S U M M A R YHepatoblastoma is a pediatric liver tumor with epithelial components resembling embryonal and fetal liver cells. The existence of teratoid hepatoblastoma suggests the presence of stem cells in hepatoblastoma. The aim of this study was to analyze the expression of stem cell markers in hepatoblastomas. We studied specimens from 10 hepatoblastomas. Five of the hepatoblastomas were of epithelial and five of mixed type. Immunohistochemistry (IHC) for the stem cell markers CD34, Thy1, c-kit, and the hepatic or biliary lineage markers CK-18, OCH, CK-7, and CD56 was performed. Double IHC for stem cell and lineage markers was used to identify putative liver stem cells. The different markers showed distinct distributions on the tumor cells. Cells in atypical ducts were found to express simultaneously stem cell markers and hepatocytic or biliary lineage markers. Other cells in connective tissue showed c-kit expression, but not hepatic or biliary marker expression. The data show the presence of different cell populations bearing stem cell markers in human hepatoblastoma. Ductal cells co-expressing stem cell markers and hepatic lineage markers phenotypically resemble hepatic stem-like cells. These findings support the thesis that stem cells play a role in the histogenesis of hepatoblastoma.

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.

Peel formation and ICC derangement were significantly reduced by prenatal coverage of gastroschisis. Moreover, this animal model mimics the histopathological bowel changes as seen in human gastroschisis and may, therefore, be used for further research on the pathophysiology and fetal therapy of this malformation.

The project was funded by a DFG grant to K.v.K. (KO 4769/2-1). The authors declare they have no conflicts of interest.

Although technically demanding, we were able to produce and reassess six cases of gastroschisis by fetoscopy. As primary repositioning appears unfavorable, fetoscopic prosthetic bag placement may become an alternative.

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Introduction: The embryogenesis of gastroschisis is not completely understood. The aim of our study was to evaluate the impact of a simple abdominal wall defect versus a defect including eviscerated intestine or omentum for the development of gastroschisis in a fetal lamb model. Material and Methods: At mid-gestation (day 77) an abdominal wall defect was fetoscopically created with three different approaches in 19 German blackhead sheep. The intestine was eviscerated in 7 fetuses (group 1). The peritoneum was incised and a patch of the omentum pulled through the incision in 5 fetuses (group 2). In 7 fetuses (group 3) the skin and rectus muscle were incised until the peritoneum was visible. In this group, no abdominal contents were exteriorized and the peritoneum was left intact. A second fetoscopic procedure was performed 21 days later, assessing the condition and extension of eviscerated bowel. The fetus was retrieved by Cesarean section on day 132 and evaluated. Results: The second fetoscopy acting as a control for the creation of gastroschisis demonstrated eviscerated and inflamed intestine in all 3 groups. The amount of eviscerated intestine did not appear to depend on the size of the defect nor on its duration. Discussion: It appears that a simple incision of the abdominal wall with intact peritoneum is sufficient for the development of gastroschisis in a fetal sheep model. This finding may improve the understanding of the etiology of gastroschisis.

The data suggest that distension of the gut hinders normal development of the ENS in the gut ligation model of chicken embryos. The changes were observed sequentially, starting with rarification of the axonal network between the PM and PSM. Future studies will be required to show whether the changes of the ENS are reversible.