Basal and Steroid Hormone-Regulated Expression of CXCR4 and CXCL12 in Human Endometrium and Endometriosis.

Endometriosis is a gynecological disease characterized by the presence of stroma and epithelial cells outside the uterine cavity, causing pain and infertility. This disease is estrogen-dependent and is associated with the activation of inflammatory mechanisms in the peritoneal cavity, including increased levels of chemokines. We have previously reported an increase in mRNA expression of CXCR4, the specific receptor for the chemokine CXCL12, in the rat model of endometriosis. In addition, CXCR4 and CXCL12 have been shown to be elevated in ovarian endometriosis vs. ovary and ovarian cancer. CXCR4 gene expression has been shown to be upregulated by HIF-1, VEGF, and estradiol, factors that are known to be increased in patients with endometriosis. The CXCR4-CXCL12 axis also has non-immune functions, including roles in angiogenesis, invasion, migration and proliferation. The aim of this study is to determine CXCR4 and CXCL12 expression in endometrial and endometriotic cell lines and its regulation by estradiol (E2) and progesterone (P4). Also, we aimed to determine the levels and cellular localization of these proteins in eutopic and ectopic endometrium. Our hypothesis is that CXCR4 and CXCL12 are up regulated in endometriosis leading to an increase in their protein products. In order to confirm our hypothesis we use RT-PCR and Western Blot to analyze the steroid hormone regulation of CXCR4 and CXCL12 in the endometrial and endometriotic cell lines. We also compared the protein expression level by immunohistochemistry in normal endometrium versus endometriotic tissue in human model. Basal levels of CXCR4 were higher in epithelial cells as compared to stromal; in contrast its ligand, CXCL12, was expressed at higher levels in stromal vs epithelial cells. E2 significantly increased the gene expression of CXCL12 in endometrial epithelial cells. CXCR4 gene expression was not significantly modulated by sex steroid treatments in neither stromal nor epithelial cells, although a trend towards downregulation by P4 was noted. Immunohistochemistry showed a statistically significant increase in CXCR4 protein levels in endometriotic lesions (epithelial, stroma and glands) compared to normal endometrium. These data suggest a role for the CXCR4-CXCL12 axis in endometriosis, regulating angiogenesis and facilitating invasion and cell proliferation during early stages of the disease. Our findings also have implications for future therapeutic strategies that target the inflammatory component in endometriosis.Grant Support: R01 HD050559 (IF); S06 GM08239 (IF) (poster)