Elevated plasma levels of lysophosphatidic acid and aberrant expression of lysophosphatidic acid receptors in adenomyosis

BACKGROUND Given the important roles of the receptor-mediated lysophosphatidic acid (LPA) signaling in both reproductive tract function and gynecological cancers, it will be informative to investigate the potential role of LPA in the development of adenomyosis. The objective of this study was to evaluate the levels of LPA in plasma and the expression of six LPA receptors in the endometrial tissue collected from women with and without adenomyosis. METHODS Plasma and endometrial tissue samples were collected form women with and without adenomyosis. The levels of LPA in plasma were determined by using high-performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). Immunohistochemistry was performed to evaluate the expression of six LPA receptors (LPA1-6) in endometrial tissue samples. The effects of LPA on IL-8 production, VEGF production and cell proliferation in human endometrial stromal cells (ESCs) were also assessed. RESULTS LPA1 staining was localized to the cytoplasm, membrances of the epithelial cells of the endometrial glands, and there was little staining in the stromal cells. LPA2-5 staining were localized to the nuclei of stromal and glandular cells. Plasma levels of LPA were increased in adenomyosis. LPA1, LPA4 and LPA5 immunoreactivity were significantly higher in the adenomyosis group than in the control group, while LPA2 and LPA3 immunoreactivity were significantly lower in the adenomyosis group than in the control group. LPA6 was undetectable in the endometria. LPA induced the release of IL-8 from ESCs but did not affect cell proliferation and VEGF production. CONCLUSION These results indicate that elevated plasma levels of LPA and aberrant expression of LPA receptors in the endometria may be associated with the development of adenomyosis.