Epidermal growth factor induces Bcl-xL gene expression and reduces apoptosis in porcine parthenotes developing in vitro

Spindlin1 alters the metaphase to anaphase transition in meiosis I through regulation of BUB3 expression in porcine oocytes

Spindlin 1 (SPIN1), which contains Tudor-like domains, regulates maternal transcripts via interaction with a messenger RNA (mRNA)-binding protein. SPIN1 is involved in tumorigenesis in somatic cells and is highly expressed in cancer cells. Nevertheless, the role of SPIN1 in porcine oocyte maturation remains totally unknown. To explore the function of SPIN1 in porcine oocyte maturation, knockdown, and overexpression techniques were used. SPIN1 mRNA was identified in maternal stages ranging from GV to MII. SPIN1 was localized in the cytoplasm and to chromosomes during meiosis. SPIN1 knockdown accelerated first polar body extrusion. Oocytes with overexpressed SPIN1 were arrested at the MI stage. SPIN1 depletion caused meiotic spindle defects and chromosome instability. The BUB3 signal was investigated, confirming that SPIN1 affects the stability of Bub3 mRNA as well as BUB3 expression. Further, overexpression of SPIN1 inhibited the degradation and regulation of G2/mitotic-specific cyclin-B1. In summation, SPIN1 regulates the meiotic cell cycle by modulating the activation of the spindle assembly checkpoint.

Embryotropic effects of vascular endothelial growth factor on porcine embryos produced by in vitro fertilization

Current research suggests that supplementing in vitro culture (IVC) media with vascular endothelial growth factor (VEGF) may have beneficial effects on the development of porcine embryos in vitro. However, the molecular signaling mechanisms underlying this effect are unclear. Therefore, we aimed to investigate the effects of VEGF on molecular signaling events during in vitro embryonic development of porcine embryos. Porcine oocytes matured in vitro were fertilized, and the resultant zygotes were cultured with 5 ng/mL of VEGF supplemented with or without fetal bovine serum from day 4 till day 7. Without VEGF and/or FBS served as the control group. Real-time quantitative PCR was used to detect expression patterns of apoptosis- and oxidative stress-related genes in day 7 blastocysts (BLs). Early-stage apoptosis was detected by annexin-V assays in day 2 and day 7 embryos. We found that the addition of VEGF throughout the culture period with or without FBS supplementation significantly improved embryo survival and development. Supplementation with VEGF in the IVC medium significantly increased early BL formation (p < 0.05), although addition of FBS on day 4 significantly increased hatched BL formation (p < 0.05) regardless of VEGF supplementation. However, supplementation of media with both VEGF and FBS increased the formation of expanded BLs synergistically. The average total cell numbers per BL were significantly (p < 0.05) higher in embryos supplemented with VEGF and FBS than in those supplemented with either VEGF or FBS alone. We also found that accumulation of reactive oxygen species in VEGF-treated embryos was significantly lower (p < 0.05) than that in untreated embryos. The mRNA levels of caspase-3 were significantly lower (p < 0.05), and those of Bcl-2 and Nrf-2 were significantly higher (p < 0.05) in embryos grown in VEGF-supplemented media than in embryos grown in non-supplemented media. Furthermore, on day 2, the numbers of viable embryos (44.06 ± 3.94%) and blastomeres (67.18 ± 3.60%) were significantly higher (p < 0.05), and the numbers of early apoptotic embryos (55.94 ± 3.94) and blastomeres (23.23 ± 4.22) were significantly lower (p < 0.05) in VEGF-treated BLs than in controls. Furthermore, the numbers of early apoptotic cells in BLs on day 7 were also significantly lower (p < 0.05) in VEGF-treated BLs than in controls. Overall, our results indicate that supplementing IVC media with VEGF during in vitro culture of porcine embryos increases their developmental potential.

Liver receptor homolog 1 influences blastocyst hatching in pigs

Liver receptor homolog 1 (Lrh1, also known as Nr5a2) belongs to the orphan nuclear receptor superfamily and has diverse functions in development, metabolism, and cell differentiation and death. Lrh1 regulates the expression of Oct4, which is a key factor of early embryonic differentiation. However, the role of Lrh1 in early development of mammalian embryo is unknown. In the present study, the localization, Lrh1 mRNA expression, and LRH1 protein levels in porcine early parthenotes were examined by immunofluorescence and real-time reverse-transcription polymerase chain reaction. To determine the role of Lrh1 in porcine early embryo development, the parthenotes were treated with the specific LRH1 antagonist 505601. The immunofluorescence signal for LRH1 was only observed in the nucleus of blastocysts. The blastocyst developmental rate in the presence of 50 and 100 μM 505601 was significantly lower than that in the control group. The blastocyst hatching rate was also reduced in the presence of 50 and 100 μM 505601 than that under control conditions. The latter effect was possibly due to the decreased expression of hatching-related genes such as Fn1, Itgα5, and Cox2 upon the inhibition of Lrh1. Incubation with the LRH1 antagonist also increased the number of apoptotic cells among the blastocysts. Moreover, LRH1 inhibition enhanced the expression of the pro-apoptotic genes Bax and Casp3, and reduced the expression of the anti-apoptotic gene Bcl2. Lrh1 inhibition also led to significant decrease in the expression levels of Oct4 mRNA and octamer-binding transcription factor 4 (OCT4) protein in the blastocysts. In conclusion, Lrh1 affects blastocyst formation and hatching in porcine embryonic development through the regulation of OCT4 expression and cell apoptosis.

Combination effects of epidermal growth factor and glial cell line-derived neurotrophic factor on the in vitro developmental potential of porcine oocytes

The developmental potential of in vitro matured porcine oocytes is still lower than that of oocytes matured and fertilized in vivo. Major problems that account for the lower efficiency of in vitro production include the improper nuclear and cytoplasmic maturation of oocytes. With the aim of improving this issue, the single and combined effects of epidermal growth factor (EGF) and glial cell line-derived neurotrophic factor (GDNF) on oocyte developmental competence were investigated. Porcine cumulus-oocyte cell complexes (COCs) were matured in serum-free medium supplemented with EGF (0, 10 or 50 ng/ml) and/or GDNF (0, 10 or 50 ng/ml) for 44 h, and subsequently subjected to fertilization and cultured for 7 days in vitro. The in vitro-formed blastocysts derived from selected growth factor groups (i.e. EGF = 50 ng/ml; GDNF = 50 ng/ml; EGF = 50 ng/ml + GDNF = 50 ng/ml) were also used for mRNA expression analysis, or were subjected to Hoechst staining. The results showed that the addition of EGF and/or GDNF during oocyte maturation dose dependently enhanced oocyte developmental competence. Compared with the embryos obtained from control or single growth factor-treated oocytes, treatment with the combination of EGF and GDNF was shown to significantly improve oocyte competence in terms of blastocyst formation, blastocyst cell number and blastocyst hatching rate (P < 0.05), and also simultaneously induced the expression of BCL-xL and TERT and suppressed the expression of caspase-3 in resulting blastocysts (P < 0.05). These results suggest that both GDNF and EGF may play an important role in the regulation of porcine in vitro oocyte maturation and the combination of these growth factors could promote oocyte competency and blastocyst quality.

Beneficial effect of two culture systems with small groups of embryos on the development and quality of in vitro-produced bovine embryos

Currently, in vitro-produced embryos derived by ovum pick up (OPU) and in vitro fertilization (IVF) technologies represent approximately one-third of the embryos worldwide in cattle. Nevertheless, the culture of small groups of embryos from an individual egg donor is an issue that OPU-IVF laboratories have to face. In this work, we tested whether the development and quality of the preimplantation embryos in vitro cultured in low numbers (five embryos) could be improved by the addition of epidermal growth factor, insulin, transferrin and selenium (EGF-ITS) or by the WOW system. With this aim, immature oocytes recovered from slaughtered heifers were in vitro matured and in vitro fertilized. Presumptive zygotes were then randomly cultured in four culture conditions: one large group (LG) (50 embryos/500 μl medium) and three smaller groups [five embryos/50 μl medium without (control) or with EGF-ITS (EGF-ITS) and five embryos per microwell in the WOW system (WOW)]. Embryos cultured in LG showed a greater ability to develop to blastocyst stage than embryos cultured in smaller groups, while the blastocyst rate of WOW group was significantly higher than in control. The number of cells/blastocyst in LG was higher than control or WOW, whereas the apoptosis rate per blastocyst was lower. On the other hand, the addition of EGF-ITS significantly improved both parameters compared to the control and resulted in similar embryo quality to LG. In conclusion, the WOW system improved embryo development, while the addition of EGF-ITS improved the embryo quality when smaller groups of embryos were cultured.

Autophagy influences maternal mRNA degradation and apoptosis in porcine parthenotes developing in vitro

Autophagy, an essential process for cellular maintenance, cell viability, and development, is the bulk degradation of proteins and organelles. This study investigated the expression levels of autophagy-related genes and the effect of 3-methyladenine (3-MA, an autophagy inhibitor) or rapamycin (an autophagy inducer) on maternal gene degradation and apoptosis in porcine parthenotes developing in vitro. LC3, which is essential for the formation of autophagosomes, was widely expressed in porcine parthenotes. High levels of autophagy-related genes, Atg5, Beclin1 and Lc3 transcripts were expressed in the 1-cell (1C) stage and gradually decreased through the 2-cell (2C) to blastocyst stages. The mRNA expression of Gdf9, c-mos and cyclin B maintained high levels in 2C and 4-cell (4C) embryos treated with 3-MA compared with the control. The Bmp15 and cyclin B mRNA levels were significantly reduced in embryos treated with rapamycin compared with the control. These results suggest that autophagy influences the degradation of these maternal genes. Furthermore, 3-MA-treated embryos exhibited significantly reduced developmental rates, decreased total cell numbers and increased rates of apoptosis. Expression of Atg5, Beclin1 and Lc3 and synthesis of LC3 protein were significantly reduced at the blastocyst stage. Although rapamycin treatment did not affect the developmental rate, it decreased the cell number and increased the rate of apoptosis, and the expression of Atg5, Beclin1 and Lc3 and LC3 protein synthesis were increased. Finally, blastocysts derived following treatment with 3-MA or rapamycin exhibited significantly decreased expression of selected transcription factors, including Pou5f1, Sox2 and Nanog. In conclusion, our results demonstrate that autophagy influences maternal mRNA degradation and apoptosis at the blastocyst stage and suggest that autophagy plays an important role in early embryo development in the pig.

Interleukin-6 enhances porcine parthenote development in vitro, through the IL-6/Stat3 signaling pathway

Signal transducer and activator of transcription-3 (Stat3) plays a central role in interleukin-6 (IL-6)-mediated cell proliferation by inhibiting apoptosis in a variety of cell types. The Stat3 pathway is essential for embryonic development. The aim of this study was to determine the effects of recombinant IL-6 on the viability and development of porcine diploid parthenotes cultured in vitro. Four-cell parthenotes, derived in vitro, were cultured to the blastocyst stage, with or without recombinant IL-6. The addition of 10 or 100 ng/ml of recombinant swine IL-6 into PZM3 medium increased the development rate of parthenotes to the blastocyst stage (P<0.05). When supplemented with 10 ng/ml of recombinant swine IL-6, the number of parthenotes at the blastocyst stage increased (P<0.05) and apoptosis decreased (P<0.05). Real-time RT-PCR experiments revealed that the addition of recombinant swine IL-6 decreased the mRNA expression of the pro-apoptotic gene Caspase3 (P<0.01) but increased the expression levels of the anti-apoptotic genes Bcl2l1 and Survivin. IL-6 receptors and Stat3 mRNA expression were upregulated after treatment with 10 ng/ml recombinant swine IL-6. Immunoblots and fluorescence labeling experiments showed that the levels of phosphorylated Stat3 were upregulated. These results suggest that recombinant swine IL-6 prevents apoptosis of porcine parthenotes and enhances porcine embryo viability through the IL-6/Stat3 signaling pathway in vitro.

Leptin accelerates pronuclear formation following intracytoplasmic sperm injection of porcine oocytes: Possible role for MAP kinase inactivation

Leptin, a multifunctional hormone, is present in mammalian oocytes and follicular fluids and cumulus cells. While leptin modulates oocyte maturation in vitro which seems to result in enhancement of embryo development, it is unclear whether leptin treatment of oocytes affects cytoplasmic maturation and fertilization processes. In order to gain a better understanding of the role of leptin during oocyte maturation, we examined microtubule and microfilament assembly following oocyte maturation and blastocyst formation, mitogen-activated protein kinase (MAPK) activity, and pronuclear formation following parthenogenetic stimuli or intracytoplasmic sperm injection (ICSI) in leptin-treated oocytes. Addition of 10 or 100 ng/ml leptin during oocyte maturation did not increase the proportion of metaphase II oocytes, but enhanced development to blastocyst stage by day 7 (P<0.01) after parthenogenetic activation (PA), accompanied by increased cell number. However there was no effect on the number of apoptotic cells in blastocysts. Following maturation in the presence of leptin, there were more oocytes with normal spindle formation. MAPK activity decreased more rapidly, and pronuclear formation was accelerated after parthenogenetic activation or ICSI of leptin-treated oocytes. These results suggested that exogeneous leptin enhanced spindle assembly and accelerated pronuclear formation following fertilization, possibly via the MAPK pathway.

High mobility group box 1 (HMGB1) is implicated in preimplantation embryo development in the mouse

High mobility group box 1 (HMGB1) regulates multiple cell functions, including transcription, DNA repair, differentiation, and apoptosis. In order to obtain insight into the role of HMGB1 in embryo development, we first evaluated its gene expression levels in mouse preimplantation embryos. Quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) revealed high expression levels in zygotes, and expression steadily increased after zygotic genome activation when normalized to the rabbit Globin mRNA. Indirect immunocytochemistry showed that the HMGB1 protein was also produced in mouse embryos. Injection of a small interfering RNA (siRNA) specific for HMGB1 into zygotes specifically reduced both mRNA expression (P < 0.001) and protein synthesis of HMGB1 in early embryos developed in vitro. Injection of siRNA into the zygote did not affect development to the blastocyst stage, but significantly decreased cell numbers (P < 0.01) in the blastocyst and increased caspase3 (Casp3, P < 0.05) gene expression and apoptosis (P < 0.005). Addition of recombinant HMGB1 (Sigma, H-4652) into the culture medium enhanced the development of zygote stage mouse embryos to blastocysts, in the absence of BSA supplementation. These findings suggest that endogenous and exogenous HMGB1 are implicated in preimplantation embryo development in the mouse.

Unidirectional crosstalk between Bcl-xL and Bcl-2 enhances the angiogenic phenotype of endothelial cells

Expression of Bcl-x(L) correlates with the clinical outcomes of patients with cancer. While the role of Bcl-2 in angiogenesis is becoming increasingly evident, the function of Bcl-x(L) in angiogenesis is unclear. Here, we showed that epidermal growth factor (EGF) induces in vitro capillary sprouting and Bcl-x(L) expression in primary endothelial cells. Bcl-x(L)-transduced human dermal microvascular endothelial cells (HDMEC-Bcl-x(L)), but not empty vector control cells, spontaneously organize into capillary-like sprouts. Searching for a mechanism to explain these responses, we observed that Bcl-x(L) induced expression of the pro-angiogenic chemokines CXC ligand-1 (CXCL1) and CXC ligand-8 (CXCL8), and that blockade of CXC receptor-2 (CXCR2) signaling inhibited spontaneous sprouting of HDMEC-Bcl-x(L). Bcl-x(L) led to Bcl-2 upregulation, but Bcl-2 did not upregulate Bcl-x(L), suggesting the existence of a unidirectional crosstalk from Bcl-x(L) to Bcl-2. EGF and Bcl-x(L) activate the mitogen-activated protein kinase/ERK pathway resulting in upregulation of vascular endothelial growth factor (VEGF), a known inducer of Bcl-2 in endothelial cells. Inhibition of VEGF receptor signaling in HDMEC-Bcl-x(L) prevented Bcl-2 upregulation and demonstrated the function of a VEGF-mediated autocrine loop. Bcl-2 downregulation by RNAi blocked CXCL1 and CXCL8 expression downstream of Bcl-x(L), and markedly decreased angiogenesis in vivo. We conclude that Bcl-x(L) functions as a pro-angiogenic signaling molecule controlling Bcl-2 and VEGF expression. These results emphasize a complex interplay between Bcl-2 family members beyond their classical roles in apoptosis.

High mobility group box 1 (HMGB1) enhances porcine parthenotes developing in vitro in the absence of BSA

High mobility group box 1 (HMGB1) is considered a component of chromatin and membranes with a role in a variety of biologically important processes. The aim of this study was to determine the effects of HMGB1 on the viability and development of porcine diploid parthenotes cultured in vitro. In vitro derived 4-cell parthenotes were cultured to blastocysts, with or without recombinant HMGB1, in the presence or absence of BSA. The addition of 1, 10, 100 or 1000ng/mL HMGB1 into NCSU 23 medium containing 0.4% BSA did not enhance the development of 4-cell parthenotes to the blastocyst stage and did not change the total number of nuclei in the blastocysts. However, addition of 10 or 100ng/mL HMGB1 into NCSU 23 medium in the absence of BSA increased (P<0.05) both the development rate of parthenotes to the blastocyst stage and total cell numbers. When cultured in NCSU23 medium supplemented with 10 or 100ng/mL HMGB1 and without BSA, apoptosis in parthenotes at the blastocyst stage was decreased (P<0.05). Based on real time RT-PCR, the addition of HMGB1 to the culture medium in the absence of BSA decreased mRNA expression of pro-apoptotic genes Bak (P<0.005) or Caspase3 (Casp3, P<0.01), but not Bcl-xL (Bcl2l2). In conclusion, we inferred that recombinant HMGB1 in the culture medium in the absence of BSA prevented apoptosis of porcine parthenotes and enhanced porcine embryo viability.

Anti-apoptotic effect of insulin-like growth factor (IGF)-I and its receptor in porcine preimplantation embryos derived from in vitro fertilization and somatic cell nuclear transfer

Insulin-like growth factor (IGF)-I is a receptor-mediated autocrine and/or paracrine growth and/or survival factor for mammalian embryo development. It is known to promote the growth and development of mouse preimplantation embryos. The present study was designed to investigate the effects of IGF-I (50 ng/ml), anti-IGF-I receptor antibody (50 ng/ml) and their combination on porcine preimplantation embryo development. Furthermore, the mechanism underlying the embryotropic effects of IGF-I was evaluated by monitoring the incidence of apoptosis and expression of apoptosis-related genes. In both in vitro fertilized (IVF) and somatic cell nuclear transfer (SCNT) embryos, culturing with IGF-I increased the rate of blastocyst formation and this embryotrophic effect was neutralized by culturing with IGF-I along with anti-IGF-I receptor (IGF-IR) antibody. Culturing IVF and SCNT embryos with IGF-I significantly increased the number of total cells in blastocysts and decreased the number of apoptotic nuclei. These effects of IGF-I were also neutralized by culturing with IGF-I along with anti-IGF-IR antibody. Expression of the anti-apoptotic Bcl-2 gene was increased, while expression of the pro-apoptotic Bax was decreased in both IVF and SCNT embryos cultured with IGF-I. In both IVF and SCNT embryos, anti-IGF-IR antibody along with IGF-I neutralized the effect of IGF-I on expression of Bcl-2 and Bax genes. In conclusion, the present study demonstrated that IGF-I through its specific receptors improved the developmental competence of IVF and SCNT embryos by decreasing the incidence of apoptosis and regulating apoptosis-related genes in porcine preimplantation embryos.

Epidermal growth factor enhances meiotic resumption of canine oocytes in the presence of BSA

Despite many attempts to improve the in vitro maturation (IVM) of canine oocytes using various culture conditions, the efficiency of canine IVM remains very low compared with that of other domestic animals. In the present study we examined the effect of ovarian estrus stage on oocyte quality, and the effect of epidermal growth factor (EGF) in the presence and absence of macromolecules on the IVM of canine oocytes. More oocytes >or=100 microm in diameter were obtained from follicular ovaries than from ovaries at other estrus stages. After 72 h of culture, significantly more oocytes recovered from follicular ovaries than from anestrous and luteal ovaries were in germinal vesicle break down (GVBD). Bovine serum albumin (BSA) or fetal bovine serum (FBS) supplementation improved meiotic resumption as compared to polyvinyl alcohol (PVA) supplementation; however, there was no difference between the BSA and FBS supplements. The oocytes matured in North Carolina State University (NCSU) 37 medium containing 0.4% BSA and 100 ng/ml EGF showed the highest rates of development to the metaphase II (MII) stage when compared with the control treatment (P < 0.05). These results suggest that the estrous cycle of bitches influences the meiotic resumption of oocytes cultured in vitro, and EGF increases the meiotic resumption of canine oocytes in the presence of BSA in vitro.

Insulin-like growth factor-I alters apoptosis related genes and reduces apoptosis in porcine parthenotes developing in vitro

The aim of this study was to determine the effects of IGF-I on the viability and development of porcine presumptive diploid parthenotes developing in vitro. In vitro derived 2-cell parthenotes were cultured to blastocysts with or without exogenous IGF-I in the presence or absence of BSA. The addition of 10 or 100 ng/ml IGF-I into NCSU 23 medium did not enhance the development of 2-cell parthenotes to the blastocyst stage. However, IGF-I increased cell numbers (P < 0.001) in the presence of BSA. Similarly, IGF-I alone did not affect apoptosis in the blastocysts but when combined with BSA, it reduced apoptosis (P < 0.05). Real time reverse-transcription polymerase chain reaction revealed that IGF-I significantly decreased the mRNA expression (pro-apoptotic gene Fas or Bak and anti-apoptotic gene Bcl-xL) ratios of both Fas/Bcl-xL (P < 0.01) and Bak/Bcl-xL (P < 0.01) in the presence of 0.4% BSA. These data suggest that IGF-I synergies with BSA to act as a mitogen and apoptotic survival factor in porcine preimplantation parthenotes.

Polyamines inhibit apoptosis in porcine parthenotes developing in vitro

Polyamines, namely putrescine, spermidine, and spermine, are biogenic low-molecular-weight aliphatic amines which play essential roles in cell growth and proliferation. The aim of this study was to determine the effects of polyamines on the viability and development of porcine diploid parthenotes developing in vitro. The addition of 0.1 or 1.0 microM of putrescine, spermidine, or spermine, individually, to the culture medium did not enhance the development of 2-cell parthenotes to the blastocyst stage and did not change the total number of nuclei in the blastocysts. However, combined addition of these three compounds increased developmental rate to blastocyst and total cell numbers. Apoptosis in blastocyst stage parthenotes was decreased in the presence of exogenous polyamines. Real time PCR revealed that addition of polyamines to the culture media decreased the ratio of mRNA expression of Bak/Bcl-xL, Fas/Bcl-xL, and caspase 3, and enhanced mRNA expression of ornithine decarboxylase (ODC) and spermidine synthase, enzymes of polyamine biosynthesis. In the presence of L-alpha-difluoromethyl ornithine (an inhibitor of ODC) or cyclohexylamine (an inhibitor of spermidine synthase) development of porcine parthenotes decreased, apoptosis increased, and mRNA expression of the ratio of Bak/Bcl-xL and Fas/Bcl-xL, and caspase 3 increased. These results suggest that exogenous polyamines in the culture medium prevent apoptosis of porcine parthenotes and results in the net enhancement of porcine embryo viability.