Adipose tissue-derived mesenchymal stem cells and hepatic differentiation: old concepts and future perspectives.

Mesenchymal stem cells (MSCs) are multipotent cells, able to differentiate into elements of the mesodermal lineage. Bone marrow and adipose tissue represent the main sources for MSC isolation. In the last decade, several studies have reported the plasticity of MSCs toward a hepatocyte-like phenotype. The use of MSCs to generate hepatocyte-like cells holds great promises to overcome the scarcity of available organs for transplantation. However, little is known about the molecular pathways involved in lineage cross-differentiation and several issues remain to be answered before MSC application in clinical settings. Aim of this review is to critically analyze the possible sources of MSCs suitable for liver repopulation and the molecular mechanisms underlying MSC hepatic differentiation.

Post-translational modulation of CD133 expression during sodium butyrate-induced differentiation of HT29 human colon cancer cells: implications for its detection.

The CD133 molecule has been proposed as a surface marker of cancer stem cells in several human malignancies, including colon cancers. The function and the mechanisms regulating CD133 expression remain unknown. The HT29 human colon cancer cells undergo differentiation following treatment with various agents and represent a useful in vitro model of colon differentiation. This study evaluated the behavior of CD133 during sodium butyrate-induced differentiation of HT29 cells. Treatment with sodium butyrate induced a progressive decrease of CD133 expression, as assessed by flow cytometry using the AC133 monoclonal antibody. Indeed, expression of CD133, which was about 47% in untreated control cells, gradually decreased down to about 3% after 72 h in a time- and dose-dependent manner. No relationship was observed between CD133 protein evaluated by flow cytometry and mRNA expression level, and no changes were detected in the methylation status of the CD133 gene promoter during HT29 differentiation. Moreover, the expression of the CD133 protein, evaluated by Western blot analysis using a specific anti-CD133 antibody directed against the C-terminal intracytoplasmic region of human CD133 protein, did not correlate with flow cytometry results. Different results were also obtained using the two antibodies to analyze the expression of the CD133 molecule in human colon cancers. These findings demonstrate that membrane expression of the CD133 stem cell marker might undergo a complex regulation during differentiation of colon cells and suggest that HT29 cells are a useful in vitro model to study the mechanisms involved in this regulation which likely occurs at a post-transcriptional level.

Isolation and characterization of CD133+ cell population within human primary and metastatic colon cancer.

BACKGROUND: "Cancer stem cells" (CSC) have been identified as a minority of cancer cells responsible for tumor initiation, maintenance and spreading. Although a universal marker for CSC has not yet been identified, CD133 has been proposed as the hallmark of CSC in colon cancer. The aim of our study was to assess the presence of a CD133+ cell fraction in samples of colon cancer and liver metastasis from colon cancer and evaluate their potential as tumor-initiating cells. METHODS: Tissue samples from 17 colon cancers and 8 liver metastasis were fragmented and digested using collagenase. Cell suspensions were characterized by flow cytometry using anti-CD133, CD45 and CD31 antibodies. CD133+ cells were also isolated by magnetic cell sorting and their tumor-initiating potential was assessed versus the remaining CD133- fraction by soft-agar assay. RESULTS: Our results confirmed the existence of a subset of CD133+ tumor cells within human colon cancers. Interestingly, CD133+ cells were detectable in liver metastasis at a higher percentage when compared to primary tumors. Soft-agar assay showed that CD133+ cell fraction was able to induce larger and more numerous colonies than CD133-cells. CONCLUSION: Our findings data that the CD133+ colon cancer cells might play an important role in both primary tumors as well as in metastatic lesions thus warranting further studies on the role(s) of this subset of cells in the metastatic process.

Mesenchymal stromal cells multipotency and plasticity: induction toward the hepatic lineage.

BACKGROUND: Human mesenchymal stromal cells (MSCs) can be isolated from a variety of adult and perinatal tissues and exert multipotency and self renewal properties which make them suitable for cell-based therapy. Their potential plasticity extended to non-mesodermal-derived tissues has been indicated, although it is still a debated issue. In this study we have isolated MSCs from both adult and fetal tissues. Their growth, immunophenotype and multi-lineage differentiation potentials have been analyzed, focusing, in particular, on the hepatic differentiation. METHODS: Cells were isolated from bone marrow (BMSC), adipose tissue (ATSC) and second trimester amniotic fluid (AFSC), upon a written informed consent obtained from donor patients. Cells were expanded and growth kinetics was assessed by means of proliferation assay. Their immunophenotype was analyzed using cytometry and multi-lineage differentiation potential was evaluated by means of in vitro differentiation assays. Finally, the expression of tissue-specific markers was also assessed by mean of semi-quantitative PCR. RESULTS: Bipolar spindle-shaped cells were successfully isolated from all these tissues. Interestingly, ATSCs and AFSCs showed a higher proliferation potential than BMSCs. Mesodermal differentiation capacity was verified in all MSC populations, even if AFSCs were not able to undergo adipogenesis in our culture conditions. Furthermore, we showed that MSC cultured in appropriate conditions were able to induce hepatic-associated genes, such as ALB and TDO2. CONCLUSION: Taken together the data here reported suggest that MSCs from both adult and fetal tissues are capable of tissue-specific commitment along mesodermal and non-mesodermal lineages. In particular we have demonstrated that a specific hepatogenic commitment can be efficiently induced, proposing these cells as suitable tool for cell-based applications aimed at liver regeneration.

Identification and characterization of a novel expandable adult stem/progenitor cell population in the human exocrine pancreas.

It is a general opinion that tissue-specific stem cells are present in adult tissues but their specific properties remain elusive. They are rare in tissues and heterogeneous; in addition, their identification and the characterization of their progeny has encountered technical difficulties. In particular, the existence of pancreatic stem cells remains elusive because specific markers for their identification are not available. We established a method for the isolation of a population of stem/progenitor cells from the human exocrine pancreas, and propose it as a model for other human compact organs. We also used markers that identified and finally characterized these cells. Spheroids with self-replicative potential were obtained from all specimens. The isolated population contained a subset of CD34+ CD45- cells and was able to generate, in appropriate conditions, colonies that produce insulin. We obtained evidence that most freshly isolated spheroids, when co-cultured with the c-kit positive neuroblastoma cell line LAN 5, produced a c-kit positive progeny of cells larger in their cytoplasmic content than the original spheroid population, with elongated morphology resembling the neuronal phenotype. We identified a novel predominant functional type of stem/progenitor cell within the human exocrine pancreas, able to generate insulin-producing cells and potentially non-pancreatic cells.