The impact of subclinical inflammation on the bovine endometrial proteome and secretome

• Applicants: Dr. Thomas Fröhlich; Dr. Marie Margarete Meyerholz-Wohllebe
• Subject Area: Veterinary Medical Science
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 555245615

In high-yielding dairy cows, subclinical endometritis (SE) has been identified as a pathological condition leading to non-receptiveness of the endometrium. This results in lower pregnancy rates, longer calving to conception intervals and higher remontation rates due to subfertility. Rates of early embryonic loss are particularly high during the pre-implantation period, and it can be assumed that immunological perturbations interfere with uterine receptivity. However, the exact mechanisms remain unknown. The aim of this research project is to investigate, how subclinical endometritis in cows impacts the uterine milieu and leads to reduced fertility. The focus here will be on the analysis of the endometrial proteome, phosphoproteome and secretome. Investigations at the proteome level are particularly relevant, since the abundance of functional proteins cannot be predicted using transcriptomics techniques only, because of several posttranscriptional regulation mechanisms (e.g., regulation by microRNA). Furthermore, important post-translational modifications such as phosphorylation can be addressed most reliably at the proteome level. Besides cellular proteomes, uterine secretions which are known to contain many proteins crucial for early embryo-maternal communication (EMC), will be analyzed. To maximize the outcome, we will use a two-step model consisting of in vivo and in vitro generated samples. First, highly-defined endometrial samples will be generated in vivo from cows with/without SE using a recently established sampling tool that allows for collection of endometrial cytobrush, uterine secretions and biopsies with only one passage through the cervix. Analysis of these samples will provide a direct readout of the clinical situation including promising candidate proteins that have an increase in abundance between cows with/without SE. The second model will be an endometrial explant cell culture system, enabling the controlled and standardized treatment of endometrial tissue samples with LPS, selected cytokines and type I interferons and the protein candidates detected in vivo, to systematically mimic aspects of subclinical inflammation and EMC. The generated data will give substantial molecular insights into perturbations of the uterine milieu caused by SE. Especially the combination of proteome profiles from endometrial cells with the proteome profiles of the corresponding secretions has the potential to reveal how far the uterine milieu is disturbed and to identify the biochemical mechanisms causing the impaired receptivity. Furthermore, the phosphoproteomics approach will give insight into cellular signaling events which may be altered or disrupted by SE. Finally, in a targeted approach based on selected-reaction monitoring of in vivo collected uterine secretions, it will be tested if some of the detected proteins are useful for diagnosing SE in vivo.

• DFG Programme: Research Grants