The Role of Vitamin D in the Expression of Endometrial Decidualization Factors in Women with Recurrent Implantation Failure

One of the concerns in assisted reproduction technology is recurrent implantation failure. The receptivity of uterine endometrium is considered as the main factor of implantation failure in assisted reproductive cycles. Decidua is a tissue originating from endometrial stromal cells, which main function is the initiation and maintenance of embryo implantation. Since the role of vitamin D has been shown in the processes of implantation and pregnancy maintenance, the present study aims to determine the serum level of vitamin D and its relationship with the expression and protein levels of the decidualization factors in women with recurrent implantation failure.

In this historical cohort study, among 36 eligible women with recurrent implantation failure, 12 women with vitamin D deficiency (less than 20 ng/ml) as the case group and 24 women with sufficient vitamin D (more than 30 ng/ml) ml) as the control group were included in the study. In the middle of the luteal phase, the endometrial biopsy was collected and assessed in both groups. The data are reported as mean ± standard deviation. Student's Man U Witny was used to compare the studied groups. P value less than 0.05 was considered statistically significant.

The results of Mann-Whitney-U test showed that the expression of IGFBP-1 (P = 0.0016), PRL (P = 0.004) and HOXA10 (P = 0.001) genes in the sufficient vitamin D group (1±  0.05, 1±  0.05, 1±  0.1 respectively) were significantly higher than the vitamin D deficiency group (0.5 ± 0.1, 0.5 ± 0.1, 0.4 ± 0.1 respectively). Also, the levels of IGFBP1 (P = 0.0001), PRL (P = 0.004) and HOXA10 (P = 0.036) proteins in the sufficient vitamin D group  (3.436 ± 0.05, 6.127 ± 1, 3.778 ± 1 respectively) were significantly higher than the vitamin D deficiency group (0.1196 ± 0.01, 2.185 ± 0.5, 0.4717 ± 0.01 respectively).

It seems VD deficiency may cause disturbances in gene expressions and protein levels of decidualization factors that are critical for embryo implantation.