1. Definition

Mouse IVF rederivation refers to the technology of completing the fertilization process of mouse sperm and eggs in an artificial, controlled environment in vitro, followed by transferring the fertilized eggs or embryos into the fallopian tubes or uterus of pseudopregnant recipient females to ultimately obtain specific pathogen-free offspring. Since the vast majority of bacteria, viruses, and parasites cannot penetrate the intact zona pellucida to enter the embryo, and the washing steps during the in vitro manipulation remove pathogens attached to the gamete surface, this achieves "rederivation" of the population.

2. Advantages

● High Rederivation Efficiency：Effectively eliminates vertically transmitted pathogens (e.g., MHV, MNV, Helicobacter, etc.) with a high success rate, far superior to cesarean section or cross-fostering.

● Genetic Background Fidelity：Directly utilizes gametes from the original strain without the need for backcrossing with wild-type mice, preserving the complete genetic background in a single generation, especially suitable for complex genetically engineered strains.

● High Resource Utilization：Sperm from one male can fertilize eggs from multiple females, yielding a large number of offspring from the same batch in a single experiment, achieving simultaneous "rederivation + expansion."

● Not Limited by Mating Behavior：IVF is the most effective rederivation method for males with normal sperm but damaged reproductive organs, aged or frail individuals, or precious strains that cannot mate naturally.

● Controllable Timeline：Compared to the uncertainty of natural mating (waiting for estrus, mating, plug detection), IVF offers a standardized process with a very clear and predictable timeline.

3. Application Scenarios

● Rederivation of Contaminated Strains (Core Application)：When mice, especially precious strains, become infected with vertically or closely contact-transmissible pathogens such as MHV or MNV, IVF is the most effective method to rederive them into SPF-grade animals and rebuild a clean population.

● Revival of Frozen Sperm：After thawing cryopreserved sperm, IVF is essential to obtain live offspring. It is the standard operating procedure for strain resurrection and genetic resource bank management.

● Rescue of Precious Strains with Reproductive Difficulties：When male mice are aged, frail, have damaged reproductive organs, or have lost natural mating ability, IVF is the most reliable method to obtain their genetic offspring.

● Efficient Expansion and Production of Age-Matched Offspring：Sperm from a single male can fertilize eggs from many superovulated females, producing a large number of embryos in a single batch. Offspring born after transfer have highly consistent ages, meeting the requirements for animal numbers and age ranges in experiments such as pharmacodynamic studies.

● Providing Large Numbers of Fertilized Eggs for Microinjection：The production of transgenic or gene-edited mice requires a stable, large supply of fertilized eggs at the pronuclear stage as injection material. IVF is the key technology to meet this demand.

● Solving Problems of Scarce Males or Limited Cage Space：IVF maximizes cage space utilization when rapid expansion is needed but breeding males are limited, or when animal facility cage space is insufficient to accommodate numerous mating cages.

● Obtaining Embryos at Specific Developmental Stages：用For studies on embryonic development, embryonic stem cell manipulation, or embryo transfer experiments, IVF provides a stable supply of large numbers of embryos ranging from the pronuclear to blastocyst stages.

● Safe Introduction of Foreign Animals：When introducing a new mouse strain from an external source with unclear health status, the IVF process can obtain offspring while cutting off potential pathogen transmission chains, ensuring facility biosecurity.

4. Service Process