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- ItemMonoclonal Antibodies 13A4 and AC133 Do Not Recognize the Canine Ortholog of Mouse and Human Stem Cell Antigen Prominin-1 (CD133)(San Francisco, California, US : PLOS, 2016) Thamm, Kristina; Graupner, Sylvi; Werner, Carsten; Huttner, Wieland B.; Corbeil, Denis; Nabi, Ivan RThe pentaspan membrane glycoprotein prominin-1 (CD133) is widely used in medicine as a cell surface marker of stem and cancer stem cells. It has opened new avenues in stem cell-based regenerative therapy and oncology. This molecule is largely used with human samples or the mouse model, and consequently most biological tools including antibodies are directed against human and murine prominin-1. Although the general structure of prominin-1 including its membrane topology is conserved throughout the animal kingdom, its primary sequence is poorly conserved. Thus, it is unclear if anti-human and -mouse prominin-1 antibodies cross-react with their orthologs in other species, especially dog. Answering this issue is imperative in light of the growing number of studies using canine prominin-1 as an antigenic marker. Here, we address this issue by cloning the canine prominin-1 and use its overexpression as a green fluorescent protein fusion protein in Madin-Darby canine kidney cells to determine its immunoreactivity with antibodies against human or mouse prominin-1. We used immunocytochemistry, flow cytometry and immunoblotting techniques and surprisingly found no cross-species immunoreactivity. These results raise some caution in data interpretation when anti-prominin-1 antibodies are used in interspecies studies.
- ItemGuidance of mesenchymal stem cells on fibronectin structured hydrogel films(San Francisco, California, US : PLOS, 2014) Kasten, Annika; Naser, Tamara; Brüllhoff, Kristina; Fiedler, Jörg; Müller, Petra; Möller, Martin; Rychly, Joachim; Groll, Jürgen; Brenner, Rolf E.; Engler, Adam J.Designing of implant surfaces using a suitable ligand for cell adhesion to stimulate specific biological responses of stem cells will boost the application of regenerative implants. For example, materials that facilitate rapid and guided migration of stem cells would promote tissue regeneration. When seeded on fibronectin (FN) that was homogeneously immmobilized to NCO-sP(EO-stat-PO), which otherwise prevents protein binding and cell adhesion, human mesenchymal stem cells (MSC) revealed a faster migration, increased spreading and a more rapid organization of different cellular components for cell adhesion on fibronectin than on a glass surface. To further explore, how a structural organization of FN controls the behavior of MSC, adhesive lines of FN with varying width between 10 µm and 80 µm and spacings between 5 µm and 20 µm that did not allow cell adhesion were generated. In dependance on both line width and gaps, cells formed adjacent cell contacts, were individually organized in lines, or bridged the lines. With decreasing sizes of FN lines, speed and directionality of cell migration increased, which correlated with organization of the actin cytoskeleton, size and shape of the nuclei as well as of focal adhesions. Together, defined FN lines and gaps enabled a fine tuning of the structural organization of cellular components and migration. Microstructured adhesive substrates can mimic the extracellular matrix in vivo and stimulate cellular mechanisms which play a role in tissue regeneration.
- ItemSimultaneous statistical inference for epigenetic data(San Francisco, California, US : PLOS, 2015) Schildknecht, Konstantin; Olek, Sven; Dickhaus, ThorstenEpigenetic research leads to complex data structures. Since parametric model assumptions for the distribution of epigenetic data are hard to verify we introduce in the present work a nonparametric statistical framework for two-group comparisons. Furthermore, epigenetic analyses are often performed at various genetic loci simultaneously. Hence, in order to be able to draw valid conclusions for specific loci, an appropriate multiple testing correction is necessary. Finally, with technologies available for the simultaneous assessment of many interrelated biological parameters (such as gene arrays), statistical approaches also need to deal with a possibly unknown dependency structure in the data. Our statistical approach to the nonparametric comparison of two samples with independent multivariate observables is based on recently developed multivariate multiple permutation tests. We adapt their theory in order to cope with families of hypotheses regarding relative effects. Our results indicate that the multivariate multiple permutation test keeps the pre-assigned type I error level for the global null hypothesis. In combination with the closure principle, the family-wise error rate for the simultaneous test of the corresponding locus/parameter-specific null hypotheses can be controlled. In applications we demonstrate that group differences in epigenetic data can be detected reliably with our methodology.
- ItemNonlinear Structured Illumination Using a Fluorescent Protein Activating at the Readout Wavelength(San Francisco, California, US : PLOS, 2016) Lu-Walther, Hui-Wen; Hou, Wenya; Kielhorn, Martin; Arai, Yoshiyuki; Nagai, Takeharu; Kessels, Michael M.; Qualmann, Britta; Heintzmann, RainerStructured illumination microscopy (SIM) is a wide-field technique in fluorescence microscopy that provides fast data acquisition and two-fold resolution improvement beyond the Abbe limit. We observed a further resolution improvement using the nonlinear emission response of a fluorescent protein. We demonstrated a two-beam nonlinear structured illumination microscope by introducing only a minor change into the system used for linear SIM (LSIM). To achieve the required nonlinear dependence in nonlinear SIM (NL-SIM) we exploited the photoswitching of the recently introduced fluorophore Kohinoor. It is particularly suitable due to its positive contrast photoswitching characteristics. Contrary to other reversibly photoswitchable fluorescent proteins which only have high photostability in living cells, Kohinoor additionally showed little degradation in fixed cells over many switching cycles.
- ItemPhenotypic, Morphological and Adhesive Differences of Human Hematopoietic Progenitor Cells Cultured on Murine versus Human Mesenchymal Stromal Cells([London] : Macmillan Publishers Limited, part of Springer Nature, 2015) Reichert, Doreen; Friedrichs, Jens; Ritter, Steffi; Käubler, Theresa; Werner, Carsten; Bornhäuser, Martin; Corbeil, DenisXenogenic transplantation models have been developed to study human hematopoiesis in immunocompromised murine recipients. They still have limitations and therefore it is important to delineate all players within the bone marrow that could account for species-specific differences. Here, we evaluated the proliferative capacity, morphological and physical characteristics of human CD34+ hematopoietic stem and progenitor cells (HSPCs) after co-culture on murine or human bone marrow-derived mesenchymal stromal cells (MSCs). After seven days, human CD34+CD133– HSPCs expanded to similar extents on both feeder layers while cellular subsets comprising primitive CD34+CD133+ and CD133+CD34– phenotypes are reduced fivefold on murine MSCs. The number of migrating HSPCs was also reduced on murine cells suggesting that MSC adhesion influences cellular polarization of HSPC. We used atomic force microscopy-based single-cell force spectroscopy to quantify their adhesive interactions. We found threefold higher detachment forces of human HSPCs from murine MSCs compared to human ones. This difference is related to the N-cadherin expression level on murine MSCs since its knockdown abolished their differential adhesion properties with human HSPCs. Our observations highlight phenotypic, morphological and adhesive differences of human HSPCs when cultured on murine or human MSCs, which raise some caution in data interpretation when xenogenic transplantation models are used.
- ItemZebrafish In-Vivo Screening for Compounds Amplifying Hematopoietic Stem and Progenitor Cells: - Preclinical Validation in Human CD34+ Stem and Progenitor Cells(London : Nature Publishing Group, 2017) Arulmozhivarman, Guruchandar; Kräter, Martin; Wobus, Manja; Friedrichs, Jens; Bejestani, Elham Pishali; Müller, Katrin; Lambert, Katrin; Alexopoulou, Dimitra; Dahl, Andreas; Stöter, Martin; Bickle, Marc; Shayegi, Nona; Hampe, Jochen; Stölzel, Friedrich; Brand, Michael; von Bonin, Malte; Bornhäuser, MartinThe identification of small molecules that either increase the number and/or enhance the activity of human hematopoietic stem and progenitor cells (hHSPCs) during ex vivo expansion remains challenging. We used an unbiased in vivo chemical screen in a transgenic (c-myb:EGFP) zebrafish embryo model and identified histone deacetylase inhibitors (HDACIs), particularly valproic acid (VPA), as significant enhancers of the number of phenotypic HSPCs, both in vivo and during ex vivo expansion. The long-term functionality of these expanded hHSPCs was verified in a xenotransplantation model with NSG mice. Interestingly, VPA increased CD34+ cell adhesion to primary mesenchymal stromal cells and reduced their in vitro chemokine-mediated migration capacity. In line with this, VPA-treated human CD34+ cells showed reduced homing and early engraftment in a xenograft transplant model, but retained their long-term engraftment potential in vivo, and maintained their differentiation ability both in vitro and in vivo. In summary, our data demonstrate that certain HDACIs lead to a net expansion of hHSPCs with retained long-term engraftment potential and could be further explored as candidate compounds to amplify ex-vivo engineered peripheral blood stem cells.
- ItemLimbal stromal cells derived from porcine tissue demonstrate mesenchymal characteristics in vitro(London : Nature Publishing Group, 2017) Fernández-Pérez, Julia; Binner, Marcus; Werner, Carsten; Bray, Laura J.Limbal stromal cells (LSCs) from the human ocular surface display mesenchymal stromal cell characteristics in vitro. In this study, we isolated cells from the porcine limbal stroma (pLSCs), characterised them, and evaluated their ability to support angiogenesis and the culture of porcine limbal epithelial stem cells (pLESCs). The isolated cells adhered to plastic and grew in monolayers in vitro using serum-supplemented or serum-free medium. The pLSCs demonstrated expression of CD29, and cross-reactivity with anti-human CD45, CD90, CD105, CD146, and HLA-ABC. However, expression of CD105, CD146 and HLA-ABC reduced when cultured in serum-free medium. PLSCs did not undergo adipogenic or osteogenic differentiation, but differentiated towards the chondrogenic lineage. Isolated cells were also co-cultured with human umbilical vein endothelial cells (HUVECs) in star-shaped Poly(ethylene glycol) (starPEG)-heparin hydrogels to assess their pericyte capacity which supported angiogenesis networks of HUVECs. PLSCs supported the three dimensional HUVEC network for 7 days. The isolated cells were further growth-arrested and evaluated as feeder cells for pLESC expansion on silk fibroin membranes, as a potential carrier material for transplantation. PLSCs supported the growth of pLESCs comparably to murine 3T3 cells. In conclusion, although pLSCs were not completely comparable to their human counterpart, they display several mesenchymal-like characteristics in vitro.
- ItemPopulation density gratings induced by few-cycle optical pulses in a resonant medium(London : Nature Publishing Group, 2017) Arkhipov, R.M.; Pakhomov, A.V.; Arkhipov, M.V.; Babushkin, I.; Demircan, A.; Morgner, U.; Rosanov, N.N.Creation, erasing and ultrafast control of population density gratings using few-cycle optical pulses coherently interacting with resonant medium is discussed. In contrast to the commonly used schemes, here the pulses do not need to overlap in the medium, interaction between the pulses is mediated by excitation of polarization waves. We investigate the details of the dynamics arising in such ultrashort pulse scheme and develop an analytical theory demonstrating the importance of the phase memory effects in the dynamics.
- ItemBone marrow niche-mimetics modulate HSPC function via integrin signaling(London : Nature Publishing Group, 2017) Kräter, Martin; Jacobi, Angela; Otto, Oliver; Tietze, Stefanie; Müller, Katrin; Poitz, David M.; Palm, Sandra; Zinna, Valentina M.; Biehain, Ulrike; Wobus, Manja; Chavakis, Triantafyllos; Werner, Carsten; Guck, Jochen; Bornhauser, MartinThe bone marrow (BM) microenvironment provides critical physical cues for hematopoietic stem and progenitor cell (HSPC) maintenance and fate decision mediated by cell-matrix interactions. However, the mechanisms underlying matrix communication and signal transduction are less well understood. Contrary, stem cell culture is mainly facilitated in suspension cultures. Here, we used bone marrow-mimetic decellularized extracellular matrix (ECM) scaffolds derived from mesenchymal stromal cells (MSCs) to study HSPC-ECM interaction. Seeding freshly isolated HSPCs adherent (AT) and non-adherent (SN) cells were found. We detected enhanced expansion and active migration of AT-cells mediated by ECM incorporated stromal derived factor one. Probing cell mechanics, AT-cells displayed naïve cell deformation compared to SN-cells indicating physical recognition of ECM material properties by focal adhesion. Integrin αIIb (CD41), αV (CD51) and β3 (CD61) were found to be induced. Signaling focal contacts via ITGβ3 were identified to facilitate cell adhesion, migration and mediate ECM-physical cues to modulate HSPC function.
- ItemNon-thermal plasma-treated solution demonstrates antitumor activity against pancreatic cancer cells in vitro and in vivo([London] : Macmillan Publishers Limited, 2017) Liedtke, Kim Rouven; Bekeschus, Sander; Kaeding, André; Hackbarth, Christine; Kuehn, Jens-Peter; Heidecke, Claus-Dieter; von Bernstorff, Wolfram; von Woedtke, Thomas; Partecke, Lars IvoPancreatic cancer is associated with a high mortality rate. In advanced stage, patients often experience peritoneal carcinomatosis. Using a syngeneic murine pancreatic cancer cell tumor model, the effect of non-thermal plasma (NTP) on peritoneal metastatic lesions was studied. NTP generates reactive species of several kinds which have been proven to be of relevance in cancer. In vitro, exposure to both plasma and plasma-treated solution significantly decreased cell viability and proliferation of 6606PDA cancer cells, whereas mouse fibroblasts were less affected. Repeated intraperitoneal treatment of NTP-conditioned medium decreased tumor growth in vivo as determined by magnetic resonance imaging, leading to reduced tumor mass and improved median survival (61 vs 52 days; p < 0.024). Tumor nodes treated by NTP-conditioned medium demonstrated large areas of apoptosis with strongly inhibited cell proliferation. Contemporaneously, no systemic effects were found. Apoptosis was neither present in the liver nor in the gut. Also, the concentration of different cytokines in splenocytes or blood plasma as well as the distribution of various hematological parameters remained unchanged following treatment with NTP-conditioned medium. These results suggest an anticancer role of NTP-treated solutions with little to no systemic side effects being present, making NTP-treated solutions a potential complementary therapeutic option for advanced tumors.