Characterization of inflammatory responses by cervical cytology, cytokine expression and ultrastructure changes in a goat subclinical endometritis model

Endometritis is a common puerperal disease in livestock. Thus, a practical clinical test for the establishment of diagnosis is needed. We developed a goat model for subclinical endometritis diagnosis by examining cytological, ultrastructural features and molecular expression in cervical discharge collected by cervical cytobrush method. A suspension of E. coli was infused into the uterine horn of goats, and cervical discharge, peripheral blood and endomertrial biopsy samples were collected before inoculation and at 3, 6, 12, 24, 72, 120 and 168 hr post-inoculation (pi). In experimental goats, total leukocytes increased at 6-12 hr pi in hematological examinations, abundant neutrophils were observed in cervical discharge smears, and some micro-villi shortened or were lost from the epithelium at 3 hr pi, with some inflammatory cells infiltrated into the uterine glands and lamina propria. The mRNA expression levels of the Toll-like receptor 4 (TLR4), cytokines and β-defensin-2 increased significantly within 12 hr pi and returned to pre-inoculation levels at 7 day pi. The results showed that subclinical endometritis was simulated in this bacterial infusion goat model, and the evaluation of cervical cytology was in good agreement with molecular changes of cytokines in cervical discharge, hematology and histology. We thus conclude that the simple cervical cytobrush technique can effectively obtain cervical discharge samples for cytology examination in the early diagnosis of subclinical endometritis in goats.