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Decellularization and oscillating pressure conditions
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The Journal of Tissue Engineering and Regenerative Medicine accepted our latest paper on „Improved rat liver decellularization by arterial perfusion under oscillating pressure conditions“ for publication. Authors are B. Struecker, A. Butter, K. Hillebrandt, D. Polenz , A. Reutzel-Selke, P. Tang, S. Lippert, A. Leder, S. Rohn, D. Geisel, T. Denecke, K. Aliyev, K. Jöhrens, N. Raschzok, P. Neuhaus, J. Pratschke and I.M. Sauer.

One approach of regenerative medicine to generate functional hepatic tissue in vitro is de- and recellularization and several protocols for the decellularization of different species have been published. To the best of our knowledge this is the first report on rat liver decellularization by perfusion via the hepatic artery under oscillating pressure conditions, intending to optimize microperfusion and minimize damage to the ECM. Four decellularization protocols were compared: perfusion via the portal vein (PV) or the hepatic artery (HA), with (+P) or without (-P) oscillating pressure conditions. All rat livers (n=24) were perfused with 1% Triton X-100 and 1% SDS, each for 90 minutes with a perfusion rate of 5ml/min. Perfusion decellularization was observed macroscopically and the decellularized liver matrices (DLMs) were analyzed by histology and biochemical analyses (e.g., levels of DNA, glycosaminoglycans (GAG), and hepatocyte growth factor (HGF). Livers decellularized via the hepatic artery and under oscillating pressure showed a more homogenous decellularization and less remaining DNA, compared to livers of the other experimental groups. The novel decellularization method described is effective, quick (3 hours) and gentle to the ECM and thus represents an improvement of existing methodology.
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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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