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Uhlmannsiek L, Shen H, Eylers H, Martinsson G, Sieme H, Wolkers WF, Oldenhof H. Preserving frozen stallion sperm on dry ice using polymers that modulate ice crystalization kinetics. Cryobiology 2024; 114:104852. [PMID: 38295927 DOI: 10.1016/j.cryobiol.2024.104852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 01/19/2024] [Accepted: 01/19/2024] [Indexed: 02/08/2024]
Abstract
Cryopreserved semen is routinely shipped in liquid nitrogen. Dry ice could serve as an alternative coolant, however, frozen storage above liquid nitrogen temperatures (LN2, -196 °C) may negatively affect shelf-life and cryosurvival. In this study, we determined critical temperatures for storage of cryopreserved stallion sperm. We evaluated: (i) effects of cooling samples to different subzero temperatures (-10 °C to -80 °C) prior to storing in LN2, (ii) stability at different storage temperatures (i.e., in LN2, dry ice, -80 °C and -20 °C freezers, 5 °C refrigerator), and (iii) sperm cryosurvival during storage on dry ice (i.e., when kept below -70 °C and during warming). Furthermore, (iv) we analyzed if addition of synthetic polymers (PVP-40, Ficoll-70) modulates ice crystallization kinetics and improves stability of cryopreserved specimens. Sperm motility and membrane intactness were taken as measures of cryosurvival, and an artificial insemination trial was performed to confirm fertilizing capacity. We found that adding PVP-40 or Ficoll-70 to formulations containing glycerol reduced ice crystal sizes and growth during annealing. Post-thaw sperm viability data indicated that samples need to be cooled below -40 °C before they can be safely plunged and stored in LN2. No negative effects of relocating specimens from dry ice to LN2 and vice versa became apparent. However, sample warming above -50 °C during transport in dry ice should be avoided to ensure preservation of viability and fertility. Moreover, addition of PVP-40 or Ficoll-70 was found to increase sperm cryosurvival, especially under non-ideal storage conditions where ice recrystallization may occur.
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Affiliation(s)
- Laura Uhlmannsiek
- Unit for Reproductive Medicine - Clinic for Horses, University of Veterinary Medicine Hannover, Hannover, Germany; National Stud of Lower Saxony, Celle, Germany
| | - Hang Shen
- Biostabilization Laboratory - Lower Saxony Centre for Biomedical Engineering, Implant Research and Development, Hannover, Germany
| | - Heinke Eylers
- Unit for Reproductive Medicine - Clinic for Horses, University of Veterinary Medicine Hannover, Hannover, Germany
| | | | - Harald Sieme
- Unit for Reproductive Medicine - Clinic for Horses, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Willem F Wolkers
- Unit for Reproductive Medicine - Clinic for Horses, University of Veterinary Medicine Hannover, Hannover, Germany; Biostabilization Laboratory - Lower Saxony Centre for Biomedical Engineering, Implant Research and Development, Hannover, Germany
| | - Harriëtte Oldenhof
- Unit for Reproductive Medicine - Clinic for Horses, University of Veterinary Medicine Hannover, Hannover, Germany; Biostabilization Laboratory - Lower Saxony Centre for Biomedical Engineering, Implant Research and Development, Hannover, Germany.
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El-Shalofy A, Gautier C, Khan Y, Aurich J, Aurich C. Shipping duration and temperature influence the characteristics of cryopreserved horse semen stored in different shipping devices for up to 14 days. Anim Reprod Sci 2023; 256:107307. [PMID: 37499284 DOI: 10.1016/j.anireprosci.2023.107307] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 07/21/2023] [Accepted: 07/21/2023] [Indexed: 07/29/2023]
Abstract
This study aimed to investigate the effects of storing horse semen either in a dry shipper (≤ -150 °C) or on dry ice (≤ -78 °C) for up to 14 days. A total of 264 frozen semen straws from male horses (n = 8) stored in liquid nitrogen were transferred on day 0 (d0) to a dry shipper or a dry ice styrofoam box. On d1, d3, d7, d10, and d14, straws from the dry shipper and dry ice were returned to the liquid nitrogen container. Semen was evaluated by CASA for total (TMot), progressive motility (PMot) and sperm velocity parameters, by fluorescence microscopy for percentage of membrane-intact sperm (SYBR14/PI), high mitochondrial membrane potential (HMMP; JC1) and DNA fragmentation. Temperature inside the containers was monitored continuously. Until d7, no changes were observed in TMot, PMot, and membrane-intact spermatozoa. Thereafter, all three parameters decreased in semen stored on dry ice but not in a dry shipper (time p < 0.001, time x shipping device p < 0.001). The HMMP decreased continuously over time in both containers with a more pronounced decrease on dry ice compared to the dry shipper (shipping device p < 0.01, time p < 0.001, time x device p < 0.001). The DNA fragmentation increased on d10-14 on dry ice and d14 in the dry shipper (time p < 0.001, time x device p < 0.01). In conclusion, frozen horse semen can be safely stored for up to 7 days on dry ice. Sperm DNA integrity and HMMP, however, were adversely affected after 14 days in both shipping devices.
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Affiliation(s)
- Amr El-Shalofy
- Artificial Insemination and Embryo Transfer, Department for Small Animals and Horses, University of Veterinary Medicine, Vienna, Austria; Theriogenology Department, Faculty of Veterinary Medicine, Cairo University, Giza, Egypt.
| | - Camille Gautier
- Artificial Insemination and Embryo Transfer, Department for Small Animals and Horses, University of Veterinary Medicine, Vienna, Austria
| | - Younis Khan
- Artificial Insemination and Embryo Transfer, Department for Small Animals and Horses, University of Veterinary Medicine, Vienna, Austria
| | - Jörg Aurich
- Obstetrics, Gynecology and Andrology, Department for Small Animals and Horses, University of Veterinary Medicine, Vienna, Austria
| | - Christine Aurich
- Artificial Insemination and Embryo Transfer, Department for Small Animals and Horses, University of Veterinary Medicine, Vienna, Austria
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Wang X, Lu F, Bai S, Wu L, Huang L, Zhou N, Xu B, Wan Y, Jin R, Jiang X, Tong X. A Simple and Efficient Method to Cryopreserve Human Ejaculated and Testicular Spermatozoa in −80°C Freezer. Front Genet 2022; 12:815270. [PMID: 35154258 PMCID: PMC8831890 DOI: 10.3389/fgene.2021.815270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Accepted: 12/27/2021] [Indexed: 11/13/2022] Open
Abstract
Human autologous sperm freezing involves ejaculated sperm, and testicular or epididymal puncture sperm freezing, and autologous sperm freezing is widely used in assisted reproductive technology. In previous studies, researchers have tried to cryopreserve sperm from mammals (rats, dogs, etc.) using a −80°C freezer and have achieved success. It is common to use liquid nitrogen vapor rapid freezing to cryopreserve human autologous sperm. However, the operation of this cooling method is complicated, and the temperature drop is unstable. In this study, we compared the quality of human ejaculation and testicular sperm after liquid nitrogen vapor rapid freezing and −80°C freezing for the first time. By analyzing sperm quality parameters of 93 ejaculated sperm and 10 testicular sperm after liquid nitrogen vapor rapid freezing and −80°C freezing, we found reactive oxygen species (ROS) of sperm of the −80°C freezer was significantly lower than liquid nitrogen vapor rapid freezing. Regression analysis showed that progressive motility, ROS, and DNA fragmentation index (DFI) in post-thaw spermatozoa were correlated with sperm progressive motility, ROS, and DFI before freezing. For the freezing method, the −80°C freezer was positively correlated with the sperm progressive motility. Among the factors of freezing time, long-term freezing was negatively correlated with sperm progressive motility and ROS. Although freezing directly at −80°C freezer had a slower temperature drop than liquid nitrogen vapor rapid freezing over the same period, the curves of the temperature drop were similar, and slight differences in the freezing point were observed. Furthermore, there were no statistically significant differences between the two methods for freezing testicular sperm. The method of direct −80°C freezing could be considered a simplified alternative to vapor freezing for short-term human sperm storage. It could be used for cryopreservation of autologous sperm (especially testicular sperm) by in vitro fertilization centers. Clinical Trial Registration: (website), identifier (ChiCTR2100050190).
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Affiliation(s)
- Xiaohan Wang
- Provincial Hospital Affiliated to Anhui Medical University, Hefei, China
| | - Fangting Lu
- Division of Life Sciences and Medicine, Reproductive and Genetic Hospital, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei, China
| | - Shun Bai
- Division of Life Sciences and Medicine, Reproductive and Genetic Hospital, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei, China
| | - Limin Wu
- Division of Life Sciences and Medicine, Reproductive and Genetic Hospital, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei, China
| | - Lingli Huang
- Division of Life Sciences and Medicine, Reproductive and Genetic Hospital, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei, China
| | - Naru Zhou
- Division of Life Sciences and Medicine, Reproductive and Genetic Hospital, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei, China
| | - Bo Xu
- Division of Life Sciences and Medicine, Reproductive and Genetic Hospital, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei, China
| | - Yangyang Wan
- Division of Life Sciences and Medicine, Reproductive and Genetic Hospital, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei, China
| | - Rentao Jin
- Division of Life Sciences and Medicine, Reproductive and Genetic Hospital, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei, China
- *Correspondence: Xiaohua Jiang, ; Xianhong Tong, , Rentao Jin,
| | - Xiaohua Jiang
- Division of Life Sciences and Medicine, Reproductive and Genetic Hospital, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei, China
- *Correspondence: Xiaohua Jiang, ; Xianhong Tong, , Rentao Jin,
| | - Xianhong Tong
- Provincial Hospital Affiliated to Anhui Medical University, Hefei, China
- *Correspondence: Xiaohua Jiang, ; Xianhong Tong, , Rentao Jin,
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Mochida K, Hasegawa A, Shikata D, Itami N, Hada M, Watanabe N, Tomishima T, Ogura A. Easy and quick (EQ) sperm freezing method for urgent preservation of mouse strains. Sci Rep 2021; 11:14149. [PMID: 34239008 PMCID: PMC8266870 DOI: 10.1038/s41598-021-93604-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 06/28/2021] [Indexed: 11/08/2022] Open
Abstract
Cryopreservation of mouse spermatozoa is widely used for the efficient preservation and safe transport of valuable mouse strains. However, the current cryopreservation method requires special containers (plastic straws), undefined chemicals (e.g., skim milk), liquid nitrogen, and expertise when handling sperm suspensions. Here, we report an easy and quick (EQ) sperm freezing method. The main procedure consists of only one step: dissecting a single cauda epididymis in a microtube containing 20% raffinose solution, which is then stored in a -80 °C freezer. The frozen-thawed spermatozoa retain practical fertilization rates after 1 (51%) or even 3 months (25%) with the C57BL/6 J strain, the most sensitive strain for sperm freezing. More than half of the embryos thus obtained developed into offspring after embryo transfer. Importantly, spermatozoa stored at -80 °C can be transferred into liquid nitrogen for indefinite storage. As far as we know, our EQ method is the easiest and quickest method for mouse sperm freezing and should be applicable in all laboratories without expertise in sperm cryopreservation. This technique can help avoid the loss of irreplaceable strains because of closure of animal rooms in emergency situations such as unexpected microbiological contamination or social emergencies such as the COVID-19 threat.
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Affiliation(s)
- Keiji Mochida
- RIKEN BioResouce Research Center, Tsukuba, Ibaraki, 305-0074, Japan.
| | - Ayumi Hasegawa
- RIKEN BioResouce Research Center, Tsukuba, Ibaraki, 305-0074, Japan
| | - Daiki Shikata
- RIKEN BioResouce Research Center, Tsukuba, Ibaraki, 305-0074, Japan
- Graduate School of Life and Environmental Science, University of Tsukuba, Tsukuba, Ibaraki, 305- 8572, Japan
| | - Nobuhiko Itami
- RIKEN BioResouce Research Center, Tsukuba, Ibaraki, 305-0074, Japan
| | - Masashi Hada
- RIKEN BioResouce Research Center, Tsukuba, Ibaraki, 305-0074, Japan
| | - Naomi Watanabe
- RIKEN BioResouce Research Center, Tsukuba, Ibaraki, 305-0074, Japan
- Graduate School of Life and Environmental Science, University of Tsukuba, Tsukuba, Ibaraki, 305- 8572, Japan
| | | | - Atsuo Ogura
- RIKEN BioResouce Research Center, Tsukuba, Ibaraki, 305-0074, Japan.
- Graduate School of Life and Environmental Science, University of Tsukuba, Tsukuba, Ibaraki, 305- 8572, Japan.
- Center for Disease Biology and Integrative Medicine, Faculty of Medicine, University of Tokyo, Bunkyo-ku, Tokyo, Japan.
- RIKEN Cluster for Pioneering Research, Hirosawa, Wako, Saitama, 351-0198, Japan.
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Hart-Johnson S, Mankelow K. Archiving genetically altered animals: a review of cryopreservation and recovery methods for genome edited animals. Lab Anim 2021; 56:26-34. [PMID: 33847177 DOI: 10.1177/00236772211007306] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
With the ever-expanding numbers of genetically altered (GA) animals created in this new age of CRISPR/Cas, tools for helping the management of this vast and valuable resource are essential. Cryopreservation of embryos and germplasm of GA animals has been a widely used tool for many years now, allowing for the archiving, distribution and colony management of stock. However, each year brings an array of advances, improving survival rates of embryos, success rates of in-vitro fertilisation and the ability to better share lines and refine the methods to preserve them. This article will focus on the mouse field, referencing the latest developments and assessing their efficacy and ease of implementation, with a brief note on other common genetically altered species (rat, zebrafish, Xenopus, avian species and non-human Primates).
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Raspa M, Putti S, Paoletti R, Barboni B, Ramal-Sanchez M, Lanuti P, Marchisio M, D'Atri M, Ortolani C, Papa S, Valbonetti L, Bernabo N, Scavizzi F. The impact of five years storage/biobanking at -80°C on mouse spermatozoa fertility, physiology, and function. Andrology 2021; 9:989-999. [PMID: 33427410 DOI: 10.1111/andr.12971] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 01/05/2021] [Accepted: 01/07/2021] [Indexed: 11/29/2022]
Abstract
BACKGROUND We previously demonstrated how mouse spermatozoa can be efficiently stored for two years in a -80°C freezer, maintaining their ability to fertilize mouse eggs. OBJECTIVES The main objective here was to evaluate the effects of five years at -80°C compared to liquid nitrogen storage (LN2 , control condition) on mouse sperm viability, physiological parameters, and fertilization capacity. MATERIALS AND METHODS Three different strains were used: C57BL/6N, C57BL/6J and CD1. Flow cytometry experiments were performed to analyze sperm viability (SYBR-14 + Propidium Iodide +Hoechst33342), the intracellular calcium concentration (Fluo 3-AM), the membrane lipid disorder (Merocyanine 540), and the mitochondrial activity (MitoTracker Red) in live spermatozoa. The in vitro fertilization (IVF) was used to evaluate the sperm fertilizing ability. RESULTS Flow cytometry analysis showed that the percentage of live cells are reduced in B6N and B6J, but not in CD1 mice. However, in the live population no differences in terms of intracellular calcium concentration, membrane lipid disorder, and mitochondrial activity were reported when comparing both biobanking methods. Spermatozoa stored at -80°C for 5 years successfully fertilized the eggs and developed mouse embryo normally both in culture and in vivo, generating live pups with no differences compared to control samples stored in LN2 . DISCUSSION Long-term mouse sperm storage at -80°C (five years) could be considered an ideal alternative to the most common LN2 approach, giving economical and logistic advantages. Moreover, the precise information originated from the flow cytometry analysis stands up this technique as an optimal strategy to evaluate the sperm quality and ranking. CONCLUSION It is demonstrated here the possibility to store mouse spermatozoa for up to five years in a -80°C freezer with no significant differences compared to the storage in LN2 in terms of fertilizing ability, sperm viability, intracellular calcium concentration, membrane lipid disorder, and mitochondrial activity.
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Affiliation(s)
- Marcello Raspa
- Institute of Biochemistry and Cell Biology (CNR-IBBC/EMMA/Infrafrontier/IMPC), National Research Council, Monterotondo Scalo (Rome, Italy
| | - Sabrina Putti
- Institute of Biochemistry and Cell Biology (CNR-IBBC/EMMA/Infrafrontier/IMPC), National Research Council, Monterotondo Scalo (Rome, Italy
| | | | - Barbara Barboni
- Faculty of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Teramo, Italy
| | - Marina Ramal-Sanchez
- Faculty of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Teramo, Italy
| | - Paola Lanuti
- Department of Medicine and Aging Sciences, University "G. d'Annunzio" Chieti-Pescara, Chieti, Italy.,Center on Aging Sciences and Translational Medicine (CeSI-MeT, University "G. d'Annunzio" Chieti-Pescara, Chieti, Italy
| | - Marco Marchisio
- Department of Medicine and Aging Sciences, University "G. d'Annunzio" Chieti-Pescara, Chieti, Italy.,Center on Aging Sciences and Translational Medicine (CeSI-MeT, University "G. d'Annunzio" Chieti-Pescara, Chieti, Italy
| | - Mario D'Atri
- Università degli Studi di Urbino "Carlo Bo", Urbino PU, Italy.,Sharp Solutions Software, Udine, Italy
| | - Claudio Ortolani
- Università degli Studi di Urbino "Carlo Bo", Urbino PU, Italy.,Sharp Solutions Software, Udine, Italy
| | - Stefano Papa
- Università degli Studi di Urbino "Carlo Bo", Urbino PU, Italy
| | - Luca Valbonetti
- Institute of Biochemistry and Cell Biology (CNR-IBBC/EMMA/Infrafrontier/IMPC), National Research Council, Monterotondo Scalo (Rome, Italy.,Faculty of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Teramo, Italy
| | - Nicola Bernabo
- Institute of Biochemistry and Cell Biology (CNR-IBBC/EMMA/Infrafrontier/IMPC), National Research Council, Monterotondo Scalo (Rome, Italy.,Faculty of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Teramo, Italy
| | - Ferdinando Scavizzi
- Institute of Biochemistry and Cell Biology (CNR-IBBC/EMMA/Infrafrontier/IMPC), National Research Council, Monterotondo Scalo (Rome, Italy
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González A, Arando A, Acosta A, Alcalá CJ, Arrebola FA, Pérez-Marín CC. Frozen dog spermatozoa are negatively affected during storage at -80, -21 and -8 ºC. Anim Reprod Sci 2019; 210:106197. [PMID: 31635782 DOI: 10.1016/j.anireprosci.2019.106197] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 09/19/2019] [Accepted: 09/27/2019] [Indexed: 11/19/2022]
Abstract
Cryopreservation in liquid nitrogen (LN2) allows for semen to be stored for long periods of time while there is sustaining of sperm viability. In this study, there was assessment of effects induced by different storage temperatures on cryopreserved dog spermatozoa. After cryopreservation at -196 °C, sperm samples were transferred to storage conditions of -80, 21 or -8 °C. Sperm motility, morphology, viability, acrosome integrity, mitochondrial membrane potential and DNA fragmentation were determined in samples stored at -196 °C (evaluation time =0 h), and then after 12 h and 1, 4, 7 and 15 d of storage at 80, -21 and -8 °C. In samples stored at -80 °C, sperm morphology, viability, acrosome integrity, mitochondrial membrane potential and DNA fragmentation did not differ at successive evaluation times. Progressive motility was less (P < 0.05) after 12 h and total motility after 4 d of storage at -80 ºC as compared with that of the 0 h sample. With storage at the other temperatures (-21 and -8 ºC), there was a reduction of mean values for sperm total and progressive motility, viability and mitochondrial membrane potential after 12 h of storage at these temperatures. Results, therefore, indicate the use of ultra-freezers at -80 ºC to store frozen dog semen allows for maintenance of sperm characteristics for at least 15 d but motility is sustained for only 1 d. Neither of the -21 or -8 ºC storage temperatures were effective for storing of frozen dog sperm and retaining viability.
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Affiliation(s)
- Antonio González
- Department of Animal Medicine and Surgery, Faculty of Veterinary Medicine, University of Cordoba, Cordoba, Spain
| | - Ander Arando
- Department of Genetics, Faculty of Veterinary Medicine, University of Cordoba, Cordoba, Spain
| | - Alberto Acosta
- Department of Animal Medicine and Surgery, Faculty of Veterinary Medicine, University of Cordoba, Cordoba, Spain
| | - Carlos J Alcalá
- Department of Animal Medicine and Surgery, Faculty of Veterinary Medicine, University of Cordoba, Cordoba, Spain
| | - Francisco A Arrebola
- Instituto de Investigación y Formación Agraria y Pesquera (IFAPA) Hinojosa del Duque, Cordoba, Spain
| | - Carlos C Pérez-Marín
- Department of Animal Medicine and Surgery, Faculty of Veterinary Medicine, University of Cordoba, Cordoba, Spain.
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Raspa M, Fray M, Paoletti R, Montoliu L, Giuliani A, Scavizzi F. A new, simple and efficient liquid nitrogen free method to cryopreserve mouse spermatozoa at -80 °C. Theriogenology 2018; 119:52-59. [PMID: 29982136 DOI: 10.1016/j.theriogenology.2018.06.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Revised: 05/28/2018] [Accepted: 06/24/2018] [Indexed: 11/26/2022]
Abstract
The mouse is widely used for biomedical research and an increasing number of genetically altered models are currently generated, therefore centralized repositories are essentials to secure the important mouse strains that have been developed. We have previously reported that spermatozoa of wild type and mutant strains frozen using standard laboratory protocols can be transported in dry ice (-79 °C) for 7 days and safely stored in a -80 °C freezer for up to two years. The objective of this new study was to compare the effects of the freezing techniques using LN2 or -80 °C freezer on fertility of frozen-thawed mouse spermatozoa. After thawing, sperm fertility was comparable (P > 0,05) between the LN2 and the -80 °C samples for at least 1 year. Furthermore, we showed that it is possible to freeze and store mouse semen directly at -80 °C and eventually transfer it to LN2 irrespective of storage time. This study is relevant because it shows for the first time that mouse spermatozoa can be efficiently frozen and stored at -80 °C with no use of liquid nitrogen for a long period of time. A new, simple, efficient and flexible, liquid nitrogen free, method was developed for freezing and maintaining spermatozoa of wild type and mutant C57BL/6N lines. Lines on this genetic background are used in collaborative research infrastructures for systematic phenotyping, e.g. the International Mouse Phenotyping Consortium (IMPC) and therefore largely cryopreserved in repositories like EMMA/Infrafrontier. The importance of this finding will be especially useful for small laboratories with no or limited access to liquid nitrogen and for laboratories generating many mouse mutant lines by CRISPR/Cas9 who do not want to saturate the limited space of a LN2 tank, using a more accessible -80 °C freezer. This study underlines, once more, that mouse spermatozoa are very resistant and can be frozen, transported, shared and stored at -80 °C for a long time without a significant loss of viability. This new approach simplifies the freezing process and facilitates the long term storage of mouse spermatozoa at -80 °C, always allowing the transfer to LN2 for indefinite storage without noticeable detrimental effects.
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Affiliation(s)
- Marcello Raspa
- National Research Council (IBCN), CNR-Campus International Development (EMMA-INFRAFRONTIER-IMPC), Monterotondo Scalo, Rome, Italy
| | - Martin Fray
- Mary Lyon Centre, MRC Harwell Institute, Harwell Campus, Oxfordshire, OX11 0RD, United Kingdom
| | | | - Lluis Montoliu
- National Centre for Biotechnology (CNB-CSIC), Department of Molecular and Cellular Biology, Campus de Cantoblanco, Darwin 3, 28049, Madrid, Spain; CIBERER-ISCIII, Madrid, Spain
| | | | | | - Ferdinando Scavizzi
- National Research Council (IBCN), CNR-Campus International Development (EMMA-INFRAFRONTIER-IMPC), Monterotondo Scalo, Rome, Italy.
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