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ABSTRACT: Regulation of early embryonal development during fertilization and implantation is crucial for mammalian reproduction. Several studies have described cell death during preimplantation embryogenesis in a range of mammalian species, both in vivo and in vitro. Therefore, apoptosis may be involved in early embryonic arrest and the characteristic cytoplasmic fragments are the equivalents of apoptotic bodies, the end-product of apoptosis. Although apoptosis is expected to associate with fragmentation in early preimplantation embryos, the mechanism through which this fragmentation occurs has not been elucidated. Recently, second mitochondria-derived activator of caspase/Direct IAP Binding Protein with Low pI (Smac/DIABLO) was identified as a mitochondrial protein that is released into the cytosol during apoptosis. Once released, the Smac/DIABLO blocks the anti-apoptotic activity of inhibitor of apoptosis proteins (IAPs). We hypothesized that the Smac/DIABLO may be involved in the fragmentation of mouse preimplantation embryos. Therefore, we investigated the expression of Smac/DIABLO mRNA and protein and its localization in mouse oocytes and preimplantation embryos. Smac/DIABLO mRNA was detected by RT-PCR in the oocytes and the preimplantation embryos. Immunohistochemistry studies showed that the Smac/DIABLO protein localized in mitochondria and was released into the cytosol in both fragmented embryos and embryos in which apoptosis was induced by staurosporine. These observations indicate that the Smac/DIABLO is involved in the fragmentation and apoptosis of preimplantation embryos.
Molecular Human Reproduction 04/2005; 11(3):183-8. · 3.85 Impact Factor
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ABSTRACT: Although ghrelin acts as a modulator of feeding behavior and energy metabolism in the central nervous system, recent studies have implicated the peripheral actions of ghrelin in reproductive tissues. Here, we investigated the expression of ghrelin and its receptor (GHS-R) in mouse oocyte and preimplantation embryos, and we examined the role of ghrelin in the regulation of early embryo development. Both ghrelin and GHS-R mRNAs were detected in morula or more advanced embryo stages. As for the origin of ghrelin, both ghrelin mRNA and protein were identified in the uterine endometrium. The levels of ghrelin in uterine fluid as well as plasma were significantly increased in fasting mice compared with animals with free access to foods. Addition of ghrelin to culture media inhibited the development of two-cell embryos to the hatched blastocysts, and the inhibitory effects of ghrelin were abolished by an antagonist for the GHS-R. In addition, ghrelin significantly decreased the number of total cells, inner cell mass, and trophectoderm cells in blastocysts. These observations suggest that ghrelin could inhibit the development of preimplantation embryos during fasting. Thus, ghrelin may act as a peripheral factor to avoid the excess metabolic demands imposed by pregnancy during malnutritional states.
Endocrinology 07/2003; 144(6):2623-33. · 4.46 Impact Factor
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ABSTRACT: Apoptosis is an essential physiologic process used in almost all tissues to remove damaged or superfluous cells. However, the early embryos are unique because no cell death is found up to the blastocyst stage during normal development. Survivin, a member of the IAP family, is capable of binding to caspases to modulate their functions. Here, we investigated the expression of survivin, and its role in preventing apoptosis in mouse preimplantation embryos. Transcripts for survivin and a splice variant lacking exon 2 were detected from unfertilized oocytes up to hatched blastocyst stage. At the protein level, survivin was also detected at all stages of early embryos. The antisense approach was used to demonstrate the role of survivin on embryo development. Development of early embryos treated with antisense survivin oligonucleotides was arrested at the morula or early blastocyst stage with disruption of tubulin formation and abnormal nuclei, associated with apoptosis. The effect of the antisense was enhanced by cotreatment with an apoptosis-inducing reagent, staurosporine. In contrast, apoptosis induced by the antisense treatment was inhibited by caspase-3 and -9 inhibitors. These results indicate that survivin is an essential antiapoptotic gene expressed in preimplantation embryos and could protect the embryos from apoptosis by inhibiting an apoptotic pathway involving caspases.
Developmental Biology 05/2003; 256(2):331-41. · 4.07 Impact Factor
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ABSTRACT: Leptin acts as a modulator of diverse reproductive functions, and recent studies have implicated involvement of leptin in the early embryo development in mammal. The aim of this study was to investigate the expression of leptin and its receptor (OB-R) in mouse oocyte and preimplantation embryo, and to examine whether leptin influenced the early embryo development. Leptin mRNA was detected in blastocyst and hatched blastocyst, and two splice variants of OB-R (OB-Ra and OB-Rb) mRNAs were detected in oocytes, 1-cell, 2-cell, morula, blastocyst, and hatched blastocyst. As for the origin of leptin, both leptin mRNA and protein were identified in the oviduct epithelium and endometrium of pregnant mouse. In the pregnant mouse, the levels of leptin in uterine fluid were higher than those in nonpregnant mouse. Addition of leptin to embryo culture media promotes the development from 2-cell stage embryos to the blastocysts, fully expanded blastocysts and hatched blastocysts. This effect was neutralized by an antibody against the extracellular domain of OB-R. Leptin significantly increased the total cell number of blastocysts, and the effect was preferentially observed in the trophectoderm. These findings raise the possibility of a paracrine/autocrine leptin signaling system regulating the development of mouse preimplantation embryo.
Endocrinology 06/2002; 143(5):1922-31. · 4.46 Impact Factor
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ABSTRACT: Apoptotic degeneration of germ cells in cryptorchid testis is associated with an increased level of reactive oxygen species, and may be prevented by antioxidant treatment. The objective of this study was to investigate whether xanthine oxidase inhibitors could confer such protection. Unilateral cryptorchidism was surgically induced in the immature rats, which were then left untreated or treated with xanthine oxidase inhibitors, and the testes were evaluated 7 days after the operation. In the control group, the weight of the cryptorchid testis was decreased to 47% of that of the contralateral scrotal testis. However, administration of a xanthine oxidase inhibitor allopurinol (> or = 1 mg/kg/day) significantly attenuated weight reduction of the cryptorchid testis (68-77% of the contralateral scrotal testis, P < 0.01 versus control). Another highly specific xanthine oxidase inhibitor, BOF-4272, also attenuated cryptorchidism-induced testis regression. The effects of allopurinol were associated with decreased apoptosis in germ cells as evaluated by in-situ staining of fragmented DNA. In testicular cells cultured at 37 degrees C, either allopurinol or BOF-4272 prevented DNA cleavage characteristic of apoptosis. In conclusion, xanthine oxidase inhibitors can inhibit germ cell apoptosis induced by experimental cryptorchidism, and may be considered for treatment of male infertility associated with heat stress.
Molecular Human Reproduction 02/2002; 8(2):118-23. · 3.85 Impact Factor
