@phdthesis{Mott2023,
  author    = {Mott, Kristina},
  title     = {Regulation of platelet biogenesis in the native and myeloablated bone marrow niche},
  doi       = {10.25972/OPUS-28963},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-289630},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {Megakaryocytes (MKs) are the largest cells of the hematopoietic system and the precursor cells of platelets. During proplatelet formation (PPF) bone marrow (BM) MKs extent large cytoplasmic protrusions into the lumen of sinusoidal blood vessels. Under homeostatic conditions PPF occurs exclusively in the direction of the sinusoid, while platelet generation into the marrow cavity is prevented. So far, the mechanisms regulating this process in vivo are still not completely understood, especially when PPF is deregulated during disease. This thesis investigated the mechanisms of PPF in native BM and after myeloablation by total body irradiation (TBI). First, we have identified a specialized type of BM stromal cells, so called CXCL12-abundant reticular (CAR) cells, as novel possible regulators of PPF. By using complementary high-resolution microscopy techniques, we have studied the morphogenetic events at the MK/vessel wall interface in new detail, demonstrating that PPF formation preferentially occurs at CAR cell-free sites at the endothelium. In the second part of this thesis, we analyzed the processes leading to BM remodeling in response to myeloablation by TBI. We used confocal laser scanning microscopy (CLSM) to study the kinetic of radiation-triggered vasodilation and mapped extracellular matrix (ECM) proteins after TBI. We could demonstrate that collagen type IV and laminin α5 are specifically degraded at BM sinusoids. At the radiation-injured vessel wall we observed ectopic release of platelet-like particles into the marrow cavity concomitantly to aberrant CAR cell morphology, suggesting that the balance of factors regulating PPF is disturbed after TBI. ECM proteolysis is predominantly mediated by the matrix metalloproteinase MMP9, as revealed by gelatin-zymography and by a newly established BM in situ zymography technique. In transgenic mice lacking MMP9 vascular recovery was delayed, hinting towards a role of MMP9 in vessel reconstitution after myeloablation. In a third series of experiments, we studied the irradiated BM in the context of hematopoietic stem cell transplantation (HSCT). By using mice as BM donors that ubiquitously express the fluorescent reporter protein dsRed we tracked engraftment of donor cells and especially MKs in the recipient BM. We found a distinct engraftment pattern and cluster formation for MKs, which is different from other blood cell lineages. Finally, we assessed platelet function after TBI and HSCT and were the first to demonstrate that platelets become massively hyporeactive, particularly upon stimulation of the collagen receptor GPVI. In summary, our findings shed light on the processes of PPF during health and disease which will help to develop treatments for aberrant thrombopoiesis.},
  subject      = {Knochenmark},
  language  = {en}
}
@article{AintablianStrozniakHeueretal.2023,
  author    = {Aintablian, Arpa and Strozniak, Sandra and Heuer, Marion and Lutz, Manfred B.},
  title     = {M-MDSC in vitro generation from mouse bone marrow with IL-3 reveals high expression and functional activity of arginase 1},
  series = {Frontiers in Immunology},
  volume    = {14},
  journal   = {Frontiers in Immunology},
  doi       = {10.3389/fimmu.2023.1130600},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-317769},
  year      = {2023},
  abstract  = {Myeloid-derived suppressor cells (MDSC) represent major regulators of immune responses, which can control T cells via their inducible nitric oxide synthase (iNOS)- and arginase 1 (Arg1)-mediated effector functions. While GM-CSF is well documented to promote MDSC development, little is known about this potential of IL-3, an established growth factor for mast cells. Here, we show that IL-3, similar to GM-CSF, generates monocytic MDSC (M-MDSC) from murine bone marrow (BM) cells after 3 days of in vitro culture. At this time point, predominantly CD11b+ CD49a+ monocytic and CD11b+ CD49a- FcεR I- neutrophilic cells were detectable, while CD11blow/neg FcεR I+ mast cells accumulated only after extended culture periods. Both growth factors were equivalent in generating M-MDSC with respect to phenotype, cell yield and typical surface markers. However, IL-3 generated M-MDSC produced less TNF, IL-1β and IL-10 after activation with LPS + IFN-γ but showed higher Arg1 expression compared to GM-CSF generated M-MDSC. Arg1 was further induced together with iNOS after MDSC activation. Accordingly, an increased Arg1-dependent suppressor activity by the IL-3 generated M-MDSC was observed using respective iNOS and Arg1 inhibitors. Together, these data indicate that M-MDSC can be generated in vitro by IL-3, similar to GM-CSF, but with increased Arg1 expression and Arg1-mediated suppression capacity. This protocol now allows further in vitro studies on the role of IL-3 for MDSC biology.},
  language  = {en}
}
@article{WeissenbergerWagenbrennerNickeletal.2023,
  author    = {Weißenberger, Manuel and Wagenbrenner, Mike and Nickel, Joachim and Ahlbrecht, Rasmus and Blunk, Torsten and Steinert, Andre F. and Gilbert, Fabian},
  title     = {Comparative in vitro treatment of mesenchymal stromal cells with GDF-5 and R57A induces chondrogenic differentiation while limiting chondrogenic hypertrophy},
  series = {Journal of Experimental Orthopaedics},
  volume    = {10},
  journal   = {Journal of Experimental Orthopaedics},
  doi       = {10.1186/s40634-023-00594-z},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-357770},
  year      = {2023},
  abstract  = {Purpose Hypertrophic cartilage is an important characteristic of osteoarthritis and can often be found in patients suffering from osteoarthritis. Although the exact pathomechanism remains poorly understood, hypertrophic de-differentiation of chondrocytes also poses a major challenge in the cell-based repair of hyaline cartilage using mesenchymal stromal cells (MSCs). While different members of the transforming growth factor beta (TGF-β) family have been shown to promote chondrogenesis in MSCs, the transition into a hypertrophic phenotype remains a problem. To further examine this topic we compared the effects of the transcription growth and differentiation factor 5 (GDF-5) and the mutant R57A on in vitro chondrogenesis in MSCs. Methods Bone marrow-derived MSCs (BMSCs) were placed in pellet culture and in-cubated in chondrogenic differentiation medium containing R57A, GDF-5 and TGF-ß1 for 21 days. Chondrogenesis was examined histologically, immunohistochemically, through biochemical assays and by RT-qPCR regarding the expression of chondrogenic marker genes. Results Treatment of BMSCs with R57A led to a dose dependent induction of chondrogenesis in BMSCs. Biochemical assays also showed an elevated glycosaminoglycan (GAG) content and expression of chondrogenic marker genes in corresponding pellets. While treatment with R57A led to superior chondrogenic differentiation compared to treatment with the GDF-5 wild type and similar levels compared to incubation with TGF-ß1, levels of chondrogenic hypertrophy were lower after induction with R57A and the GDF-5 wild type. Conclusions R57A is a stronger inducer of chondrogenesis in BMSCs than the GDF-5 wild type while leading to lower levels of chondrogenic hypertrophy in comparison with TGF-ß1.},
  language  = {en}
}