Moreover, changes in MMP-9, vimentin, E-cadherin and N-cadherin expression both in placental and HTR-8SV/neo cells were consistent with the phenotypes of preeclampsia (36–38) after treatment with collagen I. Thus, we suggest that the single injection of collagen I in early pregnancy induced preeclampsia development by interfering with placentation in early pregnancy due to impaired trophoblast invasion. This evidence concerns the gene MMP9 and preeclampsia.