Influence of Placental Metalloproteinase-9 Protein on the Branching Architecture of Chorionic Blood Vessels of Human Placenta

Introduction: In human placenta, two different branching patterns of chorionic blood vessels exist. In the dispersal type, the chorionic blood vessels undergo successive divisions with gradually diminishing caliber as the blood vessels traverse towards the placental margins. In the magistral type, the blood vessels traverse without appreciable decrease in diameter. We hypothesize, that matrix-degrading enzymes secreted by cytotrophoblasts may influence the branching patterns of these chorionic blood vessels. We, therefore, determined if placental expression of matrix metalloproteinase-9 (MMP-9) protein differed between the two vascular patterns of chorionic blood vessels of human placenta. Methods: 26 full-term delivered placentas were collected from normotensive women. Chorionic villi (CV) were isolated. CV MMP-9 protein was analyzed using human MMP-9 monoclonal antibody based ELISA kits. A novel method was used to determine the vascular patterns of the placentas from placental photographs. Independent t test was used for statistical analysis. P< 0.05 was considered significant. Results: The branching pattern of the chorionic blood vessels was 54% dispersal and 46% of the magistral types. In placentas with dispersal type of branching pattern, MMP-9 protein expression was significantly higher (p=0.035). Women who delivered placentas with magistral type of branching pattern, the mean newborn weight was found to be significantly higher (p=0.039). Conclusion: The study introduces a novel method to investigate chorionic vascular network of human placenta. Our findings underscore the importance of CV MMP-9 protein in affecting the placental branching architecture of chorionic blood vessels in humans. In the magistral type, the calibers of the chorionic blood vessels from the point of insertion of the umbilical cord to the placental margins remained more or less unchanged. We suggest, that this unchanged caliber of blood vessels in the magistral type, may have allowed better nourishment and oxygen to be catered to the fetus; resulting in fetal weight gain.