Distinct roles of Lactobacillus species in trophoblast invasion: Lactobacillus iners fails to promote HTR-8/SVneo cell invasion unlike Lactobacillus crispatus.

The role of Lactobacillus iners in the uterus during pregnancy is poorly understood. This study aimed to evaluate the effect of L. iners on trophoblast invasion. The HTR-8/SVneo cell line was cultured with culture supernatants from L. iners (SLI) or L. crispatus (SLC). SLC significantly enhanced HTR-8/SVneo invasion, which was accompanied by increased matrix metalloproteinase-2 mRNA expression, protein expression, and enzymatic activity. In contrast, SLI did not affect trophoblast invasion. These results suggest that the presence of L. iners in the endometrium is less favorable than that of L. crispatus for promoting trophoblast invasion during early pregnancy.