Agnieszka Banas

Adipose tissue-derived mesenchymal stem cells as a source of human hepatocytes

Recent observations indicate that several stem cells can differentiate into hepatocytes; thus, cell‐based therapy is a potential alternative to liver transplantation. The goal of the present study was to examine the in vitro hepatic differentiation potential of adipose tissue‐derived mesenchymal stem cells (AT‐MSCs). We used AT‐MSCs from different age patients and found that, after incubation with specific growth factors (hepatocyte growth factor [HGF], fibroblast growth factor [FGF1], FGF4) the CD105+ fraction of AT‐MSCs exhibited high hepatic differentiation ability in an adherent monoculture condition. CD105+ AT‐MSC‐derived hepatocyte‐like cells revealed several liver‐specific markers and functions, such as albumin production, low‐density lipoprotein uptake, and ammonia detoxification. More importantly, CD105+ AT‐MSC‐derived hepatocyte‐like cells, after transplantation into mice incorporated into the parenchyma of the liver. Conclusion: Adipose tissue is a source of multipotent stem cells that can be easily isolated, selected, and induced into mature, transplantable hepatocytes. The fact that they are easy to procure ex vivo in large numbers makes them an attractive tool for clinical studies in the context of establishing an alternative therapy for liver dysfunction. (HEPATOLOGY 2007;46:219–228.)

IFATS Collection: In Vivo Therapeutic Potential of Human Adipose Tissue Mesenchymal Stem Cells After Transplantation into Mice with Liver Injury

Mesenchymal stem cells (MSCs), largely present in the adult human body, represent an attractive tool for the establishment of a stem cell‐based therapy for liver diseases. Recently, the therapeutic potential and immunomodulatory activity of MSCs have been revealed. Adipose tissue‐derived mesenchymal stem cells (AT‐MSCs), so‐called adipose‐derived stem cells or adipose stromal cells, because of their high accessibility with minimal invasiveness, are especially attractive in the context of future clinical applications. The goal of the present study was to evaluate the therapeutic potential of AT‐MSCs by their transplantation into nude mice with CCl4‐caused liver injury. We observed that after transplantation, AT‐MSCs can improve liver functions, which we verified by changes in the levels of biochemical parameters. Ammonia, uric acid, glutamic‐pyruvic transaminase, and glutamic‐oxaloacetic transaminase concentrations returned to a nearly normal level after AT‐MSC transplantation. These results raised the question of how AT‐MSCs can achieve this. To discover the possible mechanisms involved in this therapeutic ability of AT‐MSCs, in vitro production of cytokines and growth factors was analyzed and compared with MSCs from bone marrow (BM‐MSCs) and normal human dermal fibroblasts (NHDFs). As a result we observed that AT‐MSCs secrete interleukin 1 receptor α (IL‐1Rα), IL‐6, IL‐8, granulocyte colony‐stimulating factor (G‐CSF), granulocyte‐macrophage colony‐stimulating factor (GM‐CSF), monocyte chemotactic protein 1, nerve growth factor, and hepatocyte growth factor in a volume higher than both BM‐MSCs and NHDFs. Thus, our findings suggest that AT‐MSCs may account for their broad therapeutic efficacy in animal models of liver diseases and in the clinical settings for liver disease treatment.

Rapid hepatic fate specification of adipose‐derived stem cells and their therapeutic potential for liver failure

Background and Aim:u2002 Multipotential mesenchymal stem cells (MSC), present in many organs and tissues, represent an attractive tool for the establishment of a successful stem cell‐based therapy in the field of regeneration medicine. Adipose tissue mesenchymal stem cells (AT‐MSC), known as adipose‐derived stem cells (ASC) are especially attractive in the context of future clinical applications because of their high accessibility and minimal invasiveness during the procedure to obtain them. The goal of the present study was to induce human ASC into functional hepatocytes in vitro within a very short period of time and to check their therapeutic potential in vivo.

Stem cells for hepatic regeneration: the role of adipose tissue derived mesenchymal stem cells.

Severe hepatic dysfunctions including hepatic cirrhosis and hepatocarcinoma are life-threatening conditions for which effective medical treatments are needed. With the only effective treatment to date being orthotropic liver transplantation, alternative approaches are needed because of the limited number of donors and the possibility of immune-rejection. One alternative is regenerative medicine, which holds promise for the development of a cell-based therapy enabling hepatic regeneration through transplantation of adipose tissue-derived mesenchymal stem cells (AT-MSCs) or hepatocyte-like cells generated from AT-MSCs. When compared with embryonic stem (ES) cells and induced pluripotent stem (iPS) cells, the use of AT-MSCs as regenerative cells would be advantageous in regard to ethical and safety issues since AT-MSCs are somatic cells and have the potential to be used without in vitro culture. These autologous cells are immuno-compatible and exhibit controlled differentiation and multi-functional abilities and do not undergo post-transplantation rejection or unwanted differentiation such as formation of teratomas. AT-MSC-based therapies may provide a novel approach for hepatic regeneration and hepatocyte differentiation and thereby support hepatic function in diseased individuals.

A comparative analysis of the transcriptome and signal pathways in hepatic differentiation of human adipose mesenchymal stem cells

The specific features of the plasticity of adult stem cells are largely unknown. Recently, we demonstrated the hepatic differentiation of human adipose tissue‐derived mesenchymal stem cells (AT‐MSCs). To identify the genes responsible for hepatic differentiation, we examined the gene expression profiles of AT‐MSC‐derived hepatocytes (AT‐MSC‐Hepa) using several microarray methods. The resulting sets of differentially expressed genes (1639u2003clones) were comprehensively analyzed to identify the pathways expressed in AT‐MSC‐Hepa. Clustering analysis revealed a striking similarity of gene clusters between AT‐MSC‐Hepa and the whole liver, indicating that AT‐MSC‐Hepa were similar to liver with regard to gene expression. Further analysis showed that enriched categories of genes and signaling pathways such as complementary activation and the blood clotting cascade in the AT‐MSC‐Hepa were relevant to liver‐specific functions. Notably, decreases in Twist and Snail expression indicated that mesenchymal‐to‐epithelial transition occurred in the differentiation of AT‐MSCs into hepatocytes. Our data show a similarity between AT‐MSC‐Hepa and the liver, suggesting that AT‐MSCs are modulated by their environmental conditions, and that AT‐MSC‐Hepa may be useful in basic studies of liver function as well as in the development of stem cell‐based therapy.

Stem cell plasticity: Learning from hepatogenic differentiation strategies

Many studies on stem cell plasticity are challenging the concept that stem cells contain an intrinsically predefined, unidirectional differentiation program. This means that the developmental fate of a stem cell is dependent on the general potential of the cell (pre‐determined stem cell fate) as well as on microenvironmental cues, such as stimuli from growth factors (stem cell niche). Here, we reviewed reports that examined the hepatocyte differentiation ability of stem cells from two different sources: embryonic stem cells and adult stem cells. All of those stem cells revealed the ability to give rise to hepatocyte‐like cells using different induction strategies. However, it is still not clear which of those stem cells would be the best source for hepatocyte replacement or which would be the best protocol. We herein present the current knowledge regarding available protocols and factors used in order to obtain functional hepatocytes from stem cells. Developmental Dynamics 236:3228–3241, 2007.

Commitment of stem cells into functional hepatocytes

Liver transplants represent the only way to treat patients suffering from terminal liver failure, but they are associated with numerous problems, including a chronic shortage of donors, high cost, rejection, and side effects for the donor. It is anticipated that regenerative medicine will provide an alternative to liver transplants for such patients. Regenerative medicine refers to the academic field of eliciting the inherent capacity of organisms for self-regeneration to the greatest possible extent in order to develop new methods of treatment for intractable disorders. From this perspective, much is expected from the use of human embryonic stem cells (ES cells) or induced pluripotent stem cells (iPS cells), and the vigorous development of technology to induce the differentiation of such stem cells into cells possessing hepatic functions is underway. Clinical applications of these human stem cells, however, have yet to reach even the earliest stages of implementation. Facing off against these versatile ES cells are stem cells derived from somatic cells present within organisms, which are attracting attention owing to their superiority in terms of ethics and safety, with many research institutes now in the process of elucidating the details of stem cell separation and identification as well as their plasticity and pluripotency. Bone marrow cells are the best-known somatic-cell-derived stem cells, but the use of mesenchymal stem cells (MSCs) found in adipose tissue has also recently attracted attention. This paper will review the differentiation ability and mechanisms of these various stem cell types to hepatocytes and their application to liver regeneration and the future outlook.

How electromagnetic fields can influence adult stem cells: positive and negative impacts

The electromagnetic field (EMF) has a great impact on our body. It has been successfully used in physiotherapy for the treatment of bone disorders and osteoarthritis, as well as for cartilage regeneration or pain reduction. Recently, EMFs have also been applied in in vitro experiments on cell/stem cell cultures. Stem cells reside in almost all tissues within the human body, where they exhibit various potential. These cells are of great importance because they control homeostasis, regeneration, and healing. Nevertheless, stem cells when become cancer stem cells, may influence the pathological condition. In this article we review the current knowledge on the effects of EMFs on human adult stem cell biology, such as proliferation, the cell cycle, or differentiation. We present the characteristics of the EMFs used in miscellaneous assays. Most research has so far been performed during osteogenic and chondrogenic differentiation of mesenchymal stem cells. It has been demonstrated that the effects of EMF stimulation depend on the intensity and frequency of the EMF and the time of exposure to it. However, other factors may affect these processes, such as growth factors, reactive oxygen species, and so forth. Exploration of this research area may enhance the development of EMF-based technologies used in medical applications and thereby improve stem cell-based therapy and tissue engineering.

Purification of Adipose Tissue Mesenchymal Stem Cells and Differentiation Toward Hepatic-Like Cells

There is a great interest in the development of functional hepatocytes in vitro from different types of stem cells. Multipotential mesenchymal stem cells (MSC) compose a great source for stem cell based therapy, especially, because they can be obtain from patients own tissues, sidestepping immunocompatibility and ethical issues. Among MSCs from different sources, adipose-tissue-derived mesenchymal stem cells (AT-MSCs) are very promising because of their high accessibility, proliferation ability, potentiality, and immunocompatibility.AT-MSCs can be easily isolated from stroma vascular fraction (SVF) of adipose tissue. They represent a heterogeneous population of cells. The precise AT-MSCss marker profile has not been defined yet; therefore, it is still not obvious how to purify these heterogeneous fraction of cells. We postulate that one of the markers defining MSC provenance is CD105 (endoglin).Therefore, we have sorted CD105(+) fraction of AT-MSCs, expanded them, and differentiated toward hepatic-like cells. In order to check their potentiality, we have firstly differentiated sorted CD105(+) AT-MSCs toward mesoderm lineages, using commercialized protocols.We have shown here, that pure CD105(+) AT-MSCs fraction revealed higher homogeneity and differentiation potential toward adipogenic, osteogenic, and chondrogenic lineages and highly inducible into the hepatogenic lineage.Generated (by using our hepatic differentiation protocol) CD105(+) AT-MSCs-derived hepatic-like cells expressed hepatocyte markers, enzymes, and functions.

Regenerative cells for transplantation in hepatic failure.

Human embryonic stem (ES) cells and induced pluripotent stem (iPS) cells have an enormous potential; however, their potential clinical application is being arrested due to various limitations such as teratoma formation followed by tumorigenesis, emergent usage, and the quality control of cells, as well as safety issues regarding long-term culture are also delaying their clinical application. In addition, human ES cells have two crucial issues: immunogenicity and ethical issues associated with their clinical application. The efficient generation of human iPS cells requires gene transfer, yet the mechanism underlying pluripotent stem cell induction has not yet been fully elucidated. Otherwise, although human adult regenerative cells including mesenchymal stem cells have a limited capacity for differentiation, they are nevertheless promising candidates for tissue regeneration in a clinical setting. This review highlights the use of regenerative cells for transplantation in hepatic failure.