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Ejaculated mouse sperm enter cumulus-oocyte complexes more efficiently in vitro than epididymal sperm.

Li H, Hung PH, Suarez SS - PLoS ONE (2015)

Bottom Line: We compared ejaculated and epididymal sperm in an in vitro fertilization setting to examine whether ejaculated sperm enter cumulus-oocyte complexes more efficiently.At the outset of incubation, ejaculated sperm stuck to the glass surfaces of slides and the incidences of sticking decreased with time; whereas, very few epididymal sperm stuck to glass at any time point, indicating differences in surface charge.We concluded that modification of sperm by male accessory gland secretions affects the behavior of ejaculated sperm, possibly providing them with an advantage over epididymal sperm for reaching the eggs in vivo.

View Article: PubMed Central - PubMed

Affiliation: Family Planning Research Institute, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; Wuhan Tongji Reproductive Medicine Hospital, Wuhan, China.

ABSTRACT
The mouse is an established and popular animal model for studying reproductive biology. Epididymal mouse sperm, which lack exposure to secretions of male accessory glands and do not precisely represent ejaculated sperm for the study of sperm functions, have been almost exclusively used in studies. We compared ejaculated and epididymal sperm in an in vitro fertilization setting to examine whether ejaculated sperm enter cumulus-oocyte complexes more efficiently. In order to prepare sperm for fertilization, they were incubated under capacitating conditions. At the outset of incubation, ejaculated sperm stuck to the glass surfaces of slides and the incidences of sticking decreased with time; whereas, very few epididymal sperm stuck to glass at any time point, indicating differences in surface charge. At the end of the capacitating incubation, when sperm were added to cumulus-oocyte complexes, the form of flagellar movement differed dramatically; specifically, ejaculated sperm predominantly exhibited increased bending on one side of the flagellum (a process termed pro-hook hyperactivation), while epididymal sperm equally exhibited increased bending on one or the other side of the flagellum (pro-hook or anti-hook hyperactivation). This indicates that accessory sex gland secretions might have modified Ca2+ signaling activities in sperm, because the two forms of hyperactivation are reported to be triggered by different Ca2+ signaling patterns. Lastly, over time, more ejaculated than epididymal sperm entered the cumulus oocyte complexes. We concluded that modification of sperm by male accessory gland secretions affects the behavior of ejaculated sperm, possibly providing them with an advantage over epididymal sperm for reaching the eggs in vivo.

No MeSH data available.


Related in: MedlinePlus

Setup for analysis of sperm penetration of COCs.A. A COC (arrow) was placed on the 14 mm diameter recessed glass insert of a glass-bottomed 35-mm petri dish and covered with a 3 mm x 3 mm coverslip supported by four dabs of silicon grease. As a negative control, four dabs of silicon grease supporting a coverslip were placed in the same recessed insert (arrowhead). A total of 50 μl mouse medium was added into the insert and then covered with mineral oil. Sperm were added at the red dot. B. Examples of MitoTracker labeled ejaculated and epididymal sperm in the negative control coverslip (left) and in the COCs (right). Fluorescence is difficult to detect in some sperm in Fig 2B, because they were located above or below the focal plane; however, the focal plane was moved up and down during video imaging in order to clearly detect all sperm.
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pone.0127753.g002: Setup for analysis of sperm penetration of COCs.A. A COC (arrow) was placed on the 14 mm diameter recessed glass insert of a glass-bottomed 35-mm petri dish and covered with a 3 mm x 3 mm coverslip supported by four dabs of silicon grease. As a negative control, four dabs of silicon grease supporting a coverslip were placed in the same recessed insert (arrowhead). A total of 50 μl mouse medium was added into the insert and then covered with mineral oil. Sperm were added at the red dot. B. Examples of MitoTracker labeled ejaculated and epididymal sperm in the negative control coverslip (left) and in the COCs (right). Fluorescence is difficult to detect in some sperm in Fig 2B, because they were located above or below the focal plane; however, the focal plane was moved up and down during video imaging in order to clearly detect all sperm.

Mentions: COCs were obtained from the mated females used for ejaculated sperm collection. Both oviducts were removed and placed in 500 μl medium in a petri dish right before dissecting the uterus of the mated female for sperm recovery. The large cumulus mass was recovered from each oviduct by tearing open the wall of oviduct with a 27g needle. The cumulus mass was gently separated into COCs containing 2–4 oocytes each. A COC was placed on the 14 mm diameter recessed glass insert of a 35 mm petri dish (MatTek Corporation, Ashland, MA; Part Number: P35G-0-14-C) and covered with a 3 mm x 3 mm coverslip supported by four dabs of silicon grease (Corning Inc., Corning, NY) (Fig 2A, arrow). As a negative control, four dabs of silicon grease supporting a coverslip were placed in the same recessed insert (Fig 2A, arrowhead). A total of 50 μl medium was added into the insert and then covered with mineral oil. The observation dish was incubated at 37°C under 5% CO2 in humidified air for at least 1.5 h before addition of sperm.


Ejaculated mouse sperm enter cumulus-oocyte complexes more efficiently in vitro than epididymal sperm.

Li H, Hung PH, Suarez SS - PLoS ONE (2015)

Setup for analysis of sperm penetration of COCs.A. A COC (arrow) was placed on the 14 mm diameter recessed glass insert of a glass-bottomed 35-mm petri dish and covered with a 3 mm x 3 mm coverslip supported by four dabs of silicon grease. As a negative control, four dabs of silicon grease supporting a coverslip were placed in the same recessed insert (arrowhead). A total of 50 μl mouse medium was added into the insert and then covered with mineral oil. Sperm were added at the red dot. B. Examples of MitoTracker labeled ejaculated and epididymal sperm in the negative control coverslip (left) and in the COCs (right). Fluorescence is difficult to detect in some sperm in Fig 2B, because they were located above or below the focal plane; however, the focal plane was moved up and down during video imaging in order to clearly detect all sperm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4440731&req=5

pone.0127753.g002: Setup for analysis of sperm penetration of COCs.A. A COC (arrow) was placed on the 14 mm diameter recessed glass insert of a glass-bottomed 35-mm petri dish and covered with a 3 mm x 3 mm coverslip supported by four dabs of silicon grease. As a negative control, four dabs of silicon grease supporting a coverslip were placed in the same recessed insert (arrowhead). A total of 50 μl mouse medium was added into the insert and then covered with mineral oil. Sperm were added at the red dot. B. Examples of MitoTracker labeled ejaculated and epididymal sperm in the negative control coverslip (left) and in the COCs (right). Fluorescence is difficult to detect in some sperm in Fig 2B, because they were located above or below the focal plane; however, the focal plane was moved up and down during video imaging in order to clearly detect all sperm.
Mentions: COCs were obtained from the mated females used for ejaculated sperm collection. Both oviducts were removed and placed in 500 μl medium in a petri dish right before dissecting the uterus of the mated female for sperm recovery. The large cumulus mass was recovered from each oviduct by tearing open the wall of oviduct with a 27g needle. The cumulus mass was gently separated into COCs containing 2–4 oocytes each. A COC was placed on the 14 mm diameter recessed glass insert of a 35 mm petri dish (MatTek Corporation, Ashland, MA; Part Number: P35G-0-14-C) and covered with a 3 mm x 3 mm coverslip supported by four dabs of silicon grease (Corning Inc., Corning, NY) (Fig 2A, arrow). As a negative control, four dabs of silicon grease supporting a coverslip were placed in the same recessed insert (Fig 2A, arrowhead). A total of 50 μl medium was added into the insert and then covered with mineral oil. The observation dish was incubated at 37°C under 5% CO2 in humidified air for at least 1.5 h before addition of sperm.

Bottom Line: We compared ejaculated and epididymal sperm in an in vitro fertilization setting to examine whether ejaculated sperm enter cumulus-oocyte complexes more efficiently.At the outset of incubation, ejaculated sperm stuck to the glass surfaces of slides and the incidences of sticking decreased with time; whereas, very few epididymal sperm stuck to glass at any time point, indicating differences in surface charge.We concluded that modification of sperm by male accessory gland secretions affects the behavior of ejaculated sperm, possibly providing them with an advantage over epididymal sperm for reaching the eggs in vivo.

View Article: PubMed Central - PubMed

Affiliation: Family Planning Research Institute, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; Wuhan Tongji Reproductive Medicine Hospital, Wuhan, China.

ABSTRACT
The mouse is an established and popular animal model for studying reproductive biology. Epididymal mouse sperm, which lack exposure to secretions of male accessory glands and do not precisely represent ejaculated sperm for the study of sperm functions, have been almost exclusively used in studies. We compared ejaculated and epididymal sperm in an in vitro fertilization setting to examine whether ejaculated sperm enter cumulus-oocyte complexes more efficiently. In order to prepare sperm for fertilization, they were incubated under capacitating conditions. At the outset of incubation, ejaculated sperm stuck to the glass surfaces of slides and the incidences of sticking decreased with time; whereas, very few epididymal sperm stuck to glass at any time point, indicating differences in surface charge. At the end of the capacitating incubation, when sperm were added to cumulus-oocyte complexes, the form of flagellar movement differed dramatically; specifically, ejaculated sperm predominantly exhibited increased bending on one side of the flagellum (a process termed pro-hook hyperactivation), while epididymal sperm equally exhibited increased bending on one or the other side of the flagellum (pro-hook or anti-hook hyperactivation). This indicates that accessory sex gland secretions might have modified Ca2+ signaling activities in sperm, because the two forms of hyperactivation are reported to be triggered by different Ca2+ signaling patterns. Lastly, over time, more ejaculated than epididymal sperm entered the cumulus oocyte complexes. We concluded that modification of sperm by male accessory gland secretions affects the behavior of ejaculated sperm, possibly providing them with an advantage over epididymal sperm for reaching the eggs in vivo.

No MeSH data available.


Related in: MedlinePlus