Influence of Insulin-Like Growth Factor-I and Its Interaction with Gonadotropins, Estradiol, and Fetal Calf Serum on In Vitro Maturation and Parthenogenic Development in Equine Oocytes1

Abstract

The effects of insulin-like growth factor-I (IGF-I) and its interaction with gonadotropins, estradiol, and fetal calf serum (FCS) on in vitro maturation (IVM) of equine oocytes were investigated in this study. We also examined the role of IGF-I in the presence or absence of gonadotropins, estradiol, and FCS in parthenogenic cleavage after oocyte activation with calcium ionophore combined with 6-dimethylaminopurine (6-DMAP), using cleavage rate as a measure of cytoplasmic maturation. Only equine cumulus-oocyte complexes with compact cumulus and homogenous ooplasm (n = 817) were used. In experiment 1, oocytes were cultured in TCM-199 supplemented with BSA, antibiotics, and IGF-I at 0 (control), 50, 100, 200 ng/ml, at 39 degrees C in air with 5% CO(2), 95% humidity for 36 or 48 h. In experiment 2, oocytes were cultured with FSH, LH, estradiol, and FCS with IGF-I at the concentration that promoted the highest nuclear maturation rate in experiment 1. In experiment 3, oocytes from the three experimental groups (IGF-I; hormones; and IGF-I + hormones) were chemically activated by exposure to calcium ionophore followed by culture in 6-DMAP. In experiment 1, IGF-I stimulated equine oocyte maturation in a dose-dependent manner with the highest nuclear maturation rate at a concentration of 200 ng/ml. No significant effect of IGF-I on nuclear maturation was observed in experiment 2. In experiment 3, a significant difference in cleavage rate was observed between the hormone + IGF-I group (15 of 33; 45.4%) compared with IGF-I (10 of 36; 27.8%) and hormone (4 of 31; 12.9%) alone (P < 0.05). These results demonstrated that IGF-I has a positive effect on nuclear maturation rate of equine oocytes in vitro. The addition of IGF-I to an IVM medium containing hormones and FCS did not increase nuclear maturation, but resulted in a positive effect on cytoplasmic maturation of equine oocytes measured by parthenogenic cleavage.

Effect of bovine cumulus–oocyte complexes‐conditioned medium on in‐vitro maturation of canine oocytes

“…In contrast with most mammalian species, in which the oocyte completes its first meiotic division in the preovulatory follicle and matured oocytes are ovulated and ready for fertilization within the oviduct, the domestic bitch ovulates immature oocytes at the germinal vesicle stage and the oocytes undergo a 48-72-h period of postovulatory maturation in the upper regions of the oviduct, and during oocyte maturation in vivo oocytes are exposed to an ever-changing environment of gonadotropins, steroids, growth factors, and many other factors, any or all of which may interact to regulate maturational changes that occur in the oocyte and its surrounding cumulus cells during the preovulatory period [1][2][3][4][5][6][7]. Clearly, these factors are assumed to be beneficial and involved in nuclear and/or cytoplasmic maturation of oocytes during IVM for several mammalian species, for example porcine [8,9], human [10], mouse [11], equine [12], and bovine [13]. The peculiarities of reproductive physiology of the dog complicate the definition of a culture system for IVM, which is currently characterized by poor and highly variable results.…”

Production of horse foals via direct injection of roscovitine-treated donor cells and activation by injection of sperm extract

“…Because rates of blastocyst production after intracytoplasmic sperm injection of in vitro-matured oocytes are acceptable (up to 38%; Hinrichs et al 2005), the low blastocyst development after NT in the horse may be related to inefficiency in activation of equine oocytes. Effective methods for equine oocyte activation were not developed before work commenced on equine NT; methods commonly used in other species, including exposure to calcium ionophore A23187, cycloheximide, ionomycin, ethanol, thimerosal, or 6-dimethylamino purine (6-DMAP), or injection of inositol 1,4,5-tripho sphate, were reported to result in low activation or cleavage rates when used on horse oocytes (Hinrichs et al 1995, Li et al 2000, Carneiro et al 2001, Choi et al 2001. Activation procedures used in equine NT have included exposure to calcium ionophore A23187 or ionomycin, followed by treatment either with cycloheximide (Choi et al 2002b, Galli et al 2003, Woods et al 2003 or with cycloheximide plus 6-DMAP (Lagutina et al 2005).…”

Influence of equine growth hormone, insulin-like growth factor-I and its interaction with gonadotropins on in vitro maturation and cytoskeleton morphology in equine oocytes

“…In previous studies, we have demonstrated that the addition of eGH to media containing IGF-I significantly increased the maturation of equine oocytes to M-I and M-II stages of development when compared with control (Pereira et al, 2006(Pereira et al, , 2012. Carneiro et al (2001Carneiro et al ( , 2002 used an IVM system in the presence of IGF-I and observed an improved cytoplasmic maturation on the basis of the migration of cortical granules to the periphery of horse oocytes and an increased cleavage rate after parthenogenetic activation. IGF-I has been reported to stimulate bovine oocyte maturation and fertilization in vitro (Lorenzo et al, 1994), and to promote rabbit blastocyst development (Herrler et al, 1998).…”

“…eGH (NHPP; Harbor-UCLA, CA, USA) was diluted in tissue culture and used at a concentration of 400 ng/ml (Pereira et al, 2012) for in vitro procedures. IGF-I was also diluted in TCM-199 and used at 200 ng/ml, in accordance with a study by Carneiro et al (2001). Base medium was composed of TCM-199, 1 mg/ml bovine serum albumin (BSA), 100 IU/ml penicillin G and 50 mg/ml streptomycin sulfate.…”