Promoted differentiation of cynomolgus monkey ES cells into hepatocyte-like cells by co-culture with mouse fetal liver-derived cells

Successful Derivation of Hepatoblasts, Cholangiocytes and Hepatocytes from Simian Induced Pluripotent Stem Cells

The use of primary cells in human liver therapy is limited by a lack of cells. Induced pluripotent stem cells (iPSCs) represent an alternative to primary cells as they are infinitely expandable and can be differentiated into different liver cell types. The aim of our work was to demonstrate that simian iPSCs (siPSCs) could be used as a new source of liver cells to be used as a large animal model for preclinical studies. We first differentiated siPSCs into a homogenous population of hepatoblasts (siHBs). We then separately differentiated them into hepatocytes (siHeps) and cholangiocytes (siChols) expressing respective specific markers and displaying epithelial polarity. Moreover, we showed that polarized siChols can self-organize into 3D structures. These results should facilitate the deciphering of liver development and open the way to exploring co-culture systems that could be assessed during preclinical studies, including in autologous monkey donors, for regenerative medicine purposes.

Hepatic Differentiation of Marmoset Embryonic Stem Cells and Functional Characterization of ESC-Derived Hepatocyte-Like Cells

Background

Primary human hepatocytes (PHHs) are the ideal candidates for studying critical liver functions such as drug metabolism and toxicity. However, as they are isolated from discarded livers that are unsuitable for transplantation, they possess limited expansion ability in vitro and their enzymatic functions deteriorate rapidly because they are often of poor quality. Therefore, there is a compelling reason to find reliable alternative sources of hepatocytes.

Methods

In this study, we report on efficient and robust differentiation of embryonic stem cells (ESC) from the common marmoset Callithrix jacchus into functional hepatocyte-like cells (HLC) using a simple, and reproducible three-step procedure. ESC-derived HLCs were examined by morphological analysis and tested for their expression of hepatocyte-specific markers using a combination of immunohistochemistry, RT-PCR, and biochemical assays. Primary human hepatocytes were used as controls.

Results

ESC-derived HLCs expressed each of the hepatocyte-specific markers tested, including albumin; α-fetoprotein; asialoglycoprotein receptor 1; α-1 antitrypsin; hepatocyte nuclear factors 1α and 4; cytokeratin 18; hepatocyte growth factor receptor; transferrin; tyrosine aminotransferase; alkaline phosphatase; c-reactive protein; cytochrome P450 enzymes CYP1A2, CYP2E1 and CYP3A4; and coagulation factors FVII and FIX. They were functionally competent as demonstrated by biochemical assays in addition to producing urea.

Conclusion

Our data strongly suggest that marmoset HLCs possess characteristics similar to those of PHHs. They could, therefore, be invaluable for studies on drug metabolism and cell transplantation therapy for a variety of liver disorders. Because of the similarities in the anatomical and physiological features of the common marmoset to that of humans, Callithrix jacchus is an appropriate animal model to study human disease conditions and cellular functions.

Leveraging Population Genomics for Individualized Correction of the Hallmarks of Alpha-1 Antitrypsin Deficiency

Deep medicine is rapidly moving towards a high-definition approach for therapeutic management of the patient as an individual given the rapid progress of genome sequencing technologies and machine learning algorithms. While considered a monogenic disease, alpha-1 antitrypsin (AAT) deficiency (AATD) patients present with complex and variable phenotypes we refer to as the "hallmarks of AATD" that involve distinct molecular mechanisms in the liver, plasma and lung tissues, likely due to both coding and non-coding variation as well as genetic and environmental modifiers in different individuals. Herein, we briefly review the current therapeutic strategies for the management of AATD. To embrace genetic diversity in the management of AATD, we provide an overview of the disease phenotypes of AATD patients harboring different AAT variants. Linking genotypic diversity to phenotypic diversity illustrates the potential for sequence-specific regions of AAT protein fold design to play very different roles during nascent synthesis in the liver and/or function in post-liver plasma and lung environments. We illustrate how to manage diversity with recently developed machine learning (ML) approaches that bridge sequence-to-function-to-structure knowledge gaps based on the principle of spatial covariance (SCV). SCV relationships provide a deep understanding of the genotype to phenotype transformation initiated by AAT variation in the population to address the role of genetic and environmental modifiers in the individual. Embracing the complexity of AATD in the population is critical for risk management and therapeutic intervention to generate a high definition medicine approach for the patient.

A microfluidic renal proximal tubule with active reabsorptive function

In the kidney, the renal proximal tubule (PT) reabsorbs solutes into the peritubular capillaries through active transport. Here, we replicate this reabsorptive function in vitro by engineering a microfluidic PT. The microfluidic PT architecture comprises a porous membrane with user-defined submicron surface topography separating two microchannels representing a PT filtrate lumen and a peritubular capillary lumen. Human PT epithelial cells and microvascular endothelial cells in respective microchannels created a PT-like reabsorptive barrier. Co-culturing epithelial and endothelial cells in the microfluidic architecture enhanced viability, metabolic activity, and compactness of the epithelial layer. The resulting tissue expressed tight junctions, kidney-specific morphology, and polarized expression of kidney markers. The microfluidic PT actively performed sodium-coupled glucose transport, which could be modulated by administration of a sodium-transport inhibiting drug. The microfluidic PT reproduces human physiology at the cellular and tissue levels, and measurable tissue function which can quantify kidney pharmaceutical efficacy and toxicity.

Alpha-1-antitrypsin deficiency: Genetic variations, clinical manifestations and therapeutic interventions

Alpha-1-antitrypsin (AAT) is an acute phase secretory glycoprotein that inhibits neutrophil proteases like elastase and is considered as the archetype of a family of structurally related serine-protease inhibitors termed serpins. Serum AAT predominantly originates from liver and increases three to five fold during host response to tissue injury and inflammation. The AAT deficiency is unique among the protein-misfolding diseases in that it causes target organ injury by both loss-of-function and gain-of-toxic function mechanisms. Lack of its antiprotease activity is associated with premature development of pulmonary emphysema and loss-of-function due to accumulation of resultant aggregates in chronic obstructive pulmonary disease (COPD). This' in turn' markedly reduces the amount of AAT that is available to protect lungs against proteolytic attack by the enzyme neutrophil elastase. The coalescence of AAT deficiency, its reduced efficacy, and cigarette smoking or poor ventilation conditions have devastating effect on lung function. On the other hand, the accumulation of retained mutant proteins in the endoplasmic reticulum of hepatocytes in a polymerized form rather than secreted into the blood in its monomeric form is associated with chronic liver disease and predisposition to hepatocellular carcinoma (HCC) by gain- of- toxic function. Liver injury resulting from this gain-of-toxic function mechanism in which mutant AAT retained in the ER initiates a series of pathologic events, eventually culminating at liver cirrhosis and HCC. Here in this review, we underline the structural, genetic, polymorphic, biochemical and pathological advances made in the field of AAT deficiency and further comprehensively emphasize on the therapeutic interventions available for the patient.

Direct conversion of adipocyte progenitors into functional neurons

Ectopic expression of a set of transcription factors in somatic cells could reprogram the differentiated cell fate into the pluripotent state, and the resultant so-called induced pluripotent stem cells (iPSCs) have been proposed as seed cells for cell therapy-based regenerative medicine. However, their tumorigenicity limited the further application of iPSCs clinically. More recently, collected evidence has shown that differentiated somatic cells could be directly converted into other types of somatic cells through overexpression of transcription factors enriched in the targeted cell types. Induced neurons have been recently converted from fibroblasts; however, it remains unknown if other cell types could be used for neuron induction. One easily accessible cell type, adipocyte progenitor cells (APCs), has the advantage of steady proliferation in vitro and lower mortality rate. In the present study, we demonstrated that APCs could also be converted into functional neurons using the three transcriptional factors (Ascl1, Brn2, Myt1l) that could convert fibroblasts into neurons. Moreover, we also demonstrated that vitamin C could elevate the efficiency of conversion of the APCs and fibroblasts into neurons. The converted cells represent another appropriate cell resource for clinical application and disease modeling.

Efficient differentiation of embryonic stem cells into hepatic cells in vitro using a feeder-free basement membrane substratum

The endoderm-inducing effect of the mesoderm-derived supportive cell line M15 on embryonic stem (ES) cells is partly mediated through the extracellular matrix, of which laminin α5 is a crucial component. Mouse ES or induced pluripotent stem cells cultured on a synthesized basement membrane (sBM) substratum, using an HEK293 cell line (rLN10-293 cell) stably expressing laminin-511, could differentiate into definitive endoderm and subsequently into pancreatic lineages. In this study, we investigated the differentiation on sBM of mouse and human ES cells into hepatic lineages. The results indicated that the BM components played an important role in supporting the regional-specific differentiation of ES cells into hepatic endoderm. We show here that knockdown of integrin β1 (Itgb1) in ES cells reduced their differentiation into hepatic lineages and that this is mediated through Akt signaling activation. Moreover, under optimal conditions, human ES cells differentiated to express mature hepatocyte markers and secreted high levels of albumin. This novel procedure for inducing hepatic differentiation will be useful for elucidating the molecular mechanisms controlling lineage-specific fates during gut regionalization. It could also represent an attractive approach to providing a surrogate cell source, not only for regenerative medicine, but also for pharmaceutical and toxicologic studies.

Directed hepatic differentiation from embryonic stem cells

The liver is the largest internal organ in mammals, and is important for the maintenance of normal physiological functions of other tissues and organs. Hepatitis, cirrhosis, liver cancer and other chronic liver diseases are serious threats to human health, and these problems are compounded by a scarcity of liver donors for transplantation therapies. Directed differentiation of embryonic stem cells to liver cells is a promising strategy for obtaining hepatocytes that can be used for cell transplantation. In vitro hepatocyte differentiation of embryonic stem cells requires a profound understanding of normal development during embryonic hepatogenesis. Here we provide a simple description of hepatogenesis in vivo and discuss directed differentiation of embryonic stem cells into hepatocytes in vitro.

Cytochrome P450 mRNA expressions along with in vitro differentiation of hepatocyte precursor cells from fetal, young and old rats

Non-differentiated cells are attractive targets for cell therapy. During liver regeneration oval cells intensively proliferate and differentiate extending their metabolic activity. Hepatic cytochromes P450 (CYPs) can be linked either with metabolic activation of toxic compounds or drug metabolism. We investigated the differentiation and biotransformative potential of non-differentiated cells in primary cell cultures isolated from livers of fetuses (16-days-old), young (4-months-old) and old (20-months-old) rats. Under the conditions of experimental hepatocarcinogenesis, adult rats were fed for three weeks with CDE diet. Liver cells were cultured and precursor cells were differentiated to hepatocytes following induction with sodium butyrate (SB) or dimethyl sulphoxide (DMSO) in culture on MesenCult medium. We identified a number of cells expressing Thy-1, CD34, alpha-fetoprotein, cytokeratines--CK18 or CK19 and glutathione transferases--GSTpi or GSTalpha. In vitro differentiation of these cells, isolated from CDE-treated rats begun earlier as compared to non-treated ones. Age-dependent changes in the cell differentiation sequence, as well as CYPmRNA expression sequence accompanying precursor cells differentiation, were also observed. mRNA expression of CYP1A2, CYP2B1/2 and CYP3A1 was higher in the cells of young rats, but in the case of CYP2E1--in the cells of old rats. It was concluded that both proliferation and differentiation potential of oval cells, decreased with age.

Factors from human embryonic stem cell-derived fibroblast-like cells promote topology-dependent hepatic differentiation in primate embryonic and induced pluripotent stem cells

The future clinical use of embryonic stem cell (ESC)-based hepatocyte replacement therapy depends on the development of an efficient procedure for differentiation of hepatocytes from ESCs. Here we report that a high density of human ESC-derived fibroblast-like cells (hESdFs) supported the efficient generation of hepatocyte-like cells with functional and mature hepatic phenotypes from primate ESCs and human induced pluripotent stem cells. Molecular and immunocytochemistry analyses revealed that hESdFs caused a rapid loss of pluripotency and induced a sequential endoderm-to-hepatocyte differentiation in the central area of ESC colonies. Knockdown experiments demonstrated that pluripotent stem cells were directed toward endodermal and hepatic lineages by FGF2 and activin A secreted from hESdFs. Furthermore, we found that the central region of ESC colonies was essential for the hepatic endoderm-specific differentiation, because its removal caused a complete disruption of endodermal differentiation. In conclusion, we describe a novel in vitro differentiation model and show that hESdF-secreted factors act in concert with regional features of ESC colonies to induce robust hepatic endoderm differentiation in primate pluripotent stem cells.

Liver tissue engineering: promises and prospects of new technology

Today, many patients suffer from acute liver failure and hepatoma. This is an area of high unmet clinical need as these conditions are associated with very high mortality. There is an urgent need to develop techniques that will enable liver tissue engineering or generate a bioartificial liver, which will maintain or improve liver function or offer the possibility of liver replacement. Liver tissue engineering is an innovative way of constructing an implantable liver and has the potential to alleviate the shortage of organ donors for orthotopic liver transplantation. In this review we describe, from an engineering perspective, progress in the field of liver tissue engineering, including three main aspects involving cell sources, scaffolds and vascularization.

Induced multilineage differentiation of chicken embryonic germ cells via embryoid body formation

Although the pluripotent and proliferative capacity of embryonic germ (EG) cells is thought to be equivalent to that of embryonic stem (ES) cells, there has been far less attention focused on the potential use of EG cells for applications in developing novel strategies of tissue transplantation in the treatment of degenerative diseases. In this study, EG cells were derived from primordial germ cells (PGCs) of genital ridges of 4-day-old chicken embryos. These cells satisfied the criteria previously used for defining chicken EG cells by using the expression of markers characteristic to ES cells. When injected subcutaneously, chicken EG cells could form teratomas that enable differentiation into a wide range of tissue types of all three primary cell lineages including neural cells, cartilage, forming bone, adipocytes, blood vessels, smooth muscle, and secretory epithelia in the recipients. Furthermore, cells in embryoid bodies (EBs) expressed lineage-specific markers of three germ layers and could be induced to differentiate into more advanced stages of various committed cell types, including dopamine and cholinergic neurons, astrocytes, oligodendrocytes, adipocytes, and hepatocytes, which were demonstrated by immunocytochemical staining or RT-PCR analysis. These findings support the multilineage differentiation capability of chicken pluripotent EG cells, thus confirming the presumption that chicken embryos may be used as a potential model for better understanding the mechanisms of tissue-specific differentiation and regeneration that will help to devise strategies based on the transplantation of stem cell-derived tissues for restoring function to damaged or diseased tissues.

Skeletal muscle-derived stem cells differentiate into hepatocyte-like cells and aid in liver regeneration

The liver is unique for its ability to regenerate after injury, however, critical injuries or disease cause it to lose this quality. Stem cells have been explored as a possibility to restore the function of seriously damaged livers, based on their self-renewability and multiple differentiation capacity. These experiments examine the ability of muscle derived stem cells (MDSCs) to differentiate into hepatocyte-like cells in vitro and acquire functional liver attributes for repairing damaged livers. In vitro experiments were performed using MDSCs from postnatal mice and mouse hepatocyte cell lines. Our data revealed that MDSCs differentiated into hepatocyte-like cells and expressed liver cell markers, albumin, hepatocyte nuclear factor 4 α, and alpha feto-protein, both at the RNA and protein level. Additionally, in vivo studies showed successful engraftment of MDSCs into hepatectomized mouse livers of mice. These results provide evidence suggesting that MDSCs have the capacity to differentiate into liver cell-like cells and may serve as potential candidates to aid in liver regeneration.

Hepatocyte differentiation

Increasingly, research suggests that for certain systems, animal models are insufficient for human toxicology testing. The development of robust, in vitro models of human toxicity is required to decrease our dependence on potentially misleading in vivo animal studies. A critical development in human toxicology testing is the use of human primary hepatocytes to model processes that occur in the intact liver. However, in order to serve as an appropriate model, primary hepatocytes must be maintained in such a way that they persist in their differentiated state. While many hepatocyte culture methods exist, the two-dimensional collagen "sandwich" system combined with a serum-free medium, supplemented with physiological glucocorticoid concentrations, appears to robustly maintain hepatocyte character. Studies in rat and human hepatocytes have shown that when cultured under these conditions, hepatocytes maintain many markers of differentiation including morphology, expression of plasma proteins, hepatic nuclear factors, phase I and II metabolic enzymes. Functionally, these culture conditions also preserve hepatic stress response pathways, such as the SAPK and MAPK pathways, as well as prototypical xenobiotic induction responses. This chapter will briefly review culture methodologies but will primarily focus on hallmark hepatocyte structural, expression and functional markers that characterize the differentiation status of the hepatocyte.

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.

The differentiation of hepatocyte-like cells from monkey embryonic stem cells

Embryonic stem cells (ESC) hold great potential for the treatment of liver diseases. Here, we report the differentiation of rhesus macaque ESC along a hepatocyte lineage. The undifferentiated monkey ESC line, ORMES-6, was cultured in an optimal culture condition in an effort to differentiate them into hepatocyte-like cells in vitro. The functional efficacy of the differentiated hepatic cells was evaluated using RT-PCR for the expression of hepatocyte specific genes, and Western blot analysis and immunocytochemistry for hepatic proteins such as alpha-fetoprotein (AFP), albumin and alpha1-antitrypsin (alpha1-AT). Functional assays were performed using the periodic acid schiff (PAS) reaction and ELISA. The final yield of ESC-derived hepatocyte-like cells was measured by flow cytometry for cells that were transduced with a liver-specific lentivirus vector containing the alpha1-AT promoter driving the expression of green fluorescence protein (GFP). The treatment of monkey ESC with an optimal culture condition yielded hepatocyte-like cells that expressed albumin, alpha1-AT, AFP, hepatocyte nuclear factor 3beta, glucose-6-phophatase, and cytochrome P450 genes and proteins as determined by RT-PCR and Western blot analysis. Immunofluorescent staining showed the cells positive for albumin, AFP, and alpha1-AT. PAS staining demonstrated that the differentiated cells showed hepatocyte functional activity. Albumin could be detected in the medium after 20 days of differentiation. Flow cytometry data showed that 6.5 +/- 1.0% of the total differentiated cells were positive for GFP. These results suggest that by using a specific, empirically determined, culture condition, we were able to direct monkey ESC toward a hepatocyte lineage.

Differentiation of mouse and human embryonic stem cells into hepatic lineages

We recently reported a novel method to induce embryonic stem (ES) cells differentiate into an endodermal fate, especially pancreatic, using a supporting cell line. Here we describe the modified culture condition with the addition and withdrawal of secreted growth factors could induce ES cells to selectively differentiate into a hepatic fate efficiently. The signaling of BMP and FGF that have been implicated in hepatic differentiation during normal embryonic development are shown to play pivotal roles in generating hepatic cells from the definitive endoderm derived from ES cells. Moreover, the expression of AFP, Albumin or a biliary molecular marker appeared sequentially thus suggested the differentiation of ES cells recapitulated normal developmental processes of liver. The ES cell-derived differentiated cells showed evidence of glycogen storage, secreted Albumin, exhibited drug metabolism activities and expressed a set of cytochrome or drug conjugate enzymes, drug transporters specifically expressed in mature hepatocytes. With the same procedure, human ES cells also gave rise to cells with mature hepatocytes' characteristics. In conclusion, this novel procedure for hepatic differentiation will be useful for elucidation of molecular mechanisms of hepatic fate decision at gut regionalization, and could represent an attractive approach for a surrogate cell source for pharmaceutical studies such as toxicology.

Derivation and cloning of a novel rhesus embryonic stem cell line stably expressing tau-green fluorescent protein

Embryonic stem cells (ESC) have the ability of indefinite self-renewal and multilineage differentiation, and they carry great potential in cell-based therapies. The rhesus macaque is the most relevant preclinical model for assessing the benefit, safety, and efficacy of ESC-based transplantations in the treatment of neurodegenerative diseases. In the case of neural cell grafting, tracing both the neurons and their axonal projections in vivo is essential for studying the integration of the grafted cells in the host brain. Tau-Green fluorescent protein (tau-GFP) is a powerful viable lineage tracer, allowing visualization of cell bodies, dendrites, and axons in exquisite detail. Here, we report the first rhesus monkey ESC line that ubiquitously and stably expresses tau-GFP. First, we derived a new line of rhesus monkey ESC (LYON-ES1) that show marker expression and cell cycle characteristics typical of primate ESCs. LYON-ES1 cells are pluripotent, giving rise to derivatives of the three germ layers in vitro and in vivo through teratoma formation. They retain all their undifferentiated characteristics and a normal karyotype after prolonged culture. Using lentiviral infection, we then generated a monkey ESC line stably expressing tau-GFP that retains all the characteristics of the parental wild-type line and is clonogenic. We show that neural precursors derived from the tau-GFP ESC line are multipotent and that their fate can be precisely mapped in vivo after grafting in the adult rat brain. Disclosure of potential conflicts of interest is found at the end of this article.

Alpha one antitrypsin deficiency: from gene to treatment

Alpha1-antitrypsin deficiency is a genetic disorder which contributes to the development of chronic obstructive pulmonary disease, bronchiectasis, liver cirrhosis and panniculitis. The discovery of alpha1-antitrypsin and its function as an antiprotease led to the protease-antiprotease hypothesis, which goes some way to explaining the pathogenesis of emphysema. This article will review the clinical features of alpha1-antitrypsin deficiency, the genetic mutations known to cause it, and how they do so at a molecular level. Specific treatments for the disorder based on this knowledge will be reviewed, including alpha1-antitrypsin replacement, gene therapy and possible future therapies, such as those based on stem cells.