Name: mouse sperm cryopreservation and recovery using the i&middot;cryo kit
Uploaded: 2011-12-12T12:00:00
Duration: 7 min 6 s
Description: Watch this Scientific Journal Video about Mouse Sperm Cryopreservation and Recovery using the IÂ·Cryo Kit at JoVE.com

The research presented here was supported by Charles River. The authors are most grateful to the Genetically Engineered Models and Services group and the Embryology staff for animal care and hormone injection.

1. Mouse sperm cryopreservation
<ol>
	<li>For each line to be cryopreserved, prepare the following before beginning.
	<ol>
		<li>1 well of a 4-well dish with 240 l of kit CPA</li>
		<li>15 sperm cryopreservation straws as follows
		<ol>
			<li>Connect the 0.25 ml straws to the 1 ml syringes with the cotton plug closest to the syringe. In each straw, load 8 cm (approximately 160 &mu;l) of IVF medium, then 1 cm of air. Label the straws with the name of the line to be preserved.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>LN2 should be 15 cm deep in the foam box. Close the lid.</li>
	<li>Euthanize 2 male mice from each line to be cryopreserved. Mice should be between 10 and 60 weeks old. Remove the two caudal epididymides along with the vas deferens from each mouse.</li>
	<li>Place the epididymides into the previously prepared CPA-containing well of a 4-well dish (step 1.1).</li>
	<li>Make 5-7 longitudinal cuts in each epididymis and gently squeeze each vas deferens to push sperm out.</li>
	<li>Shake the CPA and epididymis mixture by hand gently at room temperature for 3-5 minutes. This will allow sperm to swim out.</li>
	<li>Using the previously prepared straw, aspirate 5 mm (approximately 10 &mu;l) of sperm suspension and then 1 cm of air.</li>
	<li>Repeat this process with up to a total of 15 straws. Load and seal straws within 10 minutes for best sperm survival.</li>
	<li>Heat seal both sides of the straw carefully. Place the straws in the freezing canister with the sperm column first.</li>
	<li>Attach the 1 ml pipette provided as part of the kit to the canister to extend the handle. Place the canister in LN2 in the foam box through the hole in the lid. Allow the canister to float vertically in the LN2 for 10 minutes.</li>
	<li>Immerse the canister in the LN2. The sperm is now cryopreserved and can be moved to long-term LN2 storage.</li>
	<li>The canister should not be used for the next line until it is warmed up to room temperature.</li>
</ol>
2. Mouse superovulation
<ol>
	<li>Generally, use young female mice of the same background as the sperm donors.</li>
	<li>Mice should be &tilde;12 g (3-4 weeks of age).</li>
	<li>Perform an intraperitoneal injection with 5-10 IU of Pregnant mare serum gonadotropin (PMSG).</li>
	<li>Wait 46-48 hours.</li>
	<li>Perform an intraperitoneal injection with 5-10 IU of human chorionic gonadotropin (hCG).</li>
	<li>Harvest oocytes 14-16 h after hCG injection as described below.</li>
</ol>
3. Mouse sperm recovery and IVF
<ol>
	<li>Before IVF, for each straw to be thawed, prepare the following and equilibrate for at least one hour in a 37&deg;C CO2 incubator.
	<ol>
		<li>Sperm incubation dish: one 35 mm Petri dish, with a 90 &mu;l drop of sperm treatment medium (STM) covered with oil.</li>
		<li>Cutting dish: For oocyte collection from a maximum of 10 superovulated females, one 35 mm Petri dish with 3 ml of IVF medium.</li>
		<li>IVF well: For each group of 5 superovulated females for IVF, one well of a 4 well dish with 500 &mu;l of IVF medium (if you are using 10 superovulated females, for example, you will need 2 wells. . .)</li>
		<li>Washing dish: one 35 mm Petri dish with 3 ml of potassium simplex optimized medium (KSOM) for washing each well of the 4-well IVF dish used</li>
		<li>Culture dish: one 35 mm Petri dish with 50 &mu;l drops of KSOM medium covered with oil for embryo culture from each well of the IVF dish.</li>
	</ol>
	</li>
	<li>Remove a straw from LN2 and place in a 37&deg;C water bath for 2-3 minutes.</li>
	<li>Remove the straw from the water bath and wipe to remove excess water. Make the first cut close to the first air column nearest the cotton plug. Cut the straw in the IVF medium there will still be an air column visible before the sperm column.</li>
	<li>Then cut the end of the straw in the second air column, being careful to avoid cutting the sperm column. Cut at a 45 angle - this will make it much easier to aspirate the sperm.</li>
	<li>Aspirate the sperm suspension from the distal end of the straw with a 200 &mu;l pipettor.</li>
	<li>Place the sperm suspension in the center of the STM drop and incubate the dish for 45-60 minutes in a 37&deg;C 5% CO2 incubator.</li>
	<li>During the sperm incubation, dissect the oviducts of the superovulated females into the cutting dish. Use a 30 g needle or forceps to tear each oviduct, releasing the cumulus-oocyte complexes (COCs). Avoid fat and blood in the IVF medium as dirty media makes for extra washing steps.</li>
	<li>Once all the oviducts have been torn, transfer the COCs from 5 females to each IVF wells. The number of COCs produced by superovulation is very strain dependent.</li>
	<li>Collect 10-15 &mu;l of sperm from the periphery of the STM drop and fertilize one IVF well approximately 14-16 hours post hCG injection. Repeat fertilization for each well used. Final sperm concentration will be approximately 1 million/ml.</li>
	<li>Coculture sperm and oocytes for 4-6 hours in a 37&deg;C 5% CO2 incubator.</li>
	<li>Wash the embryos with KSOM a minimum of 2 times and culture in KSOM drops for development in a 37&deg;C 5% CO2 incubator.</li>
	<li>IVF rate was calculated as two cell stage embryos out of total oocytes used after overnight culture.</li>
</ol>
4. Representative Results
Sperm from 5 Charles River mouse inbred strains was frozen. Protection ratios are calculated by dividing frozen sperm assessment values by fresh sperm assessment values. Protection ratios of sperm motility were 60.2%, 81.3%, 78.6%, 66.5%, 61.0% for C57BL/6NCrl, 129S2/SvPasCrl, FVB/NCrl, DBA/2NCrl, and BALB/cAnNCrl, respectively . Protection ratios for rapid progressive motility were 47.3%, 69.4%, 57.0%, 52.8%, 54.1% in C57BL/6NCrl, 129S2/SvPasCrl, FVB/NCrl, DBA/2NCrl, and BALB/cAnNCrl, respectively (Fig 1).
The IVF rates with frozen-thawed sperm were 55.7%, 26.4%, 87.3%, 87.8% and 26.2% in C57BL/6NCrl, 129S2/SvPasCrl, FVB/NCrl, DBA/2NCrl, and BALB/cAnNCrl, respectively (Fig 2).
Over a 1.5 year period, 49 GM mouse lines were archived by sperm cryopreservation. These lines were later successfully recovered (as defined by live pups born) by IVF in 4 female strains (C57BL/6, BALB/c, DBA/1 and 129Sv) (Fig 3).
<img alt="Figure 1." src="/files/ftp_upload/3713/3713fig1.jpg" /> 
Figure 1. The Protection Ratios of Sperm Motility and Rapid Progressive Motility in Mice
<img alt="Figure 2." src="/files/ftp_upload/3713/3713fig2.jpg" /> 
Figure 2. In vitro Fertilization with Frozen-thawed Sperm in Mice
<img alt="Figure 3." src="/files/ftp_upload/3713/3713fig3.jpg" /> 
Figure 3. In vitro Fertilization with Frozen-thawed Sperm in GM Mice

<ol>
	<li>Tada, N., Sato, M., Yamanoi, J., Mizorogi, T., Kasai, K., Ogawa, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cryopreservation+of+mouse+spermatozoa+in+the+presence+of+raffinose+and+glycerol.">Cryopreservation of mouse spermatozoa in the presence of raffinose and glycerol.</a> J. Reprod. Fertil. 89, 511-516 (1990).</li><li>Yokoyama, M., Akiba, H., Katsuki, M., Nomura, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Production+of+normal+young+following+transfer+of+mouse+embryos+obtained+by+in+vitro+fertilization+using+cryopreserved+spermatozoa.">Production of normal young following transfer of mouse embryos obtained by in vitro fertilization using cryopreserved spermatozoa.</a> Jikken Dobutsu. 39, 125-128 (1990).</li><li>Sztein, J. M., Farley, J. S., Young, A. F., Mobraaten, L. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Motility+of+cryopreserved+mouse+spermatozoa+affected+by+temperature+of+collection+and+rate+of+thawing.">Motility of cryopreserved mouse spermatozoa affected by temperature of collection and rate of thawing.</a> Cryobiology. 35, 46-52 (1997).</li><li>Thornton, C. E., Brown, S. D., Glenister, P. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Large+numbers+of+mice+established+by+in+vitro+fertilization+with+cryopreserved+spermatozoa:+implications+and+applications+for+genetic+resource+banks,+mutagenesis+screens,+and+mouse+backcrosses.">Large numbers of mice established by in vitro fertilization with cryopreserved spermatozoa: implications and applications for genetic resource banks, mutagenesis screens, and mouse backcrosses.</a> Mamm. Genome. 10, 987-992 (1999).</li><li>Sztein, J. M., Farley, J. S., Mobraaten, L. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+fertilization+with+cryopreserved+inbred+mouse+sperm.">In vitro fertilization with cryopreserved inbred mouse sperm.</a> Biol. Reprod. 63, 1774-1780 (2000).</li><li>Liu, L., Nutter, L. M., Law, N., McKerlie, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sperm+freezing+and+in+vitro+fertilization+in+three+substrains+of+C57BL/6+mice.">Sperm freezing and in vitro fertilization in three substrains of C57BL/6 mice.</a> J. Am. Assoc. Lab. Anim. Sci. 48, 39-43 (2009).</li><li>Nakagata, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cryopreservation+of+mouse+spermatozoa+and+in+vitro+fertilization.">Cryopreservation of mouse spermatozoa and in vitro fertilization.</a> Methods. Mol. Biol. 693, 57-73 (2011).</li><li>Mazur, P., Koshimoto, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Is+intracellular+ice+formation+the+cause+of+death+of+mouse+sperm+frozen+at+high+cooling+rates.">Is intracellular ice formation the cause of death of mouse sperm frozen at high cooling rates.</a> Biol. Reprod. 66, 1485-1490 (2002).</li><li>Jin, B., Yamasaki, C., Yamada, N., Seki, S., Valdez, D. M., Kasai, M., Edashige, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+mechanism+by+which+mouse+spermatozoa+are+injured+during+freezing.">The mechanism by which mouse spermatozoa are injured during freezing.</a> J. Reprod. Dev. 54, 265-269 (2008).</li><li>Visconti, P. E., Westbrook, V. A., Chertihin, O., Demarco, I., Sleight, S., Diekman, A. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+signaling+pathways+involved+in+sperm+acquisition+of+fertilizing+capacity.">Novel signaling pathways involved in sperm acquisition of fertilizing capacity.</a> J. Reprod. Immunol. 53, 133-150 (2002).</li><li>Ostermeier, G. C., Wiles, M. V., Farley, J. S., Taft, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Conserving,+distributing+and+managing+genetically+modified+mouse+lines+by+sperm+cryopreservation.">Conserving, distributing and managing genetically modified mouse lines by sperm cryopreservation.</a> PLoS ONE. 3, e2792-e2792 (2008).</li></ol>

The authors are employees of Charles River, the maker of this kit.

Since 1990, the basic sperm freezing protocol using 18% raffinose and 3% skim milk has been proven reliable in many strains of mice and a large number of mouse lines have been cryopreserved 1,2,3,4,5,6,7. The major causes of damage to sperm cells during the freezing and thawing process have been associated with ice formation 8,9 and reactive oxygen species 10. Supplementation with free radical scavengers, such as amino acids, and reducing agents, such as monothioglycerol, in the freezing medium was investigated and proven to substantially increase IVF rate with frozen-thawed sperm in inbred strains including the C57BL/6 11,6.
In the present protocol, we developed a new I&bull;Cryo kit for mouse sperm cryopreservation by optimizing the basic CPA with commercially available antioxidants and ice blockers and by modifying the sperm freezing and IVF procedure. Protection ratios of sperm motility (&gt;60%) and rapid progressive motility (&gt;45%) were seen for sperm from five inbred mouse strains frozen with the I&bull;Cryo kit. The 2-cell stage embryo development rate with frozen-thawed sperm in 5 mouse inbred strains was markedly improved compared to that with basic CPA 11,6.
In using the kit, the user creates a concentrated sperm suspension by freezing sperm from 2 males for each line. By only freezing 15 straws the process is fast, easy and occupies less storage space for short or long-term storage. Most times, mouse lines can be recovered by thawing only 1 or 2 straws.

<table border="1">
	<tbody>
		<tr>
			<th>
				Materials</th>
			<th>
				Supplier</th>
			<th>
				Catalogue number</th>
			<th>
				Comments</th>
		</tr>
		<tr>
			<td>CPA</td>
			<td>Charles River</td>
			<td>&nbsp;</td>
			<td>Provided with kit</td>
		</tr>
		<tr>
			<td>STM</td>
			<td>Charles River</td>
			<td>&nbsp;</td>
			<td>Provided with kit</td>
		</tr>
		<tr>
			<td>IVF medium</td>
			<td>Charles River</td>
			<td>&nbsp;</td>
			<td>Provided with kit</td>
		</tr>
		<tr>
			<td>0.25 ml plastic straw</td>
			<td>Charles River</td>
			<td>&nbsp;</td>
			<td>Provided with kit</td>
		</tr>
		<tr>
			<td>Sperm freezing canister</td>
			<td>Charles River</td>
			<td>&nbsp;</td>
			<td>Provided with kit</td>
		</tr>
		<tr>
			<td>Cane and goblet</td>
			<td>Charles River</td>
			<td>&nbsp;</td>
			<td>Provided with kit</td>
		</tr>
		<tr>
			<td>Mineral oil</td>
			<td>Sigma</td>
			<td>M5310</td>
			<td>Should be embryo tested</td>
		</tr>
		<tr>
			<td>KSOM medium</td>
			<td>Millipore</td>
			<td>MR-106-D</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>35 mm Petri dish</td>
			<td>Falcon</td>
			<td>351008</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Heat sealer</td>
			<td>ABTEC</td>
			<td>TISH-200</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>4-well multidish</td>
			<td>Nunc</td>
			<td>73521-424</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Pipettor</td>
			<td>Gilson</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Pipette tips</td>
			<td>Various</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>37&deg;C + 5% CO2 incubator</td>
			<td>Various</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>LN2 storage system</td>
			<td>Various</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>37&deg;C water bath</td>
			<td>VWR</td>
			<td>89032-196</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Stereomicroscope</td>
			<td>Nikon</td>
			<td>SMZ800</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>hCG</td>
			<td>Intervet</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>PMSG</td>
			<td>EMDChemicals</td>
			<td>367222</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>1cc syringe w/ 26G 3/8 needle</td>
			<td>BD</td>
			<td>BD309625</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Micro dissecting scissors</td>
			<td>Roboz</td>
			<td>RS-5602</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>30 gauge &frac12; needle</td>
			<td>BD</td>
			<td>305106</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Scissors</td>
			<td>Roboz</td>
			<td>RS-6802</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Forceps</td>
			<td>Roboz</td>
			<td>RS-5135, RS-5110, RS-5005</td>
			<td>&nbsp;</td>
		</tr>
	</tbody>
</table>

mouse sperm cryopreservation and recovery using the i&middot;cryo kit

Thousands of new genetically modified (GM) strains of mice have been created since the advent of transgenesis and knockout technologies. Many of these valuable animals exist only as live animals, with no backup plan in case of emergency. Cryopreservation of embryos can provide this backup, but is costly, can be a lengthy procedure, and generally requires a large number of animals for success. Since the discovery that mouse sperm can be successfully cryopreserved with a basic cryoprotective agent (CPA) consisting of 18&#37; raffinose and 3&#37; skim milk, sperm cryopreservation has become an acceptable and cost-effective procedure for archiving, distributing and recovery of these valuable strains.
 Here we demonstrate a newly developed I&bull;Cryo kit for mouse sperm cryopreservation. Sperm from five commonly-used strains of inbred mice were frozen using this kit and then recovered. Higher protection ratios of sperm motility (&gt; 60&#37;) and rapid progressive motility (&gt; 45&#37;) compared to the control (basic CPA) were seen for sperm frozen with this kit in 5 inbred mouse strains. Two cell stage embryo development after IVF with the recovered sperm was improved consistently in all 5 mouse strains examined. Over a 1.5 year period, 49 GM mouse lines were archived by sperm cryopreservation with the I&bull;Cryo kit and later recovered by IVF.

Watch this Scientific Journal Video about Mouse Sperm Cryopreservation and Recovery using the IÂ·Cryo Kit at JoVE.com

Mouse Sperm Cryopreservation and Recovery using the I&middot;Cryo Kit

Here we demonstrate the newly developed I&#x2022;Cryo kit for mouse sperm cryopreservation. Two-cell stage embryo development with frozen-thawed sperm was improved consistently in 5 mouse strains with the use of this kit. Over a 1.5 year period, 49 genetically modified mouse lines were archived by sperm cryopreservation with the I&#x2022;Cryo kit and later successfully recovered by IVF.

Thousands of new genetically modified (GM) strains of mice have been created since the advent of transgenesis and knockout technologies.  Many of these ...

mouse-sperm-cryopreservation-and-recovery-using-the-icryo-kit

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JoVE Journal

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Immunohistochemistry: Paraffin Sections Using the Vectastain ABC Kit from Vector Labs

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The complete genotyping of a mouse tail sample, including tissue digestion and PCR readout, is done in one and a half hours using Sigma's SYBR Green Extract-N-Amp Tissue PCR kit.

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Collection and Cryopreservation of Hamster Oocytes and Mouse Embryos

Embryos and oocytes were first successfully cryopreserved more than 30 years ago, when Whittingham et al. 1 and Wilmut 2 separately described that mouse embryos could be frozen and stored at -196 &deg;C and, a few years later, Parkening et al. 3 reported the birth of live offspring resulting from in vitro fertilization (IVF) of cryopreserved oocytes. Since then, the use of cryopreservation techniques has rapidly spread to become an essential component in the practice of human and animal assisted reproduction and in the conservation of animal genetic resources. Currently, there are two main methods used to cryopreserve oocytes and embryos: slow freezing and vitrification. A wide variety of approaches have been used to try to improve both techniques and millions of animals and thousands of children have been born from cryopreserved embryos. However, important shortcomings associated to cryopreservation still have to be overcome, since ice-crystal formation, solution effects and osmotic shock seem to cause several cryoinjuries in post-thawed oocytes and embryos. Slow freezing with programmable freezers has the advantage of using low concentrations of cryoprotectants, which are usually associated with chemical toxicity and osmotic shock, but their ability to avoid ice-crystal formation at low concentrations is limited. Slow freezing also induces supercooling effects that must be avoided using manual or automatic seeding 4. In the vitrification process, high concentrations of cryoprotectants inhibit the formation of ice-crystals and lead to the formation of a glasslike vitrified state in which water is solidified, but not expanded. However, due to the toxicity of cyroprotectants at the concentrations used, oocytes/embryos can only be exposed to the cryoprotectant solution for a very short period of time and in a minimum volume solution, before submerging the samples directly in liquid nitrogen 5. In the last decade, vitrification has become more popular because it is a very quick method in which no expensive equipment (programmable freezer) is required. However, slow freezing continues to be the most widely used method for oocyte/embryo cryopreservation. In this video-article we show, step-by-step, how to collect and slowly freeze hamster oocytes with high post-thaw survival rates. The same procedure can also be applied to successfully freeze and thaw mouse embryos at different stages of preimplantation development.

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Embryos and oocytes were first successfully cryopreserved more than 30 years ago, when Whittingham et al. 1 and Wilmut 2 separately described that mouse ...

A High-Throughput Method For Zebrafish Sperm Cryopreservation and In Vitro Fertilization

This is a method for zebrafish sperm cryopreservation that is an adaptation of the Harvey method (Harvey et al., 1982).  We have introduced two changes to the original protocol that both streamline the procedure and increase sample uniformity.  First, we normalize all sperm volumes using freezing media that does not contain the cryoprotectant. Second, cryopreserved sperm are stored in cryovials instead of capillary tubes.  The rates of sperm freezing and thawing (&delta;&deg;C/time) are probably the two most critical variables to control in this procedure.  For this reason, do not substitute different tubes for those specified.  Working in teams of 2 it is possible to freeze the sperm of 100 males per team in ~2 hrs.  Sperm cryopreserved using this protocol has an average of 25% fertility (measured as the number of viable embryos generated in an in vitro fertilization divided by the total number of eggs fertilized) and this percent fertility is stable over many years.

A High-Throughput Method For Zebrafish Sperm Cryopreservation and In Vitro Fertilization

This is a high-throughput sperm cryopreservation protocol for zebrafish. Sperm cryopreserved using this protocol has an average of 25% fertility in subsequent vitro fertilization and is stable over many years.

This is a method for zebrafish sperm cryopreservation that is an adaptation of the Harvey method (Harvey et al., 1982).  We have introduced two changes to ...

Cryopreservation of Mouse Embryos by Ethylene Glycol-Based Vitrification

Cryopreservation of mouse embryos is a technological basis that supports biomedical sciences, because many strains of mice have been produced by genetic modifications and the number is consistently increasing year by year. Its technical development started with slow freezing methods in the 1970s1, then followed by vitrification methods developed in the late 1980s2. Generally, the latter technique is advantageous in its quickness, simplicity, and high survivability of recovered embryos. However, the cryoprotectants contained are highly toxic and may affect subsequent embryo development. Therefore, the technique was not applicable to certain strains of mice, even when the solutions are cooled to 4&deg;C to mitigate the toxic effect during embryo handling. At the RIKEN BioResource Center, more than 5000 mouse strains with different genetic backgrounds and phenotypes are maintained3, and therefore we have optimized a vitrification technique with which we can cryopreserve embryos from many different strains of mice, with the benefits of high embryo survival after vitrifying and thawing (or liquefying, more precisely) at the ambient temperature4.
Here, we present a vitrification method for mouse embryos that has been successfully used at our center. The cryopreservation solution contains ethylene glycol instead of DMSO to minimize the toxicity to embryos5. It also contains Ficoll and sucrose for prevention of devitrification and osmotic adjustment, respectively. Embryos can be handled at room temperature and transferred into liquid nitrogen within 5 min. Because the original method was optimized for plastic straws as containers, we have slightly modified the protocol for cryotubes, which are more easily accessible in laboratories and more resistant to physical damages. We also describe the procedure of thawing vitrified embryos in detail because it is a critical step for efficient recovery of live mice. These methodologies would be helpful to researchers and technicians who need preservation of mouse strains for later use in a safe and cost-effective manner.

An ethylene glycol-based vitrification method for mouse embryos is described. It is advantageous to other methods in its simplicity and low embryonic toxicity, and therefore can be broadly applicable to many strains of mice, including inbred and gene-modified mice.

Cryopreservation of mouse embryos is a technological basis that supports biomedical sciences, because many strains of mice have been produced by genetic ...

Fish Sperm Assessment Using Software and Cooling Devices

For gamete quality evaluation, there are innovative, rapid, and quantitative techniques that can provide useful data for aquaculture. Computerized systems for sperm analysis were developed to measure several parameters and one of the most commonly measured is the sperm motility.
Initially, this computer technology was designed for mammalian species, although it can also be used for fish sperm analysis. Fish have specific features that can affect sperm assessment such as a short motility time after activation and, in some cases, adaptation to lower temperatures. Thus, it is necessary to modify both software and hardware components to make motility analysis more efficient for fish sperm analysis. For mammalian sperm, the heating plate is used to maintain optimal temperatures of spermatozoa. However, for some fish species, it is advantageous to use a lower temperature to prolong the duration of motility, since the sperm remain active for less than 2 min. Therefore, cooling devices are necessary to refrigerate samples at constant temperature over the time of analysis, including on the optical microscope. This protocol describes the analysis of fish sperm motility using software for sperm analysis and new cooling devices to optimize the results.

The present protocol describes a procedure of fish sperm assessment using computer-assisted sperm analysis and cooling devices. The software gives a rapid, accurate and quantitative analysis of fish sperm quality based on spermatozoa motility, which can be a useful tool in aquaculture to improve reproduction success.

For gamete quality evaluation, there are innovative, rapid, and quantitative techniques that can provide useful data for aquaculture. Computerized systems ...

Sperm Collection of Differential Quality Using Density Gradient Centrifugation

In sexual reproduction, a male gamete or sperm cell fuses with a female gamete to bring about fertilization. However, a large number of sperm cells with fertilizing ability are required to interact with a female gamete to ensure fertilization. As such, the fertilizing ability of individual sperm cells is critical for successful reproduction. Density gradient centrifugation has been utilized for several decades as a reproducible, fast, efficient, effective and extremely adaptable method to collect only high-quality sperm to be used in assisted reproductive technology. The protocols we described herein focus on the utilization of the discontinuous Percoll density gradient centrifugation (PDGC) technique to isolate three distinct populations of rooster sperm by their quality. We were able to collect low-, medium- and high-quality sperm. We also describe reproducible protocols that entail determining fertility potential of sperm by assessing their viability, mobility and penetrability. Collection of sperm by their quality using PDGC technique would be useful to accurately and thoroughly characterize sperm with differential fertility potential.

In this paper, we aim to describe the performance of the density gradient centrifugation technique and its application in sperm physiology research.

In sexual reproduction, a male gamete or sperm cell fuses with a female gamete to bring about fertilization. However, a large number of sperm cells with ...

Natural Transformation, Protein Expression, and Cryoconservation of the Filamentous Cyanobacterium Phormidium lacuna

Cyanobacteria are the focus of basic research and biotechnological projects in which solar energy is utilized for biomass production. Phormidium lacuna is a newly isolated filamentous cyanobacterium. This paper describes how new filamentous cyanobacteria can be isolated from marine rockpools. It also describes how DNA can be extracted from filaments and how the genomes can be sequenced. Although transformation is established for many single-celled species, it is less frequently reported for filamentous cyanobacteria. A simplified method for the natural transformation of P. lacuna is described here. P. lacuna is the only member of the order Oscillatoriales for which natural transformation is established. This paper also shows how natural transformation is used to express superfolder green fluorescent protein (sfGFP). An endogenous cpcB promoter induced approximately 5 times stronger expression than cpc560, A2813, or psbA2 promoters from Synechocystis sp. PCC6803. Further, a method for the cryopreservation of P. lacuna and Synechocystis sp. CPP 6803 was established, and methods for assessing motility in a liquid medium and on agar and plastic surfaces are described.

Natural Transformation, Protein Expression, and Cryoconservation of the Filamentous Cyanobacterium Phormidium lacuna

Phormidium lacuna is a filamentous cyanobacterium that was isolated from marine rockpools. This article describes the isolation of filaments from natural sources, DNA extraction, genome sequencing, natural transformation, expression of sfGFP, cryoconservation, and motility methods.

Cyanobacteria are the focus of basic research and biotechnological projects in which solar energy is utilized for biomass production. Phormidium lacuna is ...