TNF-alpha messenger RNA and protein expression in the uteroplacental unit of mice with pregnancy loss

An elevated expression of TNF-alpha in embryonic microenvironment was found to be associated with postimplantation loss. In this work, we examined the pattern of TNF-alpha expression at both the mRNA and the protein level as well as the distribution of TNF-alpha receptor mRNA in the uteroplacental unit of mice with induced (cyclophosphamide-treated) or spontaneous (CBA/J x DBA/2J mouse combination) pregnancy loss. RNase protection analysis demonstrated an increase in TNF-alpha mRNA expression in the placentae of mice with pregnancy loss compared with that in control mice. TNF-alpha messages were localized to the uterine epithelium and stroma as well as the giant and spongiotrophoblast cells of the placenta. The intensity of the hybridization signal in placentae of mice with pregnancy loss was substantially higher than that in control mice. The up-regulation of TNF-alpha mRNA was accompanied by an increase in the expression of TNF-alpha receptor I mRNA in the same cell populations. The elevation of TNF-alpha production was also demonstrated at the protein level. Western blot analysis showed an increased level of the 18- and 26-kDa TNF-alpha protein species in the uteroplacental unit of mice with pregnancy loss. Immunostaining revealed TNF-alpha-positive leukocytes located in the uterus and placenta. Finally, we found that immunization of mice with cyclophosphamide-induced pregnancy loss while decreasing the resorption rate in these females resulted in a decline in TNF-alpha expression at the fetomaternal interface. These data clearly suggest an involvement of TNF-alpha in pathways leading to both spontaneous and induced placental death.