Abstract
BackgroundInflammatory processes and infections of the uterine wall must be accepted as a physiological event in dairy cows after calving. This might result in clinical or subclinical endometritis which is assumed to impair reproductive performance in the current lactation. Several cytokines and acute phase proteins have been discussed as local and systemic mediators of these inflammatory processes. The aim of the present study was to investigate the endometrial mRNA expression of the chemokine CXC ligand 5 (CXCL5), interleukin 1β (IL1B), IL6, IL8, tumour necrosis factor alpha (TNF), prostaglandin-endoperoxide synthase 2 (PTGS2) and haptoglobin (HP) in the postpartum period.MethodsEndometrial samples were obtained from primiparous cows (n = 5) on days 10, 17, 24, 31, 38 and 45 postpartum (pp) using the cytobrush technique. Cytological smears were prepared from cytobrush samples to determine the proportion of polymorphonuclear neutrophils (PMN). Total RNA was extracted from endometrial samples, and real-time RT-PCR was performed.ResultsA time-dependent mRNA expression of the investigated factors was found for the course of the postpartum period. In detail, a significantly higher expression of these factors was observed on day 17 pp compared to day 31 pp. Furthermore, the proportion of PMN peaked between days 10-24 pp and decreased thereafter to low percentages (< 5%) on day 31 pp and thereafter. In addition, CXCL5, IL1B, IL8 and HP mRNA expression correlated significantly with the proportion of PMN (P < 0.05). A significantly higher CXCL5, IL1B, IL6, IL8, PTGS2 and TNF mRNA content was observed in samples from cows with an inflamed endometrium compared with samples from cows with a healthy endometrium (P < 0.05).ConclusionsThese results show that inflammatory cytokines and acute phase proteins are expressed in the bovine endometrium in a time-related manner during the postpartum period, with a significant expression peak on day 17 pp as a possible mucosal immune response in the uterus. The evaluation of the expression patterns of such candidate genes may reveal more information than only determining the percentage of PMN to judge the severity of an inflammation.
Highlights
Inflammatory processes and infections of the uterine wall must be accepted as a physiological event in dairy cows after calving
Clinical endometritis is defined as an inflammation of the endometrium identified by the presence of purulent or mucopurulent discharge detectable in the vagina later than 21 days postpartum, and is not accompanied by systemic signs [2]
A significantly higher tumour necrosis factor alpha (TNF) mRNA content was observed in samples from cows with an inflamed endometrium compared with samples from healthy cows (P < 0.05; mean of normalised expression ± S.E.M. × 10-6: 34 ± 6.7 and 24 ± 14, respectively)
Summary
Inflammatory processes and infections of the uterine wall must be accepted as a physiological event in dairy cows after calving. This might result in clinical or subclinical endometritis which is assumed to impair reproductive performance in the current lactation. Depending on the pathogenicity of bacteria, bacterial load, responsiveness of the immune system and other risk factors, infection may result in acute metritis or, if persistent, in clinical endometritis. Clinical endometritis is defined as an inflammation of the endometrium identified by the presence of purulent or mucopurulent discharge detectable in the vagina later than 21 days postpartum (pp), and is not accompanied by systemic signs [2]. Additional information about the underlying mechanism of inflammation is needed to understand the pathology of these diseases and to develop new therapeutic approaches in the future
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