Derivation and growing human embryonic stem cells on feeders derived from themselves

WNT Inhibition and Increased FGF Signaling Promotes Derivation of Less Heterogeneous Primed Human Embryonic Stem Cells, Compatible with Differentiation

Human embryonic stem cells (hESCs) hold great value for future clinical applications. However, standard culture conditions maintain hESCs in a primed state, which bears heterogeneity in pluripotency and a tendency for spontaneous differentiation. To counter these drawbacks, primed hESCs have been converted to a naive state, but this has restricted the efficiency of existing directed differentiation protocols. In mouse, WNT inhibition by inhibitor of WNT production-2, together with a higher dose of fibroblast growth factor 2 (12 ng/mL) in DMEM/F12 basal medium (DhiFI), markedly improved derivation and maintenance of primed mouse epiblast stem cells. In this study, we show that DhiFI conditions similarly improved primed hESC traits, such as conferring a primed transcriptional signature with high levels of pluripotency markers and reduced levels of differentiation markers. When triggered to differentiate to neuronal and cardiac lineages, DhiFI hESCs and isogenic primed hESCs progressed similarly. Moreover, DhiFI conditions supported the derivation of hESC lines from a post-inner cell mass intermediate (PICMI). DhiFI-derived hESCs showed less spontaneous differentiation and expressed significantly lower levels of lineage-specific markers, compared to primed-derived lines from the same PICMI. Overall, DhiFI hESCs retained advantages of both primed and naive pluripotency and may ultimately represent a more favorable starting point for differentiation toward clinically desired cell types.

High-efficiency derivation of human embryonic stem cell lines using a culture system with minimized trophoblast cell proliferation

Background

Due to their extensive self-renewal and multilineage differentiation capacity, human embryonic stem cells (hESCs) have great potential for studying developmental biology, disease modeling, and developing cell replacement therapy. The first hESC line was generated in 1998 by culturing inner cell mass (ICM) cells isolated from human blastocysts using an immunosurgery technique. Since then, many techniques including mechanical ICM isolation, laser dissection, and whole embryo culture have been used to derive hESC lines. However, the hESC derivation efficiency remains low, usually less than 50%, and it requires a large number of human embryos to derive a significant number of hESC lines. Due to a shortage of and restricted access to human embryos, a novel approach with better hESC derivation efficiency is badly needed to decrease the number of embryos used.

Methods

We hypothesized that the low hESC derivation efficiency might be due to extensive proliferation of trophoblast (TE) cells which could interfere with ICM proliferation. We therefore developed a methodology to minimize TE cell proliferation by culturing ICM in a feeder-free system for 3 days before transferring them onto feeder cells.

Results

This minimized trophoblast cell proliferation (MTP) technique could be successfully used to derive hESCs from normal, abnormal, and frozen–thawed embryos with better derivation efficiency of more than 50% (range 50–100%; median 70%).

Conclusions

We successfully developed a better hESC derivation methodology using the “MTP” culture system. This methodology can be effectively used to derive hESCs from both normal and abnormal embryos under feeder-free conditions with higher efficiency when compared with other methodologies. With this methodology, large-scale production of clinical-grade hESCs is feasible.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0866-5) contains supplementary material, which is available to authorized users.

Effect of a feeder layer composed of mouse embryonic and human foreskin fibroblasts on the proliferation of human embryonic stem cells

The aim of the present study was to investigate the effects of feeder layers composed of various ratios of mouse embryonic fibroblasts (MEFs) and human foreskin fibroblasts (hFFs) on the growth of human embryonic stem cells (hESCs). In addition, the secretion levels of basic fibroblast growth factor (bFGF) by the feeder layers was detected. MEFs and hFFs were treated with mitomycin C and seeded onto gelatin-coated plates at a density of 1×10⁸ cells/l. The hFFs and MEFs were combined and plated at the following ratios: 0:1, 1:2, 1:1, 2:1 and 1:0. The secretion of bFGF by the various hFF/MEF ratio feeder layers was detected using an enzyme-linked immunosorbent assay. Subsequently, hESCs were cultured on top of the various feeder layers. The differences in the cellular morphology of the hESCs were observed using microscopy, and the expression levels alkaline phosphatase (AKP) and octamer-binding transcription factor 4 (OCT-4) were detected using immunohistochemical analysis as indicators of differentiation status. The results showed that the hFFs secreted substantial quantities of bFGF, while no bFGF was secreted by the MEFs. The clones of hESC growing on the feeder layer containing MEF or hFF alone were flat. By contrast, hESC clones grown on a mixed feeder layer containing hFFs + MEFs at a ratio of 1:1 exhibited an accumulated growth with a clear edge, as compared with the other ratios. In addition, hESCs growing on the feeder layer were positive for the expression of AKP and OCT-4. In summary, feeder layer hFFs secreted bFGF, while MEFs did not, indicating that bFGF is not the only factor that supports the growth and differentiation of hESCs. The optimal growth of hESCs was achieved using a mixed feeder layer composed of hFFs + MEFs at a ratio of 1:1.

Stem cells: a promising source for vascular regenerative medicine

The rising and diversity of many human vascular diseases pose urgent needs for the development of novel therapeutics. Stem cell therapy represents a challenge in the medicine of the twenty-first century, an area where tissue engineering and regenerative medicine gather to provide promising treatments for a wide variety of diseases. Indeed, with their extensive regeneration potential and functional multilineage differentiation capacity, stem cells are now highlighted as promising cell sources for regenerative medicine. Their multilineage differentiation involves environmental factors such as biochemical, extracellular matrix coating, oxygen tension, and mechanical forces. In this review, we will focus on human stem cell sources and their applications in vascular regeneration. We will also discuss the different strategies used for their differentiation into both mature and functional smooth muscle and endothelial cells.

Human embryonic stem cells: derivation, maintenance and cryopreservation

Human embryonic stem cells (hESCs) are the most powerful candidate for the treatment of incurable diseases through the replacement of damaged cells and/or tissues in patients, although there are some obstacles to overcome for the clinical application of hESCs such as the assurance of guided differentiation and control of the immune response following cell therapy or tissue grafting. To obtain genetically stable hESCs and use them clinically, it is important to develop appropriate culture conditions. Additionally, the establishment of a hESC bank with a large number of hESC lines will be required for their clinical application because each hESC line is directed to have a different differentiation ability and immune characteristics such as HLA type. In this review, we describe the derivation and culture conditions of hESCs based on recent advances. Then, we will introduce several cryopreservation methods for hESCs, which is important for the development of cell bank.

Derivation of human embryonic stem cells (hESC)

Stem cells are characterized by their absolute or relative lack of specialization their ability for self-renewal, as well as their ability to generate differentiated progeny through cellular lineages with one or more branches. The increased availability of embryonic tissue and greatly improved derivation methods have led to a large increase in the number of hESC lines.

Derivation of human embryonic stem cell lines without any exogenous growth factors

Human embryonic stem cell (hESC) lines are traditionally derived through immunosurgery. Their maintenance in culture requires the presence of mouse embryonic fibroblasts (MEFs) as feeder cells and media supplemented with basic fibroblast growth factor (bFGF) or other growth factors-both of which might introduce animal-derived culture components. The drawbacks associated with immunosurgery, MEF co-culture, and the cost of growth factors necessitate the exploration of a xeno-free method to maintain the self-renewal capacity of hESCs. Here, we describe an isolation method for the human inner cell mass (ICM), which was then cultured in the absence of exogenous growth factors and in the presence of human foreskin fibroblasts (HFFs) as feeder cells. Three hESC lines were obtained from poor-quality embryos by this near-xeno-free protocol. After culturing for more than 10 months, the hESCs retained normal morphology, expressed all expected cell surface markers, could differentiate to embryoid bodies upon culture in vitro, and formed teratomas in vivo. Furthermore, secretion of bFGF by HFFs was observed. In conclusion, this is the first study to describe an inexpensive, xeno-free culture system for the isolation and maintenance of hESCs that does not require bFGF supplementation.

Developmental Competence of Buffalo (Bubalus bubalis) Pluripotent Embryonic Stem Cells Over Different Homologous Feeder Layers and the Comparative Evaluation with Various Extracellular Matrices

BACKGROUND AND OBJECTIVES

Use of somatic cells as a feeder layer to maintain the embryonic stem cells (ESCs) in undifferentiated state limits the stem cell research design, since experimental data may result from a combined ESCs and feeder cell response to various stimuli. Therefore, present study was designed to evaluate the developmental competence of the buffalo ESCs over different homogenous feeders and compare with various extracellular matrices using different concentrations of LIF.

METHODS AND RESULTS

Inner cell masses (ICMs) of in vitro hatched blastocysts were cultured onto homologous feeders viz. fetal fibroblast, granulosa and oviductal cell feeder layers and synthetic matrices viz. fibronectin, collagen type I and matrigel in culture medium. Developmental efficiency was found higher for ESCs cultured on fetal fibroblast and granulosa layers (83.33%) followed by fibronectin (77.78%) at 30 ng LIF. Oviductal feeder was found to be the least efficient feeder showing only 11.11% undifferentiated primary ESC colonies at 30 ng LIF. However, neither feeder layer nor synthetic matrix could support the development of primary colonies at 10 ng LIF. Expression of SSEA- 4, TRA-1-60 and Oct-4 were found positive in ESC colonies from all the feeders and synthetic matrices with 20 ng and 30 ng LIF.

CONCLUSIONS

Fetal fibroblast and granulosa cell while, amongst synthetic matrices, fibronectin were found to be equally efficient to support the growth and maintenance of ESCs pluripotency with 30 ng LIF. This well-defined culture conditions may provide an animal model for culturing human embryonic stem cells in the xeno-free or feeder-free conditions for future clinical applications.

Efficient and scalable expansion of human pluripotent stem cells under clinically compliant settings: a view in 2013

Human pluripotent stem cells (hPSCs) hold great promise for revolutionizing regenerative medicine for their potential applications in disease modeling, drug discovery, and cellular therapy. Many their applications require robust and scalable expansion of hPSCs, even under settings compliant to good clinical practices. Rapid evolution of media and substrates provided safer and more defined culture conditions for long-term expansion of undifferentiated hPSCs in either adhesion or suspension. With well-designed automatic systems or fully controlled bioreactors, production of a clinically relevant quantity of hPSCs could be achieved in the near future. The goal is to find a scalable, xeno-free, chemically defined, and economic culture system for clinical-grade expansion of hPSCs that complies the requirements of current good manufacturing practices. This review provides an updated overview of the current development and challenges on the way to accomplish this goal, including discussions on basic principles for bioprocess design, serum-free media, extracellular matric or synthesized substrate, microcarrier- or cell aggregate-based suspension culture, and scalability and practicality of equipment.

Stem cell maintenance in a different niche

To overcome the difficulty of controlling stem cell fate and function in applications to regenerative medicine, a number of alternative approaches have been made. Recent reports demonstrate that a non-cellular niche modulating the biophysical microenvironment with chemical factors can support stem cell self-renewal. In our previous studies, early establishment was executed to optimize biophysical factors and it was subsequently found that the microgeometry of the extracellular matrix made huge differences in stem cell behavior and phenotype. We review here a three-dimensional, non-cellular niche designed to support stem cell self-renewal. The characteristics of stem cells under the designed system are further discussed.

Development of a xeno-free non-contact co-culture system for derivation and maintenance of embryonic stem cells using a novel human endometrial cell line

Purpose

Mouse embryonic fibroblast feeder layers (MEF) have conventionally been used to culture and maintain the pluripotency of embryonic stem cells (ESC). This study explores the potential of using a novel human endometrial cell line to develop a non-xeno, non-contact co-culture system for ESC propagation and derivation. Such xeno-free systems may prove essential for the establishment of clinical grade human ESC lines suitable for therapeutic application.

Methods

A novel line of human endometrial cells were seeded in a 6-well dish. Filter inserts containing mouse ESCs were placed on these wells and passaged 2–3 times per week. Inner cell masses derived from mouse blastocysts were also cultured on transwells in the presence of the feeder layer. In both cases, staining for SSEA-1, SOX-2, OCT-4 and alkaline phosphatase were used to monitor the retention of stem cells.

Results

ESC colonies retained their stem cell morphology and attributes for over 120 days in culture and 44 passages to date. Inner cell mass derived ESC cultures were maintained in a pluripotent state for 45 days, through 6 passages with retention of all stem cell characteristics. The stem cell colonies expressed stem cell specific markers SSEA-1, Sox 2, Oct-4 and alkaline phosphatase. Upon removal of the human feeder layer, there was a distinct change in cell morphology within the colonies and evidence of ESC differentiation.

Conclusions

Human feeder layers offer a simple path away from the use of MEF feeder cells or MEF conditioned medium for ESC culture. Furthermore, indirect co-culture using porous membranes to separate the two cell types can prevent contamination of stem cell preparations with feeder cells during passaging.

Expansion and differentiation of germline-derived pluripotent stem cells on biomaterials

Stem cells with broad differentiation potential, such as the recently described germline-derived pluripotent stem cells (gPS cells), are an appealing source for tissue engineering strategies. Biomaterials can inhibit, support, or induce proliferation and differentiation of stem cells. Here we identified (1) polymers that maintain self-renewal and differentiation potential of gPS cells for feeder-free expansion and (2) polymers supporting the cardiomyogenic fate of gPS cells by analyzing a panel of polymers of an established biomaterial bank previously used to assess growth of diverse stem cell types. Identification of cytocompatible gPS cell/biomaterial combinations required analysis of several parameters, including morphology, viability, cytotoxicity, apoptosis, proliferation, and differentiation potential. Pluripotency of gPS cells was visualized by the endogenous Oct4-promoter-driven GFP and by Sox2 and Nanog immunofluorescence. Viability assay, proliferation assay, and flow cytometry showed that gPS cells efficiently adhere and are viable on synthetic polymers, such as Resomer(®) LR704 (poly(L-lactic-D,L-lactic acid), poly(tetrafluor ethylene) (PTFE), poly(vinylidene fluoride) (PVDF), and on gelatine-coated tissue culture polystyrene. Expansion experiments showed that Resomer LR704 is an alternative substrate for feeder-free gPS cell maintenance. Resomer LR704, PTFE, and PVDF were found to be suitable for gPS cell differentiation. Spontaneous beating in embryoid bodies cultured on Resomer LR704 occurred already on day 8 of differentiation, much earlier compared to the other surfaces. This indicates that Resomer LR704 supports spontaneous cardiomyogenic differentiation of gPS cells, which was also confirmed on molecular, protein and functional level.

Optimized protocol for derivation of human embryonic stem cell lines

For the past 12 years, the biology and applications of human embryonic stem cells (hESCs) have received great attention from the scientific community. Derivatives of the first hESC line obtained by J. Thomson's group (Science 282(5391):1145-1147, 1998) have been used in clinical trials in patients with spinal cord injury, and other hESC lines have now been used to generate cells for use in treating blindness (Lancet 379(9817):713-720, 2012). In addition to the classical protocol based on mouse or human feeder layers using open culture methods (In Vitro Cellular & Developmental Biology - Animal 46(3-4):386-394, 2010; Stem Cells 23(9):1221-1227, 2005; Nature Biotechnology 24(2):185-187, 2006; Human Reproduction 21(2):503-511, 2006; Human Reproduction 20(8):2201-2206, 2005; Fertility and Sterility 83(5):1517-1529, 2005), novel hESC lines have been derived xeno-free (without using animal derived reagents) (PLoS One 5 (4):1024-1026, 2010), feeder-free (without supporting cell monolayers) (Lancet 365(9471):1601-1603, 2005), in microdrops under oil (In Vitro Cellular & Developmental Biology - Animal 46(3-4):236-41, 2010) and in suspension with ROCK inhibitor (Nature Biotechnology 28(4):361-4, 2010). Regardless of the culture system, successful hESC derivation usually requires optimization of embryo culture, the careful and timely isolation of its inner cell mass (ICM), and precise culture conditions up to the establishment of pluripotent cell growth during hESC line derivation. Herein we address the crucial steps of the hESC line derivation protocol, and provide tips to apply quality control to each step of the procedure.

An ECM-based culture system for the generation and maintenance of xeno-free human iPS cells

Pluripotent stem cells (PSCs) including induced pluripotent stem cells (iPSCs) and embryonic stem cells (ESCs) have emerged as a promising source for treating incurable diseases. Problems that urgently need to be resolved before the clinical application include avoiding potential xenopathogenic transmission and immune rejection that may be caused by the exposure of PSCs to animal-derived products. In addition, an efficient feeder cell-free culture condition would be required for reducing batch-to-batch variation and facilitating scale-up. Therefore, establishing an efficient xeno-free and extracelluar matrix-based culture system is a prerequisite for the clinical application of PSCs. In this study, by blocking protein kinase C and histone deacetylase activities, we formulated a medium that, in combination with vitronectin as an extracellular matrix, not only allows the long-term culture of hESCs and iPSCs but also efficiently generates xeno-free iPSCs. This xeno-free and feeder cell-free culture system would facilitate the clinical applications of both iPSC- and ESC-based cell therapies in the future.

Developing defined culture systems for human pluripotent stem cells

Human pluripotent stem cells hold promising potential in many therapeutics applications including regenerative medicine and drug discovery. Over the past three decades, embryonic stem cell research has illustrated that embryonic stem cells possess two important and distinct properties: the ability to continuously self-renew and the ability to differentiate into all specialized cell types. In this article, we will discuss the continuing evolution of human pluripotent stem cell culture by examining requirements needed for the maintenance of self-renewal in vitro. We will also elaborate on the future direction of the field toward generating a robust and completely defined culture system, which has brought forth collaborations amongst biologists and engineers. As human pluripotent stem cell research progresses towards identifying solutions for debilitating diseases, it will be critical to establish a defined, reproducible and scalable culture system to meet the requirements of these clinical applications.

Human embryonic stem cell-derived mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) originally isolated from marrow have multipotent differentiation potential and favorable immunomodulatory and anti-inflammatory properties that make them very attractive for regenerative cellular therapy. Cells with similar phenotypic characteristics have now been derived from almost all fetal, neonatal, and adult tissues; furthermore, more recently similar cells have also been generated from human embryonic stem cells (ESCs). Generation of MSCs from human ESCs provides an opportunity to study the developmental biology of human mesenchymal lineage generation in vitro. Generation of bone and cartilage from human ESC-derived MSCs and their functional characterization, both in vitro and in vivo, is also an active area of investigation as ESCs could provide an unlimited source of MSCs for potential repair of bone and cartilage defects. MSCs from adult sources are being investigated in numerous Phase I-III clinical trials for a wide variety of indications, mainly based on their immunomodulatory properties. Our group and others have shown MSCs derived from human ESCs possess immunomodulatory properties similar to marrow-derived MSCs. Immunomodulatory properties of ESC-derived MSCs could prove to be highly valuable for their potential clinical applications in the future as derivatives of human ESCs have already entered clinical arena in the context of Phase I clinical trials.

Mesenchymal stem cell like (MSCl) cells generated from human embryonic stem cells support pluripotent cell growth

Mesenchymal stem cell like (MSCl) cells were generated from human embryonic stem cells (hESC) through embryoid body formation, and isolated by adherence to plastic surface. MSCl cell lines could be propagated without changes in morphological or functional characteristics for more than 15 passages. These cells, as well as their fluorescent protein expressing stable derivatives, efficiently supported the growth of undifferentiated human embryonic stem cells as feeder cells. The MSCl cells did not express the embryonic (Oct4, Nanog, ABCG2, PODXL, or SSEA4), or hematopoietic (CD34, CD45, CD14, CD133, HLA-DR) stem cell markers, while were positive for the characteristic cell surface markers of MSCs (CD44, CD73, CD90, CD105). MSCl cells could be differentiated toward osteogenic, chondrogenic or adipogenic directions and exhibited significant inhibition of mitogen-activated lymphocyte proliferation, and thus presented immunosuppressive features. We suggest that cultured MSCl cells can properly model human MSCs and be applied as efficient feeders in hESC cultures.

Efficient derivation and concise gene expression profiling of human embryonic stem cell-derived mesenchymal progenitors (EMPs)

New potential sources of stem cells for clinical application include bone marrow mesenchymal stem cells (BMMSCs), human embryonic stem cells (hESCs), and induced pluripotent stem cells (iPS). However, each source is not without its own concerns. While research continues in an effort to overcome these problems, the generation of mesenchymal progenitors from existing hESC lines may circumvent many of these issues. We report here a simple and efficient method of generating hESC-derived mesenchymal progenitors (EMPs) and transcriptome profiling using a concise, custom-designed, oligomnucleotide gene expression microarray. Characterization of EMPs shows that these cells are similar to BMMSCs in terms of differentiation capacity as well as cell surface marker expression. In addition, EMPs express several ESC markers and HLA-G, a nonclassical MHC class I molecule with immunomodulatory properties. Morevoer, EMPs possess significantly enhanced proliferative ability over BMMSCs during which karyotypic stability was maintained. Although derived from hESCs, EMPs do not form any tumors in immunocompromised mice. To efficiently profile gene expression in multiple samples, we designed an oligoarray to probe just over 11,000 genes highly expressed in stem cells. We found that the transcriptome of EMPs is more similar to BMMSCs than hESCs. Both cell types highly express genes involved in processes related to the cytoskeleton, extracellular matrix, and cell adhesion, but EMPs show higher expression of genes involved in cell proliferation whereas BMMSCs showed higher expression of immune-related genes. Based on our data, EMPs may be an accessible source of mesenchymal progenitor for therapeutic use.

An optimized small molecule inhibitor cocktail supports long-term maintenance of human embryonic stem cells

A major challenge in stem cell-mediated regenerative medicine is the development of defined culture systems for the maintenance of clinical-grade human embryonic stem (hES) cells. Here, we identify, using a feedback system control scheme, a unique combination of three small molecule inhibitors that enables the maintenance of hES cells on a fibronectin-coated surface through single cell passaging. After 20 passages, the undifferentiated state of the hES cells was confirmed by OCT4, SSEA4 and NANOG expressions, whereas their pluripotent potential and genetic integrity were demonstrated by teratoma formation and normal karyotype, respectively. Our study attests to the power of the feedback system control scheme to quickly pinpoint optimal conditions for desired biological activities, and provides a chemically defined, scalable and single cell passaging culture system for hES cells.

Human embryonic stem cell-derived mesenchymal progenitors: an overview

Mesenchymal stromal/stem cells (MSCs) were originally isolated from bone marrow (BM), but are now known to be present in all fetal and adult tissues. These multipotent cells can be differentiated into at least three downstream mesenchymal lineages that include bone, cartilage, and fat. However, under some experimental conditions, these cells can differentiate into nonmesenchymal cell types and/or participate in regeneration of damaged tissues through a variety of mechanisms. Most recently, MSCs have been derived from human embryonic stem cells (hESCs) through several different methodologies. Human MSCs derived from hESCs have been shown to possess characteristics very similar to BM-derived MSCs. Thus, the generation of MSCs from hESCs provides an opportunity to study the developmental biology of cells of mesenchymal lineages in an appropriate in vitro model. Furthermore, MSCs from different adult tissue sources are being actively investigated in a multitude of clinical trials; therefore, hESCs could provide an unlimited source of MSCs for potential clinical applications in the future. Such MSCs could be used without further differentiation for regeneration of tissues, or they could be directed towards specific lineage pathways, such as bone and cartilage, for reconstruction of tissues. Finally, immunomodulatory properties of hESC-derived MSCs are likely to prove valuable for inducing immune tolerance toward other cells or tissues derived from the same hESC lines.

Endoplasmic reticulum stress signals in defined human embryonic stem cell lines and culture conditions

Human embryonic stem cells (hESCs) are especially resistant to several cellular stresses, but the existence and induction of Endoplasmic Reticulum (ER) stress by culture conditions are unknown. Using qPCR, here, we investigated the behavior of the principal sensors of ER stress and their relation with the feeder layer, the type of conditioned media used in feeder free systems and the upregulation of several differentiation markers. We observed the preservation of pluripotency, and detected differential expression of differentiation markers in HS181 and SHEF1 hESCs growing on Adipose-derived mesenchymal stem cells (ASCs) and feeder-free system with different conditioned media (HEF-CM and ASC-CM). Taken together, these results demonstrate evidence of ER stress events that cells must resolve to survive and maintenance of markers of pluripotency. The early differentiation status defined could progress into a more differentiated state, and may be influenced by culture conditions.

Human embryonic stem cells: derivation, culture, and differentiation: a review

The greatest therapeutic promise of human embryonic stem cells (hESC) is to generate specialized cells to replace damaged tissue in patients suffering from various degenerative diseases. However, the signaling mechanisms involved in lineage restriction of ESC to adopt various cellular phenotypes are still under investigation. Furthermore, for progression of hESC-based therapies towards clinical applications, appropriate culture conditions must be developed to generate genetically stable homogenous populations of cells, to hinder possible adverse effects following transplantation. Other critical challenges that must be addressed for successful cell implantation include problems related to survival and functional efficacy of the grafted cells. This review initially describes the derivation of hESC and focuses on recent advances in generation, characterization, and maintenance of these cells. We also give an overview of original and emerging differentiation strategies used to convert hESC to different cell types. Finally, we will discuss transplantation studies of hESC-derived cells with respect to safety and functional recovery.

Worldwide Survey of Published Procedures to Culture Human Embryonic Stem Cells

Since their derivation 11 years ago, human embryonic stem (hES) cells have become a powerful tool in both basic biomedical research and developmental biology. Their capacity for self-renewal and differentiation into any tissue type has also brought interest from fields such as cell therapy and drug screening. We conducted an extensive analysis of 750 papers (51% of the total published about hES cells between 1998 and 2008) to present a spectrum of hES cell research including culture protocols developed worldwide. This review may stimulate discussions about the importance of having unvarying methods to culture hES cells, in order to facilitate comparisons among data obtained by research groups elsewhere, especially concerning preclinical studies. Moreover, the description of the most widely used cell lines, reagents, and procedures adopted internationally will help newcomers on deciding the best strategies for starting their own studies. Finally, the results will contribute with the efforts of stem cell researchers on comparing the performance of different aspects related to hES cell culture methods.

Generation of mesenchymal stromal cells from HOXB4-expressing human embryonic stem cells

BACKGROUND AIMS

HOXB4 transcription factor plays an important role in embryonic and adult hematopoiesis. Overexpression of HOXB4 in murine and human embryonic stem cells (ESC) has been used to generate hematopoietic stem cells (HSC) via the embryoid body formation method.

METHODS

We used FuGENE 6-based transfection of YPL2-HOXB4 vector to generate HOXB4-expressing colonies from human ESC line H9 and investigated the potential of these cells for differentiation into primitive CD34(+) hematopoietic cells, via co-culture methodology with OP9 murine bone marrow stromal cells. Expression of HOXB4 in transfected human ESC colonies and their derivatives was verified using immunocytochemistry and reverse-transcription polymerase chain reaction (RT-PCR).

RESULTS

Utilizing OP9 stromal cell co-culture methodology, we generated CD34(+) cells from HOXB4-expressing H9 human ESC at a frequency similar to, and not higher than, non-transfected human ESC. However, we observed that some colonies of HOXB4-expressing human ESC not co-cultured on OP9 cells, differentiated into mesenchymal stromal cells (MSC) while preserving their HOXB4 expression. These HOXB4-expressing MSC expressed CD29, CD73, CD44, CD90, CD105 and HLA-class I, were negative for the expression of CD34, CD45, CD54, CD71, CD106 and HLA-DR, and could be differentiated into adipocytes and osteocytes.

CONCLUSIONS

In our specific experimental system we observed that overexpression of HOXB4 in human ESC did not improve the generation of CD34(+) hematopoietic cells via OP9 co-culture methodology. Furthermore, we could generate MSC from human ESC over-expressing HOXB4.

Naturally immortalised mouse embryonic fibroblast lines support human embryonic stem cell growth

Human embryonic stem cell (hESC) growth is dependent on various factors released by feeder cells. Some of them have already been elucidated, although much research is still needed to understand the biology of stem cell maintenance in culture. Traditionally, primary mouse embryonic fibroblasts (PMEFs) have been used as feeder layers, and both murine and human fibroblast cell lines have been shown to support pluripotency and self-renewal of hESC. Here we report the derivation of three new mouse embryonic fibroblast cell lines, MEFLU-M, MEFLU-T, and MEFLU-TB, with different properties regarding growth and support for undifferentiated hESCs. MEFLU-TB is able to support continuous growth of the newly derived Man-1, as well as H1, HUES-1, HUES-7, HUES-8, and HUES-9 human embryonic stem cell lines. After more than 50 passages and doublings, MEFLU-TB feeders compare to early passage primary mouse embryonic fibroblasts in their ability to support undifferentiated hESC growth. Our results contradict a previous paradigm that PMEFs tend to lose their capacity to support proliferation of hESCs with increasing passages, and show that the MEFLU-TB mouse embryonic fibroblast cell line and its conditioned medium have the potential to support the maintenance of hESC lines. Also, our results clearly show that spontaneous immortalization of primary fibroblasts can be achieved in culture without any chemical addition or genetic modification.

Cardiac applications for human pluripotent stem cells

Human embryonic stem cells (hESCs) and induced pluripotent stem cells (hiPSCs) can self-renew indefinitely, while maintaining the capacity to differentiate into useful somatic cell types, including cardiomyocytes. As such, these stem cell types represent an essentially inexhaustible source of committed human cardiomyocytes of potential use in cell-based cardiac therapies, high-throughput screening and safety testing of new drugs, and modeling human heart development. These stem cell-derived cardiomyocytes have an unambiguous cardiac phenotype and proliferate robustly both in vitro and in vivo. Recent transplantation studies in preclinical models have provided exciting proof-of-principle for their use in infarct repair and in the formation of a "biological pacemaker". While these successes give reason for cautious optimism, major challenges remain to the successful application of hESCs (or hiPSCs) to cardiac repair, including the need for preparations of high cardiac purity, improved methods of delivery, and approaches to overcome immune rejection and other causes of graft cell death. In this review, we describe the phenotype of hESC- and hiPSC-derived cardiomyocytes, the state of preclinical transplantation studies with these cells, and potential approaches to overcome the aforementioned hurdles.

Role of bioinspired polymers in determination of pluripotent stem cell fate

Human pluripotent stem cells, including embryonic and induced pluripotent stem cells, hold enormous potential for the treatment of many diseases, owing to their ability to generate cell types useful for therapeutic applications. Currently, many stem cell culture propagation and differentiation systems incorporate animal-derived components for promoting self-renewal and differentiation. However, use of these components is labor intensive, carries the risk of xenogeneic contamination and yields compromised experimental results that are difficult to duplicate. From a biomaterials perspective, the generation of an animal- and cell-free biomimetic microenvironment that provides the appropriate physical and chemical cues for stem cell self-renewal or differentiation into specialized cell types would be ideal. This review presents the use of natural and synthetic polymers that support propagation and differentiation of stem cells, in an attempt to obtain a clear understanding of the factors responsible for the determination of stem cell fate.

[Growing of human embryonic stem cells on feeders derived from themselves]

This study was carried out to determine whether mesenchymal stem cells (MSCs) derived from teratoma of human embryonic stem cells (hESCs) function as feeder cells to support hESCs growth. Approximately 5x10(6) hESCs were injected into the hind limb muscle of each SCID-beige mouse to form teratoma. After 8 weeks, the MSCs were isolated from the teratoma and cultured in Mesencult medium. Purified MSCs were then used as the feeder cells for hESCs culture. High purity MSCs derived from teratoma were isolated. The cells were morphologically similar to bone marrow MSCs (bMSCs). The teratoma-derived MSCs were negative for CD34 and CD45 but positive for CD29, CD49b, CD105, CD73, and CD90, which resembled those expressed by bMSCs. After passaged on MSCs feeder cells more than 10 passages, hESCs maintained hESC characteristics in morphology. Reverse PCR showed the expression of Oct4 and Nanog. SSEA-1 was negative and SSEA-4, TRA-1-60, and TRA-1-81 were positive. Alkaline phosphatase staining showed positive results.The karyotype remained normal. Moreover, the hECSs cultured on teratoma-derived MSCs formed teratoma in vivo and embryoid body in vitro confirmed their pluripotency. Accordingly, MSCs derived from hESCs by in vivo differentiation can be used as the feeder cells for hESCs culture.

Challenges and approaches to the culture of pluripotent human embryonic stem cells

Since the establishment of the first human embryonic stem cell (hESC) lines, several groups have described the derivation and culture of hESC lines in various culture conditions. In this review, we describe how hESC lines have been derived from the inner cell mass of blastocysts or morula-stage embryos and the culture conditions used. In order to be used for therapeutic purposes, the pluripotent hESC lines must be established and propagated according to good manufacturing practice quality requirements. In addition, any use of animal-derived components should be avoided to gain safer hESC lines for clinical purposes. Here, we will describe the development in derivation and chemically defined culturing conditions of hESC towards good manufacturing practice and discuss the future challenges for hESCs in clinical use. Similarly, we discuss the challenges and future directions in optimization of standard culture conditions of hESCs for research purposes.

Engineered microenvironments for human stem cells

Regulation of cell differentiation and assembly remains a fundamental question in developmental biology. During development, tissues emerge from coordinated sequences of the renewal, differentiation, and assembly of stem cells. Likewise, regeneration of an adult tissue is driven by the migration and differentiation of repair cells. The fields of stem cells and regenerative medicine are starting to realize how important is the entire context of the cell environment, with the presence of other cells, three-dimensional matrices, and sequences of molecular and physical morphogens. The premise is that to unlock the full potential of stem cells, at least some aspects of the dynamic environments normally present in vivo need to be reconstructed in experimental systems used in vitro. We review here some recent work that utilized engineered environments for guiding the embryonic and adult human stem cells, and focus on vasculogenesis as a critical and universally important aspect of tissue development and regeneration. Birth Defects Research (Part C) 84:335-347, 2008. (c) 2008 Wiley-Liss, Inc.

Derivation and propagation of hESC under a therapeutic environment

The pluripotent nature of human embryonic stem cells (hESC) makes them very attractive as a source of various cell types that could be used therapeutically in regenerative medicine. However, eliminating all sources of contamination, animal-derived or human cell-derived, during hESC derivation and propagation is necessary before hESC derivatives can be used clinically. Although there is continuing progress toward this goal, none of the methods to date to produce hESC lines under good manufacturing practices (GMP) has been published. The long-term success for GMP compliance depends critically on maintaining and implementing a stringent quality control system which is also dictated by the regulatory authorities in different countries. In this unit, an approach is described based upon the experience of this author and others towards achieving clinical-grade hESC lines systematically involving all the steps from start to finish under GMP environment. This unit provides a basic layout for GMP set up to achieve quality controls, a step-by-step guide to producing new hESC lines under defined conditions, and standard operating procedures used to achieve this outcome.

Isolation of human placental fibroblasts

The first human embryonic stem cell lines (hESCs) were derived using mouse embryonic fibroblasts as feeder cells. In attempts to replace mouse embryonic fibroblasts with feeders of human origin, irradiated human placental fibroblasts were successfully used as feeder cells for the derivation and propagation of hESCs. Here we describe a protocol for the isolation and expansion of fibroblasts from placental villous stroma. We include a description of placental architecture to provide the background for a stepwise tissue digestion that leads to the isolation of villous stroma. Villous stroma from the first trimester tissue is different from term placenta and contains mesenchymal, fibroblast-like cells, only a few blood vessels, and a network of matrix fibers. The fibroblasts isolated from a single placenta of 6- to 8-weeks gestation proliferate rapidly and retain the ability to support hESC growth between passage doubling (PD) 8 and PD 12.

Autogeneic feeders for the culture of undifferentiated human embryonic stem cells in feeder and feeder-free conditions

Human embryonic stem cells (hESC) are pluripotent cells that proliferate indefinitely in culture while retaining their ability to differentiate to any cell type in the body. Conventionally, hESC are cultured either directly on feeders or on an extracellular matrix supplemented with conditioned medium (CM) from feeders. To minimize the risk of xenozootic infections, several sources of primary human feeders have been identified. However, this does not eliminate the risk of contaminating hESC with infectious agents from the donor human feeders. In this study, we evaluated the use of the CD105+ /CD24 hESC-derived mesenchymal stem cell (MSC) line, HuES9.E1, for its ability to support the growth of undifferentiated hESC in feeder and feeder-free cultures. This line was previously reported to be karyotypically stable and phenotypically displayed MSC-like surface antigens and gene transcription profiles. In addition, like adult MSC, HuES9.E1 can be differentiated to adipocytes, osteocytes, and chondrocytes in vitro. When tested for its ability to support hESC growth, it was found that hESC maintained the undifferentiated morphology for >12 continuous passages in coculture with HuES9.E1 and >8 passages in feeder-free cultures supplemented with CM from HuES9.E1. Furthermore, the hESC cultures continued to express the pluripotent markers, Oct-4, SSEA-4, Tra-1-60, Tra-1-81, and retained a normal karyotype. When injected into severe combined immunodeficient (SCID) mice, hESC differentiated to form teratomas comprising of tissues representative of the three embryonic germ layers. Potentially, the ability to derive and use autogeneic feeders may provide a safe and accessible source of feeders for the expansion of hESC required in clinical applications.

The benefit of human embryonic stem cell encapsulation for prolonged feeder-free maintenance

The majority of methodologies for maintaining human embryonic stem cell (hESC) pluripotency require the use of human or animal feeder cell layers, the most common being murine embryonic fibroblasts. In this study, we applied a protocol aimed at maintaining hESCs in culture without exposure to animal cells or proteins. hESCs were encapsulated in 1.1% (w/v) calcium alginate hydrogels and grown in basic maintenance medium for a period of up to 260 days. Investigation of the cell aggregates formed within the hydrogels yielded no evidence of the formation of any of the three germ layers, although the hESCs retained their pluripotency and could differentiate when they were subsequently cultured in a conditioned environment. Immunohistochemistry and RT-PCR showed that the hESC aggregates expressed protein and gene markers characteristic of pluripotency including Oct-4, Nanog, SSEA-4, TRA-1-60 and TRA-1-81. At the ultrastructural level, the cells were arranged in closely packed clusters and showed no cytoplasmic organelles, suggesting an undifferentiated state. These data show that it is possible to maintain hESCs in an undifferentiated state, without passaging or embryoid body formation, and without animal contamination.

A human endothelial cell feeder system that efficiently supports the undifferentiated growth of mouse embryonic stem cells

Feeder cells are commonly used to culture embryonic stem cells to maintain their undifferentiated and pluripotent status. Conventionally, mouse embryonic fibroblasts (MEFs), supplemented with leukemia inhibitory factor (LIF), are used as feeder cells to support the growth of mouse embryonic stem cells (mESCs) in culture. To prepare for fresh MEF feeder or for MEF-conditioned medium, sacrifice of mouse fetuses repeatedly is unavoidable in these tedious culture systems. Here we report the discovery of a human endothelial cell line (ECV-304 cell line) that efficiently supports growth of mESCs LIF-free conditions. mESCs that were successfully cultured for eight to 20 passages on ECV-304 feeders showed morphological characteristics similar to cells cultured in traditional feeder cell systems. These cells expressed the stem cell markers Oct3/4, Nanog, Sox2, and SSEA-1. Furthermore, cells cultured on the ECV-304 cell line were able to differentiate into three germ layers and were able to generate chimeric mice. Compared with traditional culture systems, there is no requirement for mouse fetuses and exogenous LIF does not need to be added to the culture system. As a stable cell line, the ECV-304 cell line efficiently replaces MEFs as an effective feeder system and allows the efficient expansion of mESCs.

Derivation of a new human embryonic stem cell line, endeavour-1, and its clonal propagation

Here we describe the derivation of a novel human embryonic stem (hES) cell line, Endeavour-1 (E1), its four new clonal lines (E1C1, E1C2, E1C3, E1C4), and their characterization. E1 and its clonal lines are propagated on human fetal fibroblasts (HFFs) derived and grown in a largely serum-free medium. Seven inner cell masses were isolated from 34 donated human embryos (27 survived), and one new hES cell line was obtained. E1 has been in culture for over 1 year and possesses all the typical features of stem cells, i.e., expression of stem cell surface markers (stage-specific embryonic antigens SSEA-3 and SSEA-4, and tumor recognition antigens TRA-1-60 and TRA-1-81), staining for alkaline phosphatase, and the presence of the pluripotent gene marker (nanog). This line shows pluripotency both under in vitro and in vivo conditions. E1 has a normal karyotype (46XX). Using our optimized procedure for cloning, four new clonal lines were derived from E1: E1C1, E1C2, E1C3, and E1C4. These clonal lines show normal characteristics: karyotype of that of the parent line (46XX) except for E1C3, which showed reciprocal translocation involving chromosomes 15 and 17; stem cell surface markers SSEA-4, TRA-1-60, and TRA-1-81; and gene expression for pluripotency (Nanog). All of these clonal lines formed embryoid bodies (EBs) in suspension cultures. After seeding, the EBs differentiated, forming cell lineages derived from all three germ layers as indicated by immunolocalization for the ectodermal marker beta-III tubulin, the mesodermal marker CD34, and the endodermal marker alpha-fetoprotein (AFP). There were subtle differences in the expression of these markers between clones. These clonal lines showed pluripotency in vivo. E1 and its clonal lines can differentiate to definitive endoderm after treatment with activin A, and, as indicated by expression of SOX17, FOXa2, and GATA-4 by RT-PCR, there are some subtle differences between these clonal lines. This may help in selecting clonal lines for specific lineage specification and for developing future cell therapy for various diseases.

Derivation and immunological characterization of mesenchymal stromal cells from human embryonic stem cells

OBJECTIVE

We have previously shown the simultaneous generation of CD73(+) mesenchymal stromal cells (MSCs) along with CD34(+) hematopoietic cells from human embryonic stem cells (ESCs) when they are cocultured with OP9 murine stromal cells. We investigated whether MSCs can be derived from human ESCs without coculturing with OP9 cells, and if such cells exhibit immunological properties similar to MSCs derived from adult human bone marrow (BM).

MATERIALS AND METHODS

Our starting populations were undifferentiated human ESCs cultured on Matrigel-coated plates without feeder cells. The differentiated fibroblast-looking cells were tested for expression of MSC markers and their potential for multilineage differentiation. We investigated surface expression of human leukocyte antigen (HLA) molecules on these MSCs before and after treatment with interferon-gamma (IFN-gamma). We also tested the proliferative response of T-lymphocytes toward MSCs and the effects of MSCs in mixed lymphocyte reaction (MLR) assays.

RESULTS

We derived populations of MSCs from human ESCs with morphology, cell surface marker characteristics, and differentiation potential similar to adult BM-derived MSCs. Similar to BM-derived MSCs, human ESC-derived MSCs express cell surface HLA class I (HLA-ABC) but not HLA class II (HLA-DR) molecules. However, stimulation with IFN-gamma induced the expression of HLD-DR molecules. Human ESC-derived MSCs did not induce proliferation of T-lymphocytes when cocultured with peripheral blood mononuclear cells. Furthermore, ESC-derived MSCs suppressed proliferation of responder T-lymphocytes in MLR assays.

CONCLUSIONS

MSCs can be derived from human ESCs without feeder cells. These human ESC-derived MSCs have cell surface markers, differentiation potentials, and immunological properties in vitro that are similar to adult BM-derived MSCs.

Xeno-free derivation and culture of human embryonic stem cells: current status, problems and challenges

Human embryonic stem cells (hESC) not only hold great promise for the treatment of degenerative diseases but also provide a valuable tool for developmental studies. However, the clinical applications of hESC are at present limited by xeno-contamination during the in vitro derivation and propagation of these cells. In this review, we summarize the current methodologies for the derivation and the propagation of hESC in conditions that will eventually enable the generation of clinical-grade cells for future therapeutic applications.

Culture conditions for human embryonic stem cells

Human embryonic stem cell (hESC) lines have been derived and cultured in variable conditions. The idea behind derivation of hESC lines is to use them in human cell transplantation after differentiation, but already now these cells are widely used for research purposes. Despite similarities among the established lines, important differences have been reported between them, and it has been difficult to compare the results obtained using different lines. Recent optimization of hESC culture conditions has moved from cultures on mouse embryonic fibroblasts (MEFs) in fetal bovine serum-containing medium towards feeder-free culture methods using more defined animal substance-free cultures. The aim has been to establish robust and cost-effective systems for culturing these cells and eliminate the risk of infection transmitted by animal pathogens and immunoreactions caused by animal substances in cell cultures before clinical treatment. It is important to take these modifications into account when carrying out research using these cells. It is known that culture conditions influence gene expression and, hence, probably many properties of the cells. Optimization and standardization of culture methods is needed for research as well as for clinical purposes.

Derivation of human embryonic stem cell lines

Human embryonic stem cells (hESC) are undifferentiated cells derived from an early embryo that can grow in vitro indefinitely, while retaining their capability to differentiate into specialized somatic cell types. Over the last decade there has been great interest in derivation and culture of these cells, as they can potentially provide a supply of readily available differentiated cells and tissues of all types to be used for therapeutic purposes in cell transplantation in humans, as well as for other medical uses such as drug discovery. The source of hESC lines is usually excess human embryos from in vitro fertilization treatments, although novel ways of producing hESCs have been suggested recently. The actual methods of hESC derivation have not changed greatly since the first report by Thomson et al. in 1998 . However, the main emphasis over the last several years has been in finding defined conditions for derivation and culture of hESCs, because to enable the clinical use of hESC for cell transplantation, the use of animal derived biological components is no longer acceptable. For basic research, the aim is to replace even human derived materials with completely defined systems. In this paper we describe methods utilized in our laboratory for hESC derivation and describe two studies conducted in an attempt to improve derivation efficiency and to enable research outcomes to be achieved using fewer embryos.