A novel hysteroscopic technique for the accurate biopsy of decidua parietalis and basalis

Visual identification of three kinds of human decidual tissues from elective termination of pregnancy

INTRODUCTION

The decidua can be classified into the decidua basalis, decidua capsularis and decidua parietalis. This study aimed to visually identify these three kinds of decidual tissues from fresh samples obtained in early pregnancy based on their macroscopic appearances, which can be discerned visually.

METHODS

Decidual samples were collected from 15 pregnant women between 6 and 8 weeks of gestation after elective termination of pregnancy. We identified the three different kinds of fresh decidual tissues in early pregnancy according to their different macroscopic appearances by only the naked eye. H&E staining, in situ immunofluorescence and flow cytometry were performed to confirm the accuracy of this method.

RESULTS

We developed a method to discern the three different kinds of decidual tissues according to their individual macroscopic features. We found that the decidua parietalis was a thick tissue with less blood, with one side being intact epidermis and the other side being rough tissue. The decidua basalis had rough surfaces, a dense texture and high blood content. The decidua capsularis was a thin membrane tissue with or without blood clots. CK+/HLA-G+ extravillous trophoblast cells (EVTs) and heme oxygenase-1+ (HMOX1+) decidual macrophages were present in large quantities in the decidua basalis and decidua capsularis but were nearly undetectable in the decidua parietalis. We also found a wide distribution of endovascular extravillous trophoblast cells (enEVTs), which participate in spiral artery remodelling in the decidua basalis.

DISCUSSION

We successfully identified three kinds of human decidual tissues from early pregnancy with the naked eye for the first time. This breakthrough method will greatly assist studies related to decidua during early pregnancy.

Differences in collagen ultrastructure of human first trimester decidua basalis and parietalis: implications for trophoblastic invasion of the placental bed

AIM

The human embryo-maternal interface in the first trimester of pregnancy is an area of extensive tissue remodeling. Because collagen is the most abundant constituent of the extracellular matrix of the placental bed, successful invasion must involve its rapid turnover. We compared the nature and distribution of collagen fibrils in decidua basalis and parietalis.

METHODS

We used a direct-vision hysteroscopic technique to obtain biopsies of the decidua basalis and parietalis from 11 women undergoing pregnancy termination in the first trimester. The biopsies were subjected to light, transmission and scanning electron microscopy, and immunohistochemical studies using mouse monoclonal antibodies against cytokeratin 7 and collagen types I, III and V.

RESULTS

Collagen fibrils in the stroma of decidua basalis were significantly thicker when compared to those in decidua parietalis (56.48 ± 1.37 nm vs 45.64 ± 0.85 nm; P < 0.0001 [mean ± standard error]) between 9 and 12 weeks gestation, but this difference in thickness was not observed at gestations below 9 weeks. In basalis, the fibrils appeared disrupted at most places surrounding the decidual/trophoblast cells while a uniform regular arrangement was preserved throughout most of parietalis.

CONCLUSION

There are differences in the ultrastructure of collagen fibrils between basalis and parietalis, with thicker and disrupted fibrils within abundant amorphous tissue in basalis, and thinner uniform fibrils in parietalis. These differences may reflect an adaptive response by decidua or a direct consequence of the invading trophoblast cells.