405. Isolation and preliminary characterisation of putative sheep embryonic stem cells

Abstract

The establishment of true, fully characterised embryonic stem (ES) cells from livestock, (eg sheep) has yet to be reported. Such cells could make a significant impact on assisted reproductive technologies, vaccine delivery, and animal health and well being in the livestock industries. To date in sheep, there is a single report of putative ES cells which were maintained in an undifferentiated state for only 2 passages. Here we report the isolation and culture of pluripotent ES-like cells from in vivo derived, vitrified, sheep blastocysts. The inner cell mass of blastocysts were isolated by immunosurgery, cultured in Stem Cell Sciences' (SCS) novel inhibitor-based media, on a feeder layer of mouse embryonic fibroblasts (MEFs), resulting in putative ovine ES cells proliferating to at least passage 5. One cell line, BMCOV002, was established out of four thaw-recovered embryos. The colonies formed compact, near homogenous, small cell, multilayered, and well defined dome shaped masses that were morphologically similar to both mouse and human ES cell colonies. A peripheral halo of filamentous differentiated cells was detected in selected colonies from passage 3 to passage 5. The putative ovine ES-like cells were passaged by mechanical excision between days 6–7, and these colonies stained positive for alkaline phosphatase at both passage 3 and passage 5. Expression levels of genes encoding the pluripotent transcription factors OCT4, SOX2, REX1 and NANOG are shown using RT PCR in cells from passage 3. An important first step in studying the properties of ovine ES-like cells is the ability shown here to isolate and culture cells. Our attention now is focussed on maintaining these cells for some months in an undifferentiated state, and on being able to successfully cryopreserve and regenerate these cell lines.