Uterine infection is associated with infertility in women and dairy cows, even after the resolution of infection. However, the mechanisms causing this persistent infertility are unclear. Here, we hypothesized that induced endometritis in non-lactating dairy cows would reduce the developmental competence of oocytes. Non-lactating Holstein cows received an intrauterine infusion of endometrial pathogenic bacteria (Escherichia coli and Trueperella pyogenes; n = 12) or vehicle control (n = 11) on day 2 of the estrous cycle. Bacterial infusion increased expression of endometrial inflammatory mediators, and a mucopurulent discharge in the vagina confirmed the establishment of endometritis. Oocytes were collected by transvaginal ultrasound guided ovum pick-up on day 2, 24, 45, and 66 following infusion, and subjected to in vitro fertilization and embryo culture. Bacterial infusion resulted in fewer cleaved oocytes developing to morulae compared to vehicle-infused controls (30.7% versus 45.0%), with the greatest effect observed in oocytes collected on day 24. Development to morula was inversely correlated with endometrial expression of IL6 on day 6. The expression of genes associated with embryo quality did not differ significantly between morulae from bacteria-infused and control cows. Artificial insemination 130 days after intrauterine infusion resulted in normal, filamentous embryos that produced interferon-tau 16 days after conception in both infusion groups. This model of experimentally induced uterine infection successfully resulted in endometritis and a reduction in the proportion of oocytes that developed to morulae following in vitro fertilization. In conclusion, endometritis reduced the capacity of oocytes to develop to morulae.

中文翻译：

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实验诱导的子宫内膜炎损害牛卵母细胞的发育能力†。

子宫感染与女性和奶牛的不孕症有关，即使在感染解决后也是如此。然而，导致这种持续不孕的机制尚不清楚。在这里，我们假设非泌乳奶牛诱发子宫内膜炎会降低卵母细胞的发育能力。非泌乳荷斯坦奶牛在发情周期的第 2 天接受子宫内膜病原菌（大肠杆菌和化脓性真肠菌；n = 12）或载体对照（n = 11）的宫内输注。细菌输注增加了子宫内膜炎症介质的表达，阴道中的粘液脓性分泌物证实了子宫内膜炎的形成。在输注后第 2、24、45 和 66 天通过经阴道超声引导取卵收集卵母细胞，并进行体外受精和胚胎培养。与注入载体的对照相比，细菌输注导致较少的卵母细胞发育为桑葚（30.7% 对 45.0%），在第 24 天收集的卵母细胞中观察到的影响最大。发育成桑椹胚与第 6 天子宫内膜的 IL6 表达呈负相关. 与胚胎质量相关的基因表达在来自注入细菌的奶牛和对照奶牛的桑椹树之间没有显着差异。宫内输注后 130 天人工授精导致两个输注组在受孕后 16 天产生正常的丝状胚胎。这种实验诱导的子宫感染模型成功地导致了子宫内膜炎和体外受精后发育为桑椹胚的卵母细胞比例减少。总之，子宫内膜炎降低了卵母细胞发育为桑葚的能力。