No abstract

Pluripotent embryonic stem (ES) cells derived from mammalian blastocyst and the adult fibroblast derived induced pluripotent stem (iPS cells) exhibit complete potential to form cells representing all the primary germ layers such as mesoderm, endoderm and ectoderm. These cells are usually co-cultured with mouse embryonic fibroblast feeders to prevent spontaneous differentiation. Feeder free cultures can provide substantial advantage to improve the efficiency and consistency of the culture conditions. In these studies, we demonstrate that a small dietary compound retinol, the alcohol form of vitamin A has capacity to regulate the pluripotency of pluripotent stem cells and maintain highly enriched population of pluripotent ES and iPS cells in feeder free suspension cultures. Retinol maintains long-term cultures of undifferentiated cells via elevated expression of stem cell specific transcription factors Nanog and Oct4. The studies provide evidence that retinol regulates the self-renewal of pluripotent stem cells via the over expression of insulin like growth factor II (IGFII) that engages PI3 kinase signaling pathway via IGF1 receptor tyrosine kinase. The ES cells retain capacity to generate high degree germline competent chimeric animals after microinjection into blastocysts. The studies offer a convenient system for long term maintenance of pluripotent stem cells via the activation of intracellular machinery for self-renewal by a physiologically relevant compound for large-scale production of high quality pluripotent stem cells.

Transgenic mice are useful tools for studying gene function and regulation but can be difficult to successfully breed. To 'rescue' transgenic lines that are difficult to propagate, researchers use a variety of techniques. One method is ovarian transplant, in which researchers remove ovaries from a donor transgenic mouse, cryopreserve the ovarian tissue, transplant this tissue into histocompatible female mice and breed these recipient females. Though it is a useful technique, cryopreservation can potentially damage ovarian tissue, which could reduce fertility. In this article, the authors describe how they carried out ovarian transplants without cryopreservation to rescue a line of transgenic C57BL/6 mice. Other researchers who have experience with mouse reproductive surgery should be able to use this technique to rescue infertile transgenic lines of mice.