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

Combinatorial Therapeutic Potential of Stem Cells and Benzimidazol Derivatives for the Reduction of Liver Fibrosis

(1) Background: Liver fibrosis is currently one of the top ten causes of death worldwide. Stem cells transplantation using mesenchymal stem cells (MSCs) is an alternative therapy which is used in the place of organ transplant, due to the incapacity of stem cells to endure oxidative stress in the damage site, thus affecting the healing process. The present study aimed to enhance the therapeutic potential of MSCs using combined therapy, along with the novel synthetic compounds of benzimidazol derivatives. (2) Methods: Eighteen compound series (benzimidazol derivatives) were screened against liver fibrosis using an in vitro CCl4-induced injury model on cultured hepatocytes. IC50 values were calculated on the bases of LDH assay and cell viability assay. (3) Results: Among the eighteen compounds, compounds (10), (14) and (18) were selected on the basis of IC50 value, and compound (10) was the most potent and had the lowest IC50 value in the LDH assay (8.399 ± 0.23 uM) and cell viability assay (4.73 ± 0.37 uM). Next, these compounds were combined with MSCs using an in vitro hepatocytes injury culture and in vivo rat fibrotic model. The effect of the MSCs + compounds treatment on injured hepatocytes was evaluated using LDH assay, cell viability assay, GSH assay and real-time PCR analysis and immuno-staining for caspase-3. Significant reductions in LDH level, caspase-3 and apoptotic marker genes were noted in MSCs + compounds-treated injured hepatocytes. In vivo data also showed the increased homing of the MSCs, along with compounds after transplantation. Real-time PCR analysis and TUNEL assay results also support our study. (4) Conclusions: It was concluded that compounds (10), (14) and (18) can be used in combination with MSCs to reduce liver fibrosis.

Role of Nrf2 signaling in development of hepatocyte-like cells

Generation of hepatocytes from human adipose-derived mesenchymal stem cells (hADSCs) could be a promising alternative source of human hepatocytes. However, mechanisms to differentiate hepatocytes from hADSCs are not fully elucidated. We have previously demonstrated that our three-step differentiation protocol with glycogen synthase kinase (GSK) 3 inhibitor was effective to improve hepatocyte functions. In this study, we investigated the activation of the nuclear factor erythroid-2 related factor 2 (Nrf2) on hADSCs undergoing differentiation to HLC (hepatocyte-like cells). Our three-step differentiation protocol was applied for 21 days (Step 1:day 1-6, Step2:day 6-11, Step3:day 11-21). Our results show that significant nuclear translocation of Nrf2 occurred from day 11 until the end of HLC differentiation. Nuclear translocation of Nrf2 and CYP3A4 activity in the GSK3 inhibitor-treated group was obviously higher than that in Activin A-treated groups at day 11. The maturation of HLCs was delayed in Nrf2-siRNA group compared to control group. Furthermore, CYP3A4 activity in Nrf2-siRNA group was decreased at the almost same level in Activin A-treated group. Nrf2 translocation might enhance the function of HLC and be a target for developing highly functional HLC. J. Med. Invest. 70 : 343-349, August, 2023.

Lineage reprogramming of human adipose mesenchymal stem cells to immune modulatory i-Heps

Pluripotent stem cell derived-hepatocytes depict fetal -hepatocyte characteristics/maturity and are immunogenic limiting their applications. Attempts have been made to derive hepatocytes from mesenchymal stem cells using developmental cocktails, epigenetic modulators and small molecules. However, achieving a stable terminally differentiated functional state had been a challenge. Inefficient hepatic differentiation could be due to lineage restrictions set during development. Hence a novel lineage reprogramming approach has been utilized to confer competence to adipose-mesenchymal stem cells (ADMSCs) to efficiently respond to hepatogenic cues and achieve a stable functional hepatic state. Lineage reprogramming involved co-transduction of ADMSCs with hepatic endoderm pioneer Transcription factor (TF)-FOXA2, HHEX-a homeobox gene and HNF4α-master TF indispensable for hepatic state maintenance. Lineage priming was evidenced by endogenous HFN4α promoter demethylation and robust responsiveness to minimal hepatic maturation cues. Induced hepatocytes (i-Heps) exhibited mesenchymal-to-epithelial transition and terminal hepatic signatures. Functional characterisation of i-Heps for hepatic drug detoxification systems, xenobiotic uptake/clearance, metabolic status and hepatotropic virus entry validated acquisition of stable hepatic state and junctional maturity Exhaustive analysis of MSC memory in i-Heps indicated loss of MSC-immunophenotype and terminal differentiation to osteogenic/adipogenic lineages. Importantly, i-Heps suppressed phytohemagglutinin-induced T-cell blasts, inhibited allogenic mixed-lymphocyte reactions (MLRs) and secreted immunomodulatory- indoleamine 2,3-dioxygenase in T-cell blast co-cultures akin to native ADMSCs. In a nutshell, the present study identifies a novel cocktail of TFs that reprogram ADMSCs to stable hepatic state. i-Heps exhibit adult hepatocyte functional maturity with robust immune-modulatory abilities rendering suitability for rigorous drug testing, hepatocyte-pathogen interaction studies and transplantation in allogenic settings.

Clinical application of collagen membrane with umbilical cord-derived mesenchymal stem cells to repair nasal septal perforation

Objective. We aimed to investigate the clinical efficacy of collagen membrane with umbilical cord-derived mesenchymal stem cells in the endoscopic repair of nasal septal perforation.Methods.We performed a prospective clinical trial between March 2017 and October 2019. Nasal septal perforations were repaired by the endoscopic sandwich technique with the collagen membrane and umbilical cord-derived mesenchymal stem cells. These patients were followed up postoperatively. Their outcomes were comprehensively evaluated by assessing the healing process of the perforations, the visual analog scale (VAS) for nasal discomfort, and the nasal mucociliary transit time (MTT) for the regenerated nasal mucosa.Results. Our study included a total of eight patients with nasal septal perforation (six males and two females, age 36.6 ± 12.8 years, diameter of perforation 1.0 ± 0.2 cm). Seven patients successfully underwent surgical repair. These patients had significantly improved VAS scores 1 month after the operations (1.1 ± 0.4) compared with the preoperative period (5.9 ± 0.7) (P< 0.05). Although the nasal MTT in the nasal septum and the inferior turbinate surface were within the normal limits before the operation and at 1 month after the operation, the postoperative transit time (11.1 ± 2.0 m) was significantly shorter than the preoperative transit time (12.1 ± 2.4 m) (P< 0.05). There were no recurrences of perforation, scab formations, or epistaxis after the operation.Conclusions. The application of the collagen membrane with umbilical cord-derived mesenchymal stem cells is a simple and feasible endoscopic procedure to repair perforated nasal septa and restore satisfactory functional mucosa.

Coagulant activity of recombinant human factor VII produced by lentiviral human F7 gene transfer in immortalized hepatocyte-like cell line

Human mesenchymal stem cells (hMSCs) have the potential to differentiate into hepatocyte-like cells, indicating that these cells may be the new target cell of interest to produce biopharmaceuticals. Our group recently established a hMSC-derived immortalized hepatocyte-like cell line (imHC) that demonstrates several liver-specific phenotypes. However, the ability of imHC to produce coagulation factors has not been characterized. Here, we examined the potential for imHC as a source of coagulation protein production by investigating the ability of imHC to produce human factor VII (FVII) using a lentiviral transduction system. Our results showed that imHC secreted a low amount of FVII (~22 ng/mL) into culture supernatant. Moreover, FVII from the transduced imHC (0.11 ± 0.005 IU/mL) demonstrated a similar coagulant activity compared with FVII from transduced HEK293T cells (0.12 ± 0.004 IU/mL) as determined by chromogenic assay. We demonstrate for the first time, to the best of our knowledge, that imHC produced FVII, albeit at a low level, indicating the unique characteristic of hepatocytes. Our study suggests the possibility of using imHC for the production of coagulation proteins.

Current understanding of adipose-derived mesenchymal stem cell-based therapies in liver diseases

The liver, the largest organ with multiple synthetic and secretory functions in mammals, consists of hepatocytes, cholangiocytes, hepatic stellate cells (HSCs), sinusoidal endothelial cells, Kupffer cells (KCs), and immune cells, among others. Various causative factors, including viral infection, toxins, autoimmune defects, and genetic disorders, can impair liver function and result in chronic liver disease or acute liver failure. Mesenchymal stem cells (MSCs) from various tissues have emerged as a potential candidate for cell transplantation to promote liver regeneration. Adipose-derived MSCs (ADMSCs) with high multi-lineage potential and self-renewal capacity have attracted great attention as a promising means of liver regeneration. The abundance source and minimally invasive procedure required to obtain ADMSCs makes them superior to bone marrow-derived MSCs (BMMSCs). In this review, we comprehensively analyze landmark studies that address the isolation, proliferation, and hepatogenic differentiation of ADMSCs and summarize the therapeutic effects of ADMSCs in animal models of liver diseases. We also discuss key points related to improving the hepatic differentiation of ADMSCs via exposure of the cells to cytokines and growth factors (GFs), extracellular matrix (ECM), and various physical parameters in in vitro culture. The optimization of culturing methods and of the transplantation route will contribute to the further application of ADMSCs in liver regeneration and help improve the survival rate of patients with liver diseases. To this end, ADMSCs provide a potential strategy in the field of liver regeneration for treating acute or chronic liver injury, thus ensuring the availability of ADMSCs for research, trial, and clinical applications in various liver diseases in the future.

Decellularization and Solubilization of Porcine Liver for Use as a Substrate for Porcine Hepatocyte Culture: Method Optimization and Comparison

Biologic substrates, prepared by decellularizing and solubilizing tissues, have been of great interest in the tissue engineering field because of the preservation of complex biochemical constituents found in the native extracellular matrix (ECM). The integrity of the ECM is critical for cell behavior, adhesion, migration, differentiation, and proliferation that in turn affect homeostasis and tissue regeneration. Previous studies have shown that various processing methods have a distinctive way of affecting the composition of the decellularized ECM. In this study, we developed a bioactive substrate for hepatocytes in vitro, made of decellularized and solubilized liver tissue. The present work is a comparative approach of 2 different methods. First, we decellularized porcine liver tissue with ammonium hydroxide versus a sodium deoxycholate method, then characterized the decellularized tissue using various methods including double stranded DNA (dsDNA) content, DNA size, immunogenicity, and mass spectrometry. Second, we solubilized the decellularized porcine liver with hydrochloric acid versus acetic acid (AA) and characterized the resultant solubilized tissues using relevant methodologies including protein yield, immunogenicity, and bioactivity. Finally, we isolated primary porcine hepatocytes, cultured, and evaluated their bioactivity on the optimized decellularized–solubilized liver substrate. The decellularized porcine liver ECM processed by the ammonium hydroxide method and solubilized with AA displayed higher ECM integrity, low dsDNA, no evidence of intact nuclei, low human monocyte chemoattraction, and the presence of key molecules typically found in the native liver, a very important element for normal cell function. In addition, primary porcine hepatocytes showed enhanced functionality including albumin and urea production and bile canaliculi formation when cultured on the developed liver substrate compared to type I collagen.

In vivo hepatic differentiation potential of human umbilical cord-derived mesenchymal stem cells: Therapeutic effect on liver fibrosis/cirrhosis

AIM

To investigate the hepatic differentiation potential of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) and to evaluate their therapeutic effect on liver fibrosis/cirrhosis.

METHODS

A CCl₄-induced liver fibrotic/cirrhotic rat model was used to assess the effect of hUC-MSCs. Histopathology was assessed by hematoxylin and eosin (H&E), Masson trichrome and Sirius red staining. The liver biochemical profile was measured using a Beckman Coulter analyzer. Expression analysis was performed using immunofluorescent staining, immunohistochemistry, Western blot, and real-time PCR.

RESULTS

We demonstrated that the infused hUC-MSCs could differentiate into hepatocytes in vivo. Functionally, the transplantation of hUC-MSCs to CCl₄-treated rats improved liver transaminases and synthetic function, reduced liver histopathology and reversed hepatobiliary fibrosis. The reversal of hepatobiliary fibrosis was likely due to the reduced activation state of hepatic stellate cells, decreased collagen deposition, and enhanced extracellular matrix remodeling via the up-regulation of MMP-13 and down-regulation of TIMP-1.

CONCLUSION

Transplanted hUC-MSCs could differentiate into functional hepatocytes that improved both the biochemical and histopathologic changes in a CCl₄-induced rat liver fibrosis model. hUC-MSCs may offer therapeutic opportunities for treating hepatobiliary diseases, including cirrhosis.

High-throughput sequencing to identify microRNA signatures during hepatic differentiation of human umbilical cord Wharton's jelly-derived mesenchymal stem cells

AIM

MicroRNAs (miRNAs) constitute a class of small non-coding RNAs involved in regulation of cognate mRNAs post-transcriptionally. MicroRNAs have been implicated in regulating the stem cell differentiation process. Limited regulatory miRNAs have been reported to date during hepatic differentiation of stem cells. The present study was designed to identify the signature miRNAs implicated in hepatic differentiation of stem cells using next-generation sequencing methods.

METHODS

We undertook sequencing of miRNAs isolated from three different time points during hepatic differentiation of human umbilical cord Wharton's jelly-derived mesenchymal stem cells (hUC-MSCs) from two biological replicates.

RESULTS

Out of a total known 2588 miRNAs (according to miRBase version 21), 880 miRNAs were identified in our study. A total of 63 significantly expressed miRNAs during hepatic differentiation, with at least 2-fold change and a false discovery rate value <0.05, were considered for further analysis. The putative target genes of significantly downregulated miRNAs during hepatic differentiation appeared to be mostly associated with biological processes that are essential for hepatic differentiation and maintenance of mature hepatic phenotype-like liver development, stem cell differentiation, Wnt receptor signaling pathway, and drug and cholesterol metabolic processes. Putative target genes of significantly upregulated miRNAs are highly enriched in regulating processes that block hepatic differentiation of hUC-MSCs like epithelial-mesenchymal transition, transforming growth factor-β receptor signaling pathway, and stem cell maintenance.

CONCLUSION

The study provides a new insight for investigation of miRNA-regulated pathways during the differentiation process.

The effect of histone deacetylase inhibitor trichostatin A on porcine mesenchymal stem cell transcriptome

The use of histone deacetylase inhibitors such as trichostatin A (TSA) for epigenetic transformation of mesenchymal stem cells (MSCs), whose nuclei will be transferred into enucleated oocytes, is a novel approach in research involving somatic cell cloning of pigs and other mammalian species. Although the effectiveness of TSA in cloning applications was confirmed, processes and mechanisms underlying achieved effects are not yet fully understood, especially for pig MSCs. To contribute to this knowledge, in this study we performed a comprehensive transcriptome analysis using high-throughput sequencing of pig bone-marrow derived MSCs, both treated and untreated with TSA, and evaluated the effect of TSA administration on their transcription profile after 24 h of in vitro culture. The expression of selected positive and negative mesenchymal surface antigens was also evaluated in these cells by flow cytometry. Subsequently, the stability of induced expression changes was evaluated after another 55-72 h of culture without TSA. The results of this study showed that TSA does not affect the expression of the selected surface antigens related to MSC mesenchymal stemness origin, namely: CD90 (positive marker), CD31 and CD34 (negative markers) and has a wide stimulating effect on MSCs transcription, affecting genes across the whole genome with some minor signs of site-specific acting in regions on SSC2 and SSC6. TSA turned out to have a higher impact on already expressed genes with only minor abilities to induce expression of silenced genes. Genes with expression affected by TSA were related to a wide range of biological processes, however, we found some evidence for specific stimulation of genes associated with development, differentiation, neurogenesis or myogenesis. TSA also seemed to interfere with Wnt signaling pathways by upregulation of several engaged genes. The analysis of cell transcriptome after prolonged culture following the TSA removal, showed that the expression level of majority of genes affected by TSA is restored to the initial level. Nonetheless, the set of about six hundred genes responsible for e.g. adhesion, signal transduction and cell communication was altered even after 55-72 h of culture without TSA. TSA also enhanced expression of some of pluripotency marker genes (FGF2, LIF, TERT) but their expression was stabilized during further culture without TSA. The detailed analysis of factors connected with neuron-like differentiation allowed us to assume that TSA mostly stimulates neurogenic differentiation pathway in the pig MSCs possibly through interaction with Wnt-mediated signaling and thus triggers mechanisms conducive to epigenetic reprograming.

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.

Role of Stem Cells Transplantation in Tissue Regeneration After Acute or Chronic Acetaminophen Induced Liver Injury

PURPOSE

Acetaminophen-induced liver injury (APAP) is recognized as a frequent etiologic factor responsible for hepatic damage in the developed world. Management remains still elusive as treatment options are limited and their results are inconclusive. Consequently new strategies are explored at the experimental level. Mesenchymal stem cells (MSCs) present a promising modality as they can promote liver regeneration (LG) and compensate acute liver injury (ALI).

MATERIALS AND METHODS

Our research was focused on articles related to drug-induced liver injury, mechanisms of liver regeneration (LG) after Acute Liver Injury (ALI) and recent experimental protocols of Mesenchymal Stem Cells (MSCs) transplantation after chemical insult. All these studies are cited on Pubmed and MedLine.

RESULTS

This review has three distinct sections. First recent developments in ALI pathogenesis are presented. The second section covers cellular pathways and histological findings relevant to liver regeneration. The final chapter analyzes MSCs transplantation protocols after ALI and interrelation between liver regeneration and hepatic differentiation of MSCs.

CONCLUSION

Adipose tissue stem cells (ADSCs) and (MSCs) transplantation represents a promising modality in severe ALI management although many aspects remain to be clarified.

Cell-based therapies of liver diseases: age-related challenges

The scope of this review is to revise recent advances of the cell-based therapies of liver diseases with an emphasis on cell donor's and patient's age. Regenerative medicine with cell-based technologies as its integral part is focused on the structural and functional restoration of tissues impaired by sickness or aging. Unlike drug-based medicine directed primarily at alleviation of symptoms, regenerative medicine offers a more holistic approach to disease and senescence management aimed to achieve restoration of homeostasis. Hepatocyte transplantation and organ engineering are very probable forthcoming options of liver disease treatment in people of different ages and vigorous research and technological innovations in this area are in progress. Accordingly, availability of sufficient amounts of functional human hepatocytes is crucial. Direct isolation of autologous hepatocytes from liver biopsy is problematic due to related discomfort and difficulties with further expansion of cells, particularly those derived from aging people. Allogeneic primary human hepatocytes meeting quality standards are also in short supply. Alternatively, autologous hepatocytes can be produced by reprogramming of differentiated cells through the stage of induced pluripotent stem cells. In addition, fibroblasts and mesenchymal stromal cells can be directly induced to undergo advanced stage hepatogenic differentiation. Reprogramming of cells derived from elderly people is accompanied by the reversal of age-associated changes at the cellular level manifesting itself by telomere elongation and the U-turn of DNA methylation. Cell reprogramming can provide high quality rejuvenated hepatocytes for cell therapy and liver tissue engineering. Further technological advancements and establishment of national and global registries of induced pluripotent stem cell lines homozygous for HLA haplotypes can allow industry-style production of livers for immunosuppression-free transplantation.

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.

Adipose-derived stem cells: A candidate for liver regeneration

The scarcity of donor livers and the impracticality of hepatocyte transplantation represent the biggest obstacles for the treatment of liver failure. Adipose-derived stem cells, with their ability to differentiate into the hepatic lineage, provide a reliable alternative cell source with clear ethical and practical advantages. Moreover, adipose-derived stem cells can effectively repair liver damage by the dominant indirect pattern and increase the number of hepatocytes by the secondary direct pattern. In recent years, the development of the indirect pattern, which mainly includes immunomodulatory and trophic effects, has become a hot topic in the field of cell engineering. Therefore, adipose-derived stem cells are considered to be ideal therapeutic stem cells for human liver regeneration. In this article, we reviewed the advantages of adipose-derived stem cells in liver regeneration, and explore their underlying mechanisms.

Repeated versus single transplantation of mesenchymal stem cells in carbon tetrachloride-induced liver injury in mice

Despite its numerous limitations, liver transplants are the only definite cure for end-stage liver disease. Various stem cell populations may contribute to liver regeneration, of which there is accumulating evidence of the contribution of mesenchymal stem cells (MSCs). This study examines the hypothesis that repeated infusions of human bone marrow-derived MSCs (hBMMSCs)can improve liver injury in an experimental model. MSCs were intravenously transplanted into immunosuppressed mice with carbon tetrachloride (CCl(4))-induced liver fibrosis. Transplanting 3x10(6) MSCs in three divided doses improved survival,liver fibrosis and necrosis compared with injection of the same number of MSCs in a single dose. This was accompanied by increased influence on the expression of the fibrogenic/fibrolytic related genes Col1a1, Timp1 and Mmp13 in the repeated transplant group. Repeat administration of MSCs was three times more effective in homing of PKH-tagged transplanted cells 3 weeks post-transplant compared with the single transplant group. The benefits of repeated transplants may be of considerable significance in clinical trials on liver failure.

Promotion of mesenchymal-to-epithelial transition by Rac1 inhibition with small molecules accelerates hepatic differentiation of mesenchymal stromal cells

In vitro differentiation of stem cells into specific cell lineages provides a stable cell supply for cell therapy and tissue engineering. Therefore, understanding the mechanisms underlying such differentiation processes is critical for generating committed lineage-specific cell progenies effectively. We previously developed a two-step protocol to differentiate mesenchymal stromal cells (MSCs) into hepatocyte-like cells. Since hepatic differentiation involves mesenchymal-epithelial transition (MET), we hypothesize that promoting MET could further accelerate the differentiation process. Ras-related C3 botulinum toxin substrate 1 (Rac1) is involved in actin polymerization and its role in MET was investigated in the study. Our results showed that inhibition of Rac1 activation by Rac1-specific inhibitor, NSC23766, led to cells favoring epithelial morphology and being more packed during hepatic differentiation. In addition, Rac1 inhibition accelerated the upregulation of hepatic marker genes accompanied by more mature hepatic functions. Taken together, promotion of MET by inhibiting Rac1 accelerates the hepatic differentiation of MSCs. Our findings open a new prospect of directing the commitment of MSCs by manipulating cell morphology and cytoskeleton arrangement through small molecules. The results provide further insight into scaffold design for rapid production of MSC-differentiated hepatocytes.

The multiple functional roles of mesenchymal stem cells in participating in treating liver diseases

Mesenchymal stem cells (MSCs) are a group of stem cells derived from the mesodermal mesenchyme. MSCs can be obtained from a variety of tissues, including bone marrow, umbilical cord tissue, umbilical cord blood, peripheral blood and adipose tissue. Under certain conditions, MSCs can differentiate into many cell types both in vitro and in vivo, including hepatocytes. To date, four main strategies have been developed to induce the transdifferentiation of MSCs into hepatocytes: addition of chemical compounds and cytokines, genetic modification, adjustment of the micro-environment and alteration of the physical parameters used for culturing MSCs. Although the phenomenon of transdifferentiation of MSCs into hepatocytes has been described, the detailed mechanism is far from clear. Generally, the mechanism is a cascade reaction whereby stimulating factors activate cellular signalling pathways, which in turn promote the production of transcription factors, leading to hepatic gene expression. Because MSCs can give rise to hepatocytes, they are promising to be used as a new treatment for liver dysfunction or as a bridge to liver transplantation. Numerous studies have confirmed the therapeutic effects of MSCs on hepatic fibrosis, cirrhosis and other liver diseases, which may be related to the differentiation of MSCs into functional hepatocytes. In addition to transdifferentiation into hepatocytes, when MSCs are used to treat liver disease, they may also inhibit hepatocellular apoptosis and secrete various bioactive molecules to promote liver regeneration. In this review, the capacity and molecular mechanism of MSC transdifferentiation, and the therapeutic effects of MSCs on liver diseases are thoroughly discussed.

Homing effect of adipose-derived stem cells to the injured liver: the shift of stromal cell-derived factor 1 expressions

BACKGROUND

Whether systemically transplanted human adipose-derived stem cells (ADSCs) homed to the injured liver in nude mice under stress with subsequent hepatectomy (Hx) and ischemia-reperfusion (I/R) was investigated in the present study. The types of cells in the liver that were involved in the homing of ADSCs were clarified, with focus on the stromal-derived factor-1 (SDF-1)/C-X-C chemokine receptor type 4 (CXCR-4) axis.

METHODS

Adipose-derived stem cells were transplanted intravenously immediately after 70% Hx and I/R. ADSCs were traced by in vivo imaging for 24 h after transplantation and ADSCs were histologically detected in the liver. SDF-1 and CXCR-4 expressions in the liver were evaluated by real time RT-PCR. The immunohistochemical analysis of SDF-1 was also performed to identify SDF-1 expressing cells in the liver.

RESULTS

Adipose-derived stem cells were found in various organs immediately following transplantation and almost accumulated in remnant liver or spleen at 6 h after transplantation. ADSCs were also histologically revealed in the harvested liver. Hx and I/R injury significantly enhanced SDF-1 expressions regardless of ADSCs transplantation, and only ADSC transplantation increased CXCR-4 expressions. The predominant SDF-1 positive cells in the liver were equally identified in parenchymal and non-parenchymal cells at 6 h, but shifted to non-parenchymal cells at 24 h after transplantation.

CONCLUSIONS

Systemically transplanted ADSCs homed to the injured liver after transplantation, possibly based on the mechanisms of SDF-1/CXCR-4 axis. Therefore, systemic transplantation might be an effective and practical route for the transplantation of ADSCs.

Deep sequencing-based transcriptional analysis of bovine mammary epithelial cells gene expression in response to in vitro infection with Staphylococcus aureus stains

Staphylococcus aureus (S. aureus) is an important etiological organism in chronic and subclinical mastitis in lactating cows. Given the fundamental role the primary bovine mammary epithelial cells (pBMECs) play as a major first line of defense against invading pathogens, their interactions with S. aureus was hypothesized to be crucial to the establishment of the latter’s infection process. This hypothesis was tested by investigating the global transcriptional responses of pBMECs to three S. aureus strains (S56,S178 and S36) with different virulent factors, using a tag-based high-throughput transcriptome sequencing technique. Approximately 4.9 million total sequence tags were obtained from each of the three S. aureus-infected libraries and the control library. Referenced to the control, 1720, 219, and 427 differentially expressed unique genes were identified in the pBMECs infected with S56, S178 and S36 S. aureus strains respectively. Gene ontology (GO) and pathway analysis of the S56-infected pBMECs referenced to those of the control revealed that the differentially expressed genes in S56-infected pBMECs were significantly involved in inflammatory response, cell signalling pathways and apoptosis. In the same vein, the clustered GO terms of the differentially expressed genes of the S178-infected pBMECs were found to comprise immune responses, metabolism transformation, and apoptosis, while those of the S36-infected pBMECs were primarily involved in cell cycle progression and immune responses. Furthermore, fundamental differences were observed in the levels of expression of immune-related genes in response to treatments with the three S. aureus strains. These differences were especially noted for the expression of important pro-inflammatory molecules, including IL-1α, TNF, EFNB1, IL-8, and EGR1. The transcriptional changes associated with cellular signaling and the inflammatory response in this study may reflect different immunomodulatory mechanisms that underlie the interaction between pBMECs and S. aureus strains during infection by the latter.

The generation of hepatocytes from mesenchymal stem cells and engraftment into the liver

PURPOSE OF REVIEW

Liver transplantation is the ultimate therapeutic option for the treatment of end-stage liver diseases, which, however, is restricted by the shortage of donor organs. Instead hepatocyte transplantation seemed to be a way out, but again marginal donor livers for the isolation of primary human hepatocytes are scarce. The hepatocyte differentiation capacity of mesenchymal stem cells might open a new cell resource to generate hepatocyte-like cells for therapeutical use.

RECENT FINDINGS

Apart from their potency of hepatocyte differentiation mesenchymal stem cells display pleiotropic biological features including modulation of immunogenicity, anti-inflammatory and anti-apoptotic as well as pro-proliferative impact at the site of tissue or organ lesions. They are mobilized from the bone marrow and migrate to the liver along chemoattractive gradients thus contributing to the humoral and cellular response in tissue repair. The cause of different liver diseases is varying depending on, for example, viral, toxic, nutritional, neoplastic challenges. As known from animal studies mesenchymal stem cells seem to have a beneficial impact on liver regeneration and tissue repair under a variety of liver disease conditions.

SUMMARY

Their versatile biological features render mesenchymal stem cells an alternate cell resource for the treatment of liver diseases. It is important to know the mechanisms of integration of transplanted cells into the recipient tissue and to understand the communication between donor cells and the host tissue on the molecular level in order to support efficacy of cell transplantation and thus optimize the therapeutical outcome.

The therapeutic potential of mesenchymal stem cell-derived extracellular vesicles

Extracellular vesicles (EVs), membrane vesicles that are secreted by a variety of mammalian cell types, have been shown to play an important role in intercellular communication. The contents of EVs, including proteins, microRNAs, and mRNAs, vary according to the cell type that secreted them. Accordingly, researchers have demonstrated that EVs derived from various cell types play different roles in biological phenomena. Considering the ubiquitous presence of mesenchymal stem cells (MSCs) in the body, MSC-derived EVs may take part in a wide range of events. In particular, MSCs have recently attracted much attention due to the therapeutic effects of their secretory factors. MSC-derived EVs may therefore provide novel therapeutic approaches. In this review, we first summarize the wide range of functions of EVs released from different cell types, emphasizing that EVs echo the phenotype of their parent cell. Then, we describe the various therapeutic effects of MSCs and pay particular attention to the significance of their paracrine effect. We then survey recent reports on MSC-derived EVs and consider the therapeutic potential of MSC-derived EVs. Finally, we discuss remaining issues that must be addressed before realizing the practical application of MSC-derived EVs, and we provide some suggestions for enhancing their therapeutic efficiency.

Serum from hepatectomized rats induces the differentiation of adipose tissue mesenchymal stem cells into hepatocyte-like cells and upregulates the expression of hepatocyte growth factor and interleukin-6 in vitro

Adipose tissue-derived mesenchymal stem cells (AT-MSCs) are an attractive alternative for clinical application due to their minimally invasive accessibility and availability in the body. However, the hepatic differentiation efficiency of AT-MSCs is insufficient for therapeutic application and the role of extrahepatic stem cells in liver regeneration remains poorly understood. This study was designed to investigate the effects of serum from rats subjected to 70% partial hepatectomy (PH) on the differentiation ability of rat AT-MSCs in vitro, and to explore the potential role of AT-MSCs in vivo following PH injury. Results showed that AT-MSCs treated with serum collected from rats 24 h after 70% PH differen-tiated into hepatocyte-like cells, resembled hepatocyte-like cells with round or polygonal shape, expressed α-fetoprotein, secreted albumin, synthesized urea and acquired cytochrome P450 type 3A4 enzyme activity, and upregulated the expression of interleukin (IL)-6 and hepatocyte growth factor (HGF) transiently in vitro, although the hepatic differentiation efficiency was extremely low. AT-MSC transplantation after 70% PH ameliorated liver injury and promoted liver regeneration, but did not increase the serum levels of IL-6 and HGF in vivo. This result suggests that the therapeutic effect of AT-MSCs in vivo after 24 h of 70% PH does not increase IL-6 and HGF expression.

Gene expression pattern of human chorion-derived mesenchymal stem cells during adipogenic differentiation

PURPOSE

The aim of this study was to identify the adipocyte-specific gene expression patterns in chorion-derived mesenchymal stem cells during adipogenic differentiation.

MATERIALS AND METHODS

Chorionic cells were isolated from the third trimester chorions from human placenta at birth and identified morphologically and by fluorescence-activated cell sorting analysis. After inducing adipogenic differentiation for 28 days, cells at days 3, 10, 21 and 28 were analyzed by Oil red O staining and RNA extraction in order to assess the expression levels of adipocyte marker genes, including CCAAT-enhancer binding protein α (C/EBPα), peroxisome proliferator- activated receptor γ (PPARγ), fatty acid binding protein 4 (FABP4) and Glycerol-3-phosphate dehydrogenase (GPD2). Cells not induced for differentiation were compared with the induced cells as a control group.

RESULTS

Chorion-derived cells showed the same pattern as fibroblasts, and expressed CD73, CD105, and CD166 antigens, but not CD45, CD34, and HLA-DR antigens. On day 3 after differentiation, cells began to stain positively upon Oil red O staining, and continuously increased in lipid granules for 4 weeks. The expression level of C/EBPα increased 4.6 fold on day 3 after induction, and continued to increase for 4 weeks. PPARγ was expressed at a maximum of 2.9 fold on day 21. FABP4 and GPD2 were significantly expressed at 4.7- and 3.0-fold, respectively, on day 21, compared to controls, and further increased thereafter.

CONCLUSION

Human chorion-derived mesenchymal stem cells exhibited the sequential expression pattern of adipocyte marker genes during differentiation, corresponding to adipogenesis.

Hepatocyte differentiation of mesenchymal stem cells

BACKGROUND

Liver cell transplantation and bioartificial liver may provide metabolic support of liver function temporary and are prospective treatments for patients with liver failure. Mesenchymal stem cells (MSCs) are expected to be an ideal cell source for transplantation or liver tissue engineering, however the hepatic differentiation of MSCs is still insufficient for clinical application.

DATA SOURCES

A PubMed search on "mesenchymal stem cells", "liver cell" and "hepatocyte differentiation" was performed on the topic, and the relevant articles published in the past ten years were reviewed.

RESULTS

Hepatocyte-like cells differentiated from MSCs are a promising cell source for liver regeneration or tissue engineering. Although it is still a matter of debate as to whether MSC-derived hepatocytes may efficiently repopulate a host liver to provide adequate functional substitution, the majority of animal studies support that MSCs can become key players in liver-directed regenerative medicine. However the clinical application of human stem cells in the treatment of liver diseases is still in its infancy.

CONCLUSIONS

Future studies are required to improve the efficacy and consistency of hepatic differentiation from MSCs. It is necessary to better understand the mechanism to achieve transdifferentiation with high efficiency. More clinical trials are warranted to prove their efficacy in the management of patients with liver failure.

Hepatic differentiation of rat mesenchymal stem cells by a small molecule

Mesenchymal stem cells (MSCs) are capable of self-renewal and multilineage differentiation. A periodic acid-Schiff (PAS) stain-based assay was developed to screen for small-molecule inducers of hepatic differentiation of bone marrow MSCs. 2-(4-Bromophenyl)-N-(4-fluorophenyl)-3-propyl-3H-imidazo[4,5-b]pyridin-5-amine (SJA710-6) was identified as a novel small molecule able to induce the differentiation of rat MSCs (rMSCs) toward hepatocyte-like cells in vitro, where rMSCs treated with SJA710-6 have typical morphological and functional characteristics of hepatic cells, including glycogen storage, urea secretion, uptake of low density lipoprotein (LDL) and expression of hepatocyte-specific genes and proteins. Expression of FoxH1 (FAST1/2) induces the differentiation of rMSCs towards hepatocyte-like cells, suggesting that this gene plays an important role in the hepatic fate specification of rMSCs.

Progress in research of differentiation of mesenchymal stem cells into functional hepatocytes

Mesenchymal stem cells (MSCs) are a group of stem cells deriving from mesodermal mesenchyme. They can be recovered from a variety of tissues, including bone marrow, umbilical cord tissue, umbilical cord blood, peripheral blood and adipose tissue. Under given conditions, MSCs can differentiate into bone, fat, nerve cells, hepatocytes and many other cells, and thus can be used as a new treatment to substitute for organ transplantation. In recent years, the incidence of end-stage liver disease has been increasing and it has become one of the major diseases affecting human health. Donor scarcity and immunological rejection limit the clinical application of liver transplantation. Numerous studies have confirmed the therapeutic effects of MSCs on hepatic fibrosis, cirrhosis and other liver diseases, which may be related to the differentiation of MSCs into functional hepatocytes. This paper reviews the capacity, regulation and molecular mechanism of MSC differentiation and discusses the therapeutic effects of different sources of stem cells for liver fibrosis.

Nitric oxide augments mesenchymal stem cell ability to repair liver fibrosis

Background

Liver fibrosis is a major health problem worldwide and poses a serious obstacle for cell based therapies. Mesenchymal stem cells (MSCs) are multipotent and important candidate cells for future clinical applications however success of MSC therapy depends upon their homing and survival in recipient organs. This study was designed to improve the repair potential of MSCs by transplanting them in sodium nitroprusside (SNP) pretreated mice with CCl₄ induced liver fibrosis.

Methods

SNP 100 mM, a nitric oxide (NO) donor, was administered twice a week for 4 weeks to CCl₄-injured mice. MSCs were isolated from C57BL/6 wild type mice and transplanted in the left lateral lobe of the liver in experimental animals. After 4 weeks, animals were sacrificed and liver improvement was analyzed. Analysis of fibrosis by qRT-PCR and sirius red staining, homing, bilirubin and alkaline phosphatase (ALP) serum levels between different treatment groups were compared to control.

Results

Liver histology demonstrated enhanced MSCs homing in SNP-MSCs group compared to MSCs group. The gene expression of fibrotic markers; αSMA, collagen 1α1, TIMP, NFκB and iNOS was down regulated while cytokeratin 18, albumin and eNOS was up-regulated in SNP-MSCs group. Combine treatment sequentially reduced fibrosis in SNP-MSCs treated liver compared to the other treatment groups. These results were also comparable with reduced serum levels of bilirubin and ALP observed in SNP-MSCs treated group.

Conclusion

This study demonstrated that NO effectively augments MSC ability to repair liver fibrosis induced by CCl₄ in mice and therefore is a better treatment regimen to reduce liver fibrosis.

VEGF(165) expressing bone marrow mesenchymal stem cells differentiate into hepatocytes under HGF and EGF induction in vitro

A short half-life and low levels of growth factors in an injured microenvironment necessitates the sustainable delivery of growth factors and stem cells to augment the regeneration of injured tissues. Our aim was to investigate the ability of VEGF(165) expressing bone marrow mesenchymal stem cells (BMMSCs) to differentiate into hepatocytes when cultured with hepatocyte growth factor (HGF) and epidermal growth factor (EGF) in vitro. We isolated, cultured and identified rabbit BMMSCs, then electroporated the BMMSCs with VEGF(165)-pCMV6-AC-GFP plasmid. G418 was used to select transfected cells and the efficiency was up to 70%. The groups were then divided as follows: Group A was electroporated with pCMV6-AC-GFP plasmid + HGF + EGF and Group B was electroporated with VEGF(165)-pCMV6-AC-GFP plasmid +HGF + EGF. After 14 days, BMMSCs were induced into short spindle and polygonal cells. Alpha-fetoprotein (AFP) was positive and albumin (ALB) was negative in Group A, while both AFP and ALB were positive in group B on day 10. AFP and ALB in both groups were positive on day 20, but the quantity of AFP in group B decreased with prolonged time and was about 43.5% less than group A. The quantity of the ALB gene was increased with prolonged time in both groups. However, there was no significant difference between group A and B on day 10 and 20. Our results demonstrated that VEGF(165)-pCMV6-AC-GFP plasmid modified BMMSCs still had the ability to differentiate into hepatocytes. The VEGF(165) gene promoted BMMSCs to differentiate into hepatocyte-like cells under the induction of HGF and EGF, and reduced the differentiation time. These results have implications for cell therapies.

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.

Therapeutic implications of mesenchymal stem cells in liver injury

Mesenchymal stem cells (MSCs), represent an attractive tool for the establishment of a successful stem-cell-based therapy of liver diseases. A number of different mechanisms contribute to the therapeutic effects exerted by MSCs, since these cells can differentiate into functional hepatic cells and can also produce a series of growth factors and cytokines able to suppress inflammatory responses, reduce hepatocyte apoptosis, regress liver fibrosis, and enhance hepatocyte functionality. To date, the infusion of MSCs or MSC-conditioned medium has shown encouraging results in the treatment of fulminant hepatic failure and in end-stage liver disease in experimental settings. However, some issues under debate hamper the use of MSCs in clinical trials. This paper summarizes the biological relevance of MSCs and the potential benefits and risks that can result from translating the MSC research to the treatment of liver diseases.

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-MSCs's 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.

Development of immortalized hepatocyte-like cells from hMSCs

Clones of hepatocyte-like cells were reproducibly generated from human mesenchymal stem cells immortalized with a combined transduction of both Bmi-1 and TERT genes. These hepatocyte-like cells contained selective markers and several functional properties of hepatocytes, yet still carried proliferative potential. These cells had cuboidal morphology and arranged themselves as cord-like structure in culture. The cloned cells deposited glycogen and actively synthesized albumin. The basal expressions of CYP450 isozymes was observed, albeit only 10-20% that of primary hepatocytes. These expressions were promptly increased upon the addition of rifampicin, a known enzyme inducer. These hepatocyte-like cells may serve as a close alternative to the use of primary hepatocytes for in vitro studies.

Therapeutic implications of mesenchymal stem cells in liver injury

Mesenchymal stem cells (MSCs), represent an attractive tool for the establishment of a successful stem-cell-based therapy of liver diseases. A number of different mechanisms contribute to the therapeutic effects exerted by MSCs, since these cells can differentiate into functional hepatic cells and can also produce a series of growth factors and cytokines able to suppress inflammatory responses, reduce hepatocyte apoptosis, regress liver fibrosis, and enhance hepatocyte functionality. To date, the infusion of MSCs or MSC-conditioned medium has shown encouraging results in the treatment of fulminant hepatic failure and in end-stage liver disease in experimental settings. However, some issues under debate hamper the use of MSCs in clinical trials. This paper summarizes the biological relevance of MSCs and the potential benefits and risks that can result from translating the MSC research to the treatment of liver diseases.

Upregulation of CYP 450s expression of immortalized hepatocyte-like cells derived from mesenchymal stem cells by enzyme inducers

BACKGROUND

The strenuous procurement of cultured human hepatocytes and their short lives have constrained the cell culture model of cytochrome P450 (CYP450) induction, xenobiotic biotransformation, and hepatotoxicity. The development of continuous non-tumorous cell line steadily containing hepatocyte phenotypes would substitute the primary hepatocytes for these studies.

RESULTS

The hepatocyte-like cells have been developed from hTERT plus Bmi-1-immortalized human mesenchymal stem cells to substitute the primary hepatocytes. The hepatocyte-like cells had polygonal morphology and steadily produced albumin, glycogen, urea and UGT1A1 beyond 6 months while maintaining proliferative capacity. Although these hepatocyte-like cells had low basal expression of CYP450 isotypes, their expressions could be extensively up regulated to 80 folds upon the exposure to enzyme inducers. Their inducibility outperformed the classical HepG2 cells.

CONCLUSION

The hepatocyte-like cells contained the markers of hepatocytes including CYP450 isotypes. The high inducibility of CYP450 transcripts could serve as a sensitive model for profiling xenobiotic-induced expression of CYP450.

[Preclinical experience in stem cell therapy for digestive tract diseases]

Adult stem cells are multipotent and self-renewing cells that contain several functions; i) migration and homing potential: stem cells can migrate to injured and inflamed tissues. ii) differentiation potential: stem cells which migrated to injured tissues can be differentiated into multiple cell types for repairing and regenerating the tissues. iii) immunomodulatory properties: stem cells, especially mesenchymal stem cells can suppress immune system such as inflammation. All those characteristics might be useful for the treatment of the digestive tract diseases which are complex and encompass a broad spectrum of different pathogenesis. Preclinical stem cell therapy showed some promising results, especially in liver failure, pancreatitis, sepsis, and inflammatory bowel disease. If we can understand more about the mechanism of stem cell action, stem cell therapy can become a promising alternative treatment for refractory digestive disease in the near future. In this review, we summarized current preclinical experiences in diseases of the digestive tract using stem cells. (Korean J Gastroenterol 2011;58:133-138).

Distinct stem cells subpopulations isolated from human adipose tissue exhibit different chondrogenic and osteogenic differentiation potential

Recently adipose tissue has become a research topic also for the searching for an alternative stem cells source to use in cell based therapies such as tissue engineer. In fact Adipose Stem Cells (ASCs) exhibit an important differentiation potential for several cell lineages such as chondrogenic, osteogenic, myogenic, adipogenic and endothelial cells. ASCs populations isolated using standard methodologies (i.e., based on their adherence ability) are very heterogeneous but very few studies have analysed this aspect. Consequently, several questions are still pending, as for example, on what regard the existence/ or not of distinct ASCs subpopulations. The present study is originally aimed at isolating selected ASCs subpopulations, and to analyse their behaviour towards the heterogeneous population regarding the expression of stem cell markers and also regarding their osteogenic and chondrogenic differentiation potential. Human Adipose derived Stem Cells (hASCs) subpopulations were isolated using immunomagnetic beads coated with several different antibodies (CD29, CD44, CD49d, CD73, CD90, CD 105, Stro-1 and p75) and were characterized by Real Time RT-PCR in order to assess the expression of mesenchymal stem cells markers (CD44, CD73, Stro-1, CD105 and CD90) as well as known markers of the chondrogenic (Sox 9, Collagen II) and osteogenic lineage (Osteopontin, Osteocalcin). The obtained results underline the complexity of the ASCs population demonstrating that it is composed of several subpopulations, which express different levels of ASCs markers and exhibit distinctive differentiation potentials. Furthermore, the results obtained clearly evidence of the advantages of using selected populations in cell-based therapies, such as bone and cartilage regenerative medicine approaches.

Osteogenic differentiation of two distinct subpopulations of human adipose-derived stem cells: an in vitro and in vivo study

The first stem cells considered for the reconstruction of bone were bone marrow mesenchymal stem cells (BMSCs). Subsequently, cells with similar marker expression panel and differentiation potential were found in new sources of cells, such as adipose tissue. This source of stem cells has a promising future in tissue-engineering applications, considering the abundance of this tissue in the human body, the easy harvesting and the high number of stem cells that are available from such a small amount of tissue. The isolation of the adipose stem cells is generally performed by means of enzymatic digestion of the tissues, followed by a natural selection of the stem cells based on their capacity to adhere to the culture flasks, leading to a quite heterogeneous population. This constitutes a major drawback for the use of these cells, since the heterogeneity of the cell culture obtained can compromise their proliferation and differentiation potential. In the present study we have analysed the in vitro and in vivo behaviour of two selected subpopulations with high osteogenic potential. For this purpose, ASCs(CD29+) and ASCs (STRO-1+)subpopulations were isolated and in vitro cultured onto a biodegradable polymeric scaffold, using osteogenic medium, before implantation in a nude mice model. The biodegradable polymeric scaffold used is a fibre-mesh structure based on a blend of starch and polycaprolatone (SPCL) that has been successfully used in several bone tissue-engineering studies. The implanted ASCs-scaffold constructs promoted the formation of new bone tissue in nude mice. However, the results obtained show differences in the behaviour of the two ASCs subpopulations under study, particularly regarding their potential to differentiate into the osteogenic lineage, and allowed the indentification of ASCs (STRO-1+) as the best subpopulation for bone tissue-engineering applications.

Molecular mechanisms underlying human adipose tissue-derived stromal cells differentiation into a hepatocyte-like phenotype

BACKGROUND

Adipose tissue-derived stromal cells (ATSCs) hold great promises in regenerative medicine. In the last decade, several studies have reported the plasticity of ATSCs toward a hepatocyte-like phenotype. Nonetheless, the molecular mechanisms underlying the conversion from a mesenchymal to an epithelial phenotype remain poorly understood.

AIM

In this study, we compared the full genome expression profiles of ATSCs cultured for 4 weeks under pro-hepatogenic conditions to undifferentiated ATSCs, in order to depict the molecular events involved in ATSC hepatic transdifferentiation.

METHODS

Analysis was performed using the Affymetrix human focus arrays. Sets of differentially expressed genes were functionally categorized in order to understand which pathways drive the hepatic conversion and interesting targets were validated by Q-PCR.

RESULTS

ATSC-derived hepatocyte-like cells activate several genes associated with specific liver functions, including protein metabolism, innate immune response regulation, and biodegradation of toxic compounds. Furthermore, microarray analysis highlighted downregulation of transcripts associated with the mesenchymal lineage, while epithelial-related genes were overexpressed.

CONCLUSION

Our data suggest that the in vitro system used in this study drove ATSCs toward a hepatic conversion through a subtle regulation of molecular pathways controlling lineage commitment that promote mesenchymal-epithelial transition.

Adipose tissue-derived stem cells and their application in bone and cartilage tissue engineering

The adipose tissue was considered a reserve of energy until the '80s, when it was found that this tissue was involved in the metabolism of sex steroids such as estrogens. From then on, the importance attributed to this tissue radically changed as it was then considered an active organ, involved in important functions of the human body. In 2001, for the first time, the existence of stem cells within this tissue was reported, and since then, this tissue has been gaining an increased importance as a stem cell source for a wide range of potential applications in cell therapies and/or tissue engineering and regenerative medicine strategies, mainly due to its wide availability and easy access. This manuscript provides an overview on adipose stem cells (i.e., adipose tissue-derived stem cells, ASCs) considering the tissue of origin, the niche of the ASCs, and their phenotype in all aspects. In this paper it is also discussed the markers that have been used for the characterization of these cells, their differentiation properties, and their immunological reactivity, reporting studies from 2001 until this date. The ASCs are also compared with bone marrow stem cells (BMSCs), until now considered as the gold standard source of stem cells, underlining the common characteristics and the differences between the stem cells obtained from these two sources, as well as the advantages and disadvantages of their potential use in different applications. Finally, this review will also focus on the potential application of ASCs in tissue engineering applications, particularly in the regeneration of bone and cartilage, commenting on the progress of this approach and future trends of the field.

Analysis of deep sequencing microRNA expression profile from human embryonic stem cells derived mesenchymal stem cells reveals possible role of let-7 microRNA family in downstream targeting of hepatic nuclear factor 4 alpha

Background

Recent literature has revealed that genetic exchange of microRNA between cells can be essential for cell-cell communication, tissue-specificity and developmental processes. In stem cells, as in other cells, this can be accomplished through microvesicles or exosome mediated transfer. However, molecular profiles and functions of microRNAs within the cells and in their exosomes are poorly studied. Next generation sequencing technologies could provide a broad-spectrum of microRNAs and their expression and identify possible microRNA targets. In this work, we performed deep sequencing of microRNAs to understand the profile and expression of the microRNAs in microvesicles and intracellular environment of human embryonic stem cells derived mesenchymal stem cells (hES-MSC).

We outline a workflow pertaining to visualizing, statistical analysis and interpreting deep sequencing data of known intracellular and extracellular microRNAs from hES-MSC). We utilized these results of which directed our attention towards establishing hepatic nuclear factor 4 alpha (HNF4A) as a downstream target of let-7 family of microRNAs.

Results

In our study, significant differences in expression profile of microRNAs were found in the intracellular and extracellular environment of hES-MSC. However, a high level of let-7 family of microRNAs is predominant in both intra- and extra- cellular samples of hES-MSC. Further results derived from visualization of our alignment data and network analysis showed that let-7 family microRNAs could affect the downstream target HNF4A, which is a known endodermal differentiation marker. The elevated presence of let-7 microRNA in both intracellular and extra cellular environment further suggests a possible intercellular signalling mechanism through microvesicles transfer. We suggest that let-7 family microRNAs might play a signalling role via such a mechanism amongst populations of stem cells in maintaining self renewal property by suppressing HNF4A expression. This is in line with recent paradigm where microRNAs regulate self-renewal and differentiation pathways of embryonic stem cells by forming an integral biological network with transcription factors.

Conclusion

In summary, our study using a combination of alignment, statistical and network analysis tools to examine deep sequencing data of microRNAs in hES-MSC has led to a result that (i) identifies intracellular and exosome microRNA expression profiles of hES-MSCwith a possible mechanism of miRNA mediated intercellular regulation by these cells and (ii) placed HNF4A within the cross roads of regulation by the let-7 family of microRNAs.

SLUG: a new target of lymphoid enhancer factor-1 in human osteoblasts

Background

Lymphoid Enhancer Factor-1 (Lef-1) is a member of a transcription factor family that acts as downstream mediator of the Wnt/β-catenin signalling pathway which plays a critical role in osteoblast proliferation and differentiation. In a search for Lef-1 responsive genes in human osteoblasts, we focused on the transcriptional regulation of the SLUG, a zinc finger transcription factor belonging to the Snail family of developmental proteins. Although the role of SLUG in epithelial-mesenchymal transition and cell motility during embryogenesis is well documented, the functions of this factor in most normal adult human tissues are largely unknown. In this study we investigated SLUG expression in normal human osteoblasts and their mesenchymal precursors, and its possible correlation with Lef-1 and Wnt/β-catenin signalling.

Results

The experiments were performed on normal human primary osteoblasts obtained from bone fragments, cultured in osteogenic conditions in presence of Lef-1 expression vector or GSK-3β inhibitor, SB216763. We demonstrated that the transcription factor SLUG is present in osteoblasts as well as in their mesenchymal precursors obtained from Wharton's Jelly of human umbilical cord and induced to osteoblastic differentiation. We found that SLUG is positively correlated with RUNX2 expression and deposition of mineralized matrix, and is regulated by Lef-1 and β-catenin. Consistently, Chromatin Immunoprecipitation (ChIP) assay, used to detect the direct Lef/Tcf factors that are responsible for the promoter activity of SLUG gene, demonstrated that Lef-1, TCF-1 and TCF4 are recruited to the SLUG gene promoter "in vivo".

Conclusion

These studies provide, for the first time, the evidence that SLUG expression is correlated with osteogenic commitment, and is positively regulated by Lef-1 signal in normal human osteoblasts. These findings will help to further understand the regulation of the human SLUG gene and reveal the biological functions of SLUG in the context of bone tissue.

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.

Expression of liver-specific markers in naïve adipose-derived mesenchymal stem cells

BACKGROUND

Increasing evidence suggests that adipose tissue contains mesenchymal stem cells (MSC) that possess the ability to transdifferentiate into other cell types including hepatocytes, similar to bone marrow-derived stem cells. The existence of precommitted cells in the MSC population may explain transdifferentiation.

AIMS

Our aim was to identify a population of putative hepatocyte-like precursor cells in human adipose tissue.

METHODS

We analysed the 'basal' hepatic potential of undifferentiated, naïve human adipose-derived mesenchymal stem cells (hADMSC). hADMSC were isolated from human adipose tissue and characterized for cell surface markers and for liver-specific gene expression.

RESULTS

The isolated undifferentiated naïve hADMSCs expressed MSC surface markers. They also expressed alpha-fetoprotein, CK18, CK19 and HNF4, which are known as early liver expressing genes. Interestingly, the undifferentiated naïve hADMSC were also positive for albumin, G-6-P and alpha-1-antitrypsin (AAT), which are all known to be predominantly expressed in adult liver cells. These cells acquired a hepatocyte-specific phenotype and function upon treatment with a differentiation medium, resulting in the upregulation of albumin, G-6-P and AAT. Moreover, urea production, glycogen storage ability and cellular uptake of indocyanine green, which were absent in the basal state, were evident in the treated cells.

CONCLUSIONS

Our findings suggest the presence of cells with hepatocyte-like properties that are isolated from human adipose tissue and that can readily acquire hepatocyte-like functions. Adipose tissue could thus be an exciting alternative means for repopulating the liver after various injuries, and might serve as a source for the transplantation of liver cells.

In vitro differentiation of embryonic and adult stem cells into hepatocytes: state of the art

Stem cells are a unique source of self-renewing cells within the human body. Before the end of the last millennium, adult stem cells, in contrast to their embryonic counterparts, were considered to be lineage-restricted cells or incapable of crossing lineage boundaries. However, the unique breakthrough of muscle and liver regeneration by adult bone marrow stem cells at the end of the 1990s ended this long-standing paradigm. Since then, the number of articles reporting the existence of multipotent stem cells in skin, neuronal tissue, adipose tissue, and bone marrow has escalated, giving rise, both in vivo and in vitro, to cell types other than their tissue of origin. The phenomenon of fate reprogrammation and phenotypic diversification remains, though, an enigmatic and rare process. Understanding how to control both proliferation and differentiation of stem cells and their progeny is a challenge in many fields, going from preclinical drug discovery and development to clinical therapy. In this review, we focus on current strategies to differentiate embryonic, mesenchymal(-like), and liver stem/progenitor cells into hepatocytes in vitro. Special attention is paid to intracellular and extracellular signaling, genetic modification, and cell-cell and cell-matrix interactions. In addition, some recommendations are proposed to standardize, optimize, and enrich the in vitro production of hepatocyte-like cells out of stem/progenitor cells.