BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates generally to embryonic stems cells, and more specifically to a process for obtaining human embryonic stem cells using parthenogenetically activated oocytes.

Background Information

Human embryonic stem cells (ES) cells are pluripotent cells that can differentiate into a large array of cell types. When injected into immune-deficient mice, embryonic stem cells form differentiated tumors (teratomas). However, embryonic stem into tissue types suitable for a patient's needs or the appropriate pharmacological test. Associated with this is a need for an efficient and reliable method of producing differentiated cells from embryonic stem cells.

Currently, human embryonic stem cells (hES) are derived from three sources: blastocysts remaining after infertility treatments and donated for research, blastocysts generated from donated gametes (oocytes and sperm), and the products of nuclear transfer (NT). Cadaveric fetal tissue is the only source of human embryonic germ cells (hEG). hES and hEG cells offer remarkable scientific and therapeutic possibilities, involving potential for generating more specialized cells or tissues. Ethical concerns about the sources of hES and hEG cells, however, and fears that use of NT for research could lead to use of NT to produce a human being, have fostered a great deal of public discussion and debate.

Parthenogenic activation of mammalian oocytes may be used as an alterative to fertilization by sperm/NT to prepare oocytes for embryonic stem cell generation. Parthenogenic activation is the production of embryonic cells, with or without eventual development into an adult, from a female gamete in the absence of any contribution from a male gamete.

Parthenogenetic activation of mammalian oocytes has been induced in a number of ways. Using an electrical stimulus to induce activation is of particular interest because electrofusion is part of the current nuclear transfer procedure. Parthenogenetic activation in vitro by electrical stimulation with electrofusion apparatus used for embryonic cell-oocyte membrane fusion has been reported.

Mouse oocytes have been activated by exposure to Ca+2—Mg+2free medium, medium containing hyaluronidase, exposure to ethanol, Ca+2ionophores or chelators, inhibitors of protein synthesis, and electrical stimulation. These procedures have led to high rates of parthenogenic activation and development of mouse oocytes, but did not activate and/or lead to a lower development rate of young bovine oocytes. Further, fertilization and parthenogenic activation of mouse oocytes is also dependent on post ovulatory aging.

Activation of bovine oocytes has been reported by ethanol, electrical stimulation, exposure to room temperature, and a combination of electrical stimulation and protein inhibition with cycloheximide. While these processes are thought to raise intracellular Ca+2, they are most successful when the oocytes have been aged for more than 28 hours.

SUMMARY OF THE INVENTION

The present invention is based on the seminal discovery that certain conditions are optimal for parthenogenically activating human oocytes.

In one embodiment, a method of producing human stem cells is provided including parthenogenetically activating an oocyte, where activation includes contacting the oocyte with an ionophore at high oxygen (O2) tension and contacting the oocyte with a serine-threonine kinase inhibitor under low O2tension, cultivating the activated oocyte at low O2tension until blastocyst formation, transferring the blastocyst to a layer of feeder cells, and culturing the transferred blastocyst under high O2tension, mechanically isolating an inner cell mass (ICM) from trophectoderm of the blastocyst, and culturing the cells of the ICM on a layer of feeder cells, where culturing the ICM cells is carried out under high O2tension. Preferably, the oocyte is human.

In a related aspect, low O2tension is maintained by incubation in a gas mixture environment comprising an O2concentration of about 2% O2to about 5% O2, where the gas mixture environment further comprises about 5% CO2and about 90% nitrogen (N2) to 93% N2.

In another embodiment, a method of activating human metaphase II oocytes is provided including incubating human metaphase II oocytes in in vitro fertilization (IVF) media under high O2tension, activating by incubating the cells in IVF media comprising an ionophore under high O2tension, and subsequently incubating the cells in IVF media comprising a serine-threonine kinase inhibitor (STKI) under low O2tension, and incubating the STKI treated cells until blastocyst formation under low O2tension, where inner cell masses (ICM) obtained from the blastocyst produce culturable stem cells. High O2tension may be maintained by incubating the cells in a gas mixture environment having about 5% CO2, about 20% O2, and about 75% N2.

In a related aspect, the O2tension for the incubating steps subsequent to activation is maintained by incubating the cells in a gas mixture environment comprising an O2concentration of about 2% O2to about 5% O2, where the gas mixture environment further includes about 5% CO2and about 90% N2to about 93% N2.

In another related aspect, the IVF media is essentially free of non-human products.

In a further related aspect, isolated oocytes prepared by the invention methods are provided, including isolated inner cell masses (ICM) prepared from such oocytes and corresponding stem cells isolated therefrom.

In another embodiment, human parthenogenic activation of mammalian oocytes resulting in embryogenic stem cells and their differentiated progeny is provided. Such cells and progeny are substantially isogenic to the oocyte donor, thus allowing for autologous transplantation of cells relative to the oocyte donor, and rejection by the oocyte donor's immune system is typically avoided.

In a related aspect, a cell bank of hES cell lines derived from parthenogenically activated oocytes is provided.

In one embodiment, a method for producing human stem cells from a cryopreserved oocyte or parthenote is provided, including microinjecting into the cytoplasm of the oocyte or parthenote a cryopreservation agent, freezing the oocyte or parthenote to a cryogenic temperature to cause it to enter a dormant state, storing the oocyte or parthenote in the dormant state, thawing the oocyte or parthenote, parthenogenically activating the oocyte, where the activation includes contacting the oocyte with an ionophore at high O2tension and contacting the oocyte with a serine-threonine kinase inhibitor under low O2tension, cultivating the parthenote or activated oocyte under low O2tension until blastocyst formation, isolating an inner cell mass (ICM) from the trophectoderm of the blastocyst, and culturing the cells of the ICM on a layer of feeder cells, where culturing is carried out under high O2tension.

In another embodiment, autologous stem cells derived from parthenogenetically activated oocytes from a human donor are provided. In one aspect, the stem cells possess a substantially identical haplotype as the donor cell. In a related aspect, stem cells are substantially identical genetically to the donor cell.

In one aspect, a stem cell is identified as a full sibling of the donor according to single nucleotide polymorphism (SNP) markers. In another aspect, a stem cell is genomically imprinted according to donor origin.

In one embodiment, a differentiated cell derived from a stem cell obtained from a parthenogenetically activated oocyte from a human donor is disclosed. In a related aspect, the differentiated cell includes, but is not limited to, a neuronal cell, a cardiac cell, a smooth muscle cell, a striated muscle cell, an endothelial cell, an osteoblast, an oligodendrocyte, a hematopoietic cell, an adipose cell, a stromal cell, a chondrocyte, an astrocyte, a dendritic cell, a keratinocyte, a pancreatic islet, a lymphoid precursor cell, a mast cell, a mesodermal cell, and an endodermal cell. In a further related aspect, the differentiated cell expresses one or more markers, including but not limited to, neurofiliment 68, NCAM, beta III-tubulin, GFAP, alpha-actinin, desmin, PECAM-1, VE-Cadherin, alpha-fetoprotein, or a combination thereof.

In another embodiment, a cell line comprising autologous stem cells is disclosed, where the stem cells are derived from parthenogenetically activated oocytes from a human donor. In one aspect, the cells do not express SSEA-1. In another aspect, the cells of the cell line give rise to ectodermal, mesodermal, and endodermal germ lines.

In one embodiment, a cell bank is disclosed including cryopreserved parthenotes, where the parthenotes are derived from parthenogenetically activated oocytes from one or more human donors. In a related aspect, the parthenotes have been cultivated under low O2tension until blastocyst formation.

In one embodiment, a cell bank is disclosed including cryopreserved autologous stem cells, where the stem cells are derived from parthenogenetically activated oocytes from one or more human donors.

In another embodiment, a method of treating a subject in need thereof, comprising administering a cellular composition comprising differentiated cells, wherein the differentiated cells are derived from a stem cell obtained from a parthenogenetically activated oocyte from a human donor. In one aspect, the differentiated cell is selected from the group consisting of a neuronal cell, cardiac cell, smooth muscle cell, striated muscle cell, endothelial cell, osteoblast, oligodendrocyte, hematopoietic cell, adipose cell, stromal cell, chondrocyte, astrocyte, dendritic cell, keratinocyte, pancreatic islet, lymphoid precursor cell, mast cell, mesodermal cell, and endodermal cell.

In a related aspect, the subject presents a disease selected from the group consisting of Parkinson's disease, Huntington's disease, Alzheimer's disease, ALS, spinal cord defects or injuries, multiple sclerosis, muscular dystrophy, cystic fibrosis, liver disease, diabetes, heart disease, retinal disease (such as macular degeneration and retinitis pigmentosa), cartilage defects or injuries, burns, foot ulcers, vascular disease, urinary tract disease, AIDS, and cancer.

In one embodiment, a method of generating cloned human embryonic stem cells is disclosed, including removing a first pronuclei from a previously fertilized human oocyte, transferring a second pro-nuclei into the enucleated oocyte, where the second pro-nuclei is derived from a donor oocyte or an oocyte from the mother of the donor, or a parthenogenetically activated oocyte, where the pro-nuclei of the oocyte has been replaced by the nucleus of a donor somatic cell prior to activation, and cultivating the resulting oocyte until blastocyst formation, where an inner cell mass from the blastocyst contains the embryonic stem cells.

Exemplary methods and compositions according to this invention are described in greater detail below.

