Network analysis for the identification of hub genes and related molecules as potential biomarkers associated with the differentiation of bone marrow-derived stem cells into hepatocytes

The incidence of liver diseases has been increasing steadily. However, it has some shortcomings, such as high cost and organ donor scarcity. The application of stem cell research has brought new ideas for the treatment of liver diseases. Therefore, it is particularly important to clarify the molecular and regulatory mechanisms of differentiation of bone marrow-derived stem cells (BMSCs) into liver cells. Herein, we screened differentially expressed genes between hepatocytes and untreated BMSCs to identify the genes responsible for the differentiation of BMSCs into hepatocytes. GSE30419 gene microarray data of BMSCs and GSE72088 gene microarray data of primary hepatocytes were obtained from the Gene Expression Omnibus database. Transcriptome Analysis Console software showed that 1896 genes were upregulated and 2506 were downregulated in hepatocytes as compared with BMSCs. Hub genes were analyzed using the STRING and Cytoscape v 3.8.2, revealing that twenty-four hub genes, play a pivotal role in the differentiation of BMSCs into hepatocytes. The expression of the hub genes in the BMSCs and hepatocytes was verified by reverse transcription-quantitative PCR (RT-qPCR). Next, the target miRNAs of hub genes were predicted, and then the lncRNAs regulating miRNAs was discovered, thus forming the lncRNA-miRNA-mRNA interaction chain. The results indicate that the lncRNA-miRNA-mRNA interaction chain may play an important role in the differentiation of BMSCs into hepatocytes, which provides a new therapeutic target for liver disease treatment.

A comprehensive transcriptomic comparison of hepatocyte model systems improves selection of models for experimental use

The myriad of available hepatocyte in vitro models provides researchers the possibility to select hepatocyte-like cells (HLCs) for specific research goals. However, direct comparison of hepatocyte models is currently challenging. We systematically searched the literature and compared different HLCs, but reported functions were limited to a small subset of hepatic functions. To enable a more comprehensive comparison, we developed an algorithm to compare transcriptomic data across studies that tested HLCs derived from hepatocytes, biliary cells, fibroblasts, and pluripotent stem cells, alongside primary human hepatocytes (PHHs). This revealed that no HLC covered the complete hepatic transcriptome, highlighting the importance of HLC selection. HLCs derived from hepatocytes had the highest transcriptional resemblance to PHHs regardless of the protocol, whereas the quality of fibroblasts and PSC derived HLCs varied depending on the protocol used. Finally, we developed and validated a web application (HLCompR) enabling comparison for specific pathways and addition of new HLCs. In conclusion, our comprehensive transcriptomic comparison of HLCs allows selection of HLCs for specific research questions and can guide improvements in culturing conditions.

In vitro differentiation effect of CCL4-induced liver injured mice serum on bone marrow-derived mesenchymal stem cells toward hepatocytes like cells

Liver dysfunction is a major health problem worldwide. Stem cells therapy has opened up new avenues for researches to treat liver diseases due to their multi lineage differentiation. As mesenchymal stem cells (MSCs) can be differentiated into hepatic lineages in the presence of different exogenous factors, the current study aimed to investigate the impact of carbon tetrachloride (CCl₄) induced liver injured mice serum on MSCs differentiation toward hepatocytes in vitro. Male Balb/c mice were treated for liver injury with CCl₄ as determined through biochemical tests spectrophotometrically and different growth factors (EGF, HGF) quantification through Sandwich ELISA in both normal and CCl₄-induced liver injured mice serum. Mice bone marrow derived-MSCs at second passage were treated with normal and CCl₄-induced liver injured mice serum. After 7 days, serum treated MSCs were investigated for hepatocytes like characteristics through RT-PCR. Serum biochemical tests (Bilirubin, ALT and ALP) and sandwich ELISA results of EGF and HGF showed marked increase in CCl₄ treated mice serum as compared to normal mice serum_. Periodic acid Schiff's staining and urea assay kit confirmed high level of glycogen storage and urea production in cells treated with CCl₄-induced liver injured mice serum. RT-PCR results of CCl₄-induced liver injured mice serum treated cells also showed expression of hepatic markers (Albumin, Cyto-8, Cyto-18, and Cyto-19). This study confirmed that CCl₄-induced liver injured serum treatment can differentiate MSCs into hepatocyte-like cells in vitro.

Construction of multicellular aggregate by E-cadherin coated microparticles enhancing the hepatic specific differentiation of mesenchymal stem cells

The differentiation of human mesenchymal stem cells (hMSCs) into hepatocyte-like cells in vitroprovides a promising candidate for cell therapy of liver diseases, and cell aggregates have been proposed to improve the efficiency of expansion and differentiation. Previously, we engineered multicellular aggregates incorporating human E-cadherin fusion protein (hE-cad-Fc)-coated poly(lactic-co-glycolic acid) (PLGA) microparticles (hE-cad-PLGAs), and a significant improvement was obtained in both cellular proliferation of and cytokine secretion by hMSCs. In this study, hepatic differentiation of hMSCs was induced by a biomimetic microenvironment consisting of these engineered aggregates and a cocktail of specific cytokines. The ratio of hE-cad-PLGAs to hMSCs in engineered hMSCs aggregates was optimized to 1:3 for hepatic differentiation. The expressions of hepatic-specific markers were significantly promoted, and cell polarity and activated drug metabolism enzymes were established in MSC/hE-cad-PLGA aggregates compared with MSC and MSC/PLGA aggregates. Moreover, the expressions of stemness and definitive endoderm markers confirmed effectively induced endoderm differentiation in MSC/hE-cad-PLGA aggregates, which was consistent with the pattern of embryonic development. After pre-differentiation for 1 week, the MSC/hE-cad-PLGA aggregates continuously progressed the hepatic phenotype expression in healthy rat peritoneum. Therefore, the biomimetic microenvironment constructed by hE-cad-PLGAs in engineered multicellular aggregates was able to promote the process of endoderm differentiation and the subsequent hepatic differentiation of hMSCs. It would be appropriate for applied research in hepatotoxic drug screening and cell-based treatment of liver diseases. By optimizing with other cytokine cocktail, the engineered multicellular aggregates can be applied to the construction of other endoderm-derived organs. STATEMENT OF SIGNIFICANCE: The differentiation of mesenchymal stem cells (MSCs) into hepatocyte-like cells in vitroprovides a promising for cell therapy for liver diseases, and cell aggregates have been proposed to improve the expansion and differentiation efficiency. Here, engineered multicellular aggregates were constructed by E-cadherin modified microparticles (hE-cad-PLGAs) construct a biomimetic microenvironment to promote the process of endoderm differentiation and the subsequent hepatic differentiation of hMSCs. Furthermore, after pre-differentiation for 1 week, the MSC/hE-cad-PLGA aggregates continuously progressed the hepatic phenotype expression in healthy rat peritoneum. Therefore, engineered multicellular aggregates with hE-cad-PLGAs would be appropriate for applied research in hepatotoxic drug screening and cell-based treatment of liver diseases, and provide a promising method in the construction of other endoderm-derived organs.

Serum from CCl4-induced acute rat injury model induces differentiation of ADSCs towards hepatic cells and reduces liver fibrosis

Cellular therapies hold promise to alleviate liver diseases. This study explored the potential of allogenic serum isolated from rat with acute CCl₄ injury to differentiate adipose derived stem cells (ADSCs) towards hepatic lineage. Acute liver injury was induced by CCl₄ which caused significant increase in serum levels of VEGF, SDF1α and EGF. ADSCs were preconditioned with 3% serum isolated from normal and acute liver injury models. ADSCs showed enhanced expression of hepatic markers (AFP, albumin, CK8 and CK19). These differentiated ADSCs were transplanted intra-hepatically in CCl₄-induced liver fibrosis model. After one month of transplantation, fibrosis and liver functions (alkaline phosphatase, ALAT and bilirubin) showed marked improvement in acute injury group. Elevated expression of hepatic (AFP, albumin, CK 18 and HNF4a) and pro survival markers (PCNA and VEGF) and improvement in liver architecture as deduced from results of alpha smooth muscle actin, Sirius red and Masson's trichome staining was observed.

Periodic acid‑Schiff staining method for function detection of liver cells is affected by 2% horse serum in induction medium

Developing a thorough understanding of experimental methods of hepatic differentiation in hepatic progenitor cells (HPCs) should expand the knowledge of hepatocyte induction in vitro and may help to develop cell transplantation therapies for the clinical usage of HPCs in liver diseases. A previous induction method effectively induced differentiation and metabolic abilities in HPCs. Periodic acid-Schiff (PAS) staining is used to identify glycogen synthesis and hepatocyte function; however, this method failed to detect induced hepatocytes. The present study aimed to investigate the possible factors affecting the previous confusing results of PAS staining. Removal of single induction factors, including dexamethasone, hepatic growth factor and fibroblast growth factor 4 from the induction media did not restore PAS staining, whereas replacement of 2% horse serum (HS) with 10% fetal bovine serum (FBS) significantly increased the number of PAS positive cells. Following 12 days of basal induction, replacing the induction medium with media containing 10% FBS for 12–72 h significantly improved PAS staining, but did not influence indocyanine green uptake. Furthermore, incubation in induction medium with 10% FBS following 12 days of normal induction did not affect the expression of hepatic markers and mature function of HPCs. Therefore, the present study suggested that 2% HS in the induction medium did not affect the hepatic function of induced cells, but did affect glycogen storage, whereas replacement of medium with 10% FBS in advance of PAS staining may restore the failure of PAS staining in low serum concentrations of induced hepatocytes.

Survivin inhibitor YM155 suppresses gastric cancer xenograft growth in mice without affecting normal tissues

Survivin overexpression is associated with poor prognosis of human gastric cancer, and is a target for gastric cancer therapy. YM155 is originally identified as a specific inhibitor of survivin. In this study, we investigated the antitumor effect of YM155 on human gastric cancer. Our results showed that YM155 treatment significantly inhibited cell proliferation, reduced colony formation and induced apoptosis of gastric cancer cells in a dose-dependent manner. Accordingly, YM155 treatment significantly decreased survivin expression without affecting XIAP expression and increased the cleavage of apoptosis-associated proteins caspase 3, 7, 8, 9. YM155 significantly inhibited sphere formation of gastric cancer cells, suppressed expansion and growth of the formed spheres (cancer stem cell-like cells, CSCs) and downregulated the protein levels of β-catenin, c-Myc, Cyclin D1 and CD44 in gastric cancer cells. YM155 infusion at 5 mg/kg/day for 7 days markedly inhibited growth of gastric cancer xenograft in a nude mouse model. Immunohistochemistry staining and Western Blot showed that YM155 treatment inhibited expression of survivin and CD44, induced apoptosis and reduced CD44⁺ CSCs in xenograft tumor tissues in vivo. No obvious pathological changes were observed in organs (e.g. heart, liver, lung and kidney) in YM155-treated mice. Our results demonstrated that YM155 inhibits cell proliferation, induces cell apoptosis, reduces cancer stem cell expansion, and inhibits xenograft tumor growth in gastric cancer cells. Our results elucidate a new mechanism by which YM155 inhibits gastric cancer growth by inhibition of CSCs. YM155 may be a promising agent for gastric cancer treatment.

Improvement of mesenchymal stem cell differentiation into the endoderm lineage by four step sequential method in biocompatible biomaterial

Introduction: The goal of the study described here, was to investigate the potential of umbilical cord derived mesenchymal stem cell (UC-MSCs) into hepatocyte like cells in a sequential 2D and 3D differentiation protocols as alternative therapy.

Methods: Mesenchymal stem cells (MSCs) were isolated from the umbilical cord (UC) and CD markers were analyzed by flow cytometry. For hepatic differentiation of UC-MSCs, cells were induced with a sequential 4-step protocol in 3D and 2D culture system. Urea concentration and albumin secretion into the culture medium was quantified by ELISA. Gene expression levels of AFP, ALB, and CK18 were determined by RT-PCR. Data were statistically analyzed by the SPSS software. The difference between the mean was considered significant when p < 0.05.

Results: Growth factor dependent morphological changes from elongated fibroblast-like cells to round epithelial cell morphology were observed in 2D culture. Cell proliferation analysis showed round-shaped morphology with clear cytoplasm and nucleus on the alginate scaffold in 3D culture. The mean valuses of albumin production and urea secretion were significantly higher in the 3D Culture system when compared with the 2D culture (p = 0.005 vs p = 0.001), respectively. Treatment of cells with TSA in the final step of differentiation induced an increased expression of CK18 and a decreased expression of αFP in both the 3D and 2D cultures (p = 0.026), but led to a decreased albumin gene expression, and an increased expression in the 2D culture (p = 0.001).

Conclusion: Findings of the present study indicated that sequential exposure of UC-MSCs with growth factors in 3D culture improves hepatic differentiation.

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.

In Vitro and In Vivo Hepatic Differentiation of Adult Somatic Stem Cells and Extraembryonic Stem Cells for Treating End Stage Liver Diseases

The shortage of liver donors is a major handicap that prevents most patients from receiving liver transplantation and places them on a waiting list for donated liver tissue. Then, primary hepatocyte transplantation and bioartificial livers have emerged as two alternative treatments for these often fatal diseases. However, another problem has emerged. Functional hepatocytes for liver regeneration are in short supply, and they will dedifferentiate immediately in vitro after they are isolated from liver tissue. Alternative stem-cell-based therapeutic strategies, including hepatic stem cells (HSCs), embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), and mesenchymal stem cells (MSCs), are more promising, and more attention has been devoted to these approaches because of the high potency and proliferation ability of the cells. This review will focus on the general characteristics and the progress in hepatic differentiation of adult somatic stem cells and extraembryonic stem cells in vitro and in vivo for the treatment of end stage liver diseases. The hepatic differentiation of stem cells would offer an ideal and promising source for cell therapy and tissue engineering for treating liver diseases.

Cord blood for brain injury

Recovery from neurological injuries is typically incomplete and often results in significant and permanent disabilities. Currently, most available therapies are limited to supportive or palliative measures, aimed at managing the symptoms of the condition. Because restorative therapies targeting the underlying cause of most neurological diseases do not exist, cell therapies targeting anti-inflammatory, neuroprotective and regenerative potential hold great promise. Cord blood (CB) cells can induce repair through mechanisms that involve trophic or cell-based paracrine effects or cellular integration and differentiation. Both may be operative in emerging CB therapies for neurologic conditions, and there are numerous potential applications of CB-based regenerative therapies in neurological diseases, including genetic diseases of childhood, ischemic events such as stroke and neurodegenerative diseases of adulthood. CB appears to hold promise as an effective therapy for patients with brain injuries. In this Review, we describe the state of science and clinical applications of CB therapy for brain injury.

Extracellular regulated protein kinases 1/2 phosphorylation is required for hepatic differentiation of human umbilical cord-derived mesenchymal stem cells

Mesenchymal stem cells (MSCs) have the capacity to restore liver function by differentiating into hepatocyte like cells. However, the underlying mechanisms are not well understood. Here, we have investigated the signals involved in the hepatic differentiation of human umbilical cord-derived mesenchymal stem cells (hUCMSCs). hUCMSCs were treated with mouse fetal liver-conditioned medium (FLCM) to induce hepatic differentiation. Flow cytometry, reverse transcription PCR, real-time PCR, immunocytochemistry, and polymerase chain reaction (PCR) array were used to detect the expression of MSC- and hepotocyte-specific markers in FLCM-treated hUCMSCs. Urea production and cytochrome P450 3A4 (CYP3A4) activity were used as indicators to evaluate liver cell characteristics. Raf/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) was analyzed in hUCMSCs by Western blotting. Following FLCM treatment, expression of MSC-specific markers decreased, while hepatocyte-specific gene expression was increased. Urea production, albumin secretion, glycogen storage, and CYP3A4 activity were significantly enhanced in FLCM-treated cells. In addition, ERK1/2 phosphorylation was increased in a time-dependent manner through Raf/MEK/ERK pathway, and phosphorylation was sustained at a high level during hepatic induction. Inhibition of ERK1/2 activation by U0126 (an ERK1/2 inhibitor) and pFLAG-CMV-ERK1(K71R) (negative mutant of ERK1) reversed the expression of liver-specific genes in hUCMSCs and affected hepatic function significantly. In summary, this work shows that ERK1/2 phosphorylation plays an important role in inducing hepatic differentiation of hUCMSCs in FLCM.

Differentiation-Promoting Medium Additives for Hepatocyte Cultivation and Cryopreservation

Isolated primary hepatocytes are considered as the reference system for in vitro hepatic methods. Following the isolation of primary hepatocytes from liver tissue, an unfavorable process named dedifferentiation is initiated leading to the attenuation of the hepatocellular phenotype both at the morphological and functional level. Freshly isolated hepatocytes can be used immediately or can be cryopreserved for future purposes. Currently, a number of antidedifferentiation strategies exist to extend the life span of isolated hepatocytes. The addition of differentiation-promoting compounds to the hepatocyte culture medium is the oldest and simplest antidedifferentiation approach applied. In the present chapter, the most commonly used medium additives for cultivation and cryopreservation of primary hepatocytes are reviewed.

MicroRNAs miR-26a, miR-26b, and miR-29b accelerate osteogenic differentiation of unrestricted somatic stem cells from human cord blood

BACKGROUND

MicroRNAs are a population of short non-coding RNAs with widespread negative regulatory impact on mRNA translation. Unrestricted somatic stem cells (USSC) are a rare population in human cord blood that can be induced into cells representative of all three germinal layers. Here we analyzed the functional impact of miRNAs on the osteogenic differentiation in USSC.

RESULTS

Gene expression profiling identified 20 microRNAs that were consistently upregulated during osteogenic differentiation of two different USSC cell lines (SA5/73 and SA8/25). Bioinformatic target gene prediction indicated that among these microRNAs, miR-10a, -22, -26a, -26b, and -29b recognize transcripts that encode a set of proteins inhibiting osteogenesis. We subsequently verified osteo-inhibitory CDK6, CTNNBIP1, HDAC4, and TOB1 and osteo-promoting SMAD1 as targets of these microRNAs. In Western blot analyses demonstrated that endogenous levels of CDK6 and HDAC4 were downregulated during osteogenic differentiation of USSC and reduced following ectopic expression of miR-26a/b and miR-29b. In contrast, endogenous expression of SMAD1, targeted by miR-26a/b, was unaltered during osteogenic differentiation of USSC or following ectopic expression of miR-26a/b. Functional overexpression analyses using microRNA mimics revealed that miR-26a/b, as well as miR-29b strongly accelerated osteogenic differentiation of USSC as assessed by Alizarin-Red staining and calcium-release assays.

CONCLUSIONS

miR-26a/b and miR-29b are upregulated during osteogenic differentiation of USSC and share target genes inhibiting osteogenesis. Furthermore, these microRNAs accelerate osteogenic differentiation, likely mediated by osteo-inhibitory proteins such as CDK6 and HDAC4.

High expression of cancer stem cell markers in cholangiolocellular carcinoma

PURPOSE

Cholangiolocellular carcinoma (CLC) is an extremely rare malignant liver tumor. It is thought to originate from the ductules and/or canals of Hering, where hepatic stem cells (HpSC) are located, but there are few reports on cancer stem cell markers in CLC. Thus, we evaluated the significance of cancer stem cell markers, including CD133, CD44, and EpCAM, in CLC.

METHODS

The subjects of this study were three patients with CLC and one patient with an intermediate type of combined hepatocellular cholangiocarcinoma (CHC). The cancer cell markers, CK7, CK19, and EMA, were evaluated immunohistochemically.

RESULTS

Histological examination of the CLC revealed morphologically cholangiolar features and immunohistochemical examination revealed positivity for CD133, CD44, and EpCAM. On the other hand, in the intermediate type of CHC, only CD44 was positive, whereas CD133 and EpCAM were negative.

CONCLUSION

CLC may have stronger features derived from HpSCs than an intermediate type of CHC.

Potential application of cord blood-derived stromal cells in cellular therapy and regenerative medicine

Neonatal stromal cells from umbilical cord blood (CB) are promising alternatives to bone marrow- (BM-) derived multipotent stromal cells (MSCs). In comparison to BM-MSC, the less mature CB-derived stromal cells have been described as a cell population with higher differentiation and proliferation potential that might be of potential interest for clinical application in regenerative medicine. Recently, it has become clear that cord blood contains different stromal cell populations, and as of today, a clear distinction between unrestricted somatic stromal cells (USSCs) and CB-MSC has been established. This classification is based on the expression of DLK-1, HOX, and CD146, as well as functional examination of the adipogenic differentiation potential and the capacity to support haematopoiesis in vitro and in vivo. However, a marker enabling a prospective isolation of the rare cell populations directly out of cord blood is yet to be found. Further analysis may help to reveal even more subpopulations with different properties, which could be useful for the directed application of these cells in preclinical models.

Concise review: culture mediated changes in fate and/or potency of stem cells

Although Gurdon demonstrated already in 1958 that the nucleus of intestinal epithelial cells could be reprogrammed to give rise to adult frogs, the field of cellular reprogramming has only recently come of age with the description by Takahashi and Yamanaka in 2006, which defined transcription factors can reprogram fibroblasts to an embryonic stem cell-like fate. With the mounting interest in the use of human pluripotent stem cells and culture-expanded somatic stem/progenitor cells, such as mesenchymal stem cells, increasing attention has been given to the effect of changes in the in vitro microenvironment on the fate of stem cells. These studies have demonstrated that changes in culture conditions may change the potency of pluripotent stem cells or reprogram adult stem/progenitor cells to endow them with a broader differentiation potential. The mechanisms underlying these fate and potency changes by ex vivo culture should be further investigated and considered when designing clinical therapies with stem/progenitor cells.

Stimulation of Activin A/Nodal signaling is insufficient to induce definitive endoderm formation of cord blood-derived unrestricted somatic stem cells

Introduction

Unrestricted somatic stem cells (USSC) derived from umbilical cord blood are an attractive alternative to human embryonic stem cells (hESC) for cellular therapy. USSC are capable of forming cells representative of all three germ line layers. The aim of this study was to determine the potential of USSC to form definitive endoderm following induction with Activin A, a protein known to specify definitive endoderm formation of hESC.

Methods

USSC were cultured for (1) three days with or without 100 ng/ml Activin A in either serum-free, low-serum or serum-containing media, (2) three days with or without 100 ng/ml Activin A in combination with 10 ng/ml FGF4 in pre-induction medium, or (3) four days with or without small molecules Induce Definitive Endoderm (IDE1, 100 nM; IDE2, 200 nM) in serum-free media. Formation of definitive endoderm was assessed using RT-PCR for gene markers of endoderm (Sox17, FOXA2 and TTF1) and lung epithelium (surfactant protein C; SPC) and cystic fibrosis transmembrane conductance regulator; CFTR). The differentiation capacity of Activin A treated USSC was also assessed.

Results

Activin A or IDE1/2 induced formation of Sox17+ definitive endoderm from hESC but not from USSC. Activin A treated USSC retained their capacity to form cells of the ectoderm (nerve), mesoderm (bone) and endoderm (lung). Activin A in combination with FGF4 did not induce formation of Sox17+ definitive endoderm from USSC. USSC express both Activin A receptor subunits at the mRNA and protein level, indicating that these cells are capable of binding Activin A.

Conclusions

Stimulation of the Nodal signaling pathway with Activin A or IDE1/2 is insufficient to induce definitive endoderm formation from USSC, indicating that USSC differ in their stem cell potential from hESC.