Properties of Epithelial Cells and Vaginal Secretions in Pregnant Women When Lactobacillus crispatus or Lactobacillus iners Dominate the Vaginal Microbiome

Abstract

Objective: Our objective was to determine differences in properties of vaginal epithelial cells and the composition of vaginal secretions when Lactobacillus crispatus or Lactobacillus iners are numerically dominant in the vaginal microenvironment of pregnant women.

Methods: The vaginal microbiomes of 157 first-trimester pregnant women were identified by classifying partial 16S gene sequences amplified from the V1 to V3 region of bacterial ribosomal 16S RNA genes. The extent of autophagy and cell stress in vaginal epithelial cells was determined by measuring the intracellular levels of p62 and the inducible 70-kDa heat shock protein (hsp70). Vaginal secretions were analyzed using a colorimetric assay for d- and l-lactic acid and by enzyme-linked immunosorbent assay for matrix metalloproteinase 8, neutrophil gelatinase-associated lipocalin, α-amylase, hyaluronan, calprotectin, S100A8, and extracellular matrix metalloproteinase inducer (EMMPRIN).

Results: L. crispatus was dominant in 69 (43.9%) women, while L iners dominated in 23 (14.6%) women. The median epithelial p62 levels were 0.41 and 4.26 ng/mL in women with L crispatus or L iners dominance, respectively ( P = .0035). The corresponding median hsp70 levels were 4.24 and 14.50 ng/mL, respectively ( P < .0001). The d-lactic acid concentration in vaginal fluid was highest in association with L crispatus dominance, while all other vaginal fluid compounds except for EMMPRIN were highest when L iners was dominant ( P< .03).

Conclusion: Epithelial cells exhibit a higher level of autophagy, lower induction of stress-related hsp70, and release lower level of mediators when L crispatus is most abundant as compared to when L iners dominates the vaginal microbiota.

Keywords: Lactobacillus crispatus; Lactobacillus iners; autophagy; heat shock protein; vaginal epithelial cells.