**Abstract**

The onset search for differential protein expression in endometriosis commenced more than 30 years ago, when the gel electrophoresis could not be available to distinguish serum from women with and without disease. Gradually as the proteomics allows the comprehensive analysis of peritoneal fluid, serum and tissue samples with good sensitivity and resolution, it has promised in delivering markers possibility associated with endometriosis. Cytokines and growth factors that are present in serum, peritoneal fluid, endometrium, endometriotic lesions tissues and involved in tissue implanting process including hormone regulation, angiogenesis, invading and malignancy may be the focus to develop the noninvasive diagnostic test and possible treatment target for endometriosis. Individual peptides or proteins that are present or absent (or up- or down-regulated) in various conditions can be assessed as possible biomarkers. Alternatively, proteomic profiling, using mass spectrometry in combination with bioinformatics software to identify the actual protein and peptide pattern can be used as a distinctive marker to diagnostic and treatment target contribution to the disease.

**Keywords:** diagnosis, treatment, endometriosis

## **1. Introduction**

Endometriosis (EM) is defined as a benign condition of gynecological diseases when endometrial debris including gland and stroma components outside the uterus and spread to pelvis and extrapelvic sites. It affects at least 10% reproductive women with approximately 70% of cases developing pelvic inflammatory disease and 25–30% of cases associated with infertility [1]. The classical symptoms are dysmenorrhea, chronic pelvic pain, and ovarian chocolate cysts.

Till now, the pathogenesis of endometriosis is unclear. The retrograde menstruation is the basic theory which the menstrual fragments mostly attach to the peritoneum or ovaries area [2]. Whereafter endometriosis mainly responds to fluctuations in estrogen and progesterone by growth and inflammation. And endometriosis mostly involves in the reproductive tract components, such as ovaries, fallopian tubes, uterosacral ligaments, cervix, recto-vaginal septum and vagina. There are commonly exhibited with fibrous walls, adhering to the neighbor structures and usually containing chocolate-colored content. Therefore the affected organs are forming together with serial symptoms-dysmenorrhoea, ovarian chocolate cysts and infertility are often found in the patients. Recently, stem cell theory can be

considered as perspective view of the retrograde menstruation theory [3]. Other theories like immune system dysfunction, genetic susceptibility and exposure to the environment such as dioxins can devote to the progress of the disease [4, 5].

Generally, severity of endometriosis is classified by the revised American Fertility Society (rAFS) system [6], dividing patients into one of four stages (I–IV, minimal-severe) based on lesion size and pelvic adhesions associated with infertility. However, it remains uncertain whether the disease progresses through these stages. Actually some surgeon would prefer to stage on the basis of the sites and extent of the lesions under the laparoscopy or laparotomy and describe without AFS or r-AFS stage. Sometimes they may give some complementary suggestion [7]. Meanwhile, endometriosis has a variable symptom profile which does not relate with severity of this disease [8]. Furthermore, the patients often suffer from the symptoms of infertility or chronic pain for several years before the diagnosis is lately confirmed. So it makes the clinical diagnosis even more difficult. And actually there has been a lack of precise diagnosis method in previous researches. On the aspects of clinical application and financial consideration, more effective and noninvasive test will be needed in endometriosis disease.

Currently, laparoscopy offers the most widely accepted technique and method for evaluating and treating endometriosis. And most of endometriosis patients are treated by surgical removal of lesions and/or hormonal suppression focused on reducing estrogen, such as progestins, androgens, gonadotropin-releasing hormone (GnRH) agonists, and recent aromatase inhibitors. However, both approaches are associated with various side effects and a highly recurrent incidence [9, 10]. Therefore, identification of protein molecular mechanisms involved in the pathogenesis of endometriosis and strategic therapies for treatment are critical.
