@phdthesis{Mekala2019,
  author    = {Mekala, SubbaRao},
  title     = {Generation of cardiomyocytes from vessel wall-resident stem cells},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-146046},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2019},
  abstract  = {Myocardial infarction (MI) is a major cause of health problems and is among the leading deadly ending diseases. Accordingly, regenerating functional myocardial tissue and/or cardiac repair by stem cells is one of the most desired aims worldwide. Indeed, the human heart serves as an ideal target for regenerative intervention, because the capacity of the adult myocardium to restore itself after injury or infarct is limited. Thus, identifying new sources of tissue resident adult stem or progenitor cells with cardiovascular potential would help to establish more sophisticated therapies in order to either prevent cardiac failure or to achieve a functional repair. Ongoing research worldwide in this field is focusing on a) induced pluripotent stem (iPS) cells, b) embryonic stem (ES) cells and c) adult stem cells (e. g. mesenchymal stem cells) as well as cardiac fibroblasts or myofibroblasts. However, thus far, these efforts did not result in therapeutic strategies that were transferable into the clinical management of MI and heart failure. Hence, identifying endogenous and more cardiac-related sources of stem cells capable of differentiating into mature cardiomyocytes would open promising new therapeutic opportunities. The working hypothesis of this thesis is that the vascular wall serves as a niche for cardiogenic stem cells. In recent years, various groups have identified different types of progenitors or mesenchymal stem cell-like cells in the adventitia and sub-endothelial zone of the adult vessel wall, the so called vessel wall-resident stem cells (VW-SCs). Considering the fact that heart muscle tissue contains blood vessels in very high density, the physiological relevance of VW-SCs for the myocardium can as yet only be assumed. The aim of the present work is to study whether a subset of VW-SCs might have the capacity to differentiate into cardiomyocyte-like cells. This assumption was challenged using adult mouse aorta-derived cells cultivated in different media and treated with selected factors. The presented results reveal the generation of spontaneously beating cardiomyocyte-like cells using specific media conditions without any genetic manipulation. The cells reproducibly started beating at culture days 8-10. Further analyses revealed that in contrast to several publications reporting the Sca-1+ cells as cardiac progenitors the Sca-1- fraction of aortic wall-derived VW-SCs reproducibly delivered beating cells in culture. Similar to mature cardiomyocytes the beating cells developed sarcomeric structures indicated by the typical cross striated staining pattern upon immunofluorescence analysis detecting α-sarcomeric actinin (α-SRA) and electron microscopic analysis. These analyses also showed the formation of sarcoplasmic reticulum which serves as calcium store. Correspondingly, the aortic wall-derived beating cardiomyocyte-like cells (Ao-bCMs) exhibited calcium oscillations. This differentiation seems to be dependent on an inflammatory microenvironment since depletion of VW-SC-derived macrophages by treatment with clodronate liposomes in vitro stopped the generation of Ao bCMs. These locally generated F4/80+ macrophages exhibit high levels of VEGF (vascular endothelial growth factor). To a great majority, VW-SCs were found to be positive for VEGFR-2 and blocking this receptor also stopped the generation VW-SC-derived beating cells in vitro. Furthermore, the treatment of aortic wall-derived cells with the ß-receptor agonist isoproterenol or the antagonist propranolol resulted in a significant increase or decrease of beating frequency. Finally, fluorescently labeled aortic wall-derived cells were implanted into the developing chick embryo heart field where they became positive for α-SRA two days after implantation. The current data strongly suggest that VW-SCs resident in the vascular adventitia deliver both progenitors for an inflammatory microenvironment and beating cells. The present study identifies that the Sca-1- rather than Sca-1+ fraction of mouse aortic wall-derived cells harbors VW-SCs differentiating into cardiomyocyte-like cells and reveals an essential role of VW-SCs-derived inflammatory macrophages and VEGF-signaling in this process. Furthermore, this study demonstrates the cardiogenic capacity of aortic VW-SCs in vivo using a chimeric chick embryonic model.},
  subject      = {Herzmuskelzelle},
  language  = {en}
}
@article{KleefeldtBoemmelBroedeetal.2019,
  author    = {Kleefeldt, Florian and B{\"o}mmel, Heike and Broede, Britta and Thomsen, Michael and Pfeiffer, Verena and W{\"o}rsd{\"o}rfer, Philipp and Karnati, Srikanth and Wagner, Nicole and Rueckschloss, Uwe and Erg{\"u}n, S{\"u}leyman},
  title     = {Aging-related carcinoembryonic antigen-related cell adhesion molecule 1 signaling promotes vascular dysfunction},
  series = {Aging Cell},
  volume    = {2019},
  journal   = {Aging Cell},
  number    = {18},
  doi       = {10.1111/acel.13025},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-201231},
  pages     = {e13025},
  year      = {2019},
  abstract  = {Aging is an independent risk factor for cardiovascular diseases and therefore of particular interest for the prevention of cardiovascular events. However, the mechanisms underlying vascular aging are not well understood. Since carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is crucially involved in vascular homeostasis, we sought to identify the role of CEACAM1 in vascular aging. Using human internal thoracic artery and murine aorta, we show that CEACAM1 is upregulated in the course of vascular aging. Further analyses demonstrated that TNF-α is CEACAM1-dependently upregulated in the aging vasculature. Vice versa, TNF-α induces CEACAM1 expression. This results in a feed-forward loop in the aging vasculature that maintains a chronic pro-inflammatory milieu. Furthermore, we demonstrate that age-associated vascular alterations, that is, increased oxidative stress and vascular fibrosis, due to increased medial collagen deposition crucially depend on the presence of CEACAM1. Additionally, age-dependent upregulation of vascular CEACAM1 expression contributes to endothelial barrier impairment, putatively via increased VEGF/VEGFR-2 signaling. Consequently, aging-related upregulation of vascular CEACAM1 expression results in endothelial dysfunction that may promote atherosclerotic plaque formation in the presence of additional risk factors. Our data suggest that CEACAM1 might represent an attractive target in order to delay physiological aging and therefore the transition to vascular disorders such as atherosclerosis.},
  language  = {en}
}
@article{WoersdoerferDaldaKernetal.2019,
  author    = {W{\"o}rsd{\"o}rfer, Philipp and Dalda, Nahide and Kern, Anna and Kr{\"u}ger, Sarah and Wagner, Nicole and Kwok, Chee Keong and Henke, Erik and Erg{\"u}n, S{\"u}leyman},
  title     = {Generation of complex human organoid models including vascular networks by incorporation of mesodermal progenitor cells},
  series = {Scientific Reports},
  volume    = {9},
  journal   = {Scientific Reports},
  doi       = {10.1038/s41598-019-52204-7},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-202681},
  pages     = {15663},
  year      = {2019},
  abstract  = {Organoids derived from human pluripotent stem cells are interesting models to study mechanisms of morphogenesis and promising platforms for disease modeling and drug screening. However, they mostly remain incomplete as they lack stroma, tissue resident immune cells and in particular vasculature, which create important niches during development and disease. We propose, that the directed incorporation of mesodermal progenitor cells (MPCs) into organoids will overcome the aforementioned limitations. In order to demonstrate the feasibility of the method, we generated complex human tumor as well as neural organoids. We show that the formed blood vessels display a hierarchic organization and mural cells are assembled into the vessel wall. Moreover, we demonstrate a typical blood vessel ultrastructure including endothelial cell-cell junctions, a basement membrane as well as luminal caveolae and microvesicles. We observe a high plasticity in the endothelial network, which expands, while the organoids grow and is responsive to anti-angiogenic compounds and pro-angiogenic conditions such as hypoxia. We show that vessels within tumor organoids connect to host vessels following transplantation. Remarkably, MPCs also deliver Iba1\(^+\) cells that infiltrate the neural tissue in a microglia-like manner.},
  language  = {en}
}
@article{AktasUpcinHenkeetal.2019,
  author    = {Aktas, Bertal H. and Upcin, Berin and Henke, Erik and Padmasekar, Manju and Qin, Xuebin and Erg{\"u}n, S{\"u}leyman},
  title     = {The Best for the Most Important: Maintaining a Pristine Proteome in Stem and Progenitor Cells},
  series = {Stem Cells International},
  journal   = {Stem Cells International},
  doi       = {10.1155/2019/1608787},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-227769},
  pages     = {1-20},
  year      = {2019},
  abstract  = {Pluripotent stem cells give rise to reproductively enabled offsprings by generating progressively lineage-restricted multipotent stem cells that would differentiate into lineage-committed stem and progenitor cells. These lineage-committed stem and progenitor cells give rise to all adult tissues and organs. Adult stem and progenitor cells are generated as part of the developmental program and play critical roles in tissue and organ maintenance and/or regeneration. The ability of pluripotent stem cells to self-renew, maintain pluripotency, and differentiate into a multicellular organism is highly dependent on sensing and integrating extracellular and extraorganismal cues. Proteins perform and integrate almost all cellular functions including signal transduction, regulation of gene expression, metabolism, and cell division and death. Therefore, maintenance of an appropriate mix of correctly folded proteins, a pristine proteome, is essential for proper stem cell function. The stem cells' proteome must be pristine because unfolded, misfolded, or otherwise damaged proteins would interfere with unlimited self-renewal, maintenance of pluripotency, differentiation into downstream lineages, and consequently with the development of properly functioning tissue and organs. Understanding how various stem cells generate and maintain a pristine proteome is therefore essential for exploiting their potential in regenerative medicine and possibly for the discovery of novel approaches for maintaining, propagating, and differentiating pluripotent, multipotent, and adult stem cells as well as induced pluripotent stem cells. In this review, we will summarize cellular networks used by various stem cells for generation and maintenance of a pristine proteome. We will also explore the coordination of these networks with one another and their integration with the gene regulatory and signaling networks.},
  language  = {en}
}