Efeito do fator de crescimento IGF-I sobre a maturação in vitro de oócitos caninos (Canis familiaris): avaliação da maturação nuclear e citoplasmática

Abstract

A presente pesquisa foi desenvolvida com o objetivo de avaliar os prováveis efeitos do fator de crescimento semelhante à insulina I (IGF-I) sobre a maturação in vitro (MIV), nuclear e citoplasmática, de oócitos caninos retirados de ovários de cadelas. Os complexos cumulus oócitos (COCs) foram maturados in vitro em meio SOF (“synthetic oviductal fluid”). Foram utilizadas 40 cadelas submetidas ovario-histerectomias para esterilização cirúrgica ou para o tratamento de piometra. As doadoras foram classificadas em grupos conforme raça, faixa etária, condição reprodutiva e fase do ciclo estral. Os COCs (n=1474) foram liberados dos folículos pela técnica de fatiamento dos ovarios e maturados por 72 horas, exceto o grupo M0 (momento zero). O meio de cultivo base, foi o SOF, suplementado ou não com o IGF-I. Foram selecionados apenas COCs classificados como grau 1 para a MIV. Os COCs foram distribuidos em três grupos

This study was performed to identify the possible effects of insulin-like growth factor-i (IGF-I) on in vitro maturation (IVM) evaluated by nuclear and cytoplasmic of bitch cumulus oocyte complexes (COCs) matured in vitro in synthetic oviductal fluid (SOF) medium. For this purpose ovaries were collected from 40 bitches undergoing ovariohysterectomy for neutering or due to pyometra. The donors females were classified into groups based on breed, age, reproductive status and stage of the estrous cycle. The COCs (n=1474) were released from the follicles by slicing the ovaries and matured in vitro for 72 hours in the base culture medium SOF supplemented or no with IGF-I. Only grade 1 COCs were used for IVM, and were divided into three groups: M0 (zero collection time), C (SOF) and E (SOF + IGF-I). After incubation period, the maturation of the nucleus was examined by staining the oocytes with Hoechst 33342 and the cytoplasmic maturation by means of Lens culinaris agglutinin. The M0 group also was examined to cytoplasmic and nuclear maturation with the same staining dyes. From all females donors were collected 35.21, 39.69, 39.83 and 39.2% COCs per bitch were collected from mongrel, adult (>10 months), multiparous, and diestrus females, respectively (P<0.05). The percentage of degenerated oocytes was very high in the total sum (74.0%) and amongst experimental groups (M0=59.43; C=75.44; E=80.52%) with significant statistical differences (P<0.05) between them. And from all groups only 3.02% oocytes reached MI (M0= 2.83; C=4.19; E=2.10%). Alike nuclear meiotic resumption the cytoplasmic maturation rates were low, 15.83% in the total and 12.90 (M0); 25.58 (C); E (8.69%)...(Complete abstract, click electronic access below)