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DFG Research Grant
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Priv.-Doz. Dr. Nathanael Raschzok receives a research grant from the Deutsche Forschungsgemeinschaft (DFG) for his project "Defatting of steatotic liver grafts by normothermic ex vivo machine perfusion with DNP" in collaboration with Prof. Dr. med. Andreas Birkenfeld, Universitätsklinikum Carl Gustav Carus, Dresden.

Transplantation of steatotic marginal liver grafts is associated with a certain risk of graft dysfunction, primary non-function, and biliary complications, which results in a worse outcome compared to transplantation of unimpaired livers.
We hypothesize, that normothermic machine perfusion combined with adequate pharmacological intervention can prevent the deleterious effect of ischemia-reperfusion injury on macrovesicular grafts by a) minimizing the negative effect of cold storage, and by b) actively decreasing the intracellular fat content of the graft.
Mild mitochondrial uncoupling by DNP decreases the intrahepatic fat content of steatotic liver grafts during normothermic ex vivo machine perfusion. Efficient defatting can be safely achieved ex vivo with DNP concentrations that would be toxic in vivo. Systemic side effects of DNP are prevented by exclusive hepatic exposure through machine perfusion, and by washing DNP out of the liver graft at the end of the perfusion period. The synergetic effects of normothermic perfusion and defatting with DNP will prevent ischemia-reperfusion injury and make severely steatotic liver grafts acceptable for transplantation.
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Our manuscript "Depletion of donor dendritic cells ameliorates immunogenicity of both skin and hind limb transplants" has been accepted for publication in Frontiers in Immunology, section Alloimmunity and Transplantation. Authors are Muhammad Imtiaz Ashraf, Joerg Mengwasser, Anja Reutzel-Selke, Dietrich Polenz, Kirsten Führer, Steffen Lippert, Peter Tang, Edward Michaelis, Rusan Catar, Johann Pratschke, Christian Witzel, Igor M. Sauer, Stefan G. Tullius, and Barbara Kern.

Acute cellular rejection remains a significant obstacle affecting successful outcomes of organ transplantation including vascularized composite tissue allografts (VCA). Donor antigen presenting cells (APC), particularly dendritic cells (DC), orchestrate early alloimmune responses by activating recipient effector T cells. Employing a targeted approach, we investigated the impact of donor-derived conventional DC (cDC) and APC on the immunogenicity of skin and skin-containing VCA grafts, using mouse models of skin and hind limb transplantation.
By post-transplantation day 6, skin grafts demonstrated severe rejections, characterized by predominance of recipient CD4 T cells. In contrast, hind limb grafts showed moderate rejection, primarily infiltrated by CD8 T cells. While donor depletion of cDC and APC reduced frequencies, maturation, and activation of DC in all analysed tissues of skin transplant recipients, reduction in DC activities was only observed in the spleen of hind limb recipients. Donor cDC and APC depletion did not impact all lymphocyte compartments but significantly affected CD8 T cells and activated CD4 T in lymph nodes of skin recipients. Moreover, both donor APC and cDC depletion attenuated the Th17 immune response, evident by significantly reduced Th17 (CD4+IL-17+) cells in the spleen of skin recipients and reduced levels of IL-17E and lymphotoxin-α in the serum samples of both skin and hind limb recipients. In conclusion, our findings underscore the highly immunogenic nature of skin component in VCA. The depletion of donor APC and cDC mitigates the immunogenicity of skin grafts while exerting minimal impact on VCA.

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