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For the production and bio-banking of differentiated derivatives from human pluripotent stem cells (hPSCs) in large quantities for drug screening and cellular therapies, well-defined and robust procedures for differentiation and cryopreservation are required. Definitive endoderm (DE) gives rise to respiratory and digestive epithelium, as well as thyroid, thymus, liver, and pancreas. Here, we present a scalable, universal process for the generation of DE from human-induced pluripotent stem cells (hiPSCs) and embryonic stem cells (hESCs). Optimal control during the differentiation process was attained in chemically-defined and xeno-free suspension culture, and high flexibility of the workflow was achieved by the introduction of an efficient cryopreservation step at the end of DE differentiation. DE aggregates were capable of differentiating into hepatic-like, pancreatic, intestinal, and lung progenitor cells. Scale-up of the differentiation process using stirred-tank bioreactors enabled production of large quantities of DE aggregates. This process provides a useful advance for versatile applications of DE lineages, in particular for cell therapies and drug screening., Competing Interests: The authors declare no conflict of interest.

The quest for physiologically active human hepatocyte-like cells for in vitro research and drug screening is high. The recent progress in the field of pluripotent stem cell (PSC)-derived hepatic cells within the last decade brings those cells closer to applications in translational medicine. However, the classical two-dimensional (2D) cell culture systems are of limited use, because relevant cell-cell interactions based on cell polarity, which is a major prerequisite for proper hepatic cell metabolisms, are not provided. In this study, we report a scalable 3D suspension culture system, in which PSC-derived hepatic cells can be maintained for up to 3 weeks with stable gene expression profiles and metabolic features in a suspension culture system ranging from a 1.5 mL up to a 15 mL. Adjustments of culture conditions and, most importantly, the size of the organoids resulted in the robust generation of hepatic organoids consisting of a quite homogenous cell population. Importantly, the generation of these hepatic organoids was highly reproducible and allowed, in contrast to hepatic PSC derivatives in 2D culture conditions, a sensitive assessment of acetaminophen-related toxicity, the most common source for drug-induced liver failure.

Based on their almost unlimited self-renewal capacity and their ability to differentiate into derivatives of all three germ layers, human induced pluripotent stem cells (hiPSCs) might serve as a preferable source for hepatic transplants in metabolic liver disorders or acute liver failure. Furthermore, the generation of patient specific hiPSCs might facilitate the development of innovative therapeutic strategies by accurately modelling disease in vitro. In our study, we aimed for an efficient hepatic differentiation protocol that is applicable for both human embryonic stem cells (hESCs) and hiPSCs. We attempted to accomplish this goal by using a cytokine and small molecule-based protocol for direct differentiation of hESCs and hiPSCs into hepatic cells. Selecting differentiated hepatic cells was possible using an albumin promoter-driven G418 resistance system. Due to IRES-dependent dTomato reporter expression, we were able to track hepatic differentiated cells and we evaluated the most efficient time frame for G418 selection. The status of hepatic differentiation was determined by qRT-PCR comparing the expression of hepatic markers such as AFP, ALB, SOX17, and HNF4 to standard hepatic cells. Functional analysis of the hepatic phenotype was obtained by measuring secreted albumin levels and by analysis of cytochrome P450 type 1A1 activity (EROD). The percentage of differentiated cells was quantified by FACS analysis. In conclusion, our improved protocol demonstrates that both pluripotent cell sources (hESC and hiPSC) can efficiently be differentiated into mature hepatic cells with functional characteristics similar to those of standard hepatic cell lines such as HepG2.

Alveolar epithelial type II (ATII)-like cells can be generated from murine embryonic stem cells (ESCs), although to date, no robust protocols applying specific differentiation factors are established. We hypothesized that the keratinocyte growth factor (KGF), an important mediator of lung organogenesis and primary ATII cell maturation and proliferation, together with dexamethasone, 8-bromoadenosine-cAMP, and isobutylmethylxanthine (DCI), which induce maturation of primary fetal ATII cells, also support the alveolar differentiation of murine ESCs. Here we demonstrate that the above stimuli synergistically potentiate the alveolar differentiation of ESCs as indicated by increased expression of the surfactant proteins (SP-) C and SP-B. This effect is most profound if KGF is supplied not only in the late stage, but at least also during the intermediate stage of differentiation. Our results indicate that KGF most likely does not enhance the generation of (mes)endodermal or NK2 homeobox 1 (Nkx2.1) expressing progenitor cells but rather, supported by DCI, accelerates further differentiation/maturation of respiratory progeny in the intermediate phase and maturation/proliferation of emerging ATII cells in the late stage of differentiation. Ultrastructural analyses confirmed the presence of ATII-like cells with intracellular composite and lamellar bodies. Finally, induced pluripotent stem cells (iPSCs) were generated from transgenic mice with ATII cell-specific lacZ reporter expression. Again, KGF and DCI synergistically increased SP-C and SP-B expression in iPSC cultures, and lacZ expressing ATII-like cells developed. In conclusion, ATII cell-specific reporter expression enabled the first reliable proof for the generation of murine iPSC-derived ATII cells. In addition, we have shown KGF and DCI to synergistically support the generation of ATII-like cells from ESCs and iPSCs. Combined application of these factors will facilitate more efficient generation of stem cell-derived ATII cells for future basic research and potential therapeutic application.

Heterogeneity among induced pluripotent stem cell (iPSC) lines with regard to their gene expression profile and differentiation potential has been described and at least partly linked to the tissue of origin. Here, we generated iPSCs from primitive [lineage negative (Lin(neg))] and nonadherent differentiated [lineage positive (Lin(pos))] bone marrow cells (BM-iPSC), and compared their differentiation potential to that of fibroblast-derived iPSCs (Fib-iPSC) and embryonic stem cells (ESC). In the undifferentiated state, individual iPSC clones but also ESCs proved remarkably similar when analyzed for alkaline phosphatase and SSEA-1 staining, endogenous expression of the pluripotency genes Nanog, Oct4, and Sox2, or global gene expression profiles. However, substantial differences between iPSC clones were observed after induction of differentiation, which became most obvious upon cytokine-mediated instruction toward the hematopoietic lineage. All 3 BM-iPSC lines derived from undifferentiated Lin(neg) cells yielded high proportions of cells expressing the hematopoietic differentiation marker CD41 and in 2 of these lines high proportions of CD41+/ CD45+ cells were detected. In contrast, little hematopoiesis-specific surface marker expression was detected in 4 Lin(pos) BM-iPSC and 3 Fib-iPSC lines. These results were corroborated by functional studies demonstrating robust colony outgrowth from hematopoietic progenitors in 2 of the Lin(neg) BM-iPSCs only. Thus, in conclusion, our data demonstrate efficient generation of iPSCs from primitive hematopoietic tissue as well as efficient hematopoietic redifferentiation for Lin(neg) BM-iPSC lines, thereby supporting the notion of an epigenetic memory in iPSCs.

In regenerative medicine pluripotent stem cells are considered to be a valuable self-renewing source for therapeutic cell transplantations, given that a functional organ-specific phenotype can be acquired by in vitro differentiation protocols. Furthermore, derivatives of pluripotent stem cells that mimic fetal progenitor stages could serve as an important tool to analyze organ development with in vitro approaches. Because of ethical issues regarding the generation of human embryonic stem (ES) cells, other sources for pluripotent stem cells are intensively studied. Like in less developed vertebrates, pluripotent stem cells can be generated from the female germline even in mammals, via parthenogenetic activation of oocytes. Recently, testis-derived pluripotent stem cells were derived from the male germline. Therefore, we compared two different hepatic differentiation approaches and analyzed the generation of definitive endoderm progenitor cells and their further maturation into a hepatic phenotype using murine parthenogenetic ES cells, germline-derived pluripotent stem cells, and ES cells. Applying quantitative RT-PCR, both germline-derived pluripotent cell lines show similar differentiation capabilities as normal murine ES cells and can be considered an alternative source for pluripotent stem cells in regenerative medicine.

Unlabelled: We characterized the functional properties of mesenchymal stem cells from various human tissues for their potential to differentiate into hepatocyte-like cells in vitro., Methods: Mesenchymal stem cells were isolated from human bone marrow (hBM-MSC) and peritoneal and subcutaneous adipose tissues (hpAT-MSC and hsAT-MSC) based on their capacity to adhere to plastic culture surfaces. Cells were analyzed by reverse transcriptase polymerase chain reaction and for urea as well as glycogen synthesis. Their potential for multiple differentiation pathways was investigated by incubation in culture media triggering osteogenic, adipogenic, or hepatogenic features. Global gene expression patterns were analyzed in hepatocyte differentiated hBM-MSC compared with undifferentiated MSC and adult and fetal human liver., Results: Applying osteogenic or adipogenic differentiation conditions, the cells from each tissue under investigation differentiated appropriately. Treatment of the cells with hepatogenic medium induced mRNA transcripts typical for hepatocytes, as well as the onset of urea synthesis and glycogen storage. Analysis of global gene expression patterns revealed that hepatocytes differentiated from hBM-MSC were clearly distinct from undifferentiated MSC. These cells had acquired features of adult as well as fetal human hepatocytes., Conclusion: In vitro, MSC from human bone marrow and adipose tissue differentiated to hepatocyte-like cells closely related to adult elements on the molecular and functional levels.

Mesenchymal tissues harbour stromal cells capable of multilineage differentiation. Here, we demonstrate the isolation of mesenchymal stem cells (MSC) from rat peritoneal adipose tissue capable of osteogenic and adipogenic differentiation. Under in vitro conditions favouring hepatocyte differentiation, these MSC gained characteristic functions of hepatocytes such as the capacity to synthesize urea or store glycogen. Hepatocyte-specific transcripts of dipeptidylpeptidase type IV (CD26), albumin, cytochrome P450 type 1A1 (CYP1A1) and connexin CX32 (CX32) were detected only in differentiated but not undifferentiated cells. Transient transgenic expression of luciferase could be stimulated by cAMP when driven by the hepatocyte-specific promoter of the cytosolic phosphoenolpyruvate carboxykinase (PCK1) gene. Finally, stem cell-derived hepatocytes from wild type (CD26+/+) rats were transplanted into the livers of CD26-deficient animals after lentiviral transduction with the GFP gene under the control of the ubiquitin promoter. GFP-positive cells engrafted in the host liver predominantly in the periportal region of the liver lobule. They continued to express CD26, a prominent feature of differentiated hepatocytes, indicating their topologically and functionally proper integration into the host liver parenchyma. Thus, MSCs from rat peritoneal adipose tissue exhibit the potential to differentiate into hepatocyte-like cells in vitro and in vivo.