Transcriptome signature identifies distinct cervical pathways induced in lipopolysaccharide-mediated preterm birth†,‡

Abstract

With half a million babies born preterm each year in the USA and about 15 million worldwide, preterm birth (PTB) remains a global health issue. Preterm birth is a primary cause of infant morbidity and mortality and can impact lives long past infancy. The fact that there are numerous, and many currently unidentified, etiologies of PTB has hindered development of tools for risk evaluation and preventative therapies. Infection is estimated to be involved in nearly 40% of PTBs of known etiology; therefore, understanding how infection-mediated inflammation alters the cervical milieu and leads to preterm tissue biomechanical changes are questions of interest. Using RNA-seq, we identified enrichment of components involved in inflammasome activation and unique proteases in the mouse cervix during lipopolysaccharide (LPS)-mediated PTB and not physiologically at term before labor. Despite transcriptional induction of inflammasome components, there was no evidence of functional activation based on assessment of mature IL1B and IL18 proteins. The increased transcription of proteases that target both elastic fibers and collagen and concentration of myeloid-derived cells capable of protease synthesis in the cervical stroma support the structural disruption of elastic fibers as a functional output of protease activity. The recent demonstration that elastic fibers contribute to the biomechanical function of the pregnant cervix suggests their protease-induced disruption in the infection model of LPS-mediated PTB and may contribute to premature loss of mechanical competency and preterm delivery. Collectively, the transcriptomics and ultrastructural data provide new insights into the distinct mechanisms of premature cervical remodeling in response to infection.

The mechanical response of the mouse cervix to tensile cyclic loading in term and preterm pregnancy

“…Through cyclic mechanical testing, we quantitatively show certain features of the mechanical behaviour of the pregnant mouse cervix are uniquely altered by infection (LPS-treatment). This mechanical testing evidence parallels previous studies [26, 27, 24, 25] showing infectionmediated tissue remodeling is regulated by a distinct pathway as compared to progesterone withdrawal mediated premature and term remodeling. The cyclic tensile test performed here enables assessment of the cervix s ability to accommodate loading and provides an estimate of the evolving damage mechanical state of the sample with increasing load level.…”

“…Collectively the biochemical studies also suggest that d15-RU486 preterm and d18 term are similar but not identical while premature cervical remodeling with d15-LPS is dissimilar from both term and the d15-RU486 PTB model. Recent transcriptomic studies further highlight the marked differences in the transcriptional pathways that direct term and LPS-mediated preterm cervical remodeling [24]. Of particular relevance is the noted increase in proteases that target collagen and elastic fibers in the d15-LPS group.…”

“…11b). Compared to the elastic fibers of d15 and d15-LPS sham, the d15-LPS tissue have disrupted elastic fibers with elastin not being properly integrated in the microfibrillar scaffold of the elastic fibers [24](Fig. 11b).…”

“…Uni-axial tensile tests on cervices of mice with structural defects in elastic fibers exhibit overall degraded mechanical properties [15]. The importance of understanding the collective contributions of both collagen and elastic fibers to the mechanical behavior of the cervix is also supported by our recent studies demonstrating a change in collagen fiber morphology by second harmonic generation (SHG) and disruption of elastic fiber ultrastructure by transmission electron microscopy, in the subepithelial stroma of mice undergoing inflammation-induced premature cervical ripening [24, 25](see figure in discussion).…”

“…Cervical ripening induced by LPS treatment is achieved by a transcriptional pathway that is distinct from term ripening [26, 24], and noted structural changes in collagen and elastic fibers are hypothesized to result from the increased expression of ECM-degrading proteases and proinflammatory genes. In contrast, RU486-mediated ripening is most similar to term ripening [26].…”