CONICET | Buscador de Institutos y Recursos Humanos

Introduction: Despite the advances in assisted reproduction, poor and high ovarian response to gonadotropins remains a problem. Patients who fail to obtain an adequate number of mature follicles after gonadotropin stimulation are considered to be poor responders. On the other hand, the retrieval of >15 oocytes is one of the main criteria for deeming a patient as high responder. In women, ovarian angiogenesis seems to be involved in the selection of follicles during stimulated IVF cycles. Gonadotropins, steroids and vasoactive substances such as vascular endothelial growth factor (VEGF) and angiopoietin-1 (ANGPT1) are involved in the regulation of vascularization. The ANGPTs/Tie-2 system acts in concert with VEGF. ANGPT-1 is necessary to stabilize blood vessels while ANGPT2 and the soluble receptor Tie-2 (sTie-2) act as natural antagonists for ANGPT1. The balance between ANGPT1, ANGPT2 and sTie-2, and VEGF is important for angiogenesis in the ovary. It is important to note that one of our previous reports demonstrated that levels of ANGPT1 were increased in follicular fluid (FF) from high responder patients undergoing ART in comparison with those from normoresponder patients. Our objectives were: 1) To analyze the levels of ANGPT1 and sTie-2 in FF from young poor responders and 2) To determine the effect of ANGPT1 in high responder patients undergoing ART on endothelial cell migration. Material and methods: This study was performed in 51 patients aged 25-39 years old undergoing ART. Written informed consent was given by all the patients before recruitment. Patients with pelvic pathologies such as endometriosis, uterine fibroids or pelvic inflammatory disease were excluded from the study. Patients were classified into three groups with respect to the number of aspirated oocytes: normoresponders (n=15; 8-13 oocytes), low responder (n=17; 0-5 oocytes) and high responder (n=19; 15-25 oocytes). The FF was centrifuged immediately for 10 min at 2000 x g to remove cellular components and debris and then transferred to sterile polypropylene tubes. The supernatant was stored at 80º C until assayed. The levels of ANGPT1 and sTie-2 were measured in FF by ELISA assay. To assess the specific effect of ANGPT1 on ovarian angiogenesis, we evaluated the effect of FF from high responders on endothelial cell migration in the presence of a neutralizing antibody against ANGPT1. For this purpose, a wound healing assay using the EA.hy926 endothelial cell line was performed. Results: In FF from patients undergoing ART with poor response, the levels of ANGPT1 were higher than in normoresponders (Normoresponders: 165.1 ± 21.7 vs Poor responders: 318.5 ± 61.6 pg / ml, p<0.05). No difference was found in the levels of sTie-2 between the groups analyzed. Incubation with FF from high responders in the presence of an ANGPT1 antibody resulted in a significant decrease in cell migration compared to FF without antibody (p<0.05). It is worth to note that in the absence of neutralizing antibody against ANGPT1, endothelial migration was significantly greater in the presence of FF from high responders than in the presence of FF from normoresponders (p<0.001). Conclusions: Our results suggest that the levels of ANGPT1 are associated with the type of response to gonadotropin therapy. Balanced levels of this protein appear to be crucial for a normal ovarian response to gonadotropins. In addition, the results described regarding the levels of ANGPT1 in FF and the altered endothelial cell migration in the presence of FF from high responders with ANGPT1 antibody may provide new insights into the mechanisms by which ANGPT1 has an effect on ovarian disorders such as poor ovarian responders and OHSS. Supported by: ANPCYT (PICT 2008/747).