Zygote 18 (November), pp. 331–338. C  Cambridge University Press 2010 doi:10.1017/S0967199409990360 First Published Online 25 June 2010 Effect of donor cell age on development of ovine nuclear transfer embryos in vitro B. Heidari 2,3 , A. Shirazi 1,2 , P. Tajic 4 , E. Ahmadi 2 , H. Nazari 2 , N. Shams-Esfandabadi 2 and H. Ghasemzadeh-Nava 4 Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada; Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran; and Research Institute of Animal Embryo Technology, Shahrekord University, Shahrekord, Iran Date submitted: 02.09.09. Date accepted: 22.11.09 Summary The effects of the age of cell donor animal on in vitro development of ovine nuclear transfer (NT) embryos were investigated. Somatic donor cells were obtained from two different sources: (1) adult cells (adult fibroblast cells; AFC and adult cumulus cells; ACC); and (2) fetal fibroblasts (40-day-old; FFC-40 and 65-day-old; FFC-65). The fibroblast cell lines were used for NT procedures within 4–13 subpassages. While the cumulus cells were used as non-cultured (fresh) cells. The in vitro matured abattoir-derived oocytes were considered as recipients. No differences in the rates of fusion (75.7, 77.7, 76.3 and 86.7%) and cleavage (80.1, 84.3, 77.8 and 74%) were detected among couplets reconstructed with FFC-40, FFC-65, AFC and ACC, respectively. Blastocyst formation rate of those oocytes reconstructed with FFC-40 was higher (18%; p < 0.001) than those reconstructed with FFC-65 (13%) and AFC (10.9) and comparable with those reconstructed with ACC (17.5%). When the effect of passage number was analysed within groups (FFC-40, FFC-65 and AFC) there were no significant differences in fusion, cleavage and blastocyst rates between reconstructed oocytes. The present study demonstrates that the fetal and adult fibroblasts as well as fresh cumulus cells are comparable in their ability to attain cell fusion and embryonic cleavage. Moreover, the blastocyst formation rate is influenced by the age of the donor animal and the fresh cumulus cells have similar remodelling potential to that of fetal fibroblasts in term of blastocyst formation rate. Keywords: Embryo, Fibroblast, Nuclear transfer, Ovine Introduction Cloning by nuclear transfer of somatic cells into oocytes is currently the most efficient technique for producing copies of elite livestock and transgenic 1 All correspondence to: Abolfazl Shirazi. Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon SK S7N 5B4, Canada. Tel: +1 306 966 4317. Fax: +1 306 966 7376. e-mail: shiraziabbas@ yahoo.com; a.shirazi@avicenna.ac.ir 2 Research Institute of Animal Embryo Technology, Shahrekord University, Shahrekord, Iran. 3 Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada. 4 Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran. animals. Many factors influence the production of cloned animals when using the technique of nuclear transfer. One is the remodelling of the donor cell nucleus within the cytoplasm of the recipient oocyte to organize the first embryonic division. Usually, greater extents of donor cell nuclear remodelling and embryonic development can be achieved when transferring embryonic rather than somatic cell nuclei into the cytoplasm of metaphase II oocytes, although this general rule does not hold true for all species (Campbell et al., 1996; Kato et al., 2000; Westhusin et al., 2001). In cattle, sheep, pigs and goats, fetal cells have been used to produce transgenic livestock because of their rapid growth and potential for multiple cell divisions before senescence in culture (Schnieke et al., 1997; Cibelli et al., 1998; Baguisi et al., 1999; Kuhholzer et al., 2000), whereas adult somatic cell cloning primarily has been used to replicate a particular