Morphogenetic changes in the rat placenta under vitamin D3 deficiency

The placenta is a vital temporary organ that ensures metabolic, respiratory, endocrine, immunological, and barrier functions between the mother and the fetus. Morphofunctional integrity of the placenta is essential for the physiological course of pregnancy, and its structural alterations contribute to the pathogenesis of various gestational complications. Beyond its classical role in calcium-phosphate metabolism, vitamin D3 exhibits pleiotropic effects, including immunomodulation, angiogenesis, and regulation of trophoblast invasion. This study aimed to evaluate the morphofunctional status of the placenta in pregnant female rats depending on vitamin D3 status, using histological and morphometric analysis. Thirty-six Wistar female rats were divided into three groups: D3-deficient, D3-deficient with cholecalciferol correction (1000 IU/kg), and control. On gestational day 16, placentas were collected for examination. Histological techniques and morphometric analysis were used to detect changes in placental architectonics. Specific areas of fetal capillaries (Fv), maternal blood lacunae (Mv), cytotrophoblasts (Ct) and syncytiotrophoblasts (Syn) were selected for morphometric analysis. In the D3-deficient group, we observed a significant reduction in the area of syncytiotrophoblast and cytotrophoblast, an increase in maternal lacunae, and a higher Fv/Syn index (fetal capillaries to syncytiotrophoblast ratio), indicating compensatory microvascular remodeling under hypoxic stress. Changes in the placenta architecture, which consist in an increase in the blood supply of maternal lacunae and a decrease in the number of cellular components in the fetal part of the placenta, indicate a compensatory restructuring of the placental architecture under conditions of hypoxia. Correction with vitamin D3 partially restored placental architecture, with most morphometric parameters approaching control values. These findings demonstrate the essential role of vitamin D3 in labyrinth zone development and suggest that its deficiency may lead to placental dysfunction and fetal growth restriction. As a conclusion, an experimental study proved that vitamin D3 is necessary for the normal morphogenesis of the placenta, the development of cytotrophobrasts and syncytiotrophoblasts of its labyrinthine zone, which prevents the occurrence of placental dysfunction. The findings could be used to develop approaches for early prevention of gestational complications associated with vitamin D3 deficiency.