Pulmonary vascular changes in extremely preterm sheep after intra-amniotic exposure to Ureaplasma parvum and lipopolysaccharide

Abstract

BackgroundChorioamnionitis can induce pulmonary inflammation and promote bronchopulmonary dysplasia development, distinguished by alveolar simplification and impaired vascular growth. Chorioamnionitis is more common during the extremely preterm canalicular lung stage (crucial for vascular development); and increases the risk for subsequent sepsis. We hypothesized that single/combined exposure to chronic and/or acute inflammation induces pulmonary inflammatory responses and vascular changes.MethodsOvine fetuses were intra-amniotically exposed to chronic Ureaplasma parvum (UP) at 24 days (d) before extreme preterm delivery at 94d (term 147d) and/or to lipopolysaccharide (LPS) 7 or 2d before delivery. Pulmonary inflammation, vascular remodeling and angiogenic factors were assessed.ResultsLPS exposure increased CD3-positive and myeloperoxidase-positive cells. Combined UP-LPS exposure increased pulmonary inflammation compared with 2d LPS or UP groups. The UP+2d LPS group had an increased adventitial fibrosis score when compared with UP-treated animals. A reduced wall-to-lumen ratio was found in the 7d LPS animals when compared to the 2d LPS-treated animals. Exposure to UP+2d LPS reduced VEGF and VEGFR-2 levels compared with 2d LPS-treated animals. Angiopoietin-1 (Ang1) and tunica interna endothelial cell kinase 2 (Tie-2) levels were decreased after UP+7d LPS as well as after 7d LPS, but not with UP alone.ConclusionChronic UP and subsequent LPS exposure increased pulmonary inflammation and decreased expression of angiogenic growth factors and receptors when compared to single hit-exposed animals.

Cervical epithelial damage promotes Ureaplasma parvum ascending infection, intrauterine inflammation and preterm birth induction in mice

“…To investigate whether N-9-induced cervical epithelial challenge predisposes to ascending infection during pregnancy, we examined the magnitude and frequency of ascending bacterial infection following experimental vaginal inoculation of UP. UP was chosen as this is the most frequently isolated bacterial species associated with PTB 36 and the UP strain (HPA5) utilised has extensively been used in sheep models of intrauterine infection [37][38][39] .…”

Preterm birth impairs postnatal lung development in the neonatal rabbit model

“…On day 28 we deliver healthy preterm rabbits, while in humans prematurity rarely comes alone. Pre-eclampsia or chorio-amnionitis do not only predispose for preterm birth, but also affect lung development in utero as part of a multiple hit concept [34,35]. The lack of a prenatal insult however could also be a strength, as this allows us to study the individual effect of prematurity.…”

Sequential Exposure to Antenatal Microbial Triggers Attenuates Alveolar Growth and Pulmonary Vascular Development and Impacts Pulmonary Epithelial Stem/Progenitor Cells

“…Tissue sections were stained with hematoxylin and eosin (H&E) for histological evaluation. In addition, the following cellular markers were visualized: CD45 for hematopoietic cells (1:500, MCA2220GA, Biorad, Hercules, CA), PU.1 for differentiating monocytes (1:400, Santa Cruz Biotechnology, H0503), myeloperoxidase for neutrophils (MPO, 1:500, A-0398, Dako, Santa Clara, CA), tumor protein 63 for basal cells (P63, 1:8000, ab124762, Abcam), keratin 14 for differentiating basal cells (KRT-14, 1:1000, 905301, Biolegend, San Diego, CA), thyroid transcription factor-1 for Club and alveolar epithelial type (AEC) 2 cells (TTF-1, 1:8000, WRAB-1231, Seven Hills Bioreagents, Cincinnati, OH) and Ki67 for proliferation (1:1000, 15580, Abcam, Cambridge, UK) ( 7 , 12 , 16 , 21 ). Immunohistochemical protocols were performed as previously published, while the PU.1 protocol was modified for optimal signal emission.…”

“…This concept is supported by earlier findings in different preterm organ systems, showing that sequentially occurring antenatal inflammatory insults of varying exposure time points and durations, cause either preconditioning or sensitization to a consecutive inflammatory hit ( 9 – 11 ). With respect to the lungs, in utero sequential exposure to antenatal bacteria and bacteria-derived endotoxins resulted in increased inflammation, along with exacerbation of vascular disturbances in very preterm ovine lungs ( 12 ). Conversely, in fetuses of higher gestational age (GA), Kallapur et al showed that chronic UP exposure pre-conditioned the immature lungs and thereby led to a decreased pro-inflammatory response to a subsequent endotoxin hit ( 13 ).…”