The results indicate that (1) rat MSC from bone marrow can differentiate towards hepatocytic lineage in vitro, and (2) that the microenvironment plays a decisive role for the induction of hepatic differentiation of rMSC.

ABSTRACT

Today, liver transplantation is still the only curative treatment for liver failure due to end-stage liver diseases. Donor organ shortage, high cost and the need of immunosuppressive medications are still the major limitations in the field of liver transplantation. Thus, alternative innovative cell-based liver directed therapies, for example, liver tissue engineering, are under investigation with the aim that in future an artificial liver tissue could be created and be used for the replacement of the liver function in patients. Using cells instead of organs in this setting should permit (i) expansion of cells in an in vitro phase, (ii) genetic or immunological manipulation of cells for transplantation, (iii) tissue typing and cryopreservation in a cell bank and (iv) the ex vivo genetic modification of patient's own cells prior to re-implantation. Function and differentiation of liver cells are influenced by the three-dimensional organ architecture. The use of polymeric matrices permits the three-dimensional formation of a neo tissue and specific stimulation by adequate modification of the matrix surface, which might be essential for appropriate differentiation of transplanted cells. In addition, culturing hepatocytes on three-dimensional matrices permits culture in a flow bioreactor system with increased function and survival of the cultured cells. Based on bioreactor technology, bioartificial liver devices (BAL) are developed for extracorporeal liver support. Although BALs improved clinical and metabolic conditions, increased patient survival rates have not been proven yet. For intracorporeal liver replacement, a concept that combines tissue engineering using three-dimensional, highly porous matrices with cell transplantation could be useful. In such a concept, whole liver mass transplantation, long-term engraftment and function as well as correction of a metabolic defect in animal models could be achieved with a principally reversible procedure. Future studies have to investigate which environmental conditions and transplantation system would be most suitable for the development of artificial functional liver tissue including blood supply for a potential use in a clinical setting.

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.

Hepatocyte transplantation using porous matrices is under investigation as an alternative therapy for certain liver diseases. For this purpose, long-term function of transplanted hepatocytes is mandatory. This problem has not been sufficiently investigated yet. In this study Lewis rats were used as donors and recipients. Stimulated (group A, portocaval shunt) or unstimulated (group B) hepatocytes were transplanted into prevascularized polyvinyl-alcohol matrices. Cell-free matrices served as controls (group C). Matrices were harvested between 1 h and 1 year after implantation and analyzed by morphometry; albumin RNA in situ hybridization; and cytokeratin-, actin-, desmin-, and macrophage-specific antigen immunohistology. The hepatocyte number significantly decreased within the first week following implantation. Between 1 month and 1 year after transplantation a significant increase in hepatocyte number was noted in groups A and B. Albumin transcripts of transplanted hepatocytes were at normal levels at all times except for group B after 1 year. The immunohistology suggested engraftment of nonparenchymal liver cells. We conclude that 3-dimensional matrices provide a sufficient environment for long-term engraftment of transplanted liver cells. The hepatocytes are able, despite suboptimal initial engraftment, to repopulate the scaffold for at least half of the recipient's life span and maintain cell-specific function after sufficient stimulation.

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Introduction: Our aim was to highlight the characteristics of pediatric Meckel's diverticulum with a special focus on its complications. Methods: We report a group of seven patients with Meckel's diverticulum and its resection from the Department of Pediatric Surgery between 2012 and 2017. We reviewed all patient records, clinical presentation, and intraoperative findings. The diagnosis was confirmed by surgery and pathology. For a systematic literature review, we used PubMed, Medline and Google Scholar search engines to locate articles containing terms such as Meckel's diverticulum, children, pediatric, complications and symptomatic. We included article reporting on case series in English and German on pediatric patients only. Results: All included patients ( n = 7) were symptomatic. Some patients showed isolated symptoms, and others presented with a combination of symptoms that consisted of abdominal pain, bloody stool or vomiting. The median age of our seven cases was 3.5 years, including 4 male and 3 female patients. Intestinal obstruction was the most common complication; it was seen in 5 out of 7 patients (intussusception in 4 cases, volvulus in 1 case). Ectopic gastric tissue was identified in 3 cases, and inclusion of pancreatic tissue was observed in 1 case. The literature review identified 8 articles for a total of 641 patients aged between 1 day and 17 years and a male:female ratio of 2.6:1. From this group, 528 patients showed clinical symptoms related to Meckel's diverticulum. The most common symptom was abdominal pain and bloody stool. The most common surgical finding in symptomatic patients was intestinal obstruction (41%), followed by intestinal hemorrhage (34%). Complications such as perforation (10%) and diverticulitis (13%) were less frequently reported. Heterotopic tissue was confirmed on histopathology in 53% of all patients enclosing gastric, pancreatic, and both gastric and pancreatic mucosae. In one case, large intestine tissue could be found. Overall, one death was reported. Conclusion: The presented case series and literature review found similar clinical presentations and complications of Meckel's diverticulum in children. Intestinal obstruction and bleeding are more frequent than inflammation in pediatric Meckel's diverticulum. Bowel obstruction is the leading cause for complicated Meckel's diverticulum in patients younger than 12 years.