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Percoll purification after isolation of Primary Human Hepatocytes
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The manuscript "Isolation of Primary Human Hepatocytes: Is Percoll Purification Really Necessary?" was accepted for publication in Scientific Reports.
Authors are Rosa Horner, Jospeh G.M.V. Gassner, Martin Kluge M, Peter Tang, Steffen Lippert, Karl H. Hillebrandt, Simon Moosburner, Anja Reutzel-Selke, Johann Pratschke, Igor M. Sauer and Nathanael Raschzok.

Research and therapeutic applications create a high demand for primary human hepatocytes. The limiting factor for their utilization is the availability of metabolically active hepatocytes in large quantities. Centrifugation through Percoll, which is commonly performed during hepatocyte isolation, has so far not been systematically evaluated in the scientific literature. 27 hepatocyte isolations were performed using a two-step perfusion technique on tissue obtained from partial liver resections. Cells were seeded with or without having undergone the centrifugation step through 25% Percoll. Cell yield, function, purity, viability and rate of bacterial contamination were assessed over a period of 6 days. Viable yield without Percoll purification was 42.4 x 106 (SEM ± 4.6 x 106) cells/g tissue. An average of 59% of cells were recovered after Percoll treatment. There were neither significant differences in the functional performance of cells, nor regarding presence of non-parenchymal liver cells. In five cases with initial viability of <80%, viability was significantly increased by Percoll purification (71.6 to 87.7%, p=0.03). Considering our data and the massive cell loss due to Percoll purification, we suggest that this step can be omitted if the initial viability is high, whereas low viabilities can be improved by Percoll centrifugation.
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Isolation of primary human hepatocytes & LiMax-test
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Tissue Engineering (Part C: Methods) accepted our paper entitled "The predictive value of the LiMAx-test for the isolation of primary human hepatocytes".
Authors are R.D. Major, M. Kluge, M. Jara, M. Nösser, R. Horner, J. Gassner, B. Struecker, P. Tang, S. Lippert, A. Reutzel-Selke, D. Geisel, T. Denecke, M. Stockmann, J. Pratschke, I.M. Sauer, and N. Raschzok.

The need for primary human hepatocytes is constantly growing, for basic research as well as for therapeutic applications. However, the isolation outcome strongly depends on the quality of liver tissue, and we are still lacking a preoperative test that allows the prediction of the hepatocyte isolation outcome. Here we evaluated the “maximal liver function capacity test” (LiMAx) as predictive test for the quantitative and qualitative outcome of hepatocyte isolation. This test is already used in clinical routine to measure preoperative and to predict postoperative liver function.
The patient’s preoperative mean LiMAx was obtained from the patient records and preoperative CT and MRI images were used to calculate the whole liver volume in order to adjust the mean LiMAx. The outcome parameters of the hepatocyte isolation procedures were analyzed in correlation with the adjusted mean LiMAx.
Primary human hepatocytes were isolated from partial hepatectomies (n=64).
From these 64 hepatectomies we included 48 to our study and correlated their isolation outcome parameters with volume corrected LiMAx values. From a total of 11 hepatocyte isolation procedures, metabolic parameters (albumin, urea and aspartate aminotransferase) were assessed during the hepatocyte cultivation period of 5 days. The volume adjusted mean LiMAx showed a significant positive correlation with the total cell yield (p= 0.049;r= 0.242;n= 48). The correlations of volume adjusted LiMAx values with viable cell yield and cell viability did not reach statistical significance. A sub-group analysis of isolations from patients with colorectal metastasis revealed a significant correlation between volume adjusted mean LiMAx and total cell yield (p= 0.012;r= 0.488;n= 21) and viable cell yield (p=0.034;r=0.405;n=21). Whereas a sub-group analysis of isolations of patients with carcinoma of the biliary tree showed significant correlations of volume adjusted mean LiMAx with cell viability (r= 0.387;p= 0.046;n=20) and lacked significant correlations with total cell yield (r= - 0.060;p= 0.401;n=20) and viable cell yield (r= 0.012;p= 0.480;n=20). The volume-adjusted mean LiMAx did not show a significant correlation with any of the metabolic parameters. In conclusion, the LiMAx-test might be a useful tool to predict the quantitative outcome of hepatocyte isolation, as long as underlying liver disease is taken into consideration.
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NeoHybrid liver graft – proof of concept
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Cells Tissues Organs accepted our latest paper on "Allogeneic liver transplantation and subsequent syngeneic hepatocyte transplantation in a rat model – proof of concept for in vivo tissue engineering" for publication.

Authors are Susanne Rohn, Jan Schroeder, Henriette Riedel, Dietrich Polenz, Katarina Stanko, Anja Reutzel-Selke, Peter Tang, Lydia Brusendorf, Nathanael Raschzok, Peter Neuhaus, Johann Pratschke, Birgit Sawitzki, Igor M. Sauer, and Martina T. Mogl.

Aim of the project was the evaluation of a new concept for in vivo tissue engineering using autologous primary human hepatocytes and hepatic progenitor cells isolated from diseased livers explanted during orthotopic liver transplantation (LTx). Cells will be isolated and infused into the spleen for repopulation of the allogeneic liver graft. The latter is serving as biological matrix for the engraftment of autologous cells. Once these cells have engrafted, it is assumed that autologous cells will repopulate the allogeneic liver, since they should have a selective advantage due to their autologous origin. It is postulated that this will lead to a neo-hybrid liver graft, reducing immunogenicity and inducing immunoregulation thus minimizing the need for extensive immunosuppression and eventually inducing operational tolerance. 

We therefore developed a new rat model for combined liver and liver cell transplantation under stable immunosuppression. Immunohistochemistry demonstrated the engraftment of transplanted cells, as confirmed by fluorescence in-situ hybridization, showing repopulation of the liver graft with 15.6 % male cells (± 1.8 SEM) at day 90. The quantitative PCR revealed 14.15 % (mean ± 5.09 SEM) male DNA at day 90. Engraftment of transplanted autologous cells after combined liver and cell transplantation was achieved for up to 90 days under immunosuppression. Immunohistochemistry indicated cell proliferation, and the fluorescence in-situ hybridization results were partly confirmed by quantitative RT-PCR. This new protocol in rats appears feasible to address long-term function and eventually induction of operational tolerance in the future.
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Human hepatocyte isolation – new paper
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Tissue Engineering, Part C: Methods accepted our paper „Human hepatocyte isolation: Does portal vein embolization affect the outcome?“ Authors are Martin Kluge, Anja Reutzel-Selke, Hendrik Napierala, Karl H. Hillebrandt, Rebeka D. Major, Benjamin Struecker, Annekatrin Leder, Jeffrey Siefert, Peter Tang, Steffen Lippert, Daniel Seehofer, Johann Pratschke, Igor M. Sauer und Nathanael Raschzok.

Primary human hepatocytes are widely used for basic research, pharmaceutical testing, and therapeutic concepts in regenerative medicine. Human hepatocytes can be isolated from resected liver tissue. Preoperative portal vein embolization (PVE) is increasingly used to decrease the risk of delayed postoperative liver regeneration by induction of selective hypertrophy of the future remnant liver tissue. The aim of this study was to investigate the effect of PVE on the outcome of hepatocyte isolation. Primary human hepatocytes were isolated from liver tissue obtained from partial hepatectomies (n=190) using the two-step collagenase perfusion technique followed by Percoll purification. Of these hepatectomies, 27 isolations (14.2%) were performed using liver tissue obtained from patients undergoing PVE prior to surgery. All isolations were characterized using parameters that had been described in the literature as relevant for the outcome of hepatocyte isolation. The PVE and non-PVE groups were similar in regard to donor parameters (sex, age, indication for surgery), isolation parameters (liver weight, cold ischemic time), and the quality of the liver tissue. The mean initial viable cell yield did not differ between the PVE and non-PVE groups (10.16±2.03x106 cells/g vs. 9.70±0.73 x106 cells/g, p=0.499). The initial viability was slightly better in the PVE-group (77.8 ±2.03% vs. 74.4 ±1.06%). The mean viable cell yield (p=0.819) and the mean viability (p=0.141) after Percoll purification did not differ between the groups. PVE had no effect on enzyme leakage and metabolic activity of cultured hepatocytes.  Although PVE leads to drastic metabolic alterations and changes in hepatic blood flow, embolized liver tissue is a suitable source for the isolation of primary human hepatocytes and is equivalent to untreated liver tissue in regard to cell yield and viability.
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Tat-peptide modified MPIO
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Haluk Morgül and Nathanael Raschzok published their first results on "Tracking of primary human hepatocytes with clinical MRI: Initial results with Tat-peptide modified superparamagnetic iron oxide particles." in the March issue of IJAO (Int J Artif Organs 2008, 31:252-257): The transplantation of primary human hepatocytes is a promising approach in the treatment of specific liver diseases. However, little is known about the fate of the cells following application. Magnetic resonance imaging (MRI) could enable real-time tracking and long-term detection of transplanted hepatocytes. The use of superparamagnetic iron oxide particles as cellular contrast agents should allow for the non-invasive detection of labelled cells on high-resolution magnetic resonance images. Experiments were performed on primary human hepatocytes to transfer the method of detecting labelled cells via clinical MRI into human hepatocyte transplantation. For labelling, Tat-peptide modified nano-sized superparamagnetic MagForce particles were used. Cells were investigated via a clinical MR scanner at 3.0 Tesla and the particle uptake within single hepatocytes was estimated using microscopic examinations. The labelled primary human hepatocytes were clearly detectable by MRI, proving the feasibility of this new concept. Therefore, this method is a useful tool to investigate the effects of human hepatocyte transplantation and to improve safety aspects of this method.
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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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