Preterm labor is a distinct process from term labor following computational analysis of human myometrium.

Background The onset of term human parturition involves myometrial gene expression changes to transform the uterus from a quiescent to a contractile phenotype. It is uncertain whether the same changes occur in the uterus during preterm labor. Objective (s): To compare myometrial gene expression between term and preterm labor and determine if the presence of acute clinical chorioamnionitis or twin gestation affects these signatures. Study design Myometrium was collected at cesarean section from 7 different groups of patients: term not-in-labor (TNIL, n=31), term labor (TL, n=13), preterm not-in-labor (PTNIL, n=21), preterm labor with acute clinical chorioamnionitis (PTL-C, n=6), preterm labor with no acute clinical chorioamnionitis (PTL-NC, n=9), twin preterm not-in-labor (TWIN-PTNIL, n=8) and twin preterm labor with no acute clinical chorioamnionitis (TWIN-PTL-NC, n=5). RNA was extracted, reverse transcribed and qPCR was performed on 44 candidate genes (with evidence for differential expression in human term labor) using the Fluidigm platform. Computational analysis was performed using two-class unpaired Wilcoxon tests and principal component analysis. Results Computational analysis reveals gene expression in preterm myometrium, whether laboring or non-laboring, clustered tightly and is clearly different to the TL and TNIL groups. This was true for both singleton and twin pregnancies. Principal component analysis showed 57% of the variation was explained by 3 principal components. These 44 genes interact in themes of prostaglandin activity and inflammatory signaling known to be important in term labor, however, are not a full representation of the myometrium transcriptional activity. Conclusion The myometrial contractions associated with preterm labor are associated with a distinct pattern of gene expression from term labor. Therefore, preterm labor may be initiated by a different myometrial process or processes outside the myometrium.