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17
result(s) for
"Kirchhoff, Katharina"
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The Fibrin Matrix Regulates Angiogenic Responses within the Hemostatic Microenvironment through Biochemical Control
by
Dornseifer, Ulf
,
Schilling, Arndt F.
,
Hadjipanayi, Ektoras
in
Alzheimer's disease
,
Angiogenesis
,
Angiogenesis Inducing Agents - metabolism
2015
Conceptually, premature initiation of post-wound angiogenesis could interfere with hemostasis, as it relies on fibrinolysis. The mechanisms facilitating orchestration of these events remain poorly understood, however, likely due to limitations in discerning the individual contribution of cells and extracellular matrix. Here, we designed an in vitro Hemostatic-Components-Model (HCM) to investigate the role of the fibrin matrix as protein factor-carrier, independent of its cell-scaffold function. After characterizing the proteomic profile of HCM-harvested matrix releasates, we demonstrate that the key pro-/anti-angiogenic factors, VEGF and PF4, are differentially bound by the matrix. Changing matrix fibrin mass consequently alters the balance of releasate factor concentrations, with differential effects on basic endothelial cell (EC) behaviors. While increasing mass, and releasate VEGF levels, promoted EC chemotactic migration, it progressively inhibited tube formation, a response that was dependent on PF4. These results indicate that the clot's matrix component initially serves as biochemical anti-angiogenic barrier, suggesting that post-hemostatic angiogenesis follows fibrinolysis-mediated angiogenic disinhibition. Beyond their significance towards understanding the spatiotemporal regulation of wound healing, our findings could inform the study of other pathophysiological processes in which coagulation and angiogenesis are prominent features, such as cardiovascular and malignant disease.
Journal Article
Comparative Evaluation of the Angiogenic Potential of Hypoxia Preconditioned Blood-Derived Secretomes and Platelet-Rich Plasma: An In Vitro Analysis
by
Dornseifer, Ulf
,
Machens, Hans-Günther
,
Schilling, Arndt F.
in
Angiogenesis
,
Anticoagulants
,
Aorta
2020
Blood-derived factor preparations are being clinically employed as tools for promoting tissue repair and regeneration. Here we set out to characterize the in vitro angiogenic potential of two types of frequently used autologous blood-derived secretomes: platelet-rich plasma (PRP) and hypoxia preconditioned plasma (HPP)/serum (HPS). The concentration of key pro-angiogenic (VEGF) and anti-angiogenic (TSP-1, PF-4) protein factors in these secretomes was analyzed via ELISA, while their ability to induce microvessel formation and sprouting was examined in endothelial cell and aortic ring cultures, respectively. We found higher concentrations of VEGF in PRP and HPP/HPS compared to normal plasma and serum. This correlated with improved induction of microvessel formation by PRP and HPP/HPS. HPP had a significantly lower TSP-1 and PF-4 concentration than PRP and HPS. PRP and HPP/HPS appeared to induce similar levels of microvessel sprouting; however, the length of these sprouts was greater in HPP/HPS than in PRP cultures. A bell-shaped angiogenic response profile was observed with increasing HPP/HPS dilutions, with peak values significantly exceeding the PRP response. Our findings demonstrate that optimization of peripheral blood cell-derived angiogenic factor signalling through hypoxic preconditioning offers an improved alternative to simple platelet concentration and release of growth factors pre-stored in platelets.
Journal Article
In Vitro Characterization of Hypoxia Preconditioned Serum (HPS)—Fibrin Hydrogels: Basis for an Injectable Biomimetic Tissue Regeneration Therapy
by
Kükrek, Haydar
,
Dornseifer, Ulf
,
Schilling, Arndt F.
in
Angiogenesis
,
Biomaterials
,
Biomedical materials
2019
Blood-derived growth factor preparations have long been employed to improve perfusion and aid tissue repair. Among these, platelet-rich plasma (PRP)-based therapies have seen the widest application, albeit with mixed clinical results to date. Hypoxia-preconditioned blood products present an alternative to PRP, by comprising the complete wound healing factor-cascade, i.e., hypoxia-induced peripheral blood cell signaling, in addition to platelet-derived factors. This study set out to characterize the preparation of hypoxia preconditioned serum (HPS), and assess the utility of HPS–fibrin hydrogels as vehicles for controlled factor delivery. Our findings demonstrate the positive influence of hypoxic incubation on HPS angiogenic potential, and the individual variability of HPS angiogenic factor concentration. HPS–fibrin hydrogels can rapidly retain HPS factor proteins and gradually release them over time, while both functions appear to depend on the fibrin matrix mass. This offers a means of controlling factor retention/release, through adjustment of HPS fibrinogen concentration, thus allowing modulation of cellular angiogenic responses in a growth factor dose-dependent manner. This study provides the first evidence that HPS–fibrin hydrogels could constitute a new generation of autologous/bioactive injectable compositions that provide biochemical and biomaterial signals analogous to those mediating physiological wound healing. This therefore establishes a rational foundation for their application towards biomimetic tissue regeneration.
Journal Article
Club fan shop or not? A conjoint analysis of online jersey purchase behavior
by
Habenstein, Dominic
,
Schlesinger, Torsten
,
Kirchhoff, Katharina
in
Conjoint analysis
,
Consumer behavior
,
Consumers
2021
PurposeThe relevance of merchandise for professional football clubs is uncontroversial. Especially the constantly growing e-commerce sales elicits disruptive market changes such as global brand visibility or data-driven customer relationship management strategies. To exhaust these possibilities, it is a precondition that merchandising costumers choose the official online fan shop as the first choice channel instead of a third-party supplier. Thus, the purpose of this study is to figure out if the club as a retailer and the loyalty to a club influence the fans' channel choice when purchasing licensed sports merchandise online.Design/methodology/approachTo do so, a choice-based conjoint analysis for a jersey purchase embedded in an online questionnaire was conducted (sample: n = 589) to investigate the importance of the online supplier, relative to the tangible factors price, shipping speed and free added values and the influence of fan loyalty within the e-commerce purchase channel choice.FindingsThe findings reveal that the price has the highest relative importance (47%), but, as a sport specific peculiarity, the relative importance of the online supplier (22%) is higher than added values (20%) and shipping speed (11%). But, these overall findings are significantly affected by the level of fan loyalty. Based on the findings, implications that influence the fans' decision-making practices are derived for clubs.Originality/valueThis study is the one of the first in sports management research, focusing straight on the purchase channel importance (affected by fan loyalty) when purchasing merchandising online.
Journal Article
The Fibrin Matrix Regulates Angiogenic Responses within the Hemostatic Microenvironment through Biochemical Control: e0135618
2015
Conceptually, premature initiation of post-wound angiogenesis could interfere with hemostasis, as it relies on fibrinolysis. The mechanisms facilitating orchestration of these events remain poorly understood, however, likely due to limitations in discerning the individual contribution of cells and extracellular matrix. Here, we designed an in vitro Hemostatic-Components-Model (HCM) to investigate the role of the fibrin matrix as protein factor-carrier, independent of its cell-scaffold function. After characterizing the proteomic profile of HCM-harvested matrix releasates, we demonstrate that the key pro-/anti-angiogenic factors, VEGF and PF4, are differentially bound by the matrix. Changing matrix fibrin mass consequently alters the balance of releasate factor concentrations, with differential effects on basic endothelial cell (EC) behaviors. While increasing mass, and releasate VEGF levels, promoted EC chemotactic migration, it progressively inhibited tube formation, a response that was dependent on PF4. These results indicate that the clot's matrix component initially serves as biochemical anti-angiogenic barrier, suggesting that post-hemostatic angiogenesis follows fibrinolysis-mediated angiogenic disinhibition. Beyond their significance towards understanding the spatiotemporal regulation of wound healing, our findings could inform the study of other pathophysiological processes in which coagulation and angiogenesis are prominent features, such as cardiovascular and malignant disease.
Journal Article
Patient reported outcome of 33 operatively treated talar fractures
2021
Background
Management of talar fractures remains to be one of the most challenging aspects in trauma surgery. Unfortunately, the evidence regarding the correct treatment of these fractures is mainly based on retrospective case series, while studies assessing the patient-reported outcome are rare. Therefore, the aim of this trial was to analyze the patient reported outcome in context of trauma mechanism and concomitant injuries following operative treatment of talar fractures.
Methods
A retrospective outcome study of patients with operatively treated talar fractures between 2003 and 2015 was conducted. The fractures were classified according to AO-/Hawkins classification system and to the Marti-Weber classification. Data was collected via patient registry, radiographs and a validated patient-reported outcome measure (PROM) for foot and ankle pathologies (Foot and Ankle Outcome Score = FOAS). An analysis regarding the functional outcome, concomitant injury and timing of surgery using the nonparametric Mann-Whitney U test and Spearman`s rank correlation was performed.
Results
In total the functional outcome of 32 patients suffering from fractures to the talus were analyzed. The median age of the study cohort was 35±12.2 years, including 9 female (28 %) and 23 male (72 %) patients. The median FAOS score was 72±22.7 (range 13–94). Patients with an isolated talar fracture had an FAOS of 87±20 and with concomitant injury a score of 60±23.4 (
p
= 0.016). Patients with a closed talar fracture without emergency operation due to dislocation or polytrauma, showed no correlation between timing of surgery and FAOS (
r
= -0.17,
p
= 0.43). 10 % of the patients developed an avascular necrosis and 25 % showed signs of a posttraumatic arthritis. The follow-up time was 41 months (range: 16–145).
Conclusions
Talar fractures were typically caused by high-energy trauma often associated with additional injuries of the lower extremity. The majority of the patients showed a fair to poor functional long-term outcome. Concomitant injuries of the lower extremity led to a lower FAOS. In closed talar fractures without the necessity of an emergency surgical intervention, time to surgery did not influence the patient reported outcome. Relating to the presented data, delayed surgery after soft tissue consolidation was not associated with a higher risk of developing an avascular necrosis.
Journal Article
Sorangicin A Is Active against Chlamydia in Cell Culture, Explanted Fallopian Tubes, and Topical In Vivo Treatment
2023
Current treatment of Chlamydia trachomatis using doxycycline and azithromycin introduces detrimental side effects on the host’s microbiota. As a potential alternative treatment, the myxobacterial natural product sorangicin A (SorA) blocks the bacterial RNA polymerase. In this study we analyzed the effectiveness of SorA against C. trachomatis in cell culture, and explanted fallopian tubes and systemic and local treatment in mice, providing also pharmacokinetic data on SorA. Potential side effects of SorA on the vaginal and gut microbiome were assessed in mice and against human-derived Lactobacillus species. SorA showed minimal inhibitory concentrations of 80 ng/mL (normoxia) to 120 ng/mL (hypoxia) against C. trachomatis in vitro and was eradicating C. trachomatis at a concentration of 1 µg/mL from fallopian tubes. In vivo, SorA reduced chlamydial shedding by more than 100-fold within the first days of infection by topical application corresponding with vaginal detection of SorA only upon topical treatment, but not after systemic application. SorA changed gut microbial composition during intraperitoneal application only and did neither alter the vaginal microbiota in mice nor affect growth of human-derived lactobacilli. Additional dose escalations and/or pharmaceutical modifications will be needed to optimize application of SorA and to reach sufficient anti-chlamydial activity in vivo.
Journal Article
Novel algorithms for improved detection and analysis of fluorescent signal fluctuations
2023
Fluorescent dyes and genetically encoded fluorescence indicators (GEFI) are common tools for visualizing concentration changes of specific ions and messenger molecules during intra- as well as intercellular communication. Using advanced imaging technologies, fluorescence indicators are a prerequisite for the analysis of physiological molecular signaling. Automated detection and analysis of fluorescence signals require to overcome several challenges, including correct estimation of fluorescence fluctuations at basal concentrations of messenger molecules, detection, and extraction of events themselves as well as proper segmentation of neighboring events. Moreover, event detection algorithms need to be sensitive enough to accurately capture localized and low amplitude events exhibiting a limited spatial extent. Here, we present two algorithms (PBasE and CoRoDe) for accurate baseline estimation and automated detection and segmentation of fluorescence fluctuations.
Journal Article
Optimized induction of mitochondrial apoptosis for chemotherapy-free treatment of BCR-ABL+acute lymphoblastic leukemia
by
Kloos, Arnold
,
Heuser, Michael
,
Ganser, Arnold
in
631/67/1059/602
,
631/67/1990/283/2125
,
96/2
2019
BCR-ABL+acute lymphoblastic leukemia (ALL) in adults has a poor prognosis with allogeneic stem cell transplantation (SCT) considered the best curative option for suitable patients. We here characterize the curative potential of BH3-mimetics differentially targeting mitochondrial BCL2-family members using a combination therapy approach with dexamethasone and tyrosine kinase inhibitors targeting BCR-ABL. In BCR-ABL + ALL BH3-mimetics act by redistribution of mitochondrial activator BIM, which is strongly required for cytotoxicity of the BCL2-specific BH3-mimetic ABT-199, tyrosine kinase inhibitors (TKIs) and dexamethasone. BIM expression is enhanced by dexamethasone and TKIs and both synergize with ABT-199 in BCR-ABL + ALL. Triple combinations with ABT-199, dexamethasone and TKIs efficiently attenuate leukemia progression both in tissue culture and in primary cell xenotransplantation models. Notably, the dasatinib-containing combination led to treatment- and leukemia-free long-term survival in a BCR-ABL + mouse model. Finally, response to BH3-mimetics can be predicted for individual patients in a clinically relevant setting. These data demonstrate curative targeted and chemotherapy-free pharmacotherapy for BCR-ABL + ALL in a preclinical model. Clinical evaluation, in particular for patients not suitable for allogeneic SCT, is warranted.
Journal Article
In Vitro Evaluation of a Peptide-Mesoporous Silica Nanoparticle Drug Release System against HIV-1
by
Braun, Katharina
,
Kirchhoff, Frank
,
Stürzel, Christina M.
in
Adsorption
,
Antibodies
,
Antiviral activity
2020
It has been shown that the optimized VIR-576 derivative of the natural HIV-1 entry inhibitor targeting the viral gp41 fusion peptide is safe and effective in infected individuals. However, high doses of this peptide were required, and stability, as well as delivery, must be improved for clinical application. Here, we examined the loading and release of VIR-576 into/from mesoporous silica nanoparticles (MSNs) in vitro. We found that a moderately high peptide loading of 11.5 wt % could be achieved by adsorption from PBS buffer (pH 7.2), i.e., under mild, fully peptide-compatible conditions. The release rate of peptide into the same buffer was slow and the equilibrium concentration as indicated by the adsorption isotherm could not be reached even within 50 h at the particle concentrations studied. However, a faster release was observed at lower particle concentrations, indicating that partial particle dissolution had a positive influence on peptide release. To determine the antiviral activity of VIR-576-loaded MSNs, TZM-bl indicator cells were exposed to HIV-1 and the infection rates were followed as a function of time and VIR-576 concentration. The inhibitory activity observed for VIR-576 released from the MSNs was virtually identical to that of free VIR-576 at the 48 h time point, indicating that (a) VIR-576 was released in an active form from the MSNs, and (b) the release rate in the presence of serum proteins was clearly higher than that observed under protein-free conditions. These observations are discussed based on competitive peptide/protein adsorption, as well as potential influences of serum proteins on the dissolution-reprecipitation of silica under conditions where the total silica concentration is above the saturation level for dissolved silica. Our results highlight the need for studying drug release kinetics in the presence of serum proteins, in order to allow for a better extrapolation of in vitro data to in vivo conditions. Furthermore, due to the high peptide loadings that can be achieved using MSNs as carriers, such a formulation appears promising for local release applications. For systemic administration, however, peptides with a higher potency would be needed, due to their high molar masses limiting the drug loading in terms of moles per gram carrier.
Journal Article