Effects of intrauterine infection in different periods on the placenta and endometrial blood vessel formation of pregnant mice and the growth and development of fetal rats

Abstract

Objective: To investigate the effects of intrauterine infection in different periods on the placenta and endometrial blood vessel formation of pregnant rats and the growth and development of fetal rats.

Methods: According to the random number table method, 32 pregnant rats were divided into the early infection group, the mid-term infection group, the late infection group and the control group, with 8 rats in each group. On the 3^rd, 9^th and 15^th day of pregnancy, lipopolysaccharide was injected intraperitoneally to construct intrauterine infection models. The pregnant rats in the control group were intraperitoneally injected with the same dose of 0.9% sodium chloride solution. On the 18^th day of pregnancy, the inflammatory factors [interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α)], the blood vessel density of placenta and endometrium in the placental tissues of pregnant rats, dead fetus + absorbed fetus, the inflammatory factors IL-6, TNF-α and oxidation reaction indicators [malondialdehyde (MDA) and myeloperoxidase (MPO)] in the fetal rat lung and brain tissues were detected.

Results: The changing trend of IL-6 and TNF-α levels in the placental tissues of pregnant rats with intrauterine infection in different periods was: the control group < the late infection group < the mid-term infection group < the early infection group, the differences were statistically significant (p <.05). The changing trend of fetal rat weight, placental weight and placental coefficient in the intrauterine infection groups in different periods was: the control group > the late infection group > the mid-term infection group > the early infection group, the differences were statistically significant (p < .05). The blood vessel density of placenta and endometrium, the mean number of fetuses, brain coefficient and lung coefficient in the late infection group were significantly increased in comparison with the early infection group and the mid-term infection group. The total number and the ratio of dead fetus + absorbed fetus, the levels of IL-6, TNF-α, MDA and MPO in brain and lung tissues were significantly reduced, and the differences were statistically significant (p < .05). The blood vessel density of placenta and endometrium, brain coefficient and lung coefficient of pregnant rats in the mid-term infection group were significantly increased in comparison with the early infection group, and the differences were statistically significant (p < .05). There was no statistically significant difference in the other indicators between the two groups (p > .05).

Conclusions: Intrauterine infection in different periods can inhibit placental and endometrial angiogenesis, and affect the survival rate of fetal rats and the growth and development of brain and lung. The reason may be related to the aggravation of fetal inflammatory responses and oxidative stress. The earlier the intrauterine infection occurs, the severer the adverse effects on the fetal rats will be.