Fig. 1: PM exposure significantly inhibits the self-renewal and reduces the migratory ability of endometrial stem cells in vitro.

We hypothesized that PM exposure inhibited various beneficial functions of endometrial stem cells, such as self-renewal, transdifferentiation, and migration. The inhibition of endometrial stem cell self-renewal by treatment with various concentrations of PM (diesel particulate matter, NIST 1650; 25, 50, 100, and 200 μg/ml) was evaluated at 72 h by an MTT assay. Stem cell viability (%) was calculated as a percent of the viability of cells treated with vehicle control (a). Endometrial stem cells were treated with PM (25 μg/ml) for 72 h, and the inhibitory effect of PM exposure on the stem cell migratory capacity was then analyzed using a Transwell migration assay. PM exposure markedly reduced the ability of cells to migrate across the membrane compared with that of control cells (b). The relative expression of important regulators of cell migration (MMP-2/9) with and without PM exposure was evaluated by western blot analysis (c). The GEO database was further analyzed to verify the correlations between increased expression levels of MMP-2/9 and exposure to various air pollutants (d). PM-induced morphological changes and dynamic actin filament disorganization in endometrial stem cells were analyzed by staining actin filaments with phalloidin (e). DAPI was used to label nuclei. β-Actin was used as the internal control. The bar graphs show the average of three independent experiments. Significant differences are presented. *p < 0.05, **p < 0.005, and ***p < 0.001 (two-sample t-test).