Putative human liver progenitor cells in explanted liver

Isolation, characterization and cold storage of cells isolated from diseased explanted livers

INTRODUCTION

Livers discarded after standard organ retrieval are commonly used as a cell source for hepatocyte transplantation. Due to the scarcity of organ donors, this leads to a shortage of suitable cells for transplantation. Here, the isolation of liver cells from diseased livers removed during liver transplantation is studied and compared to the isolation of cells from liver specimens obtained during partial liver resection.

METHODS

Hepatocytes from 20 diseased explanted livers (Ex-group) were isolated, cultured and stored at 4°C for up to 48 hours, and compared to hepatocytes isolated from the normal liver tissue of 14 liver lobe resections (Rx-group). The nonparenchymal cell fraction (NPC) was analyzed by flow cytometry to identify potential liver progenitor cells, and OptiPrep™ (Sigma-Aldrich) density gradient centrifugation was used to enrich the progenitor cells for immediate transplantation.

RESULTS

There were no differences in viability, cell integrity and metabolic activity in cell culture and survival after cold storage when comparing the hepatocytes from the Rx-group and the Ex-group. In some cases, the latter group showed tendencies of increased resistance to isolation and storage procedures. The NPC of the Ex-group livers contained considerably more EpCAM+ and significantly more CD90+ cells than the Rx-group. Progenitor cell enrichment was not sufficient for clinical application.

CONCLUSIONS

Hepatocytes isolated from diseased explanted livers showed the essential characteristics of being adequate for cell transplantation. Increased numbers of liver progenitor cells can be isolated from diseased explanted livers. These results support the feasibility of using diseased explanted livers as a cell source for liver cell transplantation.

Fibroblast growth factor receptor-mediated activation of AKT-β-catenin-CBP pathway regulates survival and proliferation of murine hepatoblasts and hepatic tumor initiating stem cells

Fibroblast Growth Factor (FGF)-10 promotes the proliferation and survival of murine hepatoblasts during early stages of hepatogenesis through a Wnt-β-catenin dependent pathway. To determine the mechanism by which this occurs, we expanded primary culture of hepatoblasts enriched for progenitor markers CD133 and CD49f from embryonic day (E) 12.5 fetal liver and an established tumor initiating stem cell line from Mat1a(-/-) livers in media conditioned with recombinant (r) FGF10 or rFGF7. FGF Receptor (R) activation resulted in the downstream activation of MAPK, PI3K-AKT, and β-catenin pathways, as well as cellular proliferation. Additionally, increased levels of nuclear β-catenin phosphorylated at Serine-552 in cultured primary hepatoblasts, Mat1a(-/-) cells, and also in ex vivo embryonic liver explants indicate AKT-dependent activation of β-catenin downstream of FGFR activation; conversely, the addition of AKT inhibitor Ly294002 completely abrogated β-catenin activation. FGFR activation-induced cell proliferation and survival were also inhibited by the compound ICG-001, a small molecule inhibitor of β-catenin-CREB Binding Protein (CBP) in hepatoblasts, further indicating a CBP-dependent regulatory mechanism of β-catenin activity.

CONCLUSION

FGF signaling regulates the proliferation and survival of embryonic and transformed progenitor cells in part through AKT-mediated activation of β-catenin and downstream interaction with the transcriptional co-activator CBP.

Acute hepatic failure-derived bone marrow mesenchymal stem cells express hepatic progenitor cell genes

Hepatic progenitor cell (HPC) transplantation is a promising alternative to liver transplantation for patients with end-stage liver disease. However, the precise origin of HPCs is unclear. This study aimed to determine whether bone marrow mesenchymal stem cells (BMSCs) isolated from rats in acute hepatic failure (AHF) possess hepatic potential and/or characteristics. BMSCs were isolated from normal rats as well as rats in which AHF was induced by D-galactosamine. HPCs and primary hepatocytes were isolated from normal rats for comparison. The Affymetrix GeneChip Rat Genome 230 2.0 Array was used to perform transcriptome profiling of the AHF-derived BMSCs and HPCs. The results showed that AHF-derived BMSCs had a gene expression profile significantly different from that of control BMSCs. More than 87.7% of the genes/probe sets that were upregulated more than 2-fold in AHF-derived BMSCs were expressed by HPCs, including 12 genes involved in liver development, early hepatocyte differentiation and hepatocyte metabolism. Confirmatory quantitative RT-PCR analysis yielded similar results. In addition, 940 probe sets/genes were expressed in both AHF-derived BMSCs and HPCs but were absent in control cells. Compared to the control cells, AHF-derived BMSCs shared more commonly expressed genes with HPCs. AHF-derived BMSCs have a hepatic transcriptional profile and express many of the same genes expressed by HPCs, strongly suggesting that BMSCs may be a resource for hepatocyte regeneration, and further confirming their potential as a strong source of hepatocyte regeneration during severe hepatic damage.

Mobilization of hematopoietic progenitor cells in patients with liver cirrhosis

AIM

To test the hypothesis that liver cirrhosis is associated with mobilization of hematopoietic progenitor cells.

METHODS

Peripheral blood samples from 72 patients with liver cirrhosis of varying etiology were analyzed by flow cytometry. Identified progenitor cell subsets were immunoselected and used for functional assays in vitro. Plasma levels of stromal cell-derived factor-1 (SDF-1) were measured using an enzyme linked immunosorbent assay.

RESULTS

Progenitor cells with a CD133(+)/CD45(+)/CD14(+) phenotype were observed in 61% of the patients. Between 1% and 26% of the peripheral blood mononuclear cells (MNCs) displayed this phenotype. Furthermore, a distinct population of c-kit(+) progenitor cells (between 1% and 38% of the MNCs) could be detected in 91% of the patients. Additionally, 18% of the patients showed a population of progenitor cells (between 1% and 68% of the MNCs) that was characterized by expression of breast cancer resistance protein-1. Further phenotypic analysis disclosed that the circulating precursors expressed CXC chemokine receptor 4, the receptor for SDF-1. In line with this finding, elevated plasma levels of SDF-1 were present in all patients and were found to correlate with the number of mobilized CD133(+) progenitor cells.

CONCLUSION

These data indicate that in humans, liver cirrhosis leads to recruitment of various populations of hematopoietic progenitor cells that display markers of intrahepatic progenitor cells.

Mobilization of hematopoietic progenitor cells in patients with liver cirrhosis

AIM: To test the hypothesis that liver cirrhosis is associated with mobilization of hematopoietic progenitor cells.

METHODS: Peripheral blood samples from 72 patients with liver cirrhosis of varying etiology were analyzed by flow cytometry. Identified progenitor cell subsets were immunoselected and used for functional assays in vitro. Plasma levels of stromal cell-derived factor-1 (SDF-1) were measured using an enzyme linked immunosorbent assay.

RESULTS: Progenitor cells with a CD133⁺/CD45⁺/CD14⁺ phenotype were observed in 61% of the patients. Between 1% and 26% of the peripheral blood mononuclear cells (MNCs) displayed this phenotype. Furthermore, a distinct population of c-kit⁺ progenitor cells (between 1% and 38 % of the MNCs) could be detected in 91% of the patients. Additionally, 18% of the patients showed a population of progenitor cells (between 1% and 68% of the MNCs) that was characterized by expression of breast cancer resistance protein-1. Further phenotypic analysis disclosed that the circulating precursors expressed CXC chemokine receptor 4, the receptor for SDF-1. In line with this finding, elevated plasma levels of SDF-1 were present in all patients and were found to correlate with the number of mobilized CD133⁺ progenitor cells.

CONCLUSION: These data indicate that in humans, liver cirrhosis leads to recruitment of various populations of hematopoietic progenitor cells that display markers of intrahepatic progenitor cells.

Isolation and culture of adult human liver progenitor cells: in vitro differentiation to hepatocyte-like cells

Highly differentiated normal human hepatocytes represent the gold standard cellular model for basic and applied research in liver physiopathology, pharmacology, toxicology, virology, and liver biotherapy. Nowadays, although livers from organ donors or medically required resections represent the current sources of hepatocytes, the possibility to generate hepatocytes from the differentiation of adult and embryonic stem cells represents a promising opportunity. The aim of this chapter is to describe our experience with the isolation from adult human liver and culture of non-parenchymal epithelial cells. Under appropriate conditions, these cells differentiate in vitro in hepatocyte-like cells and therefore appear to behave as liver progenitor cells.

Isolation of stem/progenitor cells from normal lung tissue of adult humans

OBJECTIVES

This study aimed to isolate and characterize stem/progenitor cells, starting from normal airway epithelia, obtained from human adults.

MATERIALS AND METHODS

Cultures of multicellular spheroids were obtained from human lung tissue specimens after mechanical and enzymatic digestion. Tissue-specific markers were detected on their cells by immunohistochemical and immunofluorescent techniques. Ultrastructural morphology of the spheroids (termed as bronchospheres) was evaluated by electron microscopy, gene expression analysis was performed by reverse transcription-polymerase chain reaction, and gene down-regulation was analysed by an RNA interference technique.

RESULTS

Bronchospheres were found to be composed of cells with high expression of stem cell regulatory genes, which was not or was only weakly detectable in original tissues. Morphological analysis showed that bronchospheres were composed of mixed phenotype cells with type II alveolar and Clara cell features, highlighting their airway resident cell origin. In addition to displaying specific pulmonary and epithelial commitment, bronchospheres showed mesenchymal features. Silencing of the Slug gene, known to play a pivotal role in epithelial-mesenchymal transition processes and which was highly expressed in bronchospheres but not in original tissue, led bronchospheres to gain a differentiated bronchial/alveolar phenotype and to lose the stemness gene expression pattern.

CONCLUSIONS

Ours is the first study to describe ex vivo expansion of stem/progenitor cells resident in human lung epithelia, and our results suggest that the epithelial-mesenchymal transition process, still active in a subset of airway cells, may regulate transit of stem/progenitor cells towards epithelial differentiation.

c-Kit expression in human normal and malignant stem cells prognostic and therapeutic implications

The human stem cell factor/c-Kit signaling pathway is pivotal for the survival of embryonic, foetal and adult stem cells and for their fundamental role in generating healthy functioning cell and tissue types during embryonic, foetal and adult life. Common biological features between human stem cells and cancer cells include (A) self-renewal, (B) extensive capacity of proliferation, (C) migration to and homing at distant sites and (D) resistance to toxic agents. Given these shared attributes, cancer was proposed to originate from transforming mutation(s) in normal stem cells that dysregulate their physiological programs. This theory has been recently supported by the findings that among all malignant cells within a particular tumour, only cell fraction expressing stem cell markers such as c-Kit named 'cancer stem cells' has the exclusive potential to generate tumour cell population. The involvement of c-Kit and its mutation in various haematological malignancies and solid tumours are reviewed. The impacts of dysregulated c-Kit as oncogenic tyrosine kinase on autocrine stimulation and resistance to chemotherapy of cancer stem cells are evaluated. The significance and efficacy of molecular therapeutic targeting of c-Kit signaling pathway in the management of patients with c-Kit-positive malignancies are appraised.

Endometrial regenerative cells: a novel stem cell population

Angiogenesis is a critical component of the proliferative endometrial phase of the menstrual cycle. Thus, we hypothesized that a stem cell-like population exist and can be isolated from menstrual blood. Mononuclear cells collected from the menstrual blood contained a subpopulation of adherent cells which could be maintained in tissue culture for >68 doublings and retained expression of the markers CD9, CD29, CD41a, CD44, CD59, CD73, CD90 and CD105, without karyotypic abnormalities. Proliferative rate of the cells was significantly higher than control umbilical cord derived mesenchymal stem cells, with doubling occurring every 19.4 hours. These cells, which we termed "Endometrial Regenerative Cells" (ERC) were capable of differentiating into 9 lineages: cardiomyocytic, respiratory epithelial, neurocytic, myocytic, endothelial, pancreatic, hepatic, adipocytic, and osteogenic. Additionally, ERC produced MMP3, MMP10, GM-CSF, angiopoietin-2 and PDGF-BB at 10-100,000 fold higher levels than two control cord blood derived mesenchymal stem cell lines. Given the ease of extraction and pluripotency of this cell population, we propose ERC as a novel alternative to current stem cells sources.