Variations in plasma matrix metalloproteinases and placental pregnancy-associated glycoproteins during gestation in rabbits (Oryctolagus cuniculus)

Adaptation to pregnancy involves major maternal anatomical, physiological and metabolic modifications to support the mother's metabolic needs and those of the growing foetus. Invasion of embryonic territories and implantation in humans and other mammals is the result of an active biochemical process. The invasive faculty of cytotrophoblastic cells depends on their capacity to secrete proteolytic enzymes such as matrix metalloproteinases (MMPs). Many studies have addressed the variations in MMPs in placental tissues, but few have reported on their measurements in plasma. Furthermore, the Pregnancy-Associated Glycoproteins (PAGs), which are synthesized in the syncytiotrophoblast and used as early markers of pregnancy in domestic and wild animals, have not yet been studied in rabbits. In this study, we attempt to purify PAGs from rabbit placenta using a previously described methodology and to measure their concentrations as well as those of MMP-2 and MMP-9 in the plasma throughout pregnancy. In the course of the work, we noted certain modifications of the biochemical parameters in plasma during gestation, essentially in glycemia and lipemia. We detected proteins immunologically-related to PAGs in placental extracts between D-14 to D-21. Until now, it has been impossible to develop a homologous RIA in order to measure PAGs in rabbit plasma, as the recovery of PAGs during the purification procedure was very low and PAGs were undetectable in rabbit plasma using heterologous RIAs. Finally, we demonstrated a rise in MMP-2 and -9 at the middle and the end of the gestation. However, the small variations presented by these matrix metalloproteinases preclude the use of plasma levels of these enzymes as early markers of pregnancy progress in the rabbit.