Browsing by Subject "Fibroblasten"

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Untersuchungen des Einflusses von Chemotherapie auf Tumor-assoziierte Fibroblasten bei Karzinomen der Lunge und Brust in vivo und in verschiedenen ex vivo Modellen
(2009) Sonnenberg, Maike; Blum, Martin
Carcinomas are complex tissues in which the genetically altered epithelial tumor cells interact with their microenvironment, which plays a pivotal role in growth and survival of the whole tumor. Therefore, also the response of the tumor stroma may be important for the therapeutic success. The aim of the study was to clarify how tumor-associated fibroblasts (TAFs) respond to chemotherapy. We established a grading system for the activity of the TAFs based on cell counts and cell morphology within neoadjuvant treated breast cancer specimens. We compared both the stromal compartment and the tumor compartment before and after therapy to evaluate the response to chemotherapy. In this in vivo study a response of the stromal compartment was detected in samples with a high stromal activity grade before chemotherapy. To investigate the direct, more acute response of TAFs we established different ex vivo systems. On the one hand, the response to chemotherapy was tested in primary isolated TAFs from tumor tissue. On the other hand, a tissue slice culture was established to investigate the direct effect of the chemotherapy on TAFs and tumor cells within their intact microenvironment. For the cell culture experiments freshly isolated TAFs from breast and lung tumors were used. The chemosensitivity to Cisplatinum and Paclitaxel of the primary isolated TAFs was determined and compared with a panel of established human tumor cell lines. The TAFs turned out to be resistant to Paclitaxel, whereas they showed a heterogeneous response to Cisplatinum. One reason for this heterogeneous response to Cisplatinum could be the existence of somatic mutations and/or polymorphisms within DNA-damage response genes. Somatic mutations within the p53 tumor suppressor gene play a critical role in the response of tumor cells to chemotherapeutics. In this study, however, no somatic mutation was detected in any of the TAFs from lung. In other studies, different polymorphisms could be correlated with the sensitivity to cytotoxic stress. In this study, a non-significant trend towards the chemosensitivity of TAFs from lung carcinomas and the p53-Arg72Pro polymorphism could be observed, whereas the ERCC1-Asn118Asn und Mdm2-T/G309 polymorphisms had no influence on the chemosensitivity. The chemosensitivity of the TAFs was also determined within their microenvironment on the basis of tissue culture experiments performed with breast and lung carcinomas. Tumor tissue slices from breast carcinomas were treated for 72 h with Paclitaxel, whereas the tissue slices from lung carcinomas were treated with Cisplatinum. To investigate the response of the different cell types to the tested chemotherapeutic drugs within the intact microenvironment, the tissue slices were fixed and stained immunhistochemically for proliferative active and dead cells. Half of the cultivated tissue slices from breast carcinomas showed a decrease in cell counts of proliferating cells, whereas half of the cases showed an increase of dead cells after the treatment with Paclitaxel in tumor and stroma cells. The tissue slices of the lung carcinomas showed a decrease in proliferating tumor cells after Cisplatinum treatment in comparison to the untreated controls. The stroma compartment showed no proliferative activity so one could not expect a response regarding a decrease of proliferating stroma cells. Two cases showed a response to Cisplatinum regarding an increase in cell death in both cell compartments. Short term exposure to Paclitaxel led to a parallel reaction of both tumor and stromal cells in tissue culture experiments, whereas isolated TAFs from breast tumors turned out to be resistant to Paclitaxel. In contrast, isolated TAFs from lung carcinomas are significantly more sensitive to Cisplatinum than TAFs within their intact microenvironment. Consequently, the microenvironment of the tumor plays a crucial role in chemosensitivity. The central role of the microenvironment for response of TAFs to cytotoxic drugs is also demonstrated by the results obtained with lung cancer tissues. These observations indicate that, in addition to intrinsic factors, the microenvironment determines the sensitivity of TAFs to cytotoxic therapy. In summary, this work demonstrates for the first time, not only the tumor cells but also the stromal cells are an important target for the chemotherapy. Intrinsic and extrinsic factors play an important role in chemosensitivity. On the one hand, the tumor microenvironment is responsible for therapy response of TAFs and on the other hand the genotype may play a crucial role in chemosensitivity. Both, tumor and stroma cells react in parallel to chemotherapy, so you can assume that both cell types are responsible for the chemosensitivity. Some therapeutic approaches could be the inhibition of either the tumor or stromal cell compartment to increase the chemosensitivity of the whole tumor.
Zelluläre Mechanismen beim Neuro Tissue-Engineering
(2007) Dreesmann, Lars; Schloßhauer, Burkhard
To date, numerous tissue engineering approaches aim to develop artificial nerve guide implants for the treatment of lesioned nerves. However, the gold standard in this therapeutical application is still the autologous nerve transplantation. By allocation of a native structure, comprising Schwann cells as well as endothelial cells, an optimal supply of regenerating axons is warranted. Because this surgical procedure retrieves several risks, intensive research is done worldwide to develop alternatives. In this context, Schwann cells play an important role. By migration along the lesion site, they built up guidance rails, so called bands of Büngner. These bands offer an ideal substratum for regrowing axons. However, antagonistic fibroblasts may hamper these events. Hence, the interaction between the two cell types was analyzed in detail, setting a focus on migration. Results indicated that fibroblasts foster Schwann cell migration. Neuregulin was identified as molecular mediator causing this effect. Further experiments revealed that neuregulin promotes Schwann cell migration via erB-receptor and the RhoA pathway. With respect to the concept of a nerve guide implant this means, that the inner membrane should allow diffusion of growth factors, but exclude regeneration inhibiting fibroblasts from the inside. For this purpose, gelatin membranes were characterized regarding their physical and chemical properties. Cell biological testing with gelatin tubes shed light on permissivness for Schwann cells, semipermeability for nutrients and exclusion of fibroblasts. Because a better supply with nutrients promises an additional acceleration of regeneration, the formation of blood vessels next to the implant should be promoted by a gelatin sponge. The immigration of blood vessel forming endothelial cells was analyzed using immunocytochemistry and microscopy. Neovascularisation, biocompatibility and inflammation were investigated on the chorioallantoic membrane of the chicken egg, as well as with subcutaneous implantation into mice. Implantation of gelatin nerve guide tubes in lesioned rat sciatic nerves showed an increased angiogenesis and hardly any inflammation. Within the scope of this work, the application of several molecular and cell biological assays, in combination with three different animal models, made a contribution to the detailed comprehension of mechanisms during nerve regeneration, together with an interdisciplinary bridging between material science and biology in development of innovative therapeutical approaches.