Simple and efficient in vitro fertilization with cryopreserved C57BL/6J mouse sperm

Area of Science:

• * Animal Science
• * Reproductive Biology
• * Genetics

Background:

• * Cryopreservation of mouse sperm is a valuable archiving method due to its simplicity, speed, and cost-effectiveness.
• * However, low post-thaw fertility (0%-12%) in common inbred strains like C57BL/6J limits its utility without invasive techniques.
• * Conventional methods often require zona nicking or intracytoplasmic sperm injection (ICSI) to overcome fertilization barriers.

Purpose of the Study:

• * To enhance the fertility of cryopreserved C57BL/6J mouse sperm.
• * To establish a practical method for archiving genetically altered mouse lines using sperm cryopreservation.
• * To assess the viability and developmental potential of embryos derived from cryopreserved sperm.

Main Methods:

• * Cryopreserved C57BL/6J mouse sperm suspensions were processed to remove non-motile sperm and debris.
• * Progressively motile sperm were isolated and used for in vitro fertilization (IVF) with zona-intact eggs.
• * Developed 2-cell embryos were transferred to pseudopregnant recipient mice.

Main Results:

• * Washed, motile sperm achieved in vitro fertilization rates of 38%-88% for zona-intact eggs.
• * Embryo transfer resulted in live births, with rates of 40%-63% producing pups.
• * Successful production of live offspring demonstrates the effectiveness of the improved cryopreservation method.

Conclusions:

• * Sperm washing significantly improves the fertility of cryopreserved C57BL/6J mouse sperm.
• * Cryopreservation of sperm is a viable and practical method for archiving the haploid genome of C57BL/6J mice, including genetically altered individuals.
• * This technique bypasses the need for zona manipulation or ICSI, simplifying the process of preserving valuable mouse genetic resources.