Cell transplantation and tissue engineering with liver cells are currently under investigation as experimental therapies for certain liver diseases. In this study we evaluated a fibrin-based gel matrix as carrier for hepatocytes in culture. Furthermore, a novel technique for direct intrahepatic injection of fibrin gel-immobilized hepatocytes was developed and evaluated in a rat model. Hepatocytes were harvested from rats. Fibrin matrix was generated with modified fibrin sealant. Cells, in medium containing epidermal growth factor and insulin, were seeded in a drop of fibrin matrix onto plastic culture dishes. Cell numbers were assessed by DNA content. Hepatocyte differentiation was evaluated by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistology (IH) for cytokeratin (CK)-18 and albumin. PKH26-labeled fibrin gel-immobilized hepatocytes were transplanted into liver by direct injection underneath the capsule. Fluorescence microscopy of explanted liver was performed to identify PKH26+ donor cells. Neotissue was characterized by IH for the markers CK-18, ED1, and desmin. Culture in a fibrin matrix allowed stable cell numbers and three-dimensional neotissue formation. RT-PCR and IH showed preservation of liver-specific markers CK-18 and albumin in vitro. Transplanted cells were identified by fluorescence microscopy after 2 and 7 days. CK-18 and desmin staining showed integration of hepatocytes and hepatic stellate cells into the host liver. Fibrin matrix is an appropriate environment for hepatocytes in culture. Direct intrahepatic injection of fibrin gel-immobilized hepatocytes is technically feasible. We conclude that fibrin gel immobilization is an attractive tool for the development of tissue engineering-based liver support systems.

Background: The tomato kinase Pto confers resistance to bacterial speck disease caused by Pseudomonas syringae pv. tomato in a gene for gene manner. Upon recognition of specific avirulence factors the Pto kinase activates multiple signal transduction pathways culminating in induction of pathogen defense. The soluble cytoplasmic serine/threonine kinase Pti1 is one target of Pto phosphorylation and is involved in the hypersensitive response (HR) reaction. However, a clear role of Pti1 in plant pathogen resistance is uncertain. So far, no Pti1 homologues from monocotyledonous species have been studied.

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