Effect of 1,25(OH)2-vitamin D3 on decidualization of human endometrial stromal cells

Decidualization is the differentiation of endometrial stromal cells (eSC) to rounded, epithelioid-like cells during menstrual cycle and pregnancy. The impairment of this process leads to infertility and a variety of pregnancy disorders, including recurrent miscarriages and uteroplacental disorders. The aim of this study was to evaluate the effect of 1,25(OH)2-vitamin D3 (VD) on transformation of primary eSC into decidual cells. After isolation of eSC from biopsy samples of healthy fertile women and their characterization, the cells were cultured and propagated, and confluent cultures were decidualized for 12 days with progesterone (P4) and estradiol (E2) in presence or absence of VD. Prolactin (PRL) concentration was measured every 48 h in culture medium of eSCs, and ultrastructural changes were evaluated at the end of treatment. The results showed that PRL concentration in culture medium of eSCs was significantly increased in VD-treated decidual cells compared to control groups in a time-dependent manner. Ultrastructural analysis demonstrated that VD enhances many of the ultrastructural changes of decidualized cells including expansion of rough endoplasmic reticulum (rER), increased lipid droplets and high number of euchromatin round nuclei. These results suggest that VD may play an important role during early pregnancy by promoting cellular transformation associated with decidualization.