Menstruum induces changes in mesothelial cell morphology

In previous studies, we have shown that menstrual endometrium preferentiall y adheres to the subepithelial lining of the peritoneum. It remains to be e lucidated, however, whether this damage is preexisting or inflicted by the menstrual tissue itself. We hypothesized that the menstrual tissue itself d amages the peritoneum. To investigate this, the viability of menstrual endo metrial tissue in peritoneal fluid (PF) was evaluated and the morphologic c hanges in the mesothelial cells were studied by in vitro cocultures of mens truum with mesothelial cell monolayers. Menstruum was collected with a mens trual cup. Endometrial tissue was isolated from the menstruum, resuspended in culture medium or in the cell-free fraction of PF and cultured for 24, 4 8 or 72 h. A 3(4,5-dimethylthia-zolyl-2)-2,5-diphenyl tetrazofium bromide ( MTT) assay was performed to obtain a relative measure of viable adhered end ometrial cells. Mesothelial cells isolated from human omenta( tissue were c ultured on Matrigel or uncoated plastic. At confluence, overnight coculture s were performed and scanning electron microscopy was used to evaluate the morphologic changes. The viability of endometrial fragments was 84% (n = 36 , p < 0.05), 82% (n = 27, not significant) and 104% (n = 14, not significan t) when cultured in the cell free fraction of PF for 24, 48 and 72 h, respe ctively, when compared to medium with 10% fetal calf serum. Menstrual endom etrial fragments or menstrual serum added to and cocultured with mesothelia l cells induced severe morphologic alterations of the latter, including ret raction, shrinking and gap formation. Similar morphologic changes were obse rved when mesothelial cells were cocultured with menstrual endometrial frag ments in PF or in culture inserts. Incubation with conditioned medium from cultured menstrual endometrium induced similar but less pronounced changes in morphology. In conclusion, menstrual endometrial fragments remain viable in PF in vitro for at least 72 h. Antegradely shed menstruum induces chang es in mesothelial cell morphology, including retraction and shrinking with exposure of the underlying surface. These findings suggest that menstruum i s harmful to the peritoneal lining. Therefore, by local destruction of the mesothelial layer, menstrual endometrium is able to create sites for adhesi on. Copyright (C) 2000 S. Karger AG, Basel.