Genomics of Endometriosis

Abstract

We hypothesized that the genomics of endometriosis would elucidate the pathology of the disease. Therefore the objective of this project was to examine gene expression in eutopic vs. ectopic endometrium. To address this hypothesis, biopsies of endometriosis explants and eutopic endometrium were obtained from 6 patients at midfollicular phase. Gene expression was analyzed in each sample using DNA microarrays. Twelve CodeLink whole human genome microarrays were obtained from GE (Amersham). Samples of endometrium and ectopic endometrial implants were obtained at surgery. A portion of each sample was immediately placed into RNA Later and frozen at -70 degrees for later RNA extraction. The rest of the sample was sent to histopathology for pathologic confirmation. Total RNA was extracted from each of the 6 eutopic and 6 ectopic endometrial samples, and each sample was run on one microarray. GeneSpring software was used to perform t-tests on the gene expression data; statistical significance was accepted at p less than or equal to 0.05. Genes showing a significant p value were further analyzed by fold-expression compared to eutopic endometrium. The differential expression of selected genes was confirmed by real time RT-PCR. Statistical analysis identified 440 differentially expressed genes with p values less than or equal to 0.05. Of those genes, 200 were transcribed sequences not yet associated with a name or function. Of the remaining 240 genes, 195 exhibited greater than 2-fold difference in expression. These 195 genes were separated into categories: inflammation, cell junction/cell adhesion/transmembrane, cytoskeleton, signal transduction, receptors, transcription factors, cell cycle/cell death, channels, and uncategorized genes. The gene showing the greatest fold increase in expression with ectopic endometriotic implants was the secretory phospholipase A2 type IIA; its expression increased 147-fold (p=0.01) compared to eutopic endometrium. Another gene in the inflammation category, prostaglandin I2 (prostacyclin) synthase, increased 20-fold with endometriosis (p=0.03). As predicted from reports in the literature, the expression of inflammatory, cell adhesion, and cell death genes were differentially expressed in endometriosis explants compared to eutopic endometrium. The data also identify new avenues for exploration of the pathology of endometriosis. For example, a specific subset of inflammatory genes was up-regulated with endometriosis. Moreover, a role for many of the differentially expressed cell junction, cytoskeletal, signal transduction, and transcription factor genes has not previously been reported in endometriosis.