Abstract:
The changes in endometrial cells, both in the eutopic endometrium of patients with and
without endometriosis and in lesions at ectopic sites, are frequently described and often compared
to tumorigenesis. In tumorigenesis, the concept of “seed and soil” is well established. The seed refers
to tumor cells with metastatic potential, and the soil is any organ or tissue that provides a suitable
environment for the seed to grow. In this systematic review (PRISMA-S), we specifically compared
the development of endometriosis with the “seed and soil” hypothesis. To determine changes in the
endometrial seed, we re-analyzed the mRNA expression data of the eutopic and ectopic endometrium, paying special attention to the epithelial–mesenchymal transition (EMT). We found that the
similarity between eutopic endometrium without and with endometriosis is extremely high
(~99.1%). In contrast, the eutopic endometrium of patients with endometriosis has a similarity of
only 95.3% with the ectopic endometrium. An analysis of EMT-associated genes revealed only minor differences in the mRNA expression levels of claudin family members without the loss of other
cell–cell junctions that are critical for the epithelial phenotype. The array data suggest that the
changes in the eutopic endometrium (=seed) are quite subtle at the beginning of the disease and that
most of the differences occur after implantation into ectopic locations (=soil).
