title: Placental abnormalities associated with post-natal mortality in sheep somatic cell clones.
abstract: We report on cloning experiments designed to explore the causes of peri- and post-natal mortality of cloned lambs. A total of 93 blastocysts obtained by nuclear transfer of somatic cells (granulosa cells) were transferred into 41 recipient ewes, and pregnancies were monitored by ultrasound scanning. In vitro derived, fertilized embryos (IVF, n=123) were also transferred to assess oocyte competence, and naturally mated ewes (n=120) were analysed as well. Cloned embryos developed to the blastocyst stage and implanted at the same rate as IVF embryos. After day 30 of gestation, however, dramatic losses occurred, and only 12 out of 93 (13%) clones reached full-term development, compared to 51 out of 123 (41.6%) lambs born from the IVF control embryos. Three full-term lamb clones were delivered stillborn, as a result of placental degeneration. A further five clone recipients developed hydroallantois. Their lambs died within 24h following delivery by caesarian section, and displayed degenerative lesions in liver and kidney resulting from the severe hydroallantois. One set of twins was delivered by assisted parturition at day 150, but died 24h later due to respiratory distress syndrome. The remaining two clone recipients underwent caesarian section, and the corresponding two lambs displayed signs of respiratory dysfunction and died at approximately 1 month of age due to a bacterial complication. Blood samples collected from the cloned lambs after birth revealed a wide range of abnormalities indicative of kidney and liver dysfunction. Macroscopical and histopathological examination of the placentae revealed a marked reduction in vascularization, particularly at the apex of the villous processes, as well as a loss of differentiation of the trophoblastic epithelium. Our results strongly suggest that post-mortality in cloned lambs is mainly caused by placental abnormalities.
authors.affiliation: Dipartimento di Scienze Biomediche Comparate, Teramo University, Piazza Aldo Moro 45, 64100 Teramo, Italy. ploi@unite.it
authors.forename: Pasqualino
authors.initials: P
authors.lastname: Loi
authors.forename: Michael
authors.initials: M
authors.lastname: Clinton
authors.forename: Irena
authors.initials: I
authors.lastname: Vackova
authors.forename: Josef
authors.initials: J
authors.lastname: Fulka
authors.forename: Robert
authors.initials: R
authors.lastname: Feil
authors.forename: Chiara
authors.initials: C
authors.lastname: Palmieri
authors.forename: Leonardo
authors.initials: L
authors.lastname: Della Salda
authors.forename: Grazyna
authors.initials: G
authors.lastname: Ptak
mesh_terms: D000818:Animals; D019976:Cloning, Organism / Q000379:methods / Q000401:mortality / Q000662:veterinary*; D004624:Embryo Transfer / Q000662:veterinary; D005260:Female; D005307:Fertilization in Vitro / Q000662:veterinary; D005313:Fetal Death / Q000453:epidemiology / Q000209:etiology / Q000662:veterinary*; D005865:Gestational Age; D006107:Granulosa Cells / Q000648:ultrastructure; D053652:Nuclear Transfer Techniques; D009865:Oocytes / Q000648:ultrastructure; D010920:Placenta / Q000002:abnormalities* / Q000473:pathology; D011247:Pregnancy; D012756:Sheep; D012757:Sheep Diseases / Q000473:pathology