Submitted to: In Vitro Cellular and Developmental Biology - Animals
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/24/2005
Publication Date: 5/1/2005
Citation: Talbot, N.C., Caperna, T.J., Powell, A.M., Ealy, A.D., Blomberg, L., Garrett, W.M. 2005. Isolation and characterization of a bovine visceral endoderm cell line derived from a parthenogenetic blastocyst. Vitro Cellular and Developmental Biology. 41:130-141. Interpretive Summary: The work describes the isolation, development, and characterization of a bovine visceral endoderm cell line (designated BPE-1) that was derived from a parthenogenetic in vitro produced bovine embryo, i.e., an embryo produced without sperm having fertilizing the egg. Therefore, the cell's of the cell line only contain genes from the egg's nucleus (maternal genetic complement) and do not contain genes from a sperm (paternal genetic complement). The endoderm is the second specialized tissue of the early embryo to form. Although the endoderm does not contribute to the embryo itself, i.e., is an extraembryonic tissue, it plays vitally important roles in development prior to when the placenta is formed. Most notably visceral endoderm forms the 'yolk sac' which functions as a manufacturing site for early blood cells and blood proteins. Also, although the yolk sac does not literally surround a mass of yolk as in birds or reptiles, the tissue nonetheless still aides in providing nutrients flow from the mother's uterus to the developing enbryo. Fetuses made by cloning often have trouble surviving to the point that the placenta is form and so often abort for that reason. Parthenogenetic fetuses always have poor formation of the yolk sac and always abort. Therefore, the BPE-1 cell line provides an in vitro model of parthenogenote endoderm whose biological characteristics can be compared to endoderm cell lines derived from bovine embryos produced by normal fertilization or cloning. Such comparative studies may lead to an understanding as to why cloned animals so often fail to develop past the embryonic stage. This may help in the efforts to improve the efficiency of animal cloning which is important because, via cloning, it may be possible to rapidly improve various traits of cattle.
Technical Abstract: A cell line, BPE-1, was derived from a parthenogenetic 8-day in vitro-produced bovine blastocyst that produced a cell outgrowth on STO feeder cells. The BPE-1 cells resembled visceral endoderm previously cultured from blastocysts produced by in vitro fertilization (IVF). Analysis of the BPE-1 cells demonstrated that they produced serum proteins and were negative for interferon-tau production (a marker of trophectoderm). Transmission electron microscopy revealed that the cells were a polarized epithelium connected by complexes junctions resembling tight junctions in conjunction with desmosomes. Rough endoplasmic reticulum was prominent within the cells. BPE-1 cells also possessed numerous lipid vacuoles and numerous large microfilament associated bodies of an unidentified nature. The cells have been grown for over two years for multiple passages at 1:10 or 1:20 split ratios on STO feeder cells. The cells have also been propagated off of feeder cells for several passages in serum-free medium. The BPE-1 cell line presumably arose from blastomeres cells that became diploid soon after parthenogenetic activation and development of the early embryo. However, metaphase spreads prepared at passage 41 indicated the cell population had a hypodiploid (2n = 60) unimodal chromosome content with a mode of 53, and a median and mean of 52. The cell line will be of interest for functional comparisons with bovine endoderm cell lines derived from IVF and nuclear transfer embryos.