Immunolocalization of Insulin-Like Growth Factor Binding Protein-2 (IGFBP-2) in bovine cystic follicles.

RODRIGUEZ FM; BALDI C; ORTEGA HH; BARBEITO CG; GIMENO EJ; REY F

Aguas de Lindoia, Sao Paulo

Congreso; XIV Encontro Nacional de Patologia Veterinaria (ENAPAVE).; 2009

A widespread reproductive disorder in cattle is the cystic ovarian disease (COD). The mechanism leading to their development was proposed to be of multifactorial etiology. Although it is widely accepted that a dysfunction of the hypothalamic-pituitary-gonadal axis is an important etiological factor, several reports have discussed the association between COD and growth factors in different species. The insulin-like growth factor (IGF) system has already been shown to play a key role in the regulation of proliferation and differentiation of granulosa and theca cells. IGF binding proteins (IGFBPs) regulate the availability of IGFs to their target cells by either inhibiting or potentiating their action and sequester extracellular IGFs and hence reduce their bioavailability. Two mechanisms have been suggested by which availability of IGFs can be modified; through the activity of specific IGFBP proteases, or by changes in the IGFBPs expression. In previous studies we detected a significant low expression of IGFBP-2 in follicular fluid and evidence exists to suggest that could be due, in part, to changes in local synthesis. In the present study we proposed to analyze the mRNA expression of IGFBP-2 by RT-PCR using GAPDH as housekeeping. Moreover, we assessed the protein localization by immunohistochemistry. Ovaries of cows proceeding of a local abattoir were collected and dissected. Healthy follicles were classified into small (<5 mm), medium (5-10 mm), and large (>10 mm) antral follicles. Follicular cysts were defined as follicles of more than 20 mm in diameter, without functional corpus luteum and were evaluated macroscopically, histologically and hormonally. Additional samples were obtained from experimental cystic induction by hormonal treatment in cattles. Estrous cycle of these cows was synchronized with prostaglandin and GnRH injections and then cyst were induced with ACTH treatment. Ovaries were analyzed by ultrasonography and obtained by ovariectomy. Results obtained have evidenced a decreasing tendency in the IGFBP-2 mRNA expression as follicles increase in size and in cystic structures. Protein expression shown a differential pattern when cyst, experimental as well as spontaneous cystic structures, were compared with control follicles of healthy cows. While IGFBP-2 expression in control follicles were similar in thecal and granulosa cells, in cystic structures appeared to decrease in the theca internal. Further studies should be done in order to evaluate others IGFBPs as modulating factors of IGF response and relate them with IGF expression detected in our laboratory in previous studies. Regardless, these finding support our hypothesis providing information that an alteration in IGF system could be related to COD in cattle. (Supported by APCyT grant PICT-2007-01202 and grant UNL CAI+D program).