@article{MeirKannapinDiefenbacheretal.2021,
  author    = {Meir, Michael and Kannapin, Felix and Diefenbacher, Markus and Ghoreishi, Yalda and Kollmann, Catherine and Flemming, Sven and Germer, Christoph-Thomas and Waschke, Jens and Leven, Patrick and Schneider, Reiner and Wehner, Sven and Burkard, Natalie and Schlegel, Nicolas},
  title     = {Intestinal epithelial barrier maturation by enteric glial cells is GDNF-dependent},
  series = {International Journal of Molecular Sciences},
  volume    = {22},
  journal   = {International Journal of Molecular Sciences},
  number    = {4},
  issn      = {1422-0067},
  doi       = {10.3390/ijms22041887},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-258913},
  year      = {2021},
  abstract  = {Enteric glial cells (EGCs) of the enteric nervous system are critically involved in the maintenance of intestinal epithelial barrier function (IEB). The underlying mechanisms remain undefined. Glial cell line-derived neurotrophic factor (GDNF) contributes to IEB maturation and may therefore be the predominant mediator of this process by EGCs. Using GFAP\(^{cre}\) x Ai14\(^{floxed}\) mice to isolate EGCs by Fluorescence-activated cell sorting (FACS), we confirmed that they synthesize GDNF in vivo as well as in primary cultures demonstrating that EGCs are a rich source of GDNF in vivo and in vitro. Co-culture of EGCs with Caco2 cells resulted in IEB maturation which was abrogated when GDNF was either depleted from EGC supernatants, or knocked down in EGCs or when the GDNF receptor RET was blocked. Further, TNFα-induced loss of IEB function in Caco2 cells and in organoids was attenuated by EGC supernatants or by recombinant GDNF. These barrier-protective effects were blunted when using supernatants from GDNF-deficient EGCs or by RET receptor blockade. Together, our data show that EGCs produce GDNF to maintain IEB function in vitro through the RET receptor.},
  language  = {en}
}
@article{BurkardMeirKannapinetal.2021,
  author    = {Burkard, Natalie and Meir, Michael and Kannapin, Felix and Otto, Christoph and Petzke, Maximilian and Germer, Christoph-Thomas and Waschke, Jens and Schlegel, Nicolas},
  title     = {Desmoglein2 Regulates Claudin2 Expression by Sequestering PI-3-Kinase in Intestinal Epithelial Cells},
  series = {Frontiers in Immunology},
  volume    = {12},
  journal   = {Frontiers in Immunology},
  issn      = {1664-3224},
  doi       = {10.3389/fimmu.2021.756321},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-247059},
  year      = {2021},
  abstract  = {Inflammation-induced reduction of intestinal desmosomal cadherin Desmoglein 2 (Dsg2) is linked to changes of tight junctions (TJ) leading to impaired intestinal epithelial barrier (IEB) function by undefined mechanisms. We characterized the interplay between loss of Dsg2 and upregulation of pore-forming TJ protein Claudin2. Intraperitoneal application of Dsg2-stablising Tandem peptide (TP) attenuated impaired IEB function, reduction of Dsg2 and increased Claudin2 in DSS-induced colitis in C57Bl/6 mice. TP blocked loss of Dsg2-mediated adhesion and upregulation of Claudin2 in Caco2 cells challenged with TNFα. In Dsg2-deficient Caco2 cells basal expression of Claudin2 was increased which was paralleled by reduced transepithelial electrical resistance and by augmented phosphorylation of AKT\(^{Ser473}\) under basal conditions. Inhibition of phosphoinositid-3-kinase proved that PI-3-kinase/AKT-signaling is critical to upregulate Claudin2. In immunostaining PI-3-kinase dissociated from Dsg2 under inflammatory conditions. Immunoprecipitations and proximity ligation assays confirmed a direct interaction of Dsg2 and PI-3-kinase which was abrogated following TNFα application. In summary, Dsg2 regulates Claudin2 expression by sequestering PI-3-kinase to the cell borders in intestinal epithelium.},
  language  = {en}
}
@article{KressBaurOttoetal.2018,
  author    = {Kress, Sebastian and Baur, Johannes and Otto, Christoph and Burkard, Natalie and Braspenning, Joris and Walles, Heike and Nickel, Joachim and Metzger, Marco},
  title     = {Evaluation of a miniaturized biologically vascularized scaffold in vitro and in vivo},
  series = {Scientific Reports},
  volume    = {8},
  journal   = {Scientific Reports},
  number    = {4719},
  doi       = {10.1038/s41598-018-22688-w},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-176343},
  year      = {2018},
  abstract  = {In tissue engineering, the generation and functional maintenance of dense voluminous tissues is mainly restricted due to insufficient nutrient supply. Larger three-dimensional constructs, which exceed the nutrient diffusion limit become necrotic and/or apoptotic in long-term culture if not provided with an appropriate vascularization. Here, we established protocols for the generation of a pre-vascularized biological scaffold with intact arterio-venous capillary loops from rat intestine, which is decellularized under preservation of the feeding and draining vascular tree. Vessel integrity was proven by marker expression, media/blood reflow and endothelial LDL uptake. In vitro maintenance persisted up to 7 weeks in a bioreactor system allowing a stepwise reconstruction of fully vascularized human tissues and successful in vivo implantation for up to 4 weeks, although with time-dependent decrease of cell viability. The vascularization of the construct lead to a 1.5× increase in cellular drug release compared to a conventional static culture in vitro. For the first time, we performed proof-of-concept studies demonstrating that 3D tissues can be maintained within a miniaturized vascularized scaffold in vitro and successfully implanted after re-anastomosis to the intrinsic blood circulation in vivo. We hypothesize that this technology could serve as a powerful platform technology in tissue engineering and regenerative medicine.},
  language  = {en}
}
@phdthesis{Burkard2010,
  author    = {Burkard, Natalie},
  title     = {Signal{\"u}bertragungswege und Pr{\"a}ventionsm{\"o}glichkeiten der kardialen Hypertrophie : conditional overexpression of neuronal nitric oxide synthase is cardioprotective in ischemia-reperfusion},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-51832},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2010},
  abstract  = {Zusammenfassung: Wie fr{\"u}her schon gezeigt, wird der L-Typ Ca2+-Kanal durch eine induzierbare, myokardspezifische {\"U}berexpression der neuronalen Stickstoffmonoxidsynthase (nNOS) inhibiert. Gleichzeitig bewirkt diese {\"U}berexpression eine verminderte kardiale Kontraktilit{\"a}t1 (Burkard N. et al. (2007). Circ Res 100, 32-44). nNOS interagiert mit vielen verschiedenen Kompartimenten und Kan{\"a}len innerhalb der Zelle. In dieser Arbeit wurde gezeigt, dass eine nNOS {\"U}berexpression nach Isch{\"a}mie-Reperfusion kardioprotektiv wirkt. Dieses wird durch eine Inhibition der Mitochondrienfunktion und durch eine Verminderung der reaktiven Sauerstoffspezies (ROS) erm{\"o}glicht. In einer fr{\"u}heren Arbeit wurde der Effekt der induzierbaren und myokardspezifischen {\"U}berexpression von nNOS unter physiologischen Bedingungen am transgenen Tiermodell untersucht. Diese Arbeit besch{\"a}ftigt sich nun mit der {\"U}berexpression von nNOS unter pathophysiologischen (Isch{\"a}mie-Reperfusion) Bedingungen. Ein Isch{\"a}mie-Reperfusions-Schaden bewirkt bei Wildtyp-M{\"a}usen, sowie bei transgener nNOS {\"U}berexpression eine Anreicherung von nNOS in den Mitochondrien. Elektronenmikroskopische Aufnahmen von Mausmyokard haben gezeigt, dass bei {\"U}berexpression nNOS zus{\"a}tzlich in den Mitochondrien lokalisiert ist. Diese Translokation von nNOS in die Mitochondrien ist abh{\"a}ngig von HSP90. Isch{\"a}mie- Reperfusionsexperimente an isolierten M{\"a}useherzen zeigten einen kardioprotektiven Effekt der nNOS {\"U}berexpression (30min post ischemia, LVDP 27.0±2.5mmHg vs. 45.2±1.9mmHg, n=12, p<0.05). Dieser positive Effekt konnte bei der Bestimmung der Infarktgr{\"o}ße best{\"a}tigt werden. nNOS {\"u}berexprimierende M{\"a}use hatten eine kleinere Infarktgr{\"o}ße nach Isch{\"a}mie-Reperfusion (36.6±8.4 relative \% vs. 61.1±2.9 relative \%, n=8, p<0.05). Die {\"U}berexpression von nNOS bewirkte ebenfalls einen signifikanten Anstieg des mitochondrialen Nitrit-Levels, begleitet von einer Verminderung der Cytochrom C Oxidase Aktivit{\"a}t (72.0±8.9units/ml in nNOS overexpressing mice vs. 113.2±17.1units/ml in non-induced mice, n=12, p<0.01), was zu einer Hemmung der Mitochondrienfunktion f{\"u}hrt. Dementsprechend war der Sauerstoffverbrauch (gemessen an isolierten Herzmuskelstreifen) schon unter basalen Bedingungen beinNOS {\"U}berexpression vermindert (0.016±0.0015 vs. 0.024±0.006ml[O2] x mm-3 x min-1, n=13, p<0.05). Außerdem war die ROS Konzentration in Herzen von nNOS {\"u}berexprimierenden M{\"a}usen signifikant vermindert (6.14±0.685 vs. 14.53±1.7μM, n=8, p<0.01). Die Zugabe von verschiedenen Inhibitoren, Western Blot- und Aktivit{\"a}tsuntersuchungen zeigten schließlich, dass diese niedrigere ROS Konzentration durch eine verminderte Xanthin Oxidoreduktase Aktivit{\"a}t hervorgerufen wurde. Zusammenfassend hat diese Arbeit gezeigt, dass eine induzierbare und myokardspezifische {\"U}berexpression von nNOS unter pathophysiologischen Bedingungen (Isch{\"a}mie-Reperfusion) kardioprotektiv wirkt. Zus{\"a}tzlich zu der Verminderung des myokardialen Ca2+-{\"U}berschusses nach Reperfusion k{\"o}nnte dieser protektive Effekt durch eine Hemmung der Mitochondrienfunktion bedingt sein, schließlich wird der Sauerstoffverbrauch schon unter basalen Bedingungen reduziert},
  subject      = {Herzhypertrophie},
  language  = {en}
}