Embryonic Stem Cells in Domestic Animals No shortcuts to pig embryonic stem cells T.A.L. Brevini*, G. Pennarossa, F. Gandolfi Università degli Studi di Milano, Laboratory of Biomedical Embryology, Anatomy and Histology Unit, Milano, Italy Received 8 April 2010; received in revised form 16 April 2010; accepted 18 April 2010 Abstract The establishment of embryonic stem cell (ESC) lines in domestic species could have great impact in the agricultural as well as in the biomedical field. In particular, derivation of pig ESC would find important applications aimed at improving health and production traits of this species through genetic engineering. Similarly, the immunological, morphological, physiological, and functional similarities to the human make the pig a very effective and suitable animal model for biomedical studies and pre-clinical trials. While proven blastocyst-derived mouse and human ESC lines have been established, no validated porcine ESC (pESC) lines are available. In the present manuscript we briefly discuss some of the factors that make the establishment of ESC lines in the pig, and in animal species other than mouse and human, a very slow process. The paucity of information related to morphology, pluripotency markers, differentiation capability hampers a thorough evaluation of the validity of putative lines. These difficulties are further increased by the lack of reliable antibodies, reagents, and in vitro culture systems that could ensure reliable results in the pig and allow for the screening and long-term maintenance of pESC. Data from the literature suggest that similar regulatory pathways are likely to exist among different species. Coupling of these pathways with their distinct expression patterns, the relative concentrations of pluripotency-related molecules, and timing of embryo development, along with supportive micro-environmental conditions, would appear to vary in a species-specific manner. We feel that the understanding of these subtle but meaningful diversities may provide beneficial information about the isolation of genuine porcine embryonic stem cells. © 2010 Elsevier Inc. All rights reserved. Keywords: Pig; Embryo; Stem cells Contents 1. Introduction ............................................................................................................................. 544 2. Different species, different timing .................................................................................................. 545 3. Which culture conditions? ............................................................................................................ 546 4. How do we assess pluripotency? .................................................................................................... 547 5. Perspectives and strategies ........................................................................................................... 548 References ............................................................................................................................... 549 1. Introduction During the past 15 years, many reports of porcine ESC lines, or what are often presented as “ES-like” cell lines, have been published. However, validated pig ESC (pESC) lines still do not exist and no con- clusive results have been obtained, despite numerous Current address for all authors: Department of Animal Science, Laboratory of Biomedical Embryology - Università degli Studi di Milano - 20133 Milano (Italy). * Corresponding author. Tel.: +390250317970; fax: +390250317980. E-mail address: tiziana.brevini@unimi.it (T.A.L. Brevini). Available online at www.sciencedirect.com Theriogenology 74 (2010) 544 –550 www.theriojournal.com 0093-691X/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.theriogenology.2010.04.020