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Effect of pH value of freeze-drying solution on the chromosome integrity and developmental ability of mouse
Takehito Kaneko1, David G Whittingham, Ryuzo Yanagimachi
1The Institute for Biogenesis Research, Department of Anatomy and Reproductive Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii 96822, USA. takehito@hawaii.edu
Abstract:
The nuclei of freeze-dried mouse spermatozoa are able to retain their chromosome integrity and developmental potential. To optimize the conditions of freeze-drying, we examined whether pH values of the freeze-drying solution affect the chromosome integrity and developmental potential of sperm nuclei. The sperm freeze-drying solution we used contained a high concentration (50 mM) of calcium-chelating EGTA. Sperm chromosomes were examined at the metaphase of the first mitosis after injection of freeze-dried spermatozoa into matured oocytes. The developmental potential of sperm nuclei was assessed by examining the development of fetuses in midgestation. The results showed that both sperm chromosomes and sperm developmental potential are maintained better when the freeze-drying solution was slightly alkaline (pH 8.0) rather than near neutral or acidic (pH 7.4-6.0). The data indicated that the chromosome integrity and developmental ability of mouse spermatozoa are affected by the pH value of freeze-drying solution.
Insights
Optimizing freeze-drying solutions for mouse sperm is crucial. Slightly alkaline pH 8.0 solutions better preserve sperm chromosome integrity and developmental potential compared to neutral or acidic conditions.
Area of Science:
- Reproductive biology
- Cryopreservation science
Background:
- Freeze-drying preserves biological samples, but optimal conditions for sperm nuclei are not fully understood.
- Maintaining chromosome integrity and developmental potential in freeze-dried sperm is essential for successful reproduction.
Purpose of the Study:
- To investigate the impact of pH in freeze-drying solutions on mouse sperm nuclei.
- To determine the optimal pH for preserving chromosome integrity and developmental potential of freeze-dried spermatozoa.
Main Methods:
- Mouse spermatozoa were freeze-dried using solutions with varying pH levels (6.0-8.0), containing 50 mM EGTA.
- Chromosome integrity was assessed by examining sperm chromosomes at metaphase after oocyte injection.
- Developmental potential was evaluated by observing fetal development in midgestation.
Main Results:
- Slightly alkaline pH (8.0) significantly improved sperm chromosome integrity compared to neutral or acidic pH (7.4-6.0).
- Developmental potential of freeze-dried sperm nuclei was also better maintained at pH 8.0.
- The pH of the freeze-drying solution directly influences the preservation of sperm quality.
Conclusions:
- The pH of the freeze-drying solution is a critical factor for maintaining the genetic and developmental viability of mouse spermatozoa.
- Slightly alkaline conditions (pH 8.0) are recommended for freeze-drying mouse sperm to optimize cryopreservation outcomes.
