EG-VEGF Protein Expression in Superovulated Buffalo Corpus Luteum.

Abstract

Endocrine gland derived endothelial growth factor (EG-VEGF) also termed prokinectin 1(PK-1), is a recently identified protein, which expression has been described in a variety of tissues, including steroidogenic glands, gastrointestinal tract, and nervous system. EG-VEGF is a multifunctional factor: in bovine corpus luteum (CL) it induces endothelial cell proliferation and permeability. Superovulation has been shown to promote important morphologic and functional changes in buffaloes CL: gonadotropins stimulates progesterone synthesis and induces the expression of angiogenic factors as VEGF and bFGF increasing vascular permeability. Based on these data, we hypothesized that EG-VEGF is present in buffalo CL and that superovulatory treatment influences its expression. To test these hypotheses, we used 12 water buffaloes corpora lutea collected on day 6 post ovulation: six from non-treated (control group) and six from animals submitted to superovulatory treatment. Superovulation was carried out using repeated dosis of follicle-stimulating hormone (FSH). EG-VEGF protein expression was assessed by immunohistochemistry and western blotting (WB). Data were analyzed by Student's t test and differences were considered significant at P < 0.05. A positive immunostaining was detected in the cytoplasm of luteal and endothelial cells, but stroma cells as well as pericytes were not stained for EG-VEGF. Western blots of buffalo CL protein extracts were able to detect one band, at approximately 12 kDa, which correspond to EG-VEGF. In both immunohistochemistry and densitometry, we observed a higher expression of EG-VEGF in CL of superovulated buffaloes in relation to control group (P<0.05). Our data demonstrated that EG-VEGF protein is expressed in buffaloes CL, and that FSH stimulates its expression. Our data agree with previously studies, in which one has demonstrated that hCG stimulates the synthesis of EG-VEGF in human luteinized granulosa cells. In conclusion, the presence of EG-VEGF in CL, mainly in luteal and endothelial cells, points towards a paracrine or even autocrine role of this growth factor in modulating CL function. Moreover, the increased expression observed in superovulated CL may be related to increased vascularization and hormone production, features already described for this model. (poster)