Effect of apelin knockdown on proinflammatory cytokines. Human primary amnion cells were transfected with 200 nmol/L apelin or NS siRNA. After 72 hours of transfection, cells were incubated in the absence or presence of 1 ng/mL of IL-1β for 24 hours (n = 6 patients). A and B, IL-6 and IL-8 gene expression was analyzed by qRT-PCR, normalized to GAPDH mRNA expression and the fold change was calculated relative to IL-1β stimulated NS siRNA transfected cells. Data were displayed as mean ± SEM. *P < .05 versus IL-1β stimulated NS siRNA transfected cells (1-way ANOVA). C and D, IL-6 and IL-8 concentration in the incubation medium was analyzed by ELISA and the fold change was calculated relative to IL-1β stimulated NS siRNA transfected cells. Each bar represents the mean ± SEM. *P < .05 versus IL-1β stimulated NS siRNA transfected cells (1-way ANOVA). ANOVA indicates analysis of variance; ELISA, enzyme-linked immunosorbent assay; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; IL, interleukin; mRNA, messenger RNA; NS siRNA, nonspecific small interfering RNA; qRT-PCR, qualitative reverse transcriptase polymerase chain reaction; SEM, standard error of the mean.