Mechanismus und Modulation der regenerationsaugmentierten Alloimmunantwort nach Leberlebendspende. Untersuchungen zur Wechselwirkung zwischen Regeneration und Alloimmunantwort
Final Report Abstract
This project was designed to understand the feedback mechanism between liver regeneration and immune activation in vivo and to examine the modulation of regeneration and immune activation by substances with and without immunosuppressive properties. The applied surgical technique and techniques employed in quantitative evaluation of the resulting samples and data were optimized. Refining the surgical technique for 90% liver resection in the rat from a mass ligation into a vessel-oriented parenchyma preserving liver resection technique turned the previously lethal model into a surviving model. Preventing focal outflow obstruction caused by mass ligation enhanced the function and the regenerative capacity of the small remnant liver. This clearly demonstrated the importance of the surgical technique on the outcome after 90% liver resection. Refinement of techniques also included the development of an image analysis algorithm to quantify regeneration, the evaluation of microcirculation and the development of a quality control procedure for each step in qPCR. We could confirm that immune activation inhibits liver regeneration, when vaccinating the rats prior to liver resection and when transplanting a partial liver graft undergoing rejection. Several drugs were tested in respect to their effect on liver regeneration and liver graft rejection. FK778 blocked liver graft rejection, but did not influence liver regeneration. Several doses had to be tested due to its unexpected high frequency of side effects such as diarrhea paralysis, leading to a dose dependent high letality. GCSF, an anti-inflammatory and stem cell mobilizing cytokine, enhanced liver regeneration slightly, possibly due to a direct receptor-mediated effect on hepatocytes. Transdifferentiation of mobilized stem cells seemed to be an unlikely mechanism. Thymectomy, which is leading to a modulation of extrathymic T-cell maturation, was used as another immunological strategy to influence hepatic regeneration. Currently, other drugs influencing liver rejection and regeneration, such as Tyrosine kinase inhibitors, are being evaluated. Ultimately, we aim for developing an immunosuppressive and hepatotrophic preconditioning protocol, which reduces regeneration-augmented alloreactivity.
Publications
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Administration of granulocyte colony stimulating factor after liver transplantation leads to an increased incidence and severity of ischemic biliary lesions in the rat model. World J Gastroenterol 2006; 12:5021-7
Dirsch O, Chi H, Ji Y, Gu YL, Broelsch CE, Dahmen U
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Influence of stem cell mobilization and liver regeneration on hepatic parenchymal chimerism in the rat. Transplantation 2006; 81:1695-9
Dirsch O, Chi H, Gu YL, Ji Y, Broelsch C, Dahmen U
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Marginal hepatectomy in the rat: from anatomy to surgery. Ann Surg 2006; 244: 89-98
Madrahimov N, Dirsch O, Broelsch C, Dahmen U
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Probe Production for In Situ Hybridization by PCR and Subsequent Covalent Labeling With Fluorescent Dyes. Appl Immunohistochem Mol Morphol 2007; 15: 332-7
Dirsch O, Ji Y, Bohr J, Shen K, Levison D, Dahmen U
