Placental abnormalities in ovine somatic cells clones: a light and electron microscopic investigation.

The aim of the study is to provide, for the first time in literature, a morphologicaldescription of the ovine placental abnormalities after somatic cell nuclear transfer.Three cloned lambs were delivered stillborn at term and placental degeneration wasobserved. Tissue samples from cloned and control ovine placentae were collected andprocessed for histopathological, imunohistochemical (Factor VIII, vimentin, desmin,alpha-SMA, calponin) and TEM examination.Histologically, in the cloned placentae were observed: reduced villous vascularization,flat or cuboidal trophoblastic cells or the absence of epithelial layer covering the villoussurface, lack of binucleate cells. The immunohistochemical examination revealed areduced or absent expression of factor VIII in endothelial cells and calponin in vesselswall. At the ultrastructural level, thickening and lamination of trophoblastic basementmembrane were noted, associated with the deposition of collagen fibrils. Moreover, thenumber of duplications around some of the capillary basal lamina was found to beincreased.These results strongly suggest that a downregulation of maternofetal exchanges and anabnormal regulation of differentiation and growth of trophoblastic cells could beoccurred, both of which responsible of death and immaturity of the epithelial layer. Thisimmaturity seems to involve also the vascular endothelial and smooth muscle cells.[...