"Derivation of Pluripotent Stem Cells from Cultured Human Primordial Germ Cells" (1998), by John Gearhart et al.

In November 1998, two independent reports were published concerning the first isolation of pluripotent human stem cells [5] , one of which was “Derivation of Pluripotent Stem Cells from Cultured Human Primordial Germ Cells. ” This paper, authored by John D. Gearhart and his research team— Michael J. Shamblott [6] , Joyce Axelman [7] , Shunping Wang [8] , Elizabeth M. Bugg [9] , John W. Littlefield [10] , Peter J. Donovan [11] , Paul D. Blumenthal [12] , and George R. Huggins—was published in Proceedings of the National Academy of Science soon after James A. Thomson [13] and his research team published “Embryonic Stem Cell Lines Derived from Human Blastocysts” in Science . Gearhart’s paper suggested that pluripotent human stem cells [5] , which have the ability to develop into all cell types that make up the body, could be derived from primordial germ cells [14] , which are precursors of fully differentiated germ cells [14] , isolated from embryos. At the time, Gearhart was a professor of obstetrics and gynecology at Johns Hopkins University School of Medicine [15] . With a background in genetics, he had devoted the majority of his research to how genes [16] regulate tissue and embryo formation. However, the successful isolation of mice embryonic stem cells [17] encouraged Gearhart to pursue the isolation of similar cells in humans [18] . The principal difference between human embryonic stem (ES) cells, which Thomson’s team derived, and human embryonic germ (EG) cells, which Gearhart’s team derived, is that human embryonic germ cells [19] are derived from early germ cells [14] . Nonetheless, they are thought to share similar properties to human embryonic stem cells [17] . Gearhart and ridges [20] , the developmental precursors to gonads, and mesenteries [21] from aborted 5-to-9-week-old human embryos/fetuses. The embryos were used after the donors gave informed consent [22] . After mechanical disaggregation, where force is applied to separate a sample tissue into individual cells, the cells were cultured and placed on a mitotically inactivated mouse [23] fibroblast feeder layer. Mouse fibroblasts come from the Sandoz inbred mouse [24] and, to date, are the only cell type capable of generating human EG cells. The disaggregated cells were grown in an environment that included human recombinant leukemia inhibitory factor (hrLIF), human recombinant basic fibroblast growth factor (hrbGFG), and forskolin. These factors enable cell division, but not cell differentiation [25] . The cells were tested for alkaline phosphatase activity as well as the presence of five cell surface markers: alkaline phosphatase, stage specific antigen (SSEA)-1, SSEA-3, SSEA-4, TRA-1-60, and TRA-1-81. Immunohistochemical analysis was performed on a batch of embryoid bodies (differentiated cell aggregates) that were eventually cultured for fourteen days in absence of hrLIF, hrbFGF, and forskolin before being embedded in paraffin. After sixty to seventy days in culture (passage 8-10), cells from five different cultures underwent karyotype [26] analyses to detect human chromosomes. This paper, authored by John D. Gearhart and his research team - Michael J Shamblott, Joyce Axelman, Shunping Wang, Elizabeith M. Bugg, John W. Littlefield, Peter J. Donovan, Paul D. Blumenthal, and George R. Huggins - was published in Proceedings of the National Academy of Science soon after James A. Thomson and his research team published "Embryonic Stem Cell Lines Derived from Human Blastocysts" in Science. Gearhart 's paper suggested that pluripotent human stem cells, which have the ability to develop into all cell types that make up the body, could be derived from primordial germ cells, which are precursors of fully differentiated germ cells, isolated from embryos. At the time, Gearhart was a professor of obstetrics and gynecology at Johns Hopkins University School of Medicine. With a background in genetics, he had devoted the majority of his research to how genes regulate tissue and embryo formation. However, the successful isolation of mice embryonic stem cells encouraged Gearhart to pursue the isolation of similar cells in humans. The principal difference between human embryonic stem (ES) cells, which Thomson 's team derived, and human embryonic germ (EG) cells, which Gearhart 's team derived, is that human embryonic germ cells are derived from early germ cells. Nonetheless, they are thought to share similar properties to human embryonic stem cells.