Bovine placentomal heparanase and syndecan expression is related to placental maturation

Impaired placental maturation has been associated with retention of fetal membranes, which is a major reproductive disease in cattle. This maturation includes alterations in all tissue compartments of the placenta, specifically of epithelial and stroma cells and extracellular matrix. It is believed to be controlled by hormones, adhesion molecules and proteolytic enzymes. To investigate if the proteolytic enzyme heparanase and its substrates, the syndecans (SDCs) could be involved in the release of fetal membranes, their expression in bovine placentomes was analyzed.

Placentomes were taken from gestational day 35 until term, directly after spontaneous parturition, after preterm caesarean section, and after chemically induced parturition. Heparanase and SDCs were localized by immunohistochemistry and the respective mRNAs were quantified by qRT-PCR. Heparanase expression was additionally quantified by Western blot.

Heparanase, SDC1 and SDC4 displayed significant changes in expression and localization depending on gestational progress and mode of parturition. All three proteins showed an expression at the end of gestation, together with an altered, predominant localization in fetal and maternal epithelia. After physiological parturition, the placentomal tissue stained weaker for all syndecans. This change in staining pattern could not be observed after induced preterm parturition. SDC2 expression did not change during the course of gestation.

The changing placental expression patterns of heparanase, SDC1 and SDC4 indicate that these molecules might be involved in fetomaternal communication and placental maturation in cattle. The matrix degrading properties of heparanase could assist in a timely reduction of fetomaternal adhesion and thus promote separation of the membranes after parturition.