The Significance of Selected Collagens and Their Connection with Relevant Extracellular Matrix Proteins in Bovine Early-Mid-Pregnancy and Parturition with and Without Retained Foetal Membranes

Appropriate placental structure and function assure foetal development, delivery of nutrients, and removal of waste. Collagens, as structural proteins, are crucial for the maintenance of placental growth and function. The aim of this study was to describe the profile of collagen 1 and 4 in the placental tissues of cows and to correlate it to previously described activities of collagenases and adhesive proteins. Placental samples were collected from pregnant cows in the slaughterhouse (2nd, 4th, and 6th month; n = 12) and during parturition after caesarean section. Samples taken during caesarean section were retrospectively divided into retained (R; n = 6) and not retained foetal membranes (NR; n = 6). Determinations were performed of maternal and foetal parts separately after tissue homogenisation. Supernatants were used for the determination of COL1 and COL4 concentrations by ELISA and WB analysis. Significant differences were detected between pregnancy months and parturient samples in COL1 concentrations and between retained and released foetal membranes. The concentrations of COL4 were higher in the foetal as compared to the maternal part of the placenta. Significant differences were detected between retained and released foetal membranes, and, similarly to Col1, values were lower in retained than released foetal membranes. WB analysis showed the presence of examined collagen molecules and their molecular weights. The analysis of collagen profile together with the enzymes of their degradation and other adhesive proteins (glycodelin, decorin, and thrombospondins) in bovine placenta either during pregnancy and parturition showed a close relationship. Either attachment or detachment of the maternal and foetal parts of the bovine placenta requires actions in concert between all these adhesive proteins under the influence of pregnancy hormones.