Chorioamnionitis - new ideas from experimental models.

Antenatal inflammation may be associated with adverse neonatal outcomes in several organ systems. Bacteria and a few viruses have been detected in cases of microbial invasion of the amniotic cavity which is referred to as chorioamnionitis. Many aspects of this disease remain unclear such as the causes, time of onset and the fetal responses. Chorioamnionitis was therefore induced in pregnant sheep by injections of lipopolysaccharide (LPS) or Ureaplasma species into the amniotic cavity under ultrasound guidance. LPS-induced chorioamnionitis caused a cascade of organ injury, inflammation, and remodeling. The organ-specific changes were accompanied by systemic effects. The systemic effects after LPS-induced chorioamnionitis resulted in immune suppression against several Toll-like receptor agonists (cross-tolerance). Ureaplasma induced chorioamnionitis made changes in the fetal lung structure depending on the time of infection during pregnancy. The mechanisms of inflammation, structural damage and decreased expression of growth factors need to be further studied to determine therapeutic targets in suitable animal models.