Effect of selenium in ameliorating the effect of induced perinatalhypothyroidism on postnatal rat cerebellar cortex development:a histological and immunohistochemical study

BackgroundThyroid hormone plays a key role in the development of the cerebellar cortex.Selenium is a nutritional element with antioxidant and neuroprotective properties.AimThe aim of this study was to investigate the effect of selenium on the structuralimpairment of postnatal rat cerebellar cortex development induced by perinatalexperimental hypothyroidism.Materials and methodsPups from 20 pregnant rats were divided into four equal groups: group I: negativecontrol group, group II: methimazole-induced hypothyroid group, group III: seleniumsupplementedhypothyroid group, and group IV: selenium-supplemented group(positive control). Treatment continued from gestational day 14 to postnatal day (P)14. At P7, P14, and P28, blood samples were collected for assessment of serumthyroid hormone and right cerebellar hemisphere specimens were processed forhistological, immunohistochemical, and morphometric procedures.ResultsPups of hypothyroid group showed a retarded postnatal cerebellar cortexdevelopment, more apparent at P7 and P14, evidenced by increased thicknessof the external granular layer and delayed alignment and differentiation of Purkinjecells in addition to reduced proliferating cell nuclear antigen and increased caspase3-immunoreactivity. At P28, dark cell degeneration of most Purkinje cells wasobserved. A significant decrease in the thickness of the molecular and internalgranular layers and of the number and surface area of Purkinje cells was observedin all postnatal ages studied. Glial fibrillary acidic protein immunostaining showedincreased positive astrocytes with twisting and thickening of their glial fibers.Selenium caused a marked amelioration of most of these structural alterations.ConclusionPerinatal hypothyroidism impaired postnatal cerebellar cortex development. Seleniumshould be used as a dietary supplement during pregnancy, particularly in hypothyroidconditions.