless embryos. Thus, Id proteins play a central and evolutionarily conserved role during heart formation and provide a novel means to efficiently produce cardiovascular progenitors for regenerative medicine and drug discovery applications.

A Hyper-Crosslinked Carbohydrate Polymer Scaffold Facilitates Lineage Commitment and Maintains a Reserve Pool of Proliferating Cardiovascular Progenitors: Erratum

A Hyper-Crosslinked Carbohydrate Polymer Scaffold Facilitates Lineage Commitment and Maintains a Reserve Pool of Proliferating Cardiovascular Progenitors: Erratum

Steps toward Maturation of Embryonic Stem Cell-Derived Cardiomyocytes by Defined Physical Signals.

SummaryCardiovascular disease remains a leading cause of mortality and morbidity worldwide. Embryonic stem cell-derived cardiomyocytes (ESC-CMs) may offer significant advances in creating in vitro cardiac tissues for disease modeling, drug testing, and elucidating developmental processes; however, the induction of ESCs to a more adult-like CM phenotype remains challenging. In this study, we developed a bioreactor system to employ pulsatile flow (1.48 mL/min), cyclic strain (5%), and extended culture time to improve the maturation of murine and human ESC-CMs. Dynamically-cultured ESC-CMs showed an increased expression of cardiac-associated proteins and genes, cardiac ion channel genes, as well as increased SERCA activity and a Raman fingerprint with the presence of maturation-associated peaks similar to primary CMs. We present a bioreactor platform that can serve as a foundation for the development of human-based cardiac in vitro models to verify drug candidates, and facilitates the study of cardiovascular development and disease.

A Hyper-Crosslinked Carbohydrate Polymer Scaffold Facilitates Lineage Commitment and Maintains a Reserve Pool of Proliferating Cardiovascular Progenitors.

BackgroundCardiovascular progenitor cells (CPCs) have been cultured on various scaffolds to resolve the challenge of cell retention after transplantation and to improve functional outcome after cell-based cardiac therapy. Previous studies have reported successful culture of fully differentiated cardiomyocytes on scaffolds of various types, and ongoing efforts are focused on optimizing the mix of cardiomyocytes and endothelial cells as well as on the identification of a source of progenitors capable of reversing cardiovascular damage. A scaffold culture that fosters cell differentiation into cardiomyocytes and endothelial cells while maintaining a progenitor reserve would benefit allogeneic cell transplantation.MethodsIsl-1 + c-Kit + CPCs were isolated as clonal populations from human and sheep heart tissue. After hyper-crosslinked carbohydrate polymer scaffold culture, cells were assessed for differentiation, intracellular signaling, cell cycling, and growth factor/chemokine expression using real time polymerase chain reaction, flow cytometry, immunohistochemistry, and calcium staining.ResultsInsulin-like growth factor 1, hepatocyte growth factor, and stromal cell derived factor 1α paracrine factors were induced, protein kinase B signaling was activated, extracellular signal-regulated kinase phosphorylation was reduced and differentiation into both cardiomyocytes and endothelial cells was induced by scaffold-based cell culture. Interestingly, movement of CPCs out of the G1 phase of the cell cycle and increased expression of pluripotency genes PLOU5F1 (Oct4) and T (Brachyury) within a portion of the cultured population occurred, which suggests the maintenance of a progenitor population. Two-color immunostaining and 3-color fluorescence-activated cell sorting analysis confirmed the presence of both Isl-1 expressing undifferentiated cells and differentiated cells identified by troponin T and von Willebrand factor expression. Ki-67 labeling verified the presence of proliferating cells that remained in situ alongside the differentiated functional derivatives.ConclusionsCloned Isl-1 + c-kit + CPCs maintained on a hyper-cross linked polymer scaffold retain dual potential for proliferation and differentiation, providing a scaffold-based stem cell source for transplantation of committed and proliferating cardiovascular progenitors for functional testing in preclinical models of cell-based repair.

Nkx2.5 marks angioblasts that contribute to hemogenic endothelium of the endocardium and dorsal aorta.

Novel regenerative therapies may stem from deeper understanding of the mechanisms governing cardiovascular lineage diversification. Using enhancer mapping and live imaging in avian embryos, and genetic lineage tracing in mice, we investigated the spatio-temporal dynamics of cardiovascular progenitor populations. We show that expression of the cardiac transcription factor Nkx2.5 marks a mesodermal population outside of the cardiac crescent in the extraembryonic and lateral plate mesoderm, with characteristics of hemogenic angioblasts. Extra-cardiac Nkx2.5 lineage progenitors migrate into the embryo and contribute to clusters of CD41+/CD45+ and RUNX1+ cells in the endocardium, the aorta-gonad-mesonephros region of the dorsal aorta and liver. We also demonstrated that ectopic expression of Nkx2.5 in chick embryos activates the hemoangiogenic gene expression program. Taken together, we identified a hemogenic angioblast cell lineage characterized by transient Nkx2.5 expression that contributes to hemogenic endothelium and endocardium, suggesting a novel role for Nkx2.5 in hemoangiogenic lineage specification and diversification.

Interactions of human embryonic stem cell‐derived cardiovascular progenitor cells with immobilized extracellular matrix proteins

Human embryonic stem cell-derived cardiovascular progenitor cells (hESC-CVPCs) hold great promise for cell-based therapies of heart diseases. However, little is known about their niche microenvironment and in particular the required extracellular matrix (ECM) components. Here we screened combinations of surface-immobilized ECM proteins to identify substrates that support the attachment and survival of hESC-CVPCs. Covalent immobilization of ECM proteins laminin (Lm), fibronectin (Fn), collagen I (CI), collagen III (CIII), and collagen IV (CIV) in multiple combinations and concentrations was achieved by reductive amination on transparent acetaldehyde plasma polymer (AAPP) interlayer coatings. We identified that CI, CIII, CIV, and Fn and their combinations were important for hESC-CVPC attachment and survival, while Lm was dispensable. Moreover, for coatings displaying single ECM proteins, CI and CIII performed better than CIV and Fn, while coatings displaying the combined ECM proteins CIII + CIV and Fn + CIII + CIV at 100 µg/mL were comparable to Matrigel in regard to supporting hESC-CVPC attachment and viability. Our results identify ECM proteins required for hESC-CVPCs and demonstrate that coatings displaying multiple immobilized ECM proteins offer a suitable microenvironment for the attachment and survival of hESC-CVPCs. This knowledge contributes to the development of approaches for maintaining hESC-CVPCs and therefore to advances in cardiovascular regeneration. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1094-1104, 2017.

Thyroid Progenitors Are Robustly Derived from Embryonic Stem Cells through Transient, Developmental Stage-Specific Overexpression of Nkx2-1.

SummaryThe clinical importance of anterior foregut endoderm (AFE) derivatives, such as thyrocytes, has led to intense research efforts for their derivation through directed differentiation of pluripotent stem cells (PSCs). Here, we identify transient overexpression of the transcription factor (TF) NKX2-1 as a powerful inductive signal for the robust derivation of thyrocyte-like cells from mouse PSC-derived AFE. This effect is highly developmental stage specific and dependent on FOXA2 expression levels and precise modulation of BMP and FGF signaling. The majority of the resulting cells express thyroid TFs (Nkx2-1, Pax8, Foxe1, Hhex) and thyroid hormone synthesis-related genes (Tg, Tpo, Nis, Iyd) at levels similar to adult mouse thyroid and give rise to functional follicle-like epithelial structures in Matrigel culture. Our findings demonstrate that NKX2-1 overexpression converts AFE to thyroid epithelium in a developmental time-sensitive manner and suggest a general methodology for manipulation of cell-fate decisions of developmental intermediates.

Generating high-purity cardiac and endothelial derivatives from patterned mesoderm using human pluripotent stem cells.

Human pluripotent stem cells (hPSCs) provide a valuable model for the study of human development and a means to generate a scalable source of cells for therapeutic applications. This protocol specifies cell fate efficiently into cardiac and endothelial lineages from hPSCs. The protocol takes 2 weeks to complete and requires experience in hPSC culture and differentiation techniques. Building on lessons taken from early development, this monolayer-directed differentiation protocol uses different concentrations of activin A and bone morphogenetic protein 4 (BMP4) to polarize cells into mesodermal subtypes that reflect mid-primitive-streak cardiogenic mesoderm and posterior-primitive-streak hemogenic mesoderm. This differentiation platform provides a basis for generating distinct cardiovascular progenitor populations that enable the derivation of cardiomyocytes and functionally distinct endothelial cell (EC) subtypes from cardiogenic versus hemogenic mesoderm with high efficiency without cell sorting. ECs derived from cardiogenic and hemogenic mesoderm can be matured into >90% CD31+/VE-cadherin+ definitive ECs. To test the functionality of ECs at different stages of differentiation, we provide methods for assaying the blood-forming potential and de novo lumen-forming activity of ECs. To our knowledge, this is the first protocol that provides a common platform for directed differentiation of cardiomyocytes and endothelial subtypes from hPSCs. This protocol yields endothelial differentiation efficiencies exceeding those of previously published protocols. Derivation of these cell types is a critical step toward understanding the basis of disease and generating cells with therapeutic potential.

Yes-Associated Protein Inhibits Transcription of Myocardin and Attenuates Differentiation of Vascular Smooth Muscle Cell from Cardiovascular Progenitor Cell Lineage

Vascular smooth muscle cells (VSMCs) derived from cardiovascular progenitor cell (CVPC) lineage populate the tunica media of the aortic root. Understanding differentiation of VSMCs from CVPC will further our understanding of the molecular mechanisms contributing to aortic root aneurysms, and thus, facilitate the development of novel therapeutic agents to prevent this devastating complication. It is established that the yes-associated protein (YAP) and Hippo pathway is important for VSMC proliferation and phenotype switch. To determine the role of YAP in differentiation of VSMCs from CVPCs, we utilized the in vitro monolayer lineage specific differentiation method by differentiating human embryonic stem cells into CVPCs, and then, into VSMCs. We found that expression of YAP decreased during differentiation of VSMC from CVPCs. Overexpression of YAP attenuated expression of VSMC contractile markers and impaired VSMC function. Knockdown of YAP increased expression of contractile proteins during CVPC-VSMCs differentiation. Importantly, expression of YAP decreased transcription of myocardin during this process. Overexpression of YAP in PAC1 SMC cell line inhibited luciferase activity of myocardin proximal promoter in a dose dependent and NKX2.5 dependent manners. YAP protein interacted with NKX2.5 protein and inhibited binding of NKX2.5 to the 5'-proximal promoter region of myocardin in CVPC-derived VSMCs. In conclusion, YAP negatively regulates differentiation of VSMCs from CVPCs by decreasing transcription of myocardin in a NKX2.5-dependent manner. Stem Cells 2017;35:351-361.

Mesp1 Marked Cardiac Progenitor Cells Repair Infarcted Mouse Hearts.

Mesp1 directs multipotential cardiovascular cell fates, even though it’s transiently induced prior to the appearance of the cardiac progenitor program. Tracing Mesp1-expressing cells and their progeny allows isolation and characterization of the earliest cardiovascular progenitor cells. Studying the biology of Mesp1-CPCs in cell culture and ischemic disease models is an important initial step toward using them for heart disease treatment. Because of Mesp1’s transitory nature, Mesp1-CPC lineages were traced by following EYFP expression in murine Mesp1Cre/+; Rosa26EYFP/+ ES cells. We captured EYFP+ cells that strongly expressed cardiac mesoderm markers and cardiac transcription factors, but not pluripotent or nascent mesoderm markers. BMP2/4 treatment led to the expansion of EYFP+ cells, while Wnt3a and Activin were marginally effective. BMP2/4 exposure readily led EYFP+ cells to endothelial and smooth muscle cells, but inhibition of the canonical Wnt signaling was required to enter the cardiomyocyte fate. Injected mouse pre-contractile Mesp1-EYFP+ CPCs improved the survivability of injured mice and restored the functional performance of infarcted hearts for at least 3 months. Mesp1-EYFP+ cells are bona fide CPCs and they integrated well in infarcted hearts and emerged de novo into terminally differentiated cardiac myocytes, smooth muscle and vascular endothelial cells.

Corrigendum: Endothelin-1 supports clonal derivation and expansion of cardiovascular progenitors derived from human embryonic stem cells.

Nature Communications 7: Article number: 10774 (2016); Published: 8 March 2016; Updated: 19 July 2016. The affiliation details for Boon-Seng Soh, Lei Bu and Ronald A. Li are incorrect in this Article. The correct addresses of these authors are listed below: Boon-Seng Soh Cardiovascular Research Center, Massachusetts General Hospital, 185 Cambridge Street, Boston, Massachusetts 02114, USA; Department of Stem Cell and Regenerative Biology, Harvard University, 7 Divinity Avenue, Cambridge, Massachusetts 02138, USA; Li Dak-Sum Research Centre-HKU-Karolinska Institutet Collaboration on Regenerative Medicine, University of Hong Kong, Hong Kong, China and Department of Cell and Molecular Biology and Medicine, Karolinska Institute, Stockholm S-171 77, Sweden.

ISL1 cardiovascular progenitor cells for cardiac repair after myocardial infarction.

Cardiovascular progenitor cells (CPCs) expressing the ISL1-LIM-homeodomain transcription factor contribute developmentally to cardiomyocytes in all 4 chambers of the heart. Here, we show that ISL1-CPCs can be applied to myocardial regeneration following injury. We used a rapid 3D methylcellulose approach to form murine and human ISL1-CPC spheroids that engrafted after myocardial infarction in murine hearts, where they differentiated into cardiomyocytes and endothelial cells, integrating into the myocardium and forming new blood vessels. ISL1-CPC spheroid-treated mice exhibited reduced infarct area and increased blood vessel formation compared with control animals. Moreover, left ventricular (LV) contractile function was significantly better in mice transplanted with ISL1-CPCs 4 weeks after injury than that in control animals. These results provide proof-of-concept of a cardiac repair strategy employing ISL1-CPCs that, based on our previous lineage-tracing studies, are committed to forming heart tissue, in combination with a robust methylcellulose spheroid-based delivery approach.

Finding Expandable Induced Cardiovascular Progenitor Cells.

Expandable Cardiovascular Progenitor Cells Reprogrammed From Fibroblasts Zhang et al Cell Stem Cell . 2016;18:368–381. Lineage Reprogramming of Fibroblasts Into Proliferative Induced Cardiac Progenitor Cells by Defined Factors Lalit et al Cell Stem Cell . 2016;18:354–367. Cardiovascular progenitor cells (CPCs) are a promising cell source for cardiac regenerative therapy because of their ability for self-renewal and differentiation into various cardiovascular cell types beneficial for myocardial repair: cardiomyocytes, smooth muscle cells, and endothelial cells. Previous evaluations of exogenously derived CPCs have focused mainly on their capacity for trilineage differentiation rather than self-renewal because of the lack of an effective protocol to maintain and expand CPCs long-term in culture. In a recent issue of Cell Stem Cell , 2 groups of investigators independently reported their success in isolating, maintaining, and expanding mouse CPCs in culture for >18 to 20 passages (1010- to 1015-fold expansion), with faithful preservation of progenitor phenotype and ability for trilineage-restricted differentiation in both cell culture and mouse models of myocardial infarction (MI). This commentary will discuss the unique findings of these 2 studies, highlight the strengths and weaknesses of each CPC derivation/expansion technique, and propose additional steps necessary to accelerate their clinical translation. The past 2 decades have witnessed some of the most dramatic developments in the field of cardiac regeneration. Central to numerous controversies is the debate on whether certain stem cell types can differentiate into functional cardiomyocytes at a clinically relevant efficiency after implantation for repair of MI. Bone marrow–derived hematopoietic stem cells1,2 and c-kit+ resident cardiac stem cells3 are 2 notable cell types at the center of contention. Although many adult stem cells can still confer modest therapeutic benefits via paracrine effects, the search for a bona fide progenitor cell type that can generate a significant …

Mesp1 controls the speed, polarity, and directionality of cardiovascular progenitor migration.

During embryonic development, Mesp1 marks the earliest cardiovascular progenitors (CPs) and promotes their specification, epithelial-mesenchymal transition (EMT), and cardiovascular differentiation. However, Mesp1 deletion in mice does not impair initial CP specification and early cardiac differentiation but induces cardiac malformations thought to arise from a defect of CP migration. Using inducible gain-of-function experiments during embryonic stem cell differentiation, we found that Mesp2, its closest homolog, was as efficient as Mesp1 at promoting CP specification, EMT, and cardiovascular differentiation. However, only Mesp1 stimulated polarity and directional cell migration through a cell-autonomous mechanism. Transcriptional analysis and chromatin immunoprecipitation experiments revealed that Mesp1 and Mesp2 activate common target genes that promote CP specification and differentiation. We identified two direct Mesp1 target genes, Prickle1 and RasGRP3, that are strongly induced by Mesp1 and not by Mesp2 and that control the polarity and the speed of cell migration. Altogether, our results identify the molecular interface controlled by Mesp1 that links CP specification and cell migration.

Coupling switch of P2Y-IP3 receptors mediates differential Ca(2+) signaling in human embryonic stem cells and derived cardiovascular progenitor cells.

Purinergic signaling mediated by P2 receptors (P2Rs) plays important roles in embryonic and stem cell development. However, how it mediates Ca(2+) signals in human embryonic stem cells (hESCs) and derived cardiovascular progenitor cells (CVPCs) remains unclear. Here, we aimed to determine the role of P2Rs in mediating Ca(2+) mobilizations of these cells. hESCs were induced to differentiate into CVPCs by our recently established methods. Gene expression of P2Rs and inositol 1,4,5-trisphosphate receptors (IP3Rs) was analyzed by quantitative/RT-PCR. IP3R3 knockdown (KD) or IP3R2 knockout (KO) hESCs were established by shRNA- or TALEN-mediated gene manipulations, respectively. Confocal imaging revealed that Ca(2+) responses in CVPCs to ATP and UTP were more sensitive and stronger than those in hESCs. Consistently, the gene expression levels of most P2YRs except P2Y1 were increased in CVPCs. Suramin or PPADS blocked ATP-induced Ca(2+) transients in hESCs but only partially inhibited those in CVPCs. Moreover, the P2Y1 receptor-specific antagonist MRS2279 abolished most ATP-induced Ca(2+) signals in hESCs but not in CVPCs. P2Y1 receptor-specific agonist MRS2365 induced Ca(2+) transients only in hESCs but not in CVPCs. Furthermore, IP3R2KO but not IP3R3KD decreased the proportion of hESCs responding to MRS2365. In contrast, both IP3R2 and IP3R3 contributed to UTP-induced Ca(2+) responses while ATP-induced Ca(2+) responses were more dependent on IP3R2 in the CVPCs. In conclusion, a predominant role of P2Y1 receptors in hESCs and a transition of P2Y-IP3R coupling in derived CVPCs are responsible for the differential Ca(2+) mobilization between these cells.

Wnt/β-Catenin Stimulation and Laminins Support Cardiovascular Cell Progenitor Expansion from Human Fetal Cardiac Mesenchymal Stromal Cells.

SummaryThe intrinsic regenerative capacity of human fetal cardiac mesenchymal stromal cells (MSCs) has not been fully characterized. Here we demonstrate that we can expand cells with characteristics of cardiovascular progenitor cells from the MSC population of human fetal hearts. Cells cultured on cardiac muscle laminin (LN)-based substrata in combination with stimulation of the canonical Wnt/β-catenin pathway showed increased gene expression of ISL1, OCT4, KDR, and NKX2.5. The majority of cells stained positive for PDGFR-α, ISL1, and NKX2.5, and subpopulations also expressed the progenitor markers TBX18, KDR, c-KIT, and SSEA-1. Upon culture of the cardiac MSCs in differentiation media and on relevant LNs, portions of the cells differentiated into spontaneously beating cardiomyocytes, and endothelial and smooth muscle-like cells. Our protocol for large-scale culture of human fetal cardiac MSCs enables future exploration of the regenerative functions of these cells in the context of myocardial injury in vitro and in vivo.

Generation of iPSC from cardiac and tail-tip fibroblasts derived from a second heart field reporter mouse

Mef2c Anterior Heart Field (AHF) enhancer is activated during embryonic heart development and it is expressed in multipotent cardiovascular progenitors (CVP) giving rise to endothelial and myocardial components of the outflow tract, right ventricle and ventricular septum. Here we have generated iPSC from transgenic Mef2c-AHF-Cre x Ai6(RCLZsGreen) mice. These iPSC will provide a novel tool to investigate the AHF-CVP and their cell progeny.

Epicardial Outgrowth Culture Assay and Ex Vivo Assessment of Epicardial-derived Cell Migration.

A single layer of epicardial cells lines the heart, providing paracrine factors that stimulate cardiomyocyte proliferation and directly contributing cardiovascular progenitors during development and disease. While a number of factors have been implicated in epicardium-derived cell (EPDC) mobilization, the mechanisms governing their subsequent migration and differentiation are poorly understood. Here, we present in vitro and ex vivo strategies to study EPDC motility and differentiation. First, we describe a method of obtaining primary epicardial cells by outgrowth culture from the embryonic mouse heart. We also introduce a detailed protocol to assess three-dimensional migration of labeled EPDC in an organ culture system. We provide evidence using these techniques that genetic deletion of myocardin-related transcription factors in the epicardium attenuates EPDC migration. This approach serves as a platform to evaluate candidate modifiers of EPDC biology and could be used to develop genetic or chemical screens to identify novel regulators of EPDC mobilization that might be useful for cardiac repair.

Endothelin-1 supports clonal derivation and expansion of cardiovascular progenitors derived from human embryonic stem cells.

Coronary arteriogenesis is a central step in cardiogenesis, requiring coordinated generation and integration of endothelial cell and vascular smooth muscle cells. At present, it is unclear whether the cell fate programme of cardiac progenitors to generate complex muscular or vascular structures is entirely cell autonomous. Here we demonstrate the intrinsic ability of vascular progenitors to develop and self-organize into cardiac tissues by clonally isolating and expanding second heart field cardiovascular progenitors using WNT3A and endothelin-1 (EDN1) human recombinant proteins. Progenitor clones undergo long-term expansion and differentiate primarily into endothelial and smooth muscle cell lineages in vitro, and contribute extensively to coronary-like vessels in vivo, forming a functional human–mouse chimeric circulatory system. Our study identifies EDN1 as a key factor towards the generation and clonal derivation of ISL1+ vascular intermediates, and demonstrates the intrinsic cell-autonomous nature of these progenitors to differentiate and self-organize into functional vasculatures in vivo.

Expanding Reprogramming to Cardiovascular Progenitors

Methods to generate expandable cardiac progenitor populations are desirable for developing cellular therapies for heart failure and for studying cardiac specification. Now in Cell Stem Cell, Lalit et al. (2016) and Zhang et al. (2016) report two different strategies for reprogramming adult mouse fibroblasts into highly expandable cardiovascular progenitor cells.