SHORT COMMUNICATION The Effect of Transgenesis on Rabbit Thyroid Tissue Structure E. Tvrda 1 *, P. Massanyi 1 , N. Lukac 1 , J. Danko 2 and P. Chrenek 1,3 Addresses of authors: 1 Faculty of Biotechnology and Food Sciences, Slovak University of Agriculture, Nitra, Slovakia; 2 University of Veterinary Medicine, Kosice, Slovakia; 3 Institute for Farm Animal Genetics and Reproduction, Animal Production Research Centre, Nitra, Slovakia Introduction Transgenic technology is an established method for intro- ducing ‘new’ genes into multicellular organisms (Wheeler, 2003). Current applications of gene transfers in animals include improvement of product quality and quantity, disease resistance, production of valuable proteins in the mammary gland or other organs, xenotransplants and generation of new animal models for human diseases (Wolf et al., 2000). Transgenic rabbits have been found to be excellent ani- mal models for studying human diseases, but also proved to be suitable bioreactors for the production of pharma- ceutical proteins (Houdebine, 1995). The transgenic rab- bit system is especially valuable because it can be used to produce recombinant proteins in milk or serum, both on an experimental and commercial scale (Bosze et al., 2003). One of many examples is the transgenic rabbit whose mammary gland produces human factor VIII (hFVIII), used for haemophilia type A treatment (Fallaux et al., 1995). Usually, publications on transgenic organisms focus on the quantity and quality of produced recombinant pro- teins, not on the effects of transgenesis on the physiologi- cal state of the recipient (Palmer et al., 2006). Nevertheless, the consequences of a foreign gene presence on animal health, especially over several generations, should be thoroughly examined (Sirotkin et al., 2008). The endocrine system is responsible for the control of a wide range of biological processes, including reproduc- tion and adaptation. In rabbits, as in other mammals, the thyroid gland is one of the largest and most important endocrine glands. Thyroid hormones regulate growth and development, metabolic activity and sensitivity towards other biologically active substances (Nussey and White- head, 2001). At the same time, one should keep in mind that the thyroid gland may be negatively affected by a wide range of factors, transgenesis included, leading to potential metabolic disorders and a lower capability to survive and produce offspring. A successful integration of the mWAP–hFVIII (the human clotting factor VIII transgene under the murine whey acidic protein promoter) construct should result in the recombinant protein expression in the mammary gland only. Still, one should keep in mind that trans- genic rabbits have such construct integrated in each cell with nucleus, follicular cells included. Because it is essential to produce transgenic animals with an overall good health state and hormonal balance, the objective of this work was to evaluate possible effects of the mWAP– hFVIII gene integration on the rabbit thyroid gland structure. *Correspondence: Tel.: +421 37 641 4288; fax: +421 37 641 5387; e-mail: evina.tvrda@gmail.com With 1 figure and 3 tables Received February 2011; accepted for publication September 2011 doi: 10.1111/j.1439-0264.2011.01116.x Summary This study was aimed to compare structures of the thyroid tissue of transgenic rabbits expressing the human clotting factor VIII under the murine whey acidic protein promoter (mWAP–hFVIII rabbits) with the non-transgenic controls. Thyroid tissue samples were taken from transgenic and non-transgenic New Zealand White rabbits, examined by optical microscopy and analysed morpho- metrically. The analysis revealed no significant differences (P > 0.05) in the rel- ative volume of basic thyroid structures. Furthermore, no significant differences (P > 0.05) were observed when measuring the epithelial height and nuclear diameter of the follicular cells. Altogether, this study demonstrates no negative effect of the mWAP–hFVIII transgenesis on the rabbit thyroid gland structure. Anatomia Histologia Embryologia ª 2011 Blackwell Verlag GmbH • Anat. Histol. Embryol. 1