Comparable vitamin D3 metabolism in the endometrium of patients with recurrent spontaneous abortion and fertile controls.

Vitamin D exerts important roles during pregnancy, and its deficiency may be associated with several pregnancy complications, including pregnancy loss, yet no data are available for molecules involved in vitamin D metabolism in patients with unexplained recurrent spontaneous abortion. In this study, we investigated possible difference in endometrial expression of vitamin D3 receptor (VDR), 1α-hydroxylase (CYP27B1), and 24-hydroxylase (CYP24A1) in women with recurrent spontaneous abortion (n = 8) and healthy controls (n = 8). Gene expression of VDR, CYP27B1, and CYP24A1 was determined by real-time PCR, while VDR and CYP27B1 proteins were localized by immunohistochemistry and their abundance was validated by Western blot. We found that both patient and control groups expressed comparable levels of endometrial VDR, CYP27B1, and CYP24A1 transcripts. In line with the gene-expression results, CYP27B1 and different isoforms of VDR protein were present at the same abundance in the endometria of both groups. No significant alteration in VDR and CYP27B1 immunoreactivity pattern was found in the endometrium of patients compared to fertile controls, however. The results of the present study, therefore, do not support the hypothesis of differential expression of key molecules involved in vitamin D3 metabolism in the endometrium of recurrent spontaneous abortion patients and fertile controls.