Immunopharmacological Properties of VitD3: 1, 25VitD3 Modulates Regulatory T Cells and Th17 Cells and the Cytokine Balance in PBMCs from Women with Unexplained Recurrent Spontaneous Abortion (URSA).

Background: VitD3 may contribute to a successful pregnancy through modulation of immune responses. Therefore, VitD3 deficiency may have a role in the immunopathogenesis of unexplained recurrent spontaneous abortion (URSA). However, the mechanisms of immunomodulatory actions of VitD3 in decreasing the risk of recurrent spontaneous abortion have not been understood well.

Objective: The purpose of this research was to investigate the influence of 1,25VitD3 on regulatory T cells /Th17 axis, the gene expressions and concentrations of related cytokines including, TGF-β, IL-10, IL-6, IL-23, and IL-17A in peripheral blood mononuclear cells (PBMCs) of healthy women as a control group and women with URSA.

Methods: Isolation of PBMCs was performed from peripheral blood of the subjects of the studied groups (20 women with URSA as a case group, and 20 control women). The effects of 1,25VitD3 (50 nM, for 24 hours) on the studied parameters were evaluated and were compared to the positive and negative controls in vitro. Flow cytometry analysis was used to determine the percentages of regulatory T cells and Th17 cells. For gene expression measurement and cytokines assay, Realtime PCR and ELISA were carried out.

Results: The proportion of regulatory T cells was markedly lower, while the proportion of Th17 cells in women with URSA was considerably higher than in the control group (P=0.01, P=0.01). The ratio of the frequency of Tregs to the baseline (1,25VitD3/Untreated) increased, while the ratio of the frequency of Th17 cells to the baseline decreased in women with URSA relative to the controls (P= 0.01, P=0.04). 1,25VitD3 increased IL-10 expressions at both the protein and mRNA levels in PBMCs in women with URSA relative to the control group (P=0.0001, P=0.04). TGF-β levels in the cultured supernatants decreased significantly in the case group in the presence of 1,25Vit- D3 relative to the controls (P=0.03). 1,25VitD3 treatment also significantly decreased gene expressions of IL-6, IL-17A, and IL-23 in PBMCs of women with URSA (P=0.01, P=0.001, P=0.0005), as well as the levels of those cytokines in cell culture supernatants (P=0.03, P=0.02, P=0.01, respectively) in women with URSA relative to the controls.

Conclusion: According to the findings of this research, modulation of immune responses by 1,25VitD3 is accomplished by strengthening Tregs function and inhibiting inflammatory responses of Th17 cells, which may have a positive impact on pregnancy outcome. Thus, as an immunomodulating agent, VitD3 may be effective in reducing the risk of URSA.