Adaptation of human embryonic stem cells to feeder-free and matrix-free culture conditions directly on plastic surfaces

Previous studies have shown that cultivation of undifferentiated human embryonic stem (hES) cells requires human fibroblasts (hF) or mouse embryonic fibroblast (mEF) feeders or a coating matrix such as laminin, fibronectin or Matrigel in combination with mEF or hF conditioned medium. We here demonstrate a successful feeder-free and matrix-free culture system in which undifferentiated hES cells can be cultured directly on plastic surfaces without any supportive coating, in a hF conditioned medium. The hES cells cultured directly on plastic surfaces grow as colonies with morphology very similar to cells cultured on Matrigel(TM). Two hES cell lines SA167 and AS034.1 were adapted to matrix-free growth (MFG) and have so far been cultured up to 43 passages and cryopreserved successfully. The lines maintained a normal karyotype and expressed the expected marker profile of undifferentiated hES cells for Oct-4, SSEA-3, SSEA-4, TRA-1-60, TRA-1-81 and SSEA-1. The hES cells formed teratomas in SCID mice and differentiated in vitro into derivates of all three germ layers. Thus, the MFG-adapted hES cells appear to retain pluripotency and to remain undifferentiated. The present culture system has a clear potential to be scaleable up to a manufacturing level and become the preferred culture system for various applications such as cell therapy and toxicity testing.     

Establishment and maintenance of three Chinese human embryonic stem cell lines

To establish a potential resource for cell therapy and a developmental model for human diseases, we had isolated three Chinese human embryonic stem cell lines from the inner cell mass of human blastocysts in 2002. All the three cell lines were grown on mouse embryonic fibroblasts as feeder cells; one of these cell lines, chHES-3, has maintained its normal karyotype even after being cultured in vitro for more than 100 passages, after the standardization of mouse feeder preparation. Each hES cell line has been completely characterized. All the three cell lines expressed hES-specific markers and pluripotency-related genes. These cells maintained their normal karyotype during long-term culture and displayed a high telomerase activity. When differentiated in vivo and in vitro, the derivatives representing the three germ layers could be observed. Human leukocyte antigen, ABO blood type, and DNA fingerprinting were also performed to provide a unique identity to each cell line. By establishing these hES cell lines, we provide an appropriate in vitro model to study human development and regeneration. All the three cell lines can be obtained for research purposes by placing a request at our website at www.hescbank.cn.     

Simple autogeneic feeder cell preparation for pluripotent stem cells

Mouse embryonic fibroblasts (MEFs) are the most commonly used feeder cells for pluripotent stem cells. However, autogeneic feeder (AF) cells have several advantages such as no xenogeneic risks and reduced costs. In this report, we demonstrate that common marmoset embryonic stem (cmES) cells can be maintained on common marmoset AF (cmAF) cells. These cmES cells were maintained on cmAF cells for 6 months, retaining their morphology, normal karyotype, and expression patterns for the pluripotent markers Oct-3/4, Nanog, SSEA-3, SSEA-4, TRA-1-60, and TRA-1-81, as well as their ability to differentiate into cardiac and neural cells. Antibody array analysis revealed equivalent protein expression profiles between cmES cells maintained on cmAF cells and MEFs. In addition, similarly prepared human embryonic stem (hES) and induced pluripotent stem (hiPS) cell-derived AF cells supported the growth of and maintained the morphology and pluripotent marker expressions of hES and hiPS cells, respectively. DNA microarray analysis revealed that these hES and hiPS cells had mRNA expression profiles similar to those of hES and hiPS cells maintained on MEFs, respectively. Taken together, these findings imply that AF cells can replace MEFs in the routine maintenance of primate pluripotent stem cells.     

New culture system for human embryonic stem cells: autologous mesenchymal stem cell feeder without exogenous fibroblast growth factor 2

Human embryonic stem (hES) cells have been successfully maintained using human-cell feeder systems or feeder-free systems. However, despite advances in culture techniques, hES cells require supplementation with fibroblast growth factor 2 (FGF-2), an exogenous stemness factor, which is needed to sustain the authentic undifferentiated status. We developed a new culture system for hES cells; this system does not require supplementation with FGF-2 to obtain hES cells that are suitable for tissue engineering and regenerative medicine. This culture system employed mesenchymal stem cells derived from hES cells (hESC-MSCs) as autologous human feeder cells in the absence of FGF-2. The hES cell line SNUhES3 cultured in this new autologous feeder culture system maintained the typical morphology of hES cells and expression of pluripotency-related proteins, SSEA-4, TRA-1-60, OCT4, and alkaline phosphatase, without development of abnormal karyotypes after more than 30 passages. RNA expression of the pluripotency-related genes OCT4 and NANOG was similar to the expression in SNUhES3 cells maintained on xenofeeder STO cells. To identify the mechanism that enables the cells to be maintained without exogenous FGF-2, we checked the secretion of FGF-2 from the mitomycin-C treated autofeeder hESC-MSCs versus xenofeeder STO cells, and confirmed that hESC-MSCs secreted FGF-2 whereas STO cells did not. The level of FGF-2 in the media from the autofeeder system without exogenous FGF-2 was comparable to that from the xenofeeder system with addition of FGF-2. In conclusion, our new culture system for hES cells, which employs a feeder layer of autologous hESC-MSCs, supplies sufficient amounts of secreted FGF-2 to eliminate the requirement for exogenous FGF-2.     

Feeder-free growth of undifferentiated human embryonic stem cells

Previous studies have shown that maintenance of undifferentiated human embryonic stem (hES) cells requires culture on mouse embryonic fibroblast (MEF) feeders. Here we demonstrate a successful feeder-free hES culture system in which undifferentiated cells can be maintained for at least 130 population doublings. In this system, hES cells are cultured on Matrigel or laminin in medium conditioned by MEF. The hES cells maintained on feeders or off feeders express integrin alpha6 and beta1, which may form a laminin-specific receptor. The hES cell populations in feeder-free conditions maintained a normal karyotype, stable proliferation rate, and high telomerase activity. Similar to cells cultured on feeders, hES cells maintained under feeder-free conditions expressed OCT-4, hTERT, alkaline phosphatase, and surface markers including SSEA-4, Tra 1-60, and Tra 1-81. In addition, hES cells maintained without direct feeder contact formed teratomas in SCID/beige mice and differentiated in vitro into cells from all three germ layers. Thus, the cells retain fundamental characteristics of hES cells in this culture system and are suitable for scaleup production.     

Feeder layer- and serum-free culture of human embryonic stem cells

In addition to their contribution to the research on early human development, human embryonic stem (hES) cells may also be used for cell-based therapies. Traditionally, these cells have been cultured on mouse embryonic fibroblast feeder layers, which allow their continuous growth in an undifferentiated state. However, the use of hES cells in human therapy requires an animal-free culture system, in which exposure to mouse retroviruses is avoided. In this study we present a novel feeder layer-free culture system for hES cells, based on medium supplemented with 15% serum replacement, a combination of growth factors including transforming growth factor beta1 (TGFbeta1), leukemia inhibitory factor, basic fibroblast growth factor, and fibronectin matrix. Human ES cells grown in these conditions maintain all ES cell features after prolonged culture, including the developmental potential to differentiate into representative tissues of the three embryonic germ layers, unlimited and undifferentiated proliferative ability, and maintenance of normal karyotype. The culture system presented here has two major advantages: 1) application of a well-defined culture system for hES cells and 2) reduced exposure of hES cells to animal pathogens. The feeder layer-free culture system reported here aims at facilitating research practices and providing a safer alternative for future clinical applications of hES cells.     

Efficient derivation of Chinese human embryonic stem cell lines from frozen embryos

Human embryonic stem (hES) cells are pluripotent cells derived from the inner cell mass of blastocysts. Their unique properties of self-renewal and pluripotency make them an attractive tool for basic research as well as a potential cell resource for therapy. However, each hES cell line demonstrates different identity. It is desirable to obtain more fully characterized hES cell lines with newly developed technologies associated with hES cell culture. Here, we report our experience of efficient derivation of three new Chinese hES cell lines (SHhES2, SHhES3, and SHhES4) from in vitro fertilization discarded embryos donated by women with polycystic ovary syndrome. These cell lines were derived under conditions minimizing exposure to animal components and maintained at an undifferentiated state for long-term culture. They retained a normal karyotype and expressed ALP, OCT4, SOX2, SSEA-4, TRA-1-60 and TRA-1-81. RT-PCR analysis also revealed high expression levels of pluripotency markers such as OCT4, LEFTY A, SOX2, TDGF-1, THY1, FGF4, NANOG, and REX1. When suspended in low-attachment culture dishes, embryoid bodies formed and were comprised of various differentiated cell types from all three embryonic germ layers. However, well-shaped teratomas were only harvested from line SHhES2, not from SHhES3 and SHhES4, indicating that the differentiation ability in vivo differs among the three cell lines. Collectively, the three new hES cell lines were established and fully characterized. The effort paves the way toward generating hES cell lines without contamination by animal components. All of these cell lines are available by contact Ying Jin at yjin@sibs.ac.cn.     

一种新的人胚胎干细胞自身来源的滋养层支持其体外培养

摘要: 通过人胚胎干细胞(Human embryonic stem cells, hESCs)经体内分化获取间充质干细胞(Mesenchymal stem cells, MSCs)为人胚胎干细胞提供一种新的滋养层。将约5×106个hESCs注射入重症免疫联合缺陷小鼠形成畸胎瘤, 8周后再从畸胎瘤中分离MSCs并鉴定, 将MSCs作为hESCs的滋养层细胞, 并检测和观察hESCs的生长情况、细胞特性和分化能力。从畸胎瘤中获得了纯度较高的具有类似骨髓来源的MSC特性的细胞群, 其形态相似、表面抗原标志相似(CD34和CD45阴性, CD29、CD49b、CD105、CD73和CD90阳性), 经诱导可以向成骨细胞和成脂细胞分化。将hESCs在MSCs滋养层细胞上传代培养10代以上, hESCs依然具有正常的细胞形态, 反转录PCR证实其特异转录因子Oct4、Nanog的表达, 干细胞表面标记SSEA-1显示为阴性, SSEA-4、TRA-1-60、TRA-1-81显示为阳性, 碱性磷酸酶染色显示为阳性, 并且核型正常。体外EB形成和体内畸胎瘤形成证明了其全能性。因此来源于hESCs本身的MSCs可以被用来作为支持胚胎干细胞生长并维持其未分化状态的滋养层细胞。     

Human feeder layers for human embryonic stem cells

Human embryonic stem (hES) cells hold great promise for future use in various research areas, such as human developmental biology and cell-based therapies. Traditionally, these cells have been cultured on mouse embryonic fibroblast (MEF) feeder layers, which permit continuous growth in an undifferentiated stage. To use these unique cells in human therapy, an animal-free culture system must be used, which will prevent exposure to mouse retroviruses. Animal-free culture systems for hES cells enjoy three major advantages in the basic culture conditions: 1). the ability to grow these cells under serum-free conditions, 2). maintenance of the cells in an undifferentiated state on Matrigel matrix with 100% MEF-conditioned medium, and 3). the use of either human embryonic fibroblasts or adult fallopian tube epithelial cells as feeder layers. In the present study, we describe an additional animal-free culture system for hES cells, based on a feeder layer derived from foreskin and a serum-free medium. In this culture condition, hES cells maintain all embryonic stem cell features (i.e., pluripotency, immortality, unlimited undifferentiated proliferation capability, and maintenance of normal karyotypes) after prolonged culture of 70 passages (>250 doublings). The major advantage of foreskin feeders is their ability to be continuously cultured for more than 42 passages, thus enabling proper analysis for foreign agents, genetic modification such as antibiotic resistance, and reduction of the enormous workload involved in the continuous preparation of new feeder lines.     

小鼠孤雌胚胎干细胞系的建立及生物学特性鉴定

目的:探讨建立合适的小鼠孤雌胚胎干细胞建系方法。方法:采用氯化锶联合细胞松弛素B激活B6D2F1杂交小鼠卵母细胞,所获得的囊胚与桑椹胚分别用于孤雌胚胎干细胞的建系,观察两者的建系成功率。结果:共建立了12株小鼠孤雌胚胎干细胞系,这些细胞SSEA-1抗原阳性,SSEA-4,TRA-1-81,TRA-1-60表面抗原阴性,具有AKP活性,保持正常染色体核型,体内外分化分别形成畸胎瘤和拟胚体。结论:采用囊胚和去透明带的桑葚胚建立孤雌胚胎干细胞系获得成功。该方法为人类纯合子的胚胎干细胞建系提供基础,在自体细胞治疗领域中具有潜在的应用价值。     

Efficient derivation of human embryonic stem cell lines from discarded embryos through increases in the concentration of basic fibroblast growth factor

We describe the derivation and characterization of three novel human embryonic stem (hES) cell lines (YT1, YT2, YT3). One hES line (YT1) was obtained from six discarded blastocysts in a culture medium supplemented with 12 ng/ml basic fibroblast growth factor (bFGF), and two lines (YT2,YT3)were obtained from three discarded blastocysts in the same medium but supplemented with 16 ng/ml bFGF. These cell lines were derived by partial or whole embryo culture followed by further expansion after manual dissection of the passaged cells. These cells were passaged continuously for more than 6 or 8 months and possessed all of the typical features of pluripotent hES cell lines, such as typical morphological characteristics and the expression of hES-specific markers (TRA-1-60, TRA-1-81, SSEA-4, SSEA-3, alkaline phosphatase, Oct4, Nanog) and pluripotency-related genes (Oct4, Nanog, TDGF1, Sox2, EBAF, Thy-1, FGF4, Rex1). The lines maintained normal karyotypes after long-term cultivation. The karyotype of YT1 and YT3 was 46,XX, and that of YT2 was 46, XY. Pluripotency was confirmed by in vitro and in vivo differentiation, and genetic identity was demonstrated by DNA fingerprinting.Our results indicate that higher concentrations of bFGF at the early culture stage support efficient the hES cell derivation.     

Establishment and maintenance of human embryonic stem cell lines on human feeder cells derived from uterine endometrium under serum-free condition

Human embryonic stem (hES) cells are usually established and maintained on mouse embryonic fibroblast (MEFs) feeder layers. However, it is desirable to develop human feeder cells because animal feeder cells are associated with risks such as viral infection and/or pathogen transmission. In this study, we attempted to establish new hES cell lines using human uterine endometrial cells (hUECs) to prevent the risks associated with animal feeder cells and for their eventual application in cell-replacement therapy. Inner cell masses (ICMs) of cultured blastocysts were isolated by immunosurgery and then cultured on mitotically inactivated hUEC feeder layers. Cultured ICMs formed colonies by continuous proliferation and were allowed to proliferate continuously for 40, 50, and 55 passages. The established hES cell lines (Miz-hES-14, -15, and -9, respectively) exhibited typical hES cells characteristics, including continuous growth, expression of specific markers, normal karyotypes, and differentiation capacity. The hUEC feeders have the advantage that they can be used for many passages, whereas MEF feeder cells can only be used as feeder cells for a limited number of passages. The hUECs are available to establish and maintain hES cells, and the high expression of embryotrophic factors and extracellular matrices by hUECs may be important to the efficient growth of hES cells. Clinical applications require the establishment and expansion of hES cells under stable xeno-free culture systems.     

人胚胎干细胞优化培养的进展

人胚胎干细胞(humanembryonicstemcell,hEScell)是来源于着床前人囊胚内细胞团(innercellmass,ICM)的、具有自我更新能力和分化全能性的细胞。由于hES细胞能在一定条件下分化成三个胚层来源的各种细胞,所以它具有重要的基础研究价值和巨大的临床应用前景,可应用于人早期胚胎发育过程的研究、药物毒物筛选、细胞移植治疗、基因治疗等领域。目前,世界上已经建立了多株hES细胞系,最早建立的hES细胞系是生长在小鼠胚胎成纤维(mouseembryonicfibroblast,MEF)细胞上的,培养体系中含血清等动物源性成分,这些成分可能引起动物源性病原体或支原体的污染,从而限制了hES细胞的临床应用。近年来,科学家们在优化hES细胞的体外培养体系方面做出了很大的努力并取得了长足进展,已经开始采用无血清、无饲养层细胞、无外源性蛋白、成分明确的培养体系进行hES细胞建系及培养,从而在一定程度上解决了上述问题。本文主要从饲养层细胞、无饲养层培养体系、培养基质、细胞因子等方面综述了hES细胞建系和维持其未分化状态的优化培养所取得的最新进展和存在的问题。     

Bioluminescence reporter gene imaging characterize human embryonic stem cell-derived teratoma formation

Human embryonic stem (hES) cells have a potential use for the repair and regeneration of injured tissues. However, teratoma formation can be a major obstacle for hES-mediated cell therapy. Therefore, tracking the fate and function of transplanted hES cells with noninvasive imaging could be valuable for a better understanding of the biology and physiology of teratoma formation. In this study, hES cells were stably transduced with a double fusion reporter gene consisting of firefly luciferase and enhanced green fluorescent protein. Following bioluminescence imaging and histology, we demonstrated that engraftment of hES cells was followed by dramatically increasing signaling and led to teratoma formation confirmed by histology. Studies of the angiogenic processes within teratomas revealed that their vasculatures were derived from both differentiated hES cells and host. Moreover, FACS analysis showed that teratoma cells derived from hES cells expressed high levels of CD56 and SSEA-4, and the subcultured SSEA-4(+) cells showed a similar cell surface marker expression pattern when compared to undifferentiated hES cells. We report here for the first time that SSEA-4(+) cells derived from teratoma exhibited multipotency, retained their differentiation ability in vivo as confirmed by their differentiation into representative three germ layers.     

Isolation of multipotent stem cells in human periodontal ligament using stage-specific embryonic antigen-4

The periodontal ligament (PDL) comprises adult stem cells, which are responsible for periodontal tissue regeneration. In the present study, we investigated the specific profile of the stem cells in the human PDL. Microscopic analysis demonstrated that PDL cells showed a fibroblastic appearance, forming flat and loose aggregates. PDL cells expressed embryonic stem cell-associated antigens (SSEA-1, SSEA-3, SSEA-4, TRA-1-60, TRA-1-81, OCT4, NANOG, SOX2, and REX1, and alkaline phosphatase activity), as well as conventional mesenchymal stem cell markers. When PDL cells were cultured in the presence of all-trans-retinoic acid, the numbers of SSEA-3+ and SSEA-4+ PDL cells were significantly decreased, while that of SSEA-1+ was increased. SSEA-4+ PDL cells showed a greater telomere length and growth rate. SSEA-4+ PDL cells exhibited the potential to generate specialized cells derived from three embryonic germ layers: mesodermal (adipocytes, osteoblasts, and chondrocytes), ectodermal (neurons), and endodermal (hepatocytes) lineages. Our findings demonstrated that SSEA-4, a major antigen to distinguish human embryonic stem cells, could also be used to identify multipotent stem cells in the PDL. Hence, SSEA-4+ human PDL cells appear to be a promising source of stem cells for regenerative medicine.