Activities of matrix metalloproteinase-2 and -9 in amniotic fluid at parturition in mares with normal and high-risk pregnancy.

The research article discusses the role and activity of enzymes MMP-2 and MMP-9 in amniotic fluid at the time of parturition from mares with a normal pregnancy versus a high-risk pregnancy. The study found that mares with high-risk pregnancies, associated with placental inefficiency, showed decreased activity of MMP-2 but increased activity of MMP-9, suggesting a potential link to fetal distress.

Overview of the Study

• The research targeted MMP-2 and MMP-9 enzymes, which are part of the matrix metalloproteinases (MMPs) family, known for their role in the remodeling of the extracellular matrix. These enzymes are known to be involved in reproduction and have been detected in the placenta of various species, including horses.
• The main objective was to investigate the activities of these specific enzymes in amniotic fluid collected at parturition (the act of giving birth) from mares that had a history of normal pregnancies and those deemed high-risk.

Definition of High-Risk Pregnancy

• High-risk pregnancies in this study were identified as those with a history of premature udder development or lactation, increased thickness of the uterus and placenta, vulvar discharge, or the mare’s systemic illness.
• A diagnosis of placental insufficiency was confirmed retrospectively after an examination of the placenta.

Methodology and Findings

• Amniotic fluid was collected shortly after parturition and the activities of the enzymes were analyzed using in-gel zymography which allows the evaluation of both latent and active forms of these enzymes.
• The study included 20 mares with normal pregnancies and 8 mares with high-risk pregnancies, diagnosed with placental insufficiency.
• MMP-2 was active in both groups, but showed a lower activity in the samples from high-risk pregnancies.
• MMP-9 showed higher activity in the amniotic fluid of the high-risk group – with the latent form completely absent in all high-risk group samples.

Interpretation and Implications

• The study suggests that placental dysfunction induces a decrease in MMP-2 activity and a rise in MMP-9 activity, possibly due to the release of pro-inflammatory cytokines, which are involved in initiating labor.
• The increased MMP-9 activity could be linked to fetal distress, as fetal pulmonary secretions are a likely source of MMPs in amniotic fluid.
• These findings might offer greater understanding of the role of these enzymes in equine pregnancy, particularly high-risk pregnancies – however, the research mentions these results would need to be confirmed in a larger, more homogeneous population of high-risk mares.