Biology of reproduction
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Biology of reproduction · Mar 2018
Progesterone, the maternal immune system and the onset of parturition in the mouse.
The role of progesterone (P4) in the regulation of the local (uterine) and systemic innate immune system, myometrial expression of connexin 43 (Cx-43) and cyclooxygenase 2 (COX-2), and the onset of parturition was examined in (i) naïve mice delivering at term; (ii) E16 mice treated with RU486 (P4-antagonist) to induce preterm parturition; and (iii) in mice treated with P4 to prevent term parturition. In naïve mice, myometrial neutrophil and monocyte numbers peaked at E18 and declined with the onset of parturition. In contrast, circulating monocytes did not change and although neutrophils were increased with pregnancy, they did not change across gestation. ⋯ In mice treated with P4, the gestation-linked increase in myometrial monocyte, but not neutrophil, numbers was prevented, and expression of Cx-43 and COX-2 was reduced. On E20 of P4 supplementation, myometrial chemokine/cytokine and leukocyte numbers, but not Cx-43 and COX-2 expression, increased. These data show that during pregnancy P4 controls myometrial monocyte infiltration, cytokine and prolabor factor synthesis via mRNA-dependent and independent mechanisms and, with prolonged P4 supplementation, P4 action is repressed resulting in increased myometrial inflammation.