Spatiotemporal coupling of focal extracellular matrix degradation and reconstruction in the menstrual human endometrium

Coupling of focal degradation and renewal of the functional layer of menstrual endometrium is a key event of the female reproductive biology. The precise mechanisms by which the various endometrial cell populations control extracellular matrix (ECM) degradation in the functionalis while preserving the basalis and the respective contribution of basalis and functionalis in endometrium regeneration are still unclear. We therefore compared the transcriptome of stromal and glandular cells isolated by laser capture microdissection from the basalis as well as degraded and preserved areas of the functionalis in menstrual endometria. Data were validated by in situ hybridization. Expression profile of selected genes was further analyzed throughout the menstrual cycle, and their response to ovarian steroids withdrawal was studied in a mouse xenograft model. Immunohistochemistry confirmed the results at the protein level. Algorithms for sample clustering segregated biological samples according to cell type and tissue depth, indicating distinct gene expression profiles. Pairwise comparisons identified the greatest numbers of differentially expressed genes in the lysed functionalis when compared with the basalis. Strikingly, in addition to genes products associated with tissue degradation (matrix metalloproteinase and plasmin systems) and apoptosis, superficial lysed stroma was enriched in gene products associated with ECM biosynthesis (collagens and their processing enzymes). These results support the hypothesis that fragments of the functionalis participate in endometrial regeneration during late menstruation. Moreover, menstrual reflux of lysed fragments overexpressing ECM components and adhesion molecules could easily facilitate implantation of endometriotic lesions.