The effect of probiotic bacteria on toll-like receptor-2 and -4 expression by spermatozoa in couples with unexplained recurrent spontaneous abortion

The disturbance of microbiota composition in the female reproductive tract (FRT) can result in several reproductive disorders. Spermatozoa express toll like receptors (TLRs) and may encounter many types of microbiota in the FRT, however no study has been performed regarding the interaction between spermatozoa TLRs and FRT microbiota in unexplained recurrent spontaneous abortion (URSA) and fertile couples. In this study, we investigate the interaction of vaginal lactobacillus casei probiotic as a representative of FRT microbiota with TLR2 and 4 on spermatozoa. Ten fertile couples and ten URSA couples were involved in this study. Untreated and lactobacillus casei probiotic treated purified spermatozoa were evaluated for TLR2 and 4 expression by flow cytometry. Vaginal lactobacillus casei probiotic treatment of spermatozoa led to increased expression of TLR4 and decreased expression of TLR2 on spermatozoa in both URSA and fertile couples. Vaginal lactobacillus casei probiotic led to an increase in TLR4 expression and a decrease in TLR2 expression on spermatozoa in fertile and URSA groups. However, the disturbed expression of TLR2 and 4 was not completely correct, and further studies with other types of vaginal lactobacilli are needed. In contrast to our expectation, vaginal lactobacillus casei probiotic could not improve the disturbed expression of TLR2 and TLR4 in the RSA group. This could be due to small sample size and the use of one type of lactobacillus. Therefore, further study needs to be performed with other types of lactobacilli to determine the effect of microbiota and probiotics on spermatozoa function such as motility, acrosome reaction, sperm capacitation, sperm and egg fusion and spermatozoa motility and apoptosis and etc. Nevertheless, this study can provide a first step to investigate the effectiveness of vaginal microbiota on spermatozoa, and consequently design new strategies for RSA couples.