Aging of animals produced by somatic cell nuclear transfer.

Cloning by somatic cell nuclear transfer (NT) has been used to successfully generate viable mammalian embryos in many species. Despite the successful production of cloned animals, NT remains an inefficient technique at best. High rates of developmental failure and abnormalities are associated with NT-derived animals. Issues such as cell cycle regulation, epigenetic modification and oocyte activation have been examined in order to ultimately find ways to improve the efficiency of somatic cell NT. In reviewing the available literature regarding the generation of various mammalian species by using somatic cell NT, it becomes apparent that there are not only differences in the protocols used to generate such animals, but significant differences in the phenotypes of resultant animal clones as well. In this review we discuss the current findings about how aging and senescence are affected by somatic cell NT in mammals.