Showing papers on "Totipotent published in 2008"

The four blastomeres of a 4-cell stage human embryo are able to develop individually into blastocysts with inner cell mass and trophectoderm

Abstract: Background Early mammalian blastomeres are thought to be flexible and totipotent allowing the embryo to overcome perturbations in its organization during preimplantation development. In the past, experiments using single blastomeres from 2-, 4- and 8-cell stage mammalian embryos have provided evidence that at least some of the isolated cells can develop into healthy fertile animals and therefore are totipotent. We investigated whether isolated blastomeres of human 4-cell stage embryos could develop in vitro into blastocysts with trophectoderm (TE) and inner cell mass (ICM). Methods Six 4-cell stage human embryos were split and the four blastomeres were cultured individually. The expression of NANOG, a marker for ICM cells, was analysed by immunocytochemistry. Results The majority of the blastomere-derived embryos followed the normal pattern of development with compaction on Day 4 and cavitation on Day 5 and developed into small blastocysts with TE and ICM on Day 6 (n = 12). The four cells of one embryo were individually capable of developing into blastocysts with TE and ICM, and NANOG was expressed in the ICM. Conclusions Although based on a small number of embryos, we conclude that the blastomeres of a 4-cell stage human embryo are flexible and able to develop into blastocysts with ICM and TE.

Oogenesis: Prospects and challenges for the future.

Abstract: Oogenesis serves a singular role in the reproductive success of plants and animals. Of their remarkable differentiation pathway what stands out is the ability of oocytes to transform from a single cell into the totipotent lineages that seed the early embryo. As our understanding that commonalities between diverse organisms at the genetic, cellular and molecular levels are conserved to achieve successful reproduction, the notion that embryogenesis presupposes oogenesis has entered the day-to-day parlance of regenerative medicine and stem cell biology. With emphasis on the mammalian oocyte, this review will cover (1) current concepts regarding the birth, survival and growth of oocytes that depends on complex patterns of cell communication between germ line and soma, (2) the notion of "maternal inheritance" from a genetic and epigenetic perspective, and (3) the relative value of model systems with reference to current clinical and biotechnology applications.

Reprogramming and differentiation in mammals: motifs and mechanisms.

Abstract: The natural reprogramming of the mammalian egg and sperm genomes is an efficient process that takes place in less than 24 hours and gives rise to a totipotent zygote. Transfer of somatic nuclei to mammalian oocytes also leads to their reprogramming and formation of totipotent embryos, albeit very inefficiently and requiring an activation step. Reprogramming of differentiated cells to induced pluripotent stem (iPS) cells takes place during a period of time substantially longer than reprogramming of the egg and sperm nuclei and is significantly less efficient. The stochastic expression of endogenous proteinsduringthisprocesswouldimplythatcontrolledexpressionofspecificproteinsiscrucialforreprogrammingtotakeplace. The fact that OCT4, NANOG, and SOX2 form the core components of the pluripotency circuitry would imply that control at the transcriptional level is important for reprogramming to iPS cells. In contradistinction, the much more efficient reprogramming of the mammalian egg and sperm genomes implies that other levels of control are necessary, such as chromatin remodeling, translational regulation, and efficient degradation of no longer needed proteins and RNAs.

A Concise Review on the Classification and Nomenclature of Stem Cells.

Abstract: Stem cell biology and regenerative medicine is a relatively young field. However, in recent years there has been a tremendous interest in stem cells possibly due to their therapeutic potential in disease states. As a classical definition, a stem cell is an undifferentiated cell that can produce daughter cells that can either remain a stem cell in a process called self-renew¬al, or commit to a specific cell type via the initiation of a differentiation pathway leading to the production of mature progeny cells. Despite this acknowledged definition, the classification of stem cells has been a perplexing notion that may often raise misconception even among stem cell biologists. Therefore, the aim of this brief review is to give a conceptual approach to classifying the stem cells beginning from the early morula stage totipotent embryonic stem cells to the unipotent tissue-resident adult stem cells, also called tissue-specific stem cells.

Nuclear organisation in totipotent human nuclei and its relationship to chromosomal abnormality.

Abstract: Studies of nuclear organisation, most commonly determining the nuclear location of chromosome territories and individual loci, have furthered our understanding of nuclear function, differentiation and disease. In this study, by examining eight loci on different chromosomes, we tested hypotheses that: (1) totipotent human blastomeres adopt a nuclear organisation akin to that of committed cells; (2) nuclear organisation is different in chromosomally abnormal blastomeres; and (3) human blastomeres adopt a ;chromocentre' pattern. Analysis of in vitro fertilisation (IVF) conceptuses permits valuable insight into the cell biology of totipotent human nuclei. Here, extrapolations from images of preimplantation genetic screening (PGS) cases were used to make comparisons between totipotent blastomeres and several committed cells, showing some differences and similarities. Comparisons between chromosomally abnormal nuclei and those with no detected abnormality (NDA) suggest that the former display a significant non-random pattern for all autosomal loci, but there is a less distinct, possibly random, pattern in 'NDA' nuclei. No evidence was found that the presence of an extra chromosome is accompanied by an altered nuclear location for that chromosome. Centromeric loci on chromosomes 15 and 16 normally seen at the nuclear periphery were mostly centrally located in aneuploid cells, providing some evidence of a 'chromocentre'; however, the chromosome-18 centromere was more peripheral, similar to committed cells. Our results provide clues to the nature of totipotency in human cells and might have future applications for preimplantation diagnosis and nuclear transfer.

Stem cells in reproductive strategy of asexually reproducing invertebrates

Abstract: Original and literature data supporting the evolutionary conservation of the morphofunctional organization of totipotent cells of germ and stem lineages in metazoan animals are reviewed. We studied stem cells of the colonial rhizocephalans, Peltogasterella gracilis, Polyascus polygenea and Thylacoplethus isaevae, the turbellarian Dugesia tigrina, the colonial hydroid Obelia longissima, and cultured embryonic stem cells of mouse. The typical germinal granules of germ plasm, selective expression of the activity of alkaline phosphatase and of proliferating cell nuclear antigen (PCNA), which are known as markers of stem and primary germ cells of vertebrates, and the specific expression of the protein product of the vasa gene in cells of rhizocephalans, which is a marker of cells of germ and stem lineages of various metazoans, specified the stem cells of invertebrates of such different taxa. The self-renewing pool of totipotent stem cells is the cellular basis of the reproductive strategy, including sexual and asexual reproduction; such cells share morphofunctional features of embryonic stem and germline cells of Metazoa.

Use of umbilical cord matrix cells

Abstract: The invention relates to the isolation and use of stem cells from amniote species (potentially any animal with an umbilical cord, including humans). More particularly the invention relates to obtaining stem cells that are at least multipotent and may be totipotent or nearly totipotent and are envisaged to have a variety of end uses. The cells of the present invention are immunosuppressive and may be used to inhibit the immune response in a subject.

Potency, Patenting and Preformation: The Patentability of Totipotent Cells in Canada

Abstract: The Canadian Intellectual Property Office’s (CIPO) publication entitled, Office Practice Regarding the Patentability of Fertilized Eggs, Stem Cells and Tissues, is examined with respect to the patentability of totipotent cells. It is conjectured that its position against the patentability of totipotent cells is based upon a mistaken view of animal development and stem cell differentiation called “genetic preformationism.” This view holds that the DNA in a totipotent cell is the sole determinant of development and differentiation so that a totipotent cell containing the DNA of a higher life form is a higher life form. It ignores the fact that modern biologists have recognised an increasingly important role for non-genetic, environmental factors in both animal development and stem cell differentiation. Given that the CIPO’s views on development and differentiation are incorrect and the process of developing the Notice lacked transparency, justification and intelligibility, it cannot justifiably reject an application for a patent on a fertilised egg or totipotent stem cell on the basis of the reasons given in the Office Practice Regarding the Patentability of Fertilized Eggs, Stem Cells and Tissues. This paper suggests that there are legal, practical and scientific limits of the ability of the CIPO, like other patent offices, to apply patent legislation wisely to fundamentally new technologies.

Potency, Patenting and Preformation: The Patentability of Totipotent Cells in Canada

Abstract: The Canadian Intellectual Property Office’s (CIPO) publication entitled, Office Practice Regarding the Patentability of Fertilized Eggs, Stem Cells and Tissues, is examined with respect to the patentability of totipotent cells. It is conjectured that its position against the patentability of totipotent cells is based upon a mistaken view of animal development and stem cell differentiation called “genetic preformationism.” This view holds that the DNA in a totipotent cell is the sole determinant of development and differentiation so that a totipotent cell containing the DNA of a higher life form is a higher life form. It ignores the fact that modern biologists have recognised an increasingly important role for non-genetic, environmental factors in both animal development and stem cell differentiation. Given that the CIPO’s views on development and differentiation are incorrect and the process of developing the Notice lacked transparency, justification and intelligibility, it cannot justifiably reject an application for a patent on a fertilised egg or totipotent stem cell on the basis of the reasons given in the Office Practice Regarding the Patentability of Fertilized Eggs, Stem Cells and Tissues. This paper suggests that there are legal, practical and scientific limits of the ability of the CIPO, like other patent offices, to apply patent legislation wisely to fundamentally new technologies.