Narrow Results

Pluripotent stem (PS) cells have the ability to replicate themselves (self-renew) and to generate virtually any given cell type in the adult body (pluripotency). Human PS (hPS) cells are therefore considered promising sources for future cell replacement therapy. Embryonic stem (ES) cells are the major type of PS cells that are derived from blastocyst embryos. Germ cells from testis can also become PS cells when cultured for a long period with a combination of growth factors. Alternatively, differentiated somatic cells can also be converted to PS cells by the method called nuclear reprogramming. This includes somatic cell nuclear transfer where a somatic cell nucleus is injected into an enucleated oocyte giving rise to a reprogrammed PS cell, as well as the recently developed technique of reprogramming differentiated somatic cells into induced pluripotent stem (iPS) cells by introducing defined transcription factors. Regardless of the sources and generation methods, PS cells share common epithelial structures and maintain tight cellular interactions. Although the molecular mechanisms that regulate self-renewal and pluripotency of PS cells have been extensively studied, the basic cellular interactions that govern how PS cells control cell-cell and cell-matrix adhesions are still not fully understood. In addition, there are several obstacles in the current culture methods for hPS cells that need to be overcome in order to achieve the highest safety and consistency required for clinical applications. A Rho-mediated signaling axis has recently been determined to be the core machinery that integrates cellular interactions between PS cells. By chemically engineering this axis, hPS cells are able to self-renew under completely defined conditions while maintaining their multi-differentiation capacities. When combined with the rapid progress in research focusing on iPS cells, these studies on cell-cell and cell-matrix adhesion in PS cells may not only contribute to further understanding PS cell biology, but also lead to the development of novel technologies enabling the derivation and growth of clinically relevant hPS cells for regenerative therapies.

Redox state mediates embryonic stem cell (ESC) differentiation and thus offers an important complementary approach to understanding the pluripotency of stem cells. NADH redox ratio (NADH/(Fp + NADH)), where NADH is the reduced form of nicotinamide adenine dinucleotide and Fp is the oxidized flavoproteins, has been established as a sensitive indicator of mitochondrial redox state. In this paper, we report our redox imaging data on the mitochondrial redox state of mouse ESC (mESC) colonies and the implications thereof. The low-temperature NADH/Fp redox scanner was employed to image mESC colonies grown on a feeder layer of gamma-irradiated mouse embryonic fibroblasts (MEFs) on glass cover slips. The result showed significant heterogeneity in the mitochondrial redox state within individual mESC colonies (size: ~200–440 μm), exhibiting a core with a more reduced state than the periphery. This more reduced state positively correlates with the expression pattern of Oct4, a well-established marker of pluripotency. Our observation is the first to show the heterogeneity in the mitochondrial redox state within a mESC colony, suggesting that mitochondrial redox state should be further investigated as a potential new biomarker for the stemness of embryonic stem cells.

Embryonic stem (ES) cells are undifferentiated cell cultures that are derived from early developing animal embryos. ES cells retain the potential of differentiation into all cell types including germ cells and therefore provide a unique bridge linking in vitro and in vivo genetic manipulations. ES cells have been widely used in the production knockout mice. Attempts have been made to develop ES cells in fish. We used the medaka (Oryzias latipes) to develop the ES cell technology in a second vertebrate model. We have established feeder cell-free culture conditions and obtained several ES cell lines from midblastula embryos. These ES cells show all features of mouse ES cells including a diploid karyotype, the potential for differentiation into various cell types and chimera competence. This review is to use medaka ES cells to highlight the major advances and future prospects for obtaining and utilizing ES cells in model and aquaculture fish species.