Matrix Metalloproteinase-1 in Full-Term and Preterm Labor
Sandra Reznik, Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences
Preterm delivery, defined as delivery before 37 weeks’ gestation, occurs in 7 to 12% of pregnancies, and is associated with 85% of perinatal morbidity and mortality. Unfortunately, the existing therapeutic approaches for preterm delivery have not decreased the incidence of prematurity and can be associated with risks to both the mother and fetus. Modern genomics techniques represent a relatively novel approach to investigating the molecular complexity of preterm labor. In this work, using cDNA microarray analysis, we found that several genes affecting the integrity of the extracellular matrix are up-regulated in normal labor at full-term. We also show that a protein encoded by one of these genes, matrix metalloproteinase-1 (MMP-1), serves as a therapeutic target for infection-associated preterm labor in a murine model.
The gene expression profiles of placentas from patients at term with spontaneous vaginal deliveries and placentas from patients at term with non-laboring Cesarean deliveries were compared. Patients included in this IRB approved study were aged above 20 and below 35 and had no history of chronic hypertension, pregnancy induced hypertension, pre-eclampsia/eclampsia, diabetes mellitus, gestational diabetes mellitus, intrauterine growth restriction, abruptio placentae, fetal congenital anomaly, intrauterine fetal demise or significant maternal disease. RNA was extracted from the collected placental samples using a Qiagen RNeasy kit. RNA from laboring placentas was pooled and RNA from non-laboring placentas was pooled, to exclude individual variation of each sample. Complementary hybridizations were performed with reverse labeling, using human genome cDNA microarray chips produced by the Einstein Microarray Facility, Bronx, NY. Sequences were selected if the green/red intensity quotient was greater than or equal to 2.0 or less than or equal to 0.5.
To confirm our microarray results showing up-regulation of human placental MMP-1 in labor, we performed rt PCR of several placental samples collected from both normal spontaneous vaginal term deliveries and non-laboring Cesarean term deliveries and found that the gene was consistently up-regulated in labor. We also tested the human placental samples for levels of the expressed protein and found that up-regulation of MMP-1 was represented at the protein level as well.
The ultimate validation of microarray data is a bioassay showing that deleting or inhibiting the function of the gene product in question has a predicted biological effect. In the case of our study, we focused on MMP-1 and tested whether inhibiting the activity of this metalloproteinase, which we found to be overexpressed in human labor, had an effect on infection-associated preterm labor in a mouse model. Briefly, nine E15.5 C57Bl/6 mice in a study group, treated with lipopolysaccharide (LPS), were injected with a single dose of commercially available MMP-1 inhibitor (Chemicon) and compared to nine E15.5 C57Bl/6 mice in a control group, treated with LPS and then injected with vehicle. All of the mice in the control group delivered prematurely, with an average interval between the injection of LPS and delivery of the first pup of 15.7 hours. Only four out of the nine mice in the study group delivered prematurely, with an average interval between injection of LPS and delivery of the first pup for those mice delivering prematurely of 28.3 hours. These findings, taken together, identify MMP-1 as a critical player in the physiology of normal full-term labor and a potential therapeutic target in infection-associated preterm labor.