Abstract
Cytotrophoblasts of early placenta invade the decidual membrane, gestational endometrium, and spiral arteries during early pregnancy. Unlike tumor invasion, this physiological invasion is well controlled, although its molecular mechanisms are largely unknown. We have previously shown that cytotrophoblasts synthesize significant mRNAs for 72-KD Type IV collagenase, laminin, and Type IV collagen, proteins implicated in extracellular matrix turnover and migration. In this study we used in situ hybridization and immunohistochemistry to investigate the mRNA expression pattern of 92-KD Type IV collagenase and the matix metalloproteinase inhibitors TIMP-1, TIMP-2, and TIMP-3 in early human placenta and decidual membrane. mRNAs for 92-KD Type IV collagenase, TIMP-1, TIMP-2, and TIMP-3 were found in the cells of cytotrophoblastic columns, the endothelial and fibroblastic stromal cells of villi, and the large decidualized cells of decidual membrane. TIMP-1 expression was notably accentuated in the fibroblasts of fibrotic villi. In the decidual membrane, the signals for 92-KD Type IV collagenase and TIMP-1 mRNA were particularly strong around the glandular structures. The trophoblastic epithelium of villi and the epithelial cells of decidual glands showed a signal for 92-KD Type IV collagenase and TIMP-2, but not for TIMP-1 or TIMP-3. The coincidental expression of the proteolytic 92-KD Type IV collagenase and inhibitors TIMP-1, TIMP-2, and TIMP-3 generally in the same cells suggests that the activity of 92-KD Type IV collagenase, which is regulated by TIMPs, plays an important role in placental tissue organization and in the invasion of trophoblastic cells into the uterine wall.