Various factors can cause female infertility most of which fall in the category of female reproductive system disorders, however, a growing number of studies show that infertility can be caused by the composition of female reproductive system microbiota. Recent studies on female reproductive organ microbiota showed that the most abundant bacteria genus is Lactobacillus, and that bacteria of this genus can have a positive impact on the function of female reproductive system organs [1].
The human endometrium - inner layer of the uterus - is a dynamic tissue, which experiences cyclic changes throughout the woman’s reproductive years [2]. Endometrium decidualization refers to a process that occurs during every menstrual cycle when endometrium stromal cells (EnSCs) differentiate into specialised secretory cells in order to form the decidual lining into which the blastocyst later implants. Improper decidualization response could be a cause of several pregnancy complications, not only in early but also in advanced gestation [3,4]. This demonstrates the importance of proper decidualization process for female reproductive health.
The goal of this study was to determine the effect of the supernatant of Lactobacillus casei on decidualized and non-decidualized EnSCs by studying cell proliferation and changes in gene expression. EnSCs were isolated from endometrial tissue obtained from female patients undergoing in vitro fertilization (IVF). EnSC decidualization was induced with 8-bromo-cAMP and MPA inductors and cells were treated with 5X, 20X, 50X and 100X L. casei supernatant dilutions for 72 hours. To assess EnSC proliferation, XTT assay, a colorimetric method that detects the cellular metabolic activity was used. Using RT-qPCR, changes in IGFBP1 and PRL gene expression of control and decidualized EnSCs treated with the supernatant of L. casei were analysed. Lastly, we plan to perform western blot analysis to examine decidualization related protein expression in EnSCs.
In both pregnant and non-pregnant patient cell lines it was shown that the 5X L. casei supernatant dilution reduced EnSC proliferation by approximately 60% compared to untreated cells. However, in the case of higher supernatant dilutions such as 50X and 100X, EnSCs were not affected as much by the supernatant and proliferation activity was closer to the one seen in control cells. RT-qPCR results revealed that EnSC decidualization was successfully induced, as visible by upregulation of IGFBP1 and PRL expression levels in cells after the induction of decidualization. Furthermore, the highest gene expression levels of decidualization related gene-markers were reached in cells treated with 20X dilution of the supernatant of L. casei, showing the possible significance of L. casei metabolites for gene expression regulation during decidualization.