Richard L. Gardner

Bio: Richard L. Gardner is an academic researcher from University of Oxford. The author has contributed to research in topics: Blastocyst & Stem cell. The author has an hindex of 39, co-authored 66 publications receiving 7804 citations. Previous affiliations of Richard L. Gardner include National Foundation for Cancer Research & University of Cambridge.

New cell lines from mouse epiblast share defining features with human embryonic stem cells

Abstract: The application of human embryonic stem (ES) cells in medicine and biology has an inherent reliance on understanding the starting cell population. Human ES cells differ from mouse ES cells and the specific embryonic origin of both cell types is unclear. Previous work suggested that mouse ES cells could only be obtained from the embryo before implantation in the uterus. Here we show that cell lines can be derived from the epiblast, a tissue of the post-implantation embryo that generates the embryo proper. These cells, which we refer to as EpiSCs (post-implantation epiblast-derived stem cells), express transcription factors known to regulate pluripotency, maintain their genomic integrity, and robustly differentiate into the major somatic cell types as well as primordial germ cells. The EpiSC lines are distinct from mouse ES cells in their epigenetic state and the signals controlling their differentiation. Furthermore, EpiSC and human ES cells share patterns of gene expression and signalling responses that normally function in the epiblast. These results show that epiblast cells can be maintained as stable cell lines and interrogated to understand how pluripotent cells generate distinct fates during early development.

The origin and efficient derivation of embryonic stem cells in the mouse

Abstract: By explanting tissues isolated microsurgically from implanting strain 129 mouse blastocysts individually on STO feeder cells we have established that embryonic stem (ES) cells originate from the epiblast (primitive ectoderm). Isolated early epiblasts yielded ES cell lines at a substantially higher frequency than intact blastocysts regardless of whether they were explanted whole or as strictly single-cell suspensions. When explanted from delayed-implanting 129 blastocysts, epiblasts gave lines consistently in 100% of cases. If primary embryonic fibroblasts rather than STO cells were used as feeders, germline-competent ES cell lines were obtained readily from epiblasts of delayed-implanting blastocysts of several hitherto refractory strains, particularly when recombinant leukemia inhibitory factor was included in the medium during the initial period of culture. Because lines were obtained from the nonpermissive CBA/Ca strain at a rate of up to 56%, this approach to the derivation of germline-competent ES cell lines may not only prove generic for the mouse but also worth pursuing in other species of mammal.

Fate of teratocarcinoma cells injected into early mouse embryos

Abstract: ANALYSIS of early mammalian development is complicated by technical difficulties. The initial processes of cellular determination and differentiation in the mouse embryo take place in small populations of cells1,2, and major embryogenic events occur after uterine implantation when the embryo is largely inaccessible. Recent work, however, suggests that murine teratocarcinomas may provide a convenient model for studying mammalian development3–6. These are transplantable tumours of germ cell or embryonic cell origin3–6, typically consisting of a variety of differentiated tissues and undifferentiated stem cells. The stem cells, called embryonal carcinoma, resemble cells of early embryos in morphological, biochemical and cell surface properties, and in developmental potential3–6. They can be propagated in tissue culture to provide sufficient material for biochemical analysis. After inoculation into histocompatible adult hosts they form differentiated teratocarcinomas. They also differentiate in vitro7,8 where the first stages of their differentiation seem to parallel normal embryonic development. We show here that embryonal carcinoma cells can participate in normal embryogenesis, thus providing further evidence for the validity of the use of these cultures as a model of normal embryonic development.

Imprinted X-inactivation in extra-embryonic endoderm cell lines from mouse blastocysts.

Abstract: The extra-embryonic endoderm lineage plays a major role in the nutritive support of the embryo and is required for several inductive events, such as anterior patterning and blood island formation. Blastocyst-derived embryonic stem (ES) and trophoblast stem (TS) cell lines provide good models with which to study the development of the epiblast and trophoblast lineages, respectively. We describe the derivation and characterization of cell lines that are representative of the third lineage of the blastocyst – extra-embryonic endoderm. Extra-embryonic endoderm (XEN) cell lines can be reproducibly derived from mouse blastocysts and passaged without any evidence of senescence. XEN cells express markers typical of extra-embryonic endoderm derivatives, but not those of the epiblast or trophoblast. Chimeras generated by injection of XEN cells into blastocysts showed exclusive contribution to extra-embryonic endoderm cell types. We used female XEN cells to investigate the mechanism of X chromosome inactivation in this lineage. We observed paternally imprinted X-inactivation, consistent with observations in vivo. Based on gene expression analysis, chimera studies and imprinted X-inactivation, XEN cell lines are representative of extra-embryonic endoderm and provide a new cell culture model of an early mammalian lineage.

Investigation of the fate of 4.5 Day post-coitum mouse inner cell mass cells by blastocyst injection.

Abstract: Two distinct patterns of chimaerism were found in conceptuses produced by injecting dissociated 4.5-day inner cell mass cells into genetically dissimilar blastocysts. Pattern 1: donor cells were found in the endoderm layer of the visceral yolk sac, but not in the adjacent mesoderm layer of this organ or in the foetus itself. Pattern 2: donor cells were found in the mesoderm layer of the visceral yolk sac and/or foetus, but never in the yolk-sac endoderm as well. Primitive endoderm cells of donor inner cell masses are responsible for the first pattern and primitive ectoderm cells for the second. These results, together with those of previous studies, suggest that the entire foetus, including its endodermal components, is formed from the primitive ectoderm, and that primitive endoderm forms only extra-embryonic endoderm of the conceptus.

Induction of Pluripotent Stem Cells From Adult Human Fibroblasts by Defined Factors

Abstract: If it were possible to reprogram differentiated human somatic cells into a pluripotent state, patient-specific and disease-specific stem cells could be developed. Previous work generated induced pluripotent stem (iPS) cells capable of germline transmission from murine somatic cells by transd

Quantitative expression of Oct-3/4 defines differentiation, dedifferentiation or self-renewal of ES cells.

Abstract: Cell fate during development is defined by transcription factors that act as molecular switches to activate or repress specific gene expression programmes. The POU transcription factor Oct-3/4 (encoded by Pou5f1) is a candidate regulator in pluripotent and germline cells and is essential for the initial formation of a pluripotent founder cell population in the mammalian embryo. Here we use conditional expression and repression in embryonic stem (ES) cells to determine requirements for Oct-3/4 in the maintenance of developmental potency. Although transcriptional determination has usually been considered as a binary on-off control system, we found that the precise level of Oct-3/4 governs three distinct fates of ES cells. A less than twofold increase in expression causes differentiation into primitive endoderm and mesoderm. In contrast, repression of Oct-3/4 induces loss of pluripotency and dedifferentiation to trophectoderm. Thus a critical amount of Oct-3/4 is required to sustain stem-cell self-renewal, and up- or downregulation induce divergent developmental programmes. Our findings establish a role for Oct-3/4 as a master regulator of pluripotency that controls lineage commitment and illustrate the sophistication of critical transcriptional regulators and the consequent importance of quantitative analyses.