Hepatic differentiation of liver-derived progenitor cells and their characterization by microRNA analysis

Chimeric Livers: Interspecies Blastocyst Complementation and Xenotransplantation for End-Stage Liver Disease

Orthotopic liver transplantation (OLT) currently serves as the sole definitive treatment for thousands of patients suffering from end-stage liver disease; and the existing supply of donor livers for OLT is drastically outpaced by the increasing demand. To alleviate this significant gap in treatment, several experimental approaches have been devised with the aim of either offering interim support to patients waiting on the transplant list or bioengineering complete livers for OLT by infusing them with fresh hepatic cells. Recently, interspecies blastocyst complementation has emerged as a promising method for generating complete organs in utero over a short timeframe. When coupled with gene editing technology, it has brought about a potentially revolutionary transformation in regenerative medicine. Blastocyst complementation harbors notable potential for generating complete human livers in large animals, which could be used for xenotransplantation in humans, addressing the scarcity of livers for OLT. Nevertheless, substantial experimental and ethical challenges still need to be overcome to produce human livers in larger domestic animals like pigs. This review compiles the current understanding of interspecies blastocyst complementation and outlines future possibilities for liver xenotransplantation in humans.

Generating liver using blastocyst complementation: Opportunities and challenges

Orthotopic liver transplantation (OLT) is the only definitive treatment option for many patients with end-stage liver disease. Current supply of donor livers for OLT is not keeping up with the growing demand. To overcome this problem, a number of experimental strategies have been developed either to provide a bridge to transplant for patients on the waiting list or to bioengineer whole livers for OLT by replenishing them with fresh supplies of hepatic cells. In recent years, blastocyst complementation has emerged as the most promising approach for generating whole organs and, in combination with gene editing technology, it has revolutionized regenerative medicine. This methodology was successful in producing xenogeneic organs in animal hosts. Blastocyst complementation has the potential to produce whole livers in large animals that could be xenotransplanted in humans, thereby reducing the shortage of livers for OLT. However, significant experimental and ethical barriers remain for the production of human livers in domestic animals, such as the pig. This review summarizes the current knowledge and provides future perspectives for liver xenotransplantation in humans.

Systematic analysis of the regulatory roles of microRNAs in postnatal maturation and metergasis of liver of breeder cocks

The liver function of chickens is intensively remodeled from birth to adult, which was validated by metabolomics research in the present study. In order to understand the roles of microRNAs (miRNA) in liver maturation and metergasis, miRNA expression profiles in livers of 20 male chicks aged one day and five adult cocks aged 35 weeks were determined. A total of 191 differentially expressed miRNAs with the criteria of P < 0.05 and fold changes either >1.5 or <0.67 and 32 differentially expressed miRNAs with the criteria of false discovery value (FDR) < 0.05 and fold changes either >1.5 or <0.67 were detected. Subsequently, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses of the targets revealed that candidate miRNAs may involve in the regulation of hepatic metabolism and immune functions, and some pathways including cell cycle which were implicated in postnatal liver development. Furthermore, 1211 differentially expressed mRNAs (messenger RNA) in livers between the postnatal and matured chickens were used to define the roles of differentially expressed miRNAs in regulating the expression of target genes. Our results revealed the first miRNA profile related to the adaption of mature liver functions after birth in breeder cock.

The combination of miR-122 overexpression and Let-7f silencing induces hepatic differentiation of adipose tissue-derived stem cells

Human adipose tissue-derived stem cells (hADSCs) have been considered as a promising source for cell therapy of liver diseases due to their accessibility, abundance, and expression of hepatocyte markers. Currently, the important role of certain microRNAs (miRNAs) has been reported during hepatic differentiation of stem cells. However, the combination effect of miRNAs on hepatic differentiation of these cells needs to be more investigated. The present study seeks to determine whether the combination of miRNAs can enhance hepatic differentiation of hADSCs in the absence of any other stimulation. First, lentiviral transduction was used to overexpress miR-122 and silence d let-7f in hADSCs for up to 21 days. Then, hepatic functionality was evaluated by analyzing specific hepatocyte genes and biochemical markers at different time points of differentiation induction. Stable miR-122 overexpression and let-7f silencing together in hADSCs resulted in increased expression of hepatocyte markers including ALB, AFP, CK18, CK19, and HNF4a. In addition, urea and albumin production, immunocytochemistry, and glycogen staining confirmed that the treated cells differentiated toward hepatocyte-like cells. Therefore, our findings demonstrate the possibility of using microRNAs to induce hADSCs into functional hepatocyte-like cells.

The role of microRNAs in liver injury at the crossroad between hepatic cell death and regeneration

The liver fulfills critical metabolic functions, such as controlling blood sugar and ammonia levels, and is of central importance for lipid metabolism and detoxification of environmental and chemical agents, including drugs. Liver injuries of different etiology can elicit a spectrum of responses. Some hepatocytes initiate molecular programs resulting in cell death, whereas others undergo cellular divisions to regenerate the damaged organ. Interestingly, recent research indicates that microRNAs serve as very rapid as well as long-term regulators in these processes. In this review, we discuss their importance in liver disease etiology and progression as well as for therapy with particular focus on metabolic and inflammatory conditions. Furthermore, we highlight the central role of microRNAs in controlling hepatocyte differentiation and plasticity, which are required for successful regeneration, but under certain conditions, such as chronic liver insults, can result in the formation of hepatocellular carcinoma.

Efficient generation of functional hepatocyte-like cells from mouse liver progenitor cells via indirect co-culture with immortalized human hepatic stellate cells

BACKGROUND

Differentiation of liver progenitor cells (LPCs) to functional hepatocytes holds great potential to develop new strategies for hepatocyte transplantation and the screening of drug-induced cytotoxicity. However, reports on the efficient and convenient hepatic differentiation of LPCs to hepatocytes are few. The present study aims to investigate the possibility of generating functional hepatocytes from LPCs in an indirect co-culture system.

METHODS

Mouse LPCs were co-cultured in Transwell plates with an immortalized human hepatic stellate cell line (HSC-Li) we previously established. The morphology, expression of hepatic markers, and functions of mouse LPC-derived cells were monitored and compared with those of conventionally cultured LPCs.

RESULTS

Co-culturing with HSC-Li cells induced differentiation of mouse LPCs into functional hepatocyte-like cells. The differentiated cells were morphologically transformed into hepatocyte-like cells 3 days after co-culture initiation. In addition, the differentiated cells expressed liver-specific genes and possessed hepatic functions, including glycogen storage, low-density lipoprotein uptake, albumin secretion, urea synthesis, and cytochrome P450 1A2 enzymatic activity.

CONCLUSIONS

Our method, which employs indirect co-culture with HSC-Li cells, can efficiently induce the differentiation of LPCs into functional hepatocytes. This finding suggests that this co-culture system can be a useful method for the efficient generation of functional hepatocytes from LPCs.

Upregulation of MiR-122 via Trichostatin A Treatments in Hepatocyte-like Cells Derived from Mesenchymal Stem Cells

The miR-122 is a tissue-specific miRNA; its expression is abundant in liver. MiR-122 upregulation is crucial for differentiation, functionality, and maintenance of differentiated phenotype in hepatocytes. The improving effects of trichostatin A (TSA) on hepatic differentiation have been reported previously. The aim of this study was to determine whether TSA can affect the expression of miR-122 in hepatocyte-like cells (HLCs) generated from human adipose tissue-derived mesenchymal stem cells (hAT-MSCs). The hepatic differentiation of hAT-MSCs induced by a mixture of growth factors and cytokines either with or without TSA treatments. The functionality of HLCs generated with or without TSA and the expression levels of miR-122 were studied. The expression levels of miR-122 in TSA-treated HLCs was significantly (p < 0.05) higher than those generated by growth factors and cytokines, only. The downregulation of a-fetoprotein (AFP) levels but enhanced albumin synthesis (p < 0.05) and upregulation of liver-enriched transcription factors (LETFs) HNF4α (hepatocyte nuclear factor 4α) and HNF6 (hepatocyte nuclear factor 6) were observed in TSA-treated HLCs (p < 0.05). In conclusion, administration of TSA in hepatogenic differentiation of hAT-MSCs resulted in higher expression levels of miR-122, facilitation of differentiation, and subsequently attenuation of AFP levels.

Calcium signaling and cell proliferation

Cell proliferation is orchestrated through diverse proteins related to calcium (Ca(2+)) signaling inside the cell. Cellular Ca(2+) influx that occurs first by various mechanisms at the plasma membrane, is then followed by absorption of Ca(2+) ions by mitochondria and endoplasmic reticulum, and, finally, there is a connection of calcium stores to the nucleus. Experimental evidence indicates that the fluctuation of Ca(2+) from the endoplasmic reticulum provides a pivotal and physiological role for cell proliferation. Ca(2+) depletion in the endoplasmatic reticulum triggers Ca(2+) influx across the plasma membrane in an phenomenon called store-operated calcium entries (SOCEs). SOCE is activated through a complex interplay between a Ca(2+) sensor, denominated STIM, localized in the endoplasmic reticulum and a Ca(2+) channel at the cell membrane, denominated Orai. The interplay between STIM and Orai proteins with cell membrane receptors and their role in cell proliferation is discussed in this review.

New Tools in Experimental Cellular Therapy for the Treatment of Liver Diseases

The current standard of care for end stage liver disease is orthotopic liver transplantation (OLT). Through improvement in surgical techniques, immunosuppression, and general medical care, liver transplantation has become an effective treatment over the course of the last half-century. Unfortunately, due to the limited availability of donor organs, there is a finite limit to the number of patients who will benefit from this therapy. This review will discuss current research in experimental cellular therapies for acute, chronic, and metabolic liver failure that may be appropriate when liver transplantation is not an immediate option.

MicroRNA-27a modulates HCV infection in differentiated hepatocyte-like cells from adipose tissue-derived mesenchymal stem cells

Background and Aims

Despite the discovery of hepatitis C virus (HCV) entry factor, the mechanism by which it is regulated by miRNAs remains unclear. Adipose tissue-derived human mesenchymal stem cells (AT-hMSCs) have been widely used for differentiated hepatocyte-like cells (DHCs). Here, we established an in vitro HCV infection model using DHCs from AT-hMSCs and identified miRNAs that modulate HCV infectivity.

Methods

AT-hMSCs were differentiated into DHCs using the conditional media, and evaluated for hepatocyte characteristics using RT-PCR, immunocytochemistry, periodic acid-Schiff staining, and a urea synthesis assay. The expression of HCV candidate receptors was also verified using immunocytochemistry. The levels of candidate miRNAs targeting HCV receptors were then determined by relative quantitative RT-PCR (rqRT-PCR). Finally, DHCs were infected using HCVcc and serum from HCV-infected patients, and infectivity of the virus was measured by rqRT-PCR and transmission electron microscopy (TEM).

Results

The expected changes in morphology, function and hepatic gene expression were observed during hepatic differentiation. Moreover, the expression of candidate HCV entry factors and miR-27a were altered during hepatic differentiation. The infection and replication of HCV occurred efficiently in DHCs treated with HCVcc or infected with serum from HCV-infected patients. In addition, HCV infectivity was suppressed in miR-27a-transfected DHCs, due to the inhibition of LDLR expression by miR-27a.

Conclusions

Our results demonstrate that AT-hMSCs are a good source of DHCs, which are suitable for in vitro cultivation of HCV. Furthermore, these results suggest that miR-27a modulates HCV infectivity by regulating LDLR expression.

Regulation of microRNAs and their role in liver development, regeneration and disease

Since their discovery more than a decade ago microRNAs have been demonstrated to have profound effects on almost every aspect of biology. Numerous studies in recent years have shown that microRNAs have important roles in development and in the etiology and progression of disease. This review is focused on microRNAs and the roles they play in liver development, regeneration and liver disease; particularly chronic liver diseases such as alcoholic liver disease, non-alcoholic fatty liver disease, non-alcoholic steatohepatitis, viral hepatitis and primary liver cancer. The key microRNAs identified in liver development and chronic liver disease will be discussed together with, where possible, the target messenger RNAs that these microRNAs regulate to profoundly alter these processes. This article is part of a Directed Issue entitled: The Non-coding RNA Revolution.

Role of stem cells in repair of liver injury: Experimental and clinical benefit of transferred stem cells on liver failure

Although the liver has a high regenerative capacity, as a result of massive hepatocyte death, liver failure occurs. In addition to liver failure, for acute, chronic and hereditary diseases of the liver, cell transplantation therapies can stimulate regeneration or at least ensure sufficient function until liver transplantation can be performed. The lack of donor organs and the risks of rejection have prompted extensive experimental and clinical research in the field of cellular transplantation. Transplantation of cell lineages involved in liver regeneration, including mature hepatocytes, fetal hepatocytes, fetal liver progenitor cells, fetal stem cells, hepatic progenitor cells, hepatic stem cells, mesenchymal stem cells, hematopoietic stem cells, and peripheral blood and umbilical cord blood stem cells, have been found to be beneficial in the treatment of liver failure. In this article, the results of experimental and clinical cell transplantation trials for liver failure are reviewed, with an emphasis on regeneration.

Dynamic microRNA profiles of hepatic differentiated human umbilical cord lining-derived mesenchymal stem cells

Despite the extensive hepatic differentiation potential of human umbilical cord lining-derived mesenchymal stem cells (hUC-MSC), little is known about the molecular mechanisms of hUC-MSC differentiation. At the post-transcriptional level, microRNAs are key players in the control of cell fate determination during differentiation. In this study, we aimed to identify microRNAs involved in the hepatic differentiation of hUC-MSCs. After successfully isolating hUC- MSCs, we induced hepatocyte formation in vitro with growth factors. After 26 days of induction, hUC-MSCs could express hepatocyte-specific genes, synthesize urea and glycogen and uptake low-density lipoprotein. Cellular total RNA from hUC-MSCs and hepatic differentiated hUC-MSCs was collected at 7 time points, including 2 days, 6 days, 10 days, 14 days, 22 days and 26 days, for microRNA microarray analysis. Dynamic microRNA profiles were identified that did not overlap or only partially overlapped with microRNAs reported to be involved in human liver development, hepatocyte regeneration or hepatic differentiation of liver-derived progenitor cells. A total of 61 microRNAs among 1205 human and 144 human viral microRNAs displayed consistent changes and were altered at least 2-fold between hUC-MSCs and hepatic differentiated hUC-MSCs. Among these microRNAs, 25 were over-expressed; this over-expression occurred either gradually or increased sharply and was maintained at a high level. A total of 36 microRNAs were under-expressed, with an expression pattern similar to that of the over-expressed microRNAs. The expression of the altered expressed microRNAs was also confirmed by quantitative reverse-transcription polymerase chain reaction. We also found that microRNAs involved in hepatic differentiation were not enriched in hepatocyte or hepatocellular carcinoma cells and can potentially target liver-enriched transcription factors and genes. The elucidation of the microRNA profile during the hepatic differentiation of hUC-MSCs provides the basis for clarifying the role of microRNAs in hUC-MSC hepatic differentiation and specific microRNA selection for the conversion of hUC-MSCs to hepatocytes.

Mature hepatocytes exhibit unexpected plasticity by direct dedifferentiation into liver progenitor cells in culture

Although there have been numerous reports describing the isolation of liver progenitor cells from the adult liver, their exact origin has not been clearly defined; and the role played by mature hepatocytes as direct contributors to the hepatic progenitor cell pool has remained largely unknown. Here, we report strong evidence that mature hepatocytes in culture have the capacity to dedifferentiate into a population of adult liver progenitors without genetic or epigenetic manipulations. By using highly purified mature hepatocytes, which were obtained from untreated, healthy rat liver and labeled with fluorescent dye PKH2, we found that hepatocytes in culture gave rise to a population of PKH2-positive liver progenitor cells. These cells, liver-derived progenitor cells, which share phenotypic similarities with oval cells, were previously reported to be capable of forming mature hepatocytes, both in culture and in animals. Studies done at various time points during the course of dedifferentiation cultures revealed that hepatocytes rapidly transformed into liver progenitors within 1 week through a transient oval cell-like stage. This finding was supported by lineage-tracing studies involving double-transgenic AlbuminCreXRosa26 mice expressing β-galactosidase exclusively in hepatocytes. Cultures set up with hepatocytes obtained from these mice resulted in the generation of β-galactosidase-positive liver progenitor cells, demonstrating that they were a direct dedifferentiation product of mature hepatocytes. Additionally, these progenitors differentiated into hepatocytes in vivo when transplanted into rats that had undergone retrorsine pretreatment and partial hepatectomy.

CONCLUSION

Our studies provide strong evidence for the unexpected plasticity of mature hepatocytes to dedifferentiate into progenitor cells in culture, and this may potentially have a significant effect on the treatment of liver diseases requiring liver or hepatocyte transplantation.

High-purity hepatic lineage differentiated from dental pulp stem cells in serum-free medium

INTRODUCTION

We have previously differentiated hepatocyte like cells from deciduous tooth pulp stem and extracted third molar pulp stem cells with a protocol that used fetal bovine serum, but it showed high contaminations of nondifferentiated cells. Both the lower purity of hepatically differentiated cells and usage of serum are obstacles for application of cell therapy or regenerative medicine. Objective of this study was to investigate the capacity for and purity of hepatocyte-like differentiation of CD117-positive dental pulp stem cells without serum.

METHODS

Mesenchymal cells from human deciduous and extracted third molar pulp were isolated and expanded in vitro. We separated CD117-positive cells by using a magnetic-activated cell sorter. The cells were characterized immunofluorescently by using known stem cell markers. For hepatic differentiation, the media were supplemented with hepatic growth factor, insulin-transferrin-selenium-x, dexamethasone, and oncostatin M. Expression of hepatic markers alpha fetoprotein, albumin, hepatic nuclear factor-4 alpha, insulin-like growth factor-1, and carbamoyl phosphate synthetase was examined immunofluorescently after differentiation. The amount of differentiated cells was assessed by using flow cytometry. Glycogen storage and urea concentration in the medium were defined.

RESULTS

Both cell cultures demonstrated a number of cells positive for all tested hepatic markers after differentiation, ie, albumin-positive cells were almost 90% of differentiated deciduous pulp cells. The concentration of urea in the media increased significantly after differentiation. Significant amount of cytoplasmic glycogen storage was found in the cells.

CONCLUSIONS

Without serum both cell types differentiated into high-purity hepatocyte-like cells. These cells offer a source for hepatocyte lineage differentiation for transplantation in the future.

Improving the techniques for human hepatocyte transplantation: report from a consensus meeting in London

On September 6 and 7, 2009 a meeting was held in London to identify and discuss what are perceived to be current roadblocks to effective hepatocyte transplantation as it is currently practiced in the clinics and, where possible, to offer suggestions to overcome the blocks and improve the outcomes for this cellular therapy. Present were representatives of most of the active clinical hepatocyte transplant programs along with other scientists who have contributed substantial basic research to this field. Over the 2-day sessions based on the experience of the participants, numerous roadblocks or challenges were identified, including the source of cells for the transplants and problems with tracking cells following transplantation. Much of the discussion was focused on methods to improve engraftment and proliferation of donor cells posttransplantation. The group concluded that, for now, parenchymal hepatocytes isolated from donor livers remain the best cell source for transplantation. It was reported that investigations with other cell sources, including stem cells, were at the preclinical and early clinical stages. Numerous methods to modulate the immune reaction and vascular changes that accompany hepatocyte transplantation were proposed. It was agreed that, to obtain sufficient levels of repopulation of liver with donor cells in patients with metabolic liver disease, some form of liver preconditioning would likely be required to enhance the engraftment and/or proliferation of donor cells. It was reported that clinical protocols for preconditioning by hepatic irradiation, portal vein embolization, and surgical resection had been developed and that clinical studies using these protocols would be initiated in the near future. Participants concluded that sharing information between the groups, including standard information concerning the quality and function of the transplanted cells prior to transplantation, clinical information on outcomes, and standard preconditioning protocols, would help move the field forward and was encouraged.

Steatotic liver: a suitable source for the isolation of hepatic progenitor cells

BACKGROUND

Alternative and/or complementary sources of cells such as hepatic progenitor cells (HPC) are under investigation for hepatic cell therapy purposes. Steatotic livers are those most commonly rejected for clinical transplantation and are also unsuitable for good quality hepatocyte isolation.

AIM

Taken together these two facts, our aim was to investigate whether they could represent a suitable source for the isolation of progenitor cells.

METHODS

Rats fed for 7 weeks with methionine-choline deficient diets showing proved steatotic signs (i.e. increase in hepatic lipids; macrovesicular steatosis) and steatotic and normal human liver samples were used to study the expression of HPC markers and to isolate these cells.

RESULTS

In the liver of the steatotic rats there was a significant increase in HPC (known as oval cells in rodents) markers such as Thy-1, epithelial cell adhesion molecule (EpCAM) and OV-6 (2-, 3- and 5-fold increase respectively). Additionally, there was an increase in the yield of isolated oval cells compared to control rats. Similarly, studies using human livers clearly confirmed an increase in the expression of HPC markers in the steatotic tissue and a significant rise in the number of isolated progenitor cells (EpCAM+, Thy-1+, OV-6+) (10, 12 and 11.6 × 10(4)  cells/g of tissue respectively).

CONCLUSIONS

These data suggest that steatotic livers, discarded for orthotopic liver transplantation and hepatocyte isolation, could be a suitable source for large scale isolation of HPC which might be potential candidates in liver cell therapy.