Identification of endometriosis-related genes by cDNA microarray

Abstract

Objective: Endometriosis is the most common cause of female infertility and too often the molecular mechanisms is still unclear. This study aims to identify differential expressed genes in eutopic endometrium (uterine endometrium) versus ectopic endometrium (chocolate cyst) through the use of a membrane-based cDNA microarray. Design: Pilot study. Materials/Methods: Patients who were scheduled for surgery for endometriosis were recruited to participate in this study. Eutopic endometrial tissues from women with endometriosis (n=3) and the ectopic endometrial tissues from chocolate cysts (n=3) were collected during laparoscopy. The tissues were irrigated with lactated Ringer’s solution and divided in half. One half was immediately placed in an RNA protection reagent, RNAlater (Ambion, Austin, TX) and placed on ice for transport to the laboratory. The other half was sent to the pathology laboratory. The human cDNA microarray system (9,600 genes, including known regulatory genes and expressed sequence tag, EST) with colorimetric detection system was used to identify the differentially expressed genes. Results: The results of cDNA expression array showed that 163 genes were up-regulated 3-fold or higher in ectopic endometrium and only 14 genes were up-regulated in eutopic endometrium at the mRNA level. These differentially expressed genes were further grouped into categories by their putative functions, including: cell growth-related factors, cell adhesion molecules, signal transduction molecules, apoptotsis-related factors, hormones/cytokines, cytoskeleton/extracellular matrix proteins, and some expressed sequence tags (ESTs). Six of the genes that belong to the categories of cell apoptosis (Bcl-2, 4.6 folds), cell cycle-related genes (cyclin B1, 3.6 folds), cell migration and invasion (Vascular cell adhesion molecule 1, VCAM-1, 3.6 folds), growth factors/cytokines (BMP-4, 3.0 folds and TGF-beta receptor, 5.8 folds), metabolism (Glutathione S-transferase A2, GSTA2, 7.1 folds), and immune-response (CD36, 5.9 folds) were studied more extensively for their protein expression by immunohistochemistry. The immunostaining results showed that Bcl-2, cyclin B1, VCAM-1, BMP-4, TGF-beta receptor, GSTA2, and CD36 were over-expressed in ectopic endometrium at the protein level, validating the microarray findings. Conclusions: The globally analysis of the gene regulation in endometriosis was reported for the first time in this study. According to the results, we found that several genes related to cell invasion, cell growth, and immuno-response were highly regulated in ectopic endometrium. Overall, this study demonstrates that several genes are differentially expressed in ectopic endometrium. It is helpful to identify gene expression markers of endometriosis that can be used for noninvasive diagnosis of endometriosis, for development of new treatments for endometriosis, or to gain an understanding of the pathophysiology and etiology of the disease. Supported by: This investigation was supported by grants from the National Science Council (NSC 90-2314-B-038-049).