Abstract
BackgroundThe identification of the adipocyte-derived obesity gene product, leptin (Ob), and subsequently its association with reproduction in rodents and humans led to speculations that leptin may be involved in the regulation of oocyte and preimplantation embryo development. In mice and pigs, in vitro leptin addition significantly increased meiotic resumption and promoted preimplantation embryo development in a dose-dependent manner. This study was conducted to determine whether leptin supplementation during in vitro maturation (IVM) to horse oocytes could have effects on their developmental capacity after fertilization by IntraCytoplasmic Sperm Injection (ICSI).MethodsCompact and expanded-cumulus horse oocytes were matured in medium containing different concentrations (1, 10, 100, 1000 ng/ml) of recombinant human leptin and the effects on maturation, fertilization and embryo cleavage were evaluated. Furthermore, early developmental expression of Ob and leptin receptor (Ob-R) was investigated by immunocytochemical staining.ResultsIn expanded-cumulus oocytes, the addition of leptin in IVM medium improved maturation (74% vs 44%, for 100 ng/ml leptin-treated and control groups, respectively; P < 0.05) and fertilization after ICSI (56% vs 23% for 10 ng/ml leptin-treated and control groups, respectively; P < 0.05). However, the developmental rate and quality of 8-cell stage embryos derived from leptin-treated oocytes (100 ng/ml) was significantly reduced, in contrast to previous data in other species where leptin increased embryo cleavage. Ob and Ob-R proteins were detected up to the 8-cell stage with cortical and cytoplasmic granule-like distribution pattern in each blastomere.ConclusionLeptin plays a cumulus cell-mediated role in the regulation of oocyte maturation in the mare. Species-specific differences may exist in oocyte sensitivity to leptin.
Highlights
The identification of the adipocyte-derived obesity gene product, leptin (Ob), and subsequently its association with reproduction in rodents and humans led to speculations that leptin may be involved in the regulation of oocyte and preimplantation embryo development
These authors hypothesized that leptin might influence the synthesis and release of cumulus cell-derived factors, which reach the oocyte through gap junction coupling and/or the extracellular environment
Since oocyte developmental competence is best assessed by its ability to undergo embryonic development [30], the present study investigated the effect of leptin supplementation in in vitro maturation (IVM) medium on maturation, fertilization and development of horse oocytes after IntraCytoplasmic Sperm Injection (ICSI)
Summary
The identification of the adipocyte-derived obesity gene product, leptin (Ob), and subsequently its association with reproduction in rodents and humans led to speculations that leptin may be involved in the regulation of oocyte and preimplantation embryo development. Kawamura et al [3,4] demonstrated that leptin supplementation in the culture medium (10, 100 and 1000 ng/ml) promoted embryo development and increased the cell numbers of cultured blastocysts and the effect was preferentially observed in the trophoectoderm. PaulaLopes et al [7] showed that leptin supplementation (1 and 10 ng/ml) exerted positive effects during oocyte maturation, by influencing blastocyst development, apoptotic index in cumulus cells and transcript levels of developmentally important genes. They demonstrated a role for cumulus cells in mediating leptin effects. These authors hypothesized that leptin might influence the synthesis and release of cumulus cell-derived factors, which reach the oocyte through gap junction coupling and/or the extracellular environment
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