Cells with hematopoietic potential reside within mouse proepicardium

Prolonged generation of multi-lineage blood cells in wild-type animals from pluripotent stem cells

Regenerating prolonged multi-lineage hematopoiesis from pluripotent stem cells (PSCs), an unlimited cell source, is a crucial aim of regenerative hematology. In this study, we used a gene-edited PSC line and revealed that simultaneous expression of three transcription factors, Runx1, Hoxa9, and Hoxa10, drove the robust emergence of induced hematopoietic progenitor cells (iHPCs). The iHPCs engrafted successfully in wild-type animals and repopulated abundant and complete myeloid-, B-, and T-lineage mature cells. The generative multi-lineage hematopoiesis distributed normally in multiple organs, persisted over 6 months, and eventually declined over time with no leukemogenesis. Transcriptome characterization of generative myeloid, B, and T cells at the single-cell resolution further projected their identities to natural cell counterparts. Thus, we provide evidence that co-expression of exogenous Runx1, Hoxa9, and Hoxa10 simultaneously leads to long-term reconstitution of myeloid, B, and T lineages using PSC-derived iHPCs as the cell source.

In Vivo and In Vitro Cartilage Differentiation from Embryonic Epicardial Progenitor Cells

The presence of cartilage tissue in the embryonic and adult hearts of different vertebrate species is a well-recorded fact. However, while the embryonic neural crest has been historically considered as the main source of cardiac cartilage, recently reported results on the wide connective potential of epicardial lineage cells suggest they could also differentiate into chondrocytes. In this work, we describe the formation of cardiac cartilage clusters from proepicardial cells, both in vivo and in vitro. Our findings report, for the first time, cartilage formation from epicardial progenitor cells, and strongly support the concept of proepicardial cells as multipotent connective progenitors. These results are relevant to our understanding of cardiac cell complexity and the responses of cardiac connective tissues to pathologic stimuli.

Cardiac Development: A Glimpse on Its Translational Contributions

Cardiac development is a complex developmental process that is initiated soon after gastrulation, as two sets of precardiac mesodermal precursors are symmetrically located and subsequently fused at the embryonic midline forming the cardiac straight tube. Thereafter, the cardiac straight tube invariably bends to the right, configuring the first sign of morphological left–right asymmetry and soon thereafter the atrial and ventricular chambers are formed, expanded and progressively septated. As a consequence of all these morphogenetic processes, the fetal heart acquired a four-chambered structure having distinct inlet and outlet connections and a specialized conduction system capable of directing the electrical impulse within the fully formed heart. Over the last decades, our understanding of the morphogenetic, cellular, and molecular pathways involved in cardiac development has exponentially grown. Multiples aspects of the initial discoveries during heart formation has served as guiding tools to understand the etiology of cardiac congenital anomalies and adult cardiac pathology, as well as to enlighten novels approaches to heal the damaged heart. In this review we provide an overview of the complex cellular and molecular pathways driving heart morphogenesis and how those discoveries have provided new roads into the genetic, clinical and therapeutic management of the diseased hearts.

Proepicardium: Current Understanding of its Structure, Induction, and Fate

The proepicardium (PE) is a transitory extracardiac embryonic structure which plays a crucial role in cardiac morphogenesis and delivers various cell lineages to the developing heart. The PE arises from the lateral plate mesoderm (LPM) and is present in all vertebrate species. During development, mesothelial cells of the PE reach the naked myocardium either as free-floating aggregates in the form of vesicles or via a tissue bridge; subsequently, they attach to the myocardium and, finally, form the third layer of a mature heart-the epicardium. After undergoing epithelial-to-mesenchymal transition (EMT) some of the epicardial cells migrate into the myocardial wall and differentiate into fibroblasts, smooth muscle cells, and possibly other cell types. Despite many recent findings, the molecular pathways that control not only proepicardial induction and differentiation but also epicardial formation and epicardial cell fate are poorly understood. Knowledge about these events is essential because molecular mechanisms that occur during embryonic development have been shown to be reactivated in pathological conditions, for example, after myocardial infarction, during hypertensive heart disease or other cardiovascular diseases. Therefore, in this review we intended to summarize the current knowledge about PE formation and structure, as well as proepicardial cell fate in animals commonly used as models for studies on heart development. Anat Rec, 302:893-903, 2019. © 2018 Wiley Periodicals, Inc.