The Experts below are selected from a list of 1851 Experts worldwide ranked by ideXlab platform
Ann Van Soom - One of the best experts on this subject based on the ideXlab platform.
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why doesn t conventional ivf work in the horse the equine Oviduct as a microenvironment for capacitation fertilization
Reproduction, 2016Co-Authors: Bart Leemans, B M Gadella, T A E Stout, Hilde Nelis, Maarten Hoogewijs, Catharina De Schauwer, Ann Van SoomAbstract:In contrast to man and many other mammalian species, conventional in vitro fertilization (IVF) with horse gametes is not reliably successful. The apparent inability of stallion spermatozoa to penetrate the zona pellucida in vitro is most likely due to incomplete activation of spermatozoa (capacitation) because of inadequate capacitating or fertilizing media. In vivo, the Oviduct and its secretions provide a microenvironment that does reliably support and regulate interaction between the gametes. This review focuses on equine sperm-Oviduct interaction. Equine sperm-Oviduct binding appears to be more complex than the presumed species-specific calcium-dependent lectin binding phenomenon; unfortunately, the nature of the interaction is not understood. Various capacitation-related events are induced to regulate sperm release from the Oviduct Epithelium and most data suggest that exposure to Oviduct secretions triggers sperm capacitation in vivo However, only limited information is available about equine Oviduct secreted factors, and few have been identified. Another aspect of equine Oviduct physiology relevant to capacitation is acid-base balance. In vitro, it has been demonstrated that stallion spermatozoa show tail-associated protein tyrosine phosphorylation after binding to Oviduct epithelial cells containing alkaline secretory granules. In response to alkaline follicular fluid preparations (pH 7.9), stallion spermatozoa also show tail-associated protein tyrosine phosphorylation, hyperactivated motility and (limited) release from Oviduct epithelial binding. However, these 'capacitating conditions' are not able to induce the acrosome reaction and fertilization. In conclusion, developing a defined capacitating medium to support successful equine IVF will depend on identifying as yet uncharacterized capacitation triggers present in the Oviduct.
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Oviduct Binding and Elevated Environmental pH Induce Protein Tyrosine Phosphorylation in Stallion Spermatozoa1
2016Co-Authors: Ann Van SoomAbstract:Sperm-Oviduct binding is an essential step in the capacitation process preparing the sperm for fertilization in several mamma-lian species. In many species, capacitation can be induced in vitro by exposing spermatozoa to bicarbonate, Ca2+, and albumin; however, these conditions are insufficient in the horse. We hypothesized that binding to the Oviduct Epithelium is an essential requirement for the induction of capacitation in stallion spermatozoa. Sperm-Oviduct binding was established by co-incubating equine Oviduct explants for 2 h with stallion spermatozoa (2 3 106 spermatozoa/ml), during which it transpired that the highest density (per mm2) of Oviduct-bound spermatozoa was achieved under noncapacitating conditions. In subsequent experiments, sperm-Oviduct incubations were per-formed for 6 h under noncapacitating versus capacitatin
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an alkaline follicular fluid fraction induces capacitation and limited release of Oviduct Epithelium bound stallion sperm
Reproduction, 2015Co-Authors: Bart Leemans, B M Gadella, T A E Stout, Hilde Nelis, Maarten Hoogewijs, Ann Van SoomAbstract:Induction of hyperactivated motility is considered essential for triggering the release of Oviduct-bound mammalian spermatozoa in preparation for fertilization. In this study, Oviduct-bound stallion spermatozoa were exposed for 2 h to: i) pre-ovulatory and ii) post-ovulatory Oviductal fluid; iii) 100% and iv) 10% follicular fluid (FF); v) cumulus cells, vi) mature equine oocytes, vii) capacitating and viii) non-capacitating medium. None of these triggered sperm release or hyperactivated motility. Interestingly, native FF was detrimental to sperm viability, an effect that was negated by heat inactivation, charcoal treatment and 30 kDa filtration alone or in combination. Moreover, sperm suspensions exposed to treated FF at pH 7.9 but not pH 7.4 showed Ca(2+)-dependent hypermotility. Fluo-4 AM staining of sperm showed elevated cytoplasmic Ca(2+) in hyperactivated stallion spermatozoa exposed to treated FF at pH 7.9 compared to a modest response in defined capacitating conditions at pH 7.9 and no response in treated FF at pH 7.4. Moreover, 1 h incubation in alkaline, treated FF induced protein tyrosine phosphorylation in 20% of spermatozoa. None of the conditions tested induced widespread release of sperm pre-bound to Oviduct Epithelium. However, the hyperactivating conditions did induce release of 70-120 spermatozoa per Oviduct explant, of which 48% showed protein tyrosine phosphorylation and all were acrosome-intact, but capable of acrosomal exocytosis in response to calcium ionophore. We conclude that, in the presence of elevated pH and extracellular Ca(2+), a heat-resistant, hydrophilic, <30 kDa component of FF can trigger protein tyrosine phosphorylation, elevated cytoplasmic Ca(2+) and hyperactivated motility in stallion sperm, but infrequent release of sperm pre-bound to Oviduct Epithelium.
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Oviduct binding and elevated environmental ph induce protein tyrosine phosphorylation in stallion spermatozoa
Biology of Reproduction, 2014Co-Authors: Bart Leemans, B M Gadella, T A E Stout, Hilde Nelis, Maarten Hoogewijs, Edita Sostaric, Ann Van SoomAbstract:Sperm-Oviduct binding is an essential step in the capacitation process preparing the sperm for fertilization in several mammalian species. In many species, capacitation can be induced in vitro by exposing spermatozoa to bicarbonate, Ca 2+ ,a nd albumin; however, these conditions are insufficient in the horse. We hypothesized that binding to the Oviduct Epithelium is an essential requirement for the induction of capacitation in stallion spermatozoa. Sperm-Oviduct binding was established by coincubating equine Oviduct explants for 2 h with stallion spermatozoa (2 3 10 6 spermatozoa/ml), during which it transpired that the highest density (per mm 2 ) of Oviduct-bound spermatozoa was achieved under noncapacitating conditions. In subsequent experiments, sperm-Oviduct incubations were performed for 6 h under noncapacitating versus capacitating conditions. The Oviduct-bound spermatozoa showed a timedependent protein tyrosine phosphorylation response, which was not observed in unbound spermatozoa or spermatozoa incubated in Oviduct explant conditioned medium. Both Oviductbound and unbound sperm remained motile with intact plasma membrane and acrosome. Since protein tyrosine phosphorylation can be induced in equine spermatozoa by media with high pH, the intracellular pH (pH i ) of Oviduct explant cells and bound spermatozoa was monitored fluorometrically after staining with BCECF-AM dye. The epithelial secretory cells contained large, alkaline vesicles. Moreover, Oviduct-bound spermatozoa showed a gradual increase in pH i , presumably due to an alkaline local microenvironment created by the secretory epithelial cells, given that unbound spermatozoa did not show pH i changes. Thus, sperm-Oviduct interaction appears to facilitate equine sperm capacitation by creating an alkaline local environment that triggers intracellular protein tyrosine phosphorylation in bound sperm.
Bart Leemans - One of the best experts on this subject based on the ideXlab platform.
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why doesn t conventional ivf work in the horse the equine Oviduct as a microenvironment for capacitation fertilization
Reproduction, 2016Co-Authors: Bart Leemans, B M Gadella, T A E Stout, Hilde Nelis, Maarten Hoogewijs, Catharina De Schauwer, Ann Van SoomAbstract:In contrast to man and many other mammalian species, conventional in vitro fertilization (IVF) with horse gametes is not reliably successful. The apparent inability of stallion spermatozoa to penetrate the zona pellucida in vitro is most likely due to incomplete activation of spermatozoa (capacitation) because of inadequate capacitating or fertilizing media. In vivo, the Oviduct and its secretions provide a microenvironment that does reliably support and regulate interaction between the gametes. This review focuses on equine sperm-Oviduct interaction. Equine sperm-Oviduct binding appears to be more complex than the presumed species-specific calcium-dependent lectin binding phenomenon; unfortunately, the nature of the interaction is not understood. Various capacitation-related events are induced to regulate sperm release from the Oviduct Epithelium and most data suggest that exposure to Oviduct secretions triggers sperm capacitation in vivo However, only limited information is available about equine Oviduct secreted factors, and few have been identified. Another aspect of equine Oviduct physiology relevant to capacitation is acid-base balance. In vitro, it has been demonstrated that stallion spermatozoa show tail-associated protein tyrosine phosphorylation after binding to Oviduct epithelial cells containing alkaline secretory granules. In response to alkaline follicular fluid preparations (pH 7.9), stallion spermatozoa also show tail-associated protein tyrosine phosphorylation, hyperactivated motility and (limited) release from Oviduct epithelial binding. However, these 'capacitating conditions' are not able to induce the acrosome reaction and fertilization. In conclusion, developing a defined capacitating medium to support successful equine IVF will depend on identifying as yet uncharacterized capacitation triggers present in the Oviduct.
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an alkaline follicular fluid fraction induces capacitation and limited release of Oviduct Epithelium bound stallion sperm
Reproduction, 2015Co-Authors: Bart Leemans, B M Gadella, T A E Stout, Hilde Nelis, Maarten Hoogewijs, Ann Van SoomAbstract:Induction of hyperactivated motility is considered essential for triggering the release of Oviduct-bound mammalian spermatozoa in preparation for fertilization. In this study, Oviduct-bound stallion spermatozoa were exposed for 2 h to: i) pre-ovulatory and ii) post-ovulatory Oviductal fluid; iii) 100% and iv) 10% follicular fluid (FF); v) cumulus cells, vi) mature equine oocytes, vii) capacitating and viii) non-capacitating medium. None of these triggered sperm release or hyperactivated motility. Interestingly, native FF was detrimental to sperm viability, an effect that was negated by heat inactivation, charcoal treatment and 30 kDa filtration alone or in combination. Moreover, sperm suspensions exposed to treated FF at pH 7.9 but not pH 7.4 showed Ca(2+)-dependent hypermotility. Fluo-4 AM staining of sperm showed elevated cytoplasmic Ca(2+) in hyperactivated stallion spermatozoa exposed to treated FF at pH 7.9 compared to a modest response in defined capacitating conditions at pH 7.9 and no response in treated FF at pH 7.4. Moreover, 1 h incubation in alkaline, treated FF induced protein tyrosine phosphorylation in 20% of spermatozoa. None of the conditions tested induced widespread release of sperm pre-bound to Oviduct Epithelium. However, the hyperactivating conditions did induce release of 70-120 spermatozoa per Oviduct explant, of which 48% showed protein tyrosine phosphorylation and all were acrosome-intact, but capable of acrosomal exocytosis in response to calcium ionophore. We conclude that, in the presence of elevated pH and extracellular Ca(2+), a heat-resistant, hydrophilic, <30 kDa component of FF can trigger protein tyrosine phosphorylation, elevated cytoplasmic Ca(2+) and hyperactivated motility in stallion sperm, but infrequent release of sperm pre-bound to Oviduct Epithelium.
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Oviduct binding and elevated environmental ph induce protein tyrosine phosphorylation in stallion spermatozoa
Biology of Reproduction, 2014Co-Authors: Bart Leemans, B M Gadella, T A E Stout, Hilde Nelis, Maarten Hoogewijs, Edita Sostaric, Ann Van SoomAbstract:Sperm-Oviduct binding is an essential step in the capacitation process preparing the sperm for fertilization in several mammalian species. In many species, capacitation can be induced in vitro by exposing spermatozoa to bicarbonate, Ca 2+ ,a nd albumin; however, these conditions are insufficient in the horse. We hypothesized that binding to the Oviduct Epithelium is an essential requirement for the induction of capacitation in stallion spermatozoa. Sperm-Oviduct binding was established by coincubating equine Oviduct explants for 2 h with stallion spermatozoa (2 3 10 6 spermatozoa/ml), during which it transpired that the highest density (per mm 2 ) of Oviduct-bound spermatozoa was achieved under noncapacitating conditions. In subsequent experiments, sperm-Oviduct incubations were performed for 6 h under noncapacitating versus capacitating conditions. The Oviduct-bound spermatozoa showed a timedependent protein tyrosine phosphorylation response, which was not observed in unbound spermatozoa or spermatozoa incubated in Oviduct explant conditioned medium. Both Oviductbound and unbound sperm remained motile with intact plasma membrane and acrosome. Since protein tyrosine phosphorylation can be induced in equine spermatozoa by media with high pH, the intracellular pH (pH i ) of Oviduct explant cells and bound spermatozoa was monitored fluorometrically after staining with BCECF-AM dye. The epithelial secretory cells contained large, alkaline vesicles. Moreover, Oviduct-bound spermatozoa showed a gradual increase in pH i , presumably due to an alkaline local microenvironment created by the secretory epithelial cells, given that unbound spermatozoa did not show pH i changes. Thus, sperm-Oviduct interaction appears to facilitate equine sperm capacitation by creating an alkaline local environment that triggers intracellular protein tyrosine phosphorylation in bound sperm.
Hilde Nelis - One of the best experts on this subject based on the ideXlab platform.
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why doesn t conventional ivf work in the horse the equine Oviduct as a microenvironment for capacitation fertilization
Reproduction, 2016Co-Authors: Bart Leemans, B M Gadella, T A E Stout, Hilde Nelis, Maarten Hoogewijs, Catharina De Schauwer, Ann Van SoomAbstract:In contrast to man and many other mammalian species, conventional in vitro fertilization (IVF) with horse gametes is not reliably successful. The apparent inability of stallion spermatozoa to penetrate the zona pellucida in vitro is most likely due to incomplete activation of spermatozoa (capacitation) because of inadequate capacitating or fertilizing media. In vivo, the Oviduct and its secretions provide a microenvironment that does reliably support and regulate interaction between the gametes. This review focuses on equine sperm-Oviduct interaction. Equine sperm-Oviduct binding appears to be more complex than the presumed species-specific calcium-dependent lectin binding phenomenon; unfortunately, the nature of the interaction is not understood. Various capacitation-related events are induced to regulate sperm release from the Oviduct Epithelium and most data suggest that exposure to Oviduct secretions triggers sperm capacitation in vivo However, only limited information is available about equine Oviduct secreted factors, and few have been identified. Another aspect of equine Oviduct physiology relevant to capacitation is acid-base balance. In vitro, it has been demonstrated that stallion spermatozoa show tail-associated protein tyrosine phosphorylation after binding to Oviduct epithelial cells containing alkaline secretory granules. In response to alkaline follicular fluid preparations (pH 7.9), stallion spermatozoa also show tail-associated protein tyrosine phosphorylation, hyperactivated motility and (limited) release from Oviduct epithelial binding. However, these 'capacitating conditions' are not able to induce the acrosome reaction and fertilization. In conclusion, developing a defined capacitating medium to support successful equine IVF will depend on identifying as yet uncharacterized capacitation triggers present in the Oviduct.
-
an alkaline follicular fluid fraction induces capacitation and limited release of Oviduct Epithelium bound stallion sperm
Reproduction, 2015Co-Authors: Bart Leemans, B M Gadella, T A E Stout, Hilde Nelis, Maarten Hoogewijs, Ann Van SoomAbstract:Induction of hyperactivated motility is considered essential for triggering the release of Oviduct-bound mammalian spermatozoa in preparation for fertilization. In this study, Oviduct-bound stallion spermatozoa were exposed for 2 h to: i) pre-ovulatory and ii) post-ovulatory Oviductal fluid; iii) 100% and iv) 10% follicular fluid (FF); v) cumulus cells, vi) mature equine oocytes, vii) capacitating and viii) non-capacitating medium. None of these triggered sperm release or hyperactivated motility. Interestingly, native FF was detrimental to sperm viability, an effect that was negated by heat inactivation, charcoal treatment and 30 kDa filtration alone or in combination. Moreover, sperm suspensions exposed to treated FF at pH 7.9 but not pH 7.4 showed Ca(2+)-dependent hypermotility. Fluo-4 AM staining of sperm showed elevated cytoplasmic Ca(2+) in hyperactivated stallion spermatozoa exposed to treated FF at pH 7.9 compared to a modest response in defined capacitating conditions at pH 7.9 and no response in treated FF at pH 7.4. Moreover, 1 h incubation in alkaline, treated FF induced protein tyrosine phosphorylation in 20% of spermatozoa. None of the conditions tested induced widespread release of sperm pre-bound to Oviduct Epithelium. However, the hyperactivating conditions did induce release of 70-120 spermatozoa per Oviduct explant, of which 48% showed protein tyrosine phosphorylation and all were acrosome-intact, but capable of acrosomal exocytosis in response to calcium ionophore. We conclude that, in the presence of elevated pH and extracellular Ca(2+), a heat-resistant, hydrophilic, <30 kDa component of FF can trigger protein tyrosine phosphorylation, elevated cytoplasmic Ca(2+) and hyperactivated motility in stallion sperm, but infrequent release of sperm pre-bound to Oviduct Epithelium.
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Oviduct binding and elevated environmental ph induce protein tyrosine phosphorylation in stallion spermatozoa
Biology of Reproduction, 2014Co-Authors: Bart Leemans, B M Gadella, T A E Stout, Hilde Nelis, Maarten Hoogewijs, Edita Sostaric, Ann Van SoomAbstract:Sperm-Oviduct binding is an essential step in the capacitation process preparing the sperm for fertilization in several mammalian species. In many species, capacitation can be induced in vitro by exposing spermatozoa to bicarbonate, Ca 2+ ,a nd albumin; however, these conditions are insufficient in the horse. We hypothesized that binding to the Oviduct Epithelium is an essential requirement for the induction of capacitation in stallion spermatozoa. Sperm-Oviduct binding was established by coincubating equine Oviduct explants for 2 h with stallion spermatozoa (2 3 10 6 spermatozoa/ml), during which it transpired that the highest density (per mm 2 ) of Oviduct-bound spermatozoa was achieved under noncapacitating conditions. In subsequent experiments, sperm-Oviduct incubations were performed for 6 h under noncapacitating versus capacitating conditions. The Oviduct-bound spermatozoa showed a timedependent protein tyrosine phosphorylation response, which was not observed in unbound spermatozoa or spermatozoa incubated in Oviduct explant conditioned medium. Both Oviductbound and unbound sperm remained motile with intact plasma membrane and acrosome. Since protein tyrosine phosphorylation can be induced in equine spermatozoa by media with high pH, the intracellular pH (pH i ) of Oviduct explant cells and bound spermatozoa was monitored fluorometrically after staining with BCECF-AM dye. The epithelial secretory cells contained large, alkaline vesicles. Moreover, Oviduct-bound spermatozoa showed a gradual increase in pH i , presumably due to an alkaline local microenvironment created by the secretory epithelial cells, given that unbound spermatozoa did not show pH i changes. Thus, sperm-Oviduct interaction appears to facilitate equine sperm capacitation by creating an alkaline local environment that triggers intracellular protein tyrosine phosphorylation in bound sperm.
T A E Stout - One of the best experts on this subject based on the ideXlab platform.
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why doesn t conventional ivf work in the horse the equine Oviduct as a microenvironment for capacitation fertilization
Reproduction, 2016Co-Authors: Bart Leemans, B M Gadella, T A E Stout, Hilde Nelis, Maarten Hoogewijs, Catharina De Schauwer, Ann Van SoomAbstract:In contrast to man and many other mammalian species, conventional in vitro fertilization (IVF) with horse gametes is not reliably successful. The apparent inability of stallion spermatozoa to penetrate the zona pellucida in vitro is most likely due to incomplete activation of spermatozoa (capacitation) because of inadequate capacitating or fertilizing media. In vivo, the Oviduct and its secretions provide a microenvironment that does reliably support and regulate interaction between the gametes. This review focuses on equine sperm-Oviduct interaction. Equine sperm-Oviduct binding appears to be more complex than the presumed species-specific calcium-dependent lectin binding phenomenon; unfortunately, the nature of the interaction is not understood. Various capacitation-related events are induced to regulate sperm release from the Oviduct Epithelium and most data suggest that exposure to Oviduct secretions triggers sperm capacitation in vivo However, only limited information is available about equine Oviduct secreted factors, and few have been identified. Another aspect of equine Oviduct physiology relevant to capacitation is acid-base balance. In vitro, it has been demonstrated that stallion spermatozoa show tail-associated protein tyrosine phosphorylation after binding to Oviduct epithelial cells containing alkaline secretory granules. In response to alkaline follicular fluid preparations (pH 7.9), stallion spermatozoa also show tail-associated protein tyrosine phosphorylation, hyperactivated motility and (limited) release from Oviduct epithelial binding. However, these 'capacitating conditions' are not able to induce the acrosome reaction and fertilization. In conclusion, developing a defined capacitating medium to support successful equine IVF will depend on identifying as yet uncharacterized capacitation triggers present in the Oviduct.
-
an alkaline follicular fluid fraction induces capacitation and limited release of Oviduct Epithelium bound stallion sperm
Reproduction, 2015Co-Authors: Bart Leemans, B M Gadella, T A E Stout, Hilde Nelis, Maarten Hoogewijs, Ann Van SoomAbstract:Induction of hyperactivated motility is considered essential for triggering the release of Oviduct-bound mammalian spermatozoa in preparation for fertilization. In this study, Oviduct-bound stallion spermatozoa were exposed for 2 h to: i) pre-ovulatory and ii) post-ovulatory Oviductal fluid; iii) 100% and iv) 10% follicular fluid (FF); v) cumulus cells, vi) mature equine oocytes, vii) capacitating and viii) non-capacitating medium. None of these triggered sperm release or hyperactivated motility. Interestingly, native FF was detrimental to sperm viability, an effect that was negated by heat inactivation, charcoal treatment and 30 kDa filtration alone or in combination. Moreover, sperm suspensions exposed to treated FF at pH 7.9 but not pH 7.4 showed Ca(2+)-dependent hypermotility. Fluo-4 AM staining of sperm showed elevated cytoplasmic Ca(2+) in hyperactivated stallion spermatozoa exposed to treated FF at pH 7.9 compared to a modest response in defined capacitating conditions at pH 7.9 and no response in treated FF at pH 7.4. Moreover, 1 h incubation in alkaline, treated FF induced protein tyrosine phosphorylation in 20% of spermatozoa. None of the conditions tested induced widespread release of sperm pre-bound to Oviduct Epithelium. However, the hyperactivating conditions did induce release of 70-120 spermatozoa per Oviduct explant, of which 48% showed protein tyrosine phosphorylation and all were acrosome-intact, but capable of acrosomal exocytosis in response to calcium ionophore. We conclude that, in the presence of elevated pH and extracellular Ca(2+), a heat-resistant, hydrophilic, <30 kDa component of FF can trigger protein tyrosine phosphorylation, elevated cytoplasmic Ca(2+) and hyperactivated motility in stallion sperm, but infrequent release of sperm pre-bound to Oviduct Epithelium.
-
Oviduct binding and elevated environmental ph induce protein tyrosine phosphorylation in stallion spermatozoa
Biology of Reproduction, 2014Co-Authors: Bart Leemans, B M Gadella, T A E Stout, Hilde Nelis, Maarten Hoogewijs, Edita Sostaric, Ann Van SoomAbstract:Sperm-Oviduct binding is an essential step in the capacitation process preparing the sperm for fertilization in several mammalian species. In many species, capacitation can be induced in vitro by exposing spermatozoa to bicarbonate, Ca 2+ ,a nd albumin; however, these conditions are insufficient in the horse. We hypothesized that binding to the Oviduct Epithelium is an essential requirement for the induction of capacitation in stallion spermatozoa. Sperm-Oviduct binding was established by coincubating equine Oviduct explants for 2 h with stallion spermatozoa (2 3 10 6 spermatozoa/ml), during which it transpired that the highest density (per mm 2 ) of Oviduct-bound spermatozoa was achieved under noncapacitating conditions. In subsequent experiments, sperm-Oviduct incubations were performed for 6 h under noncapacitating versus capacitating conditions. The Oviduct-bound spermatozoa showed a timedependent protein tyrosine phosphorylation response, which was not observed in unbound spermatozoa or spermatozoa incubated in Oviduct explant conditioned medium. Both Oviductbound and unbound sperm remained motile with intact plasma membrane and acrosome. Since protein tyrosine phosphorylation can be induced in equine spermatozoa by media with high pH, the intracellular pH (pH i ) of Oviduct explant cells and bound spermatozoa was monitored fluorometrically after staining with BCECF-AM dye. The epithelial secretory cells contained large, alkaline vesicles. Moreover, Oviduct-bound spermatozoa showed a gradual increase in pH i , presumably due to an alkaline local microenvironment created by the secretory epithelial cells, given that unbound spermatozoa did not show pH i changes. Thus, sperm-Oviduct interaction appears to facilitate equine sperm capacitation by creating an alkaline local environment that triggers intracellular protein tyrosine phosphorylation in bound sperm.
B M Gadella - One of the best experts on this subject based on the ideXlab platform.
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why doesn t conventional ivf work in the horse the equine Oviduct as a microenvironment for capacitation fertilization
Reproduction, 2016Co-Authors: Bart Leemans, B M Gadella, T A E Stout, Hilde Nelis, Maarten Hoogewijs, Catharina De Schauwer, Ann Van SoomAbstract:In contrast to man and many other mammalian species, conventional in vitro fertilization (IVF) with horse gametes is not reliably successful. The apparent inability of stallion spermatozoa to penetrate the zona pellucida in vitro is most likely due to incomplete activation of spermatozoa (capacitation) because of inadequate capacitating or fertilizing media. In vivo, the Oviduct and its secretions provide a microenvironment that does reliably support and regulate interaction between the gametes. This review focuses on equine sperm-Oviduct interaction. Equine sperm-Oviduct binding appears to be more complex than the presumed species-specific calcium-dependent lectin binding phenomenon; unfortunately, the nature of the interaction is not understood. Various capacitation-related events are induced to regulate sperm release from the Oviduct Epithelium and most data suggest that exposure to Oviduct secretions triggers sperm capacitation in vivo However, only limited information is available about equine Oviduct secreted factors, and few have been identified. Another aspect of equine Oviduct physiology relevant to capacitation is acid-base balance. In vitro, it has been demonstrated that stallion spermatozoa show tail-associated protein tyrosine phosphorylation after binding to Oviduct epithelial cells containing alkaline secretory granules. In response to alkaline follicular fluid preparations (pH 7.9), stallion spermatozoa also show tail-associated protein tyrosine phosphorylation, hyperactivated motility and (limited) release from Oviduct epithelial binding. However, these 'capacitating conditions' are not able to induce the acrosome reaction and fertilization. In conclusion, developing a defined capacitating medium to support successful equine IVF will depend on identifying as yet uncharacterized capacitation triggers present in the Oviduct.
-
an alkaline follicular fluid fraction induces capacitation and limited release of Oviduct Epithelium bound stallion sperm
Reproduction, 2015Co-Authors: Bart Leemans, B M Gadella, T A E Stout, Hilde Nelis, Maarten Hoogewijs, Ann Van SoomAbstract:Induction of hyperactivated motility is considered essential for triggering the release of Oviduct-bound mammalian spermatozoa in preparation for fertilization. In this study, Oviduct-bound stallion spermatozoa were exposed for 2 h to: i) pre-ovulatory and ii) post-ovulatory Oviductal fluid; iii) 100% and iv) 10% follicular fluid (FF); v) cumulus cells, vi) mature equine oocytes, vii) capacitating and viii) non-capacitating medium. None of these triggered sperm release or hyperactivated motility. Interestingly, native FF was detrimental to sperm viability, an effect that was negated by heat inactivation, charcoal treatment and 30 kDa filtration alone or in combination. Moreover, sperm suspensions exposed to treated FF at pH 7.9 but not pH 7.4 showed Ca(2+)-dependent hypermotility. Fluo-4 AM staining of sperm showed elevated cytoplasmic Ca(2+) in hyperactivated stallion spermatozoa exposed to treated FF at pH 7.9 compared to a modest response in defined capacitating conditions at pH 7.9 and no response in treated FF at pH 7.4. Moreover, 1 h incubation in alkaline, treated FF induced protein tyrosine phosphorylation in 20% of spermatozoa. None of the conditions tested induced widespread release of sperm pre-bound to Oviduct Epithelium. However, the hyperactivating conditions did induce release of 70-120 spermatozoa per Oviduct explant, of which 48% showed protein tyrosine phosphorylation and all were acrosome-intact, but capable of acrosomal exocytosis in response to calcium ionophore. We conclude that, in the presence of elevated pH and extracellular Ca(2+), a heat-resistant, hydrophilic, <30 kDa component of FF can trigger protein tyrosine phosphorylation, elevated cytoplasmic Ca(2+) and hyperactivated motility in stallion sperm, but infrequent release of sperm pre-bound to Oviduct Epithelium.
-
Oviduct binding and elevated environmental ph induce protein tyrosine phosphorylation in stallion spermatozoa
Biology of Reproduction, 2014Co-Authors: Bart Leemans, B M Gadella, T A E Stout, Hilde Nelis, Maarten Hoogewijs, Edita Sostaric, Ann Van SoomAbstract:Sperm-Oviduct binding is an essential step in the capacitation process preparing the sperm for fertilization in several mammalian species. In many species, capacitation can be induced in vitro by exposing spermatozoa to bicarbonate, Ca 2+ ,a nd albumin; however, these conditions are insufficient in the horse. We hypothesized that binding to the Oviduct Epithelium is an essential requirement for the induction of capacitation in stallion spermatozoa. Sperm-Oviduct binding was established by coincubating equine Oviduct explants for 2 h with stallion spermatozoa (2 3 10 6 spermatozoa/ml), during which it transpired that the highest density (per mm 2 ) of Oviduct-bound spermatozoa was achieved under noncapacitating conditions. In subsequent experiments, sperm-Oviduct incubations were performed for 6 h under noncapacitating versus capacitating conditions. The Oviduct-bound spermatozoa showed a timedependent protein tyrosine phosphorylation response, which was not observed in unbound spermatozoa or spermatozoa incubated in Oviduct explant conditioned medium. Both Oviductbound and unbound sperm remained motile with intact plasma membrane and acrosome. Since protein tyrosine phosphorylation can be induced in equine spermatozoa by media with high pH, the intracellular pH (pH i ) of Oviduct explant cells and bound spermatozoa was monitored fluorometrically after staining with BCECF-AM dye. The epithelial secretory cells contained large, alkaline vesicles. Moreover, Oviduct-bound spermatozoa showed a gradual increase in pH i , presumably due to an alkaline local microenvironment created by the secretory epithelial cells, given that unbound spermatozoa did not show pH i changes. Thus, sperm-Oviduct interaction appears to facilitate equine sperm capacitation by creating an alkaline local environment that triggers intracellular protein tyrosine phosphorylation in bound sperm.
