ABSTRACT
Although assisted reproductive techniques are commonly applied in humans and animals, they are frequently associated with major developmental deficits and reduced viability. To explore abnormalities associated with cloning or nuclear transfer (NT) as the most invasive of these methods, we used a bovine model to characterize abnormalities. Detailed necropsy examinations were done on 13 calves that died soon after birth; in addition, we included data from embryos and fetuses (produced by NT) that terminated prematurely. Bovine clones that survived until the neonatal period differed quantitatively and qualitatively from in-vivo-derived cattle. Although alterations affected a variety of organs (e.g. heart, lung and liver), there was a clear association with abberant vascular developmental during the early intrauterine phase. Therefore, we concluded that vascular problems were key alterations induced by cloning (presumably via epigenetic modifications).