Investigating the expression of MMPs and TIMPs in preterm placenta and role of CpG methylation in regulating MMP‐9 expression

Matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) are crucial to the processes of normal labor and parturition. We have previously reported aberrant protein levels of MMPs in placenta of women delivering preterm as compared to term. In this study, we examine the mRNA levels of MMPs (MMP-1, MMP-2, and MMP-9) and TIMPs (TIMP-1, TIMP-2) in the placenta from women delivering preterm as compared with term and further study the promoter DNA methylation of the MMP-9 gene in a sub-sample of term and preterm placentae. A total of 110 women were included in the study; 56 delivered term and 54 delivered preterm. MMP and TIMP mRNA levels were determined by Taqman-based qPCR. Promoter CpG methylation of MMP-9 gene was studied on a subset of 10 term and 8 preterm placenta using Epitect Methyl-II PCR assay kit. The mRNA levels of MMP-1,-2 were higher and those of TIMP-1,-2 were lower in the placentae of women delivering preterm. MMP-9 levels were comparable between the two groups. Among women undergoing spontaneous vaginal deliveries, higher mRNA levels of MMP-1, -2 and -9 were seen in the placentae of those delivering preterm as compared to term. Similar results were seen in women undergoing preterm labor as compared to term. MMP-9 gene promoter was hypomethylated in preterm placenta as compared to term placenta, while the mRNA levels were comparable between the two groups. The observed imbalance between MMP and TIMP expression may have prematurely triggered the signaling cascade leading to preterm birth.