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SFB 1365 Renoprotection
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The Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) is establishing ten new Collaborative Research Centres (CRCs, Sonderforschungsbereich, SFB) to further support top-level research in Germany.
Chronic kidney diseases and acute kidney damage are widespread and reduce the life expectancy of those affected. The CRC “Renoprotection” therefore aims to decode specific signalling pathways for kidney damage and develop new approaches to treatment in the long term (Charité Berlin – FU Berlin and HU Berlin, Spokesperson: Prof. Dr. Pontus Börje Persson).
With the project "Renoprotective role of Lipocalin-2 in allograft rejection following kidney transplantation" Priv.-Doz. Dr. Felix Aigner and Dr. Muhammad Imtiaz Ashraf, PhD will be part of this SFB/CRC!

To provide allograft renoprotection, novel strategies are needed, including (i) prevention of renal allograft IRI and (ii) targeted immunosuppression and thus; reduction and avoidance of steroid and CNI usage in the long-run. Using a mouse model of kidney transplantation, we recently demonstrated a renoprotective role of exogenously administered recombinant Lcn2:Siderophore:Fe complex (rLcn2). The rLcn2 mediated mechanism of allograft renoprotection is still unknown; however, the mechanistic insight is essential for comprehensive translation of the rLcn2 therapy into clinical practice. In the funded project, we aim at (i) understanding the route and mechanisms of immunoregulation and/or cytoprotection, mediated by exogenously administered rLcn2 during the allograft damage; and (ii) characterizing the source and nature of endogenous Lcn2 i.e. whether it is complexed with mammalian iron binding catechols and may contribute to allograft survival in the long-run. Our ultimate goal is to pave the way for transplant renoprotection via recombinant Lcn2.

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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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