Bovine Corpus Luteum Proteomics during Different Reproductive and Physiological Stages

Corpus luteum (CL) is an endocrine structure that undergoes substantial changes over short intervals during the bovine reproductive (estrous) cycle. These changes are regulated by a vast array of signaling molecules, mainly proteins, that govern reproduction. We collected a comprehensive set of CLs from non-pregnant (days 1–2, 3–4, 5–7, 8–12, 13–17, and >18) and pregnant (months 1–2, 3–4, 5–6, and >7) cows, enabling a detailed characterization of temporal changes in CL biology. While previous studies have focused on a limited number of proteins, we employed a broader approach to exploring additional proteins potentially involved in CL regulation across different stages. Using high-resolution mass spectrometry (HR-LC-MS/MS), we identified approximately 3,783 individual proteins. These proteins may be useful for research in species where access to well-characterized CL tissue is limited. Our findings indicate diverse changes in protein expression across groups, highlighting proteomic patterns that may reflect key processes of bovine reproduction, particularly during the transition toward regression, a critical period that influences whether the CL is maintained to support pregnancy or undergoes regression.