High lymph vessel density and expression of lymphatic growth factors in peritoneal endometriosis

To investigate the occurrence of lymph vessels and lymphangiogenic growth factors in peritoneal lesions, we performed immunohistochemical staining of peritoneal lesions of 37 patients with antibodies against podoplanin (D2-40), lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1), prospero homeobox protein 1 (Prox-1), vascular epithelial growth factor (VEGF)-C/VEGF-D. Overall, 10 lesions were double stained against D2-40 and von Willebrand factor. The lymph vessel density in peritoneal lesion was significantly higher in comparison with healthy peritoneum. All lymph vessel makers could be detected, whereby the lymph vessel density of LYVE-1- and Prox-1-positive lymph vessels was significantly higher than the lymph vessel density of D2-40-positive lymph vessels. Endometriotic epithelial cells and stromal cells (SCs) showed a moderate-to-strong VEGF-C/VEGF-D expression. The VEGF-C-/VEGF-D-positive macrophages in endometriotic SCs could be observed. The lymphatic vasculature seems to form a further component of peritoneal lesions and could be involved in the inflammatory process. These data demonstrated a further step in the clarification of the pathogenesis of endometriosis.