**2.2 Proteins of angiogenesis process of endometrial tissue**

On behalf of endometriosis lesions, neovascularization and angiogenesis factors should be introduced. Angiogenic factors such as VEGF [19], ENDO-I [20], angiogenin [21], pleiotrophin, midkine [22], PGF [23], angiopoietin [24], and glycodelin [25, 26] have been identified association with the lesions angiogenesis in endometriosis. Angiogenic activity is supplemented by the co-existence of pathologic angiogenesis, immune suppression, and immune activation. Study from human being indicated the correlation between high MVD and symptom of pelvic pain in patients with endometriosis by transvaginal color doppler ultrasound evaluation. MVD has been described using immunohistochemical evaluation with CD34 labeled endothelial cells of vessels [27, 28]. There was no significantly increased VEGF expression but it has been found in the involvement of other angiogenic factors with the active implants showing high mitotic index and increased MVD [27]. Further findings were reported in other articles that VEGF-A role was demonstrated by its increased concentrations in the endometrium of patients with endometriosis. Moreover, it was confirmed that the expression of VEGF-A gene was higher in peritoneal endometriosis compared with normal peritoneum [29].
