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Micro-insemination: genetic aspects
S C Ng1, T A Bongso, S S Ratnam
1Department of Obstetrics and Gynaecology, National University Hospital, Singapore.
Abstract:
Micro-insemination involves sperm deposition directly into oocytes. This can be by transfer of sperm (Micro-Insemination Sperm Transfer, or MIST) or by micro-injection into the ooplasm (Micro-Insemination Micro-Injection into Cytoplasm, or MIMIC). Micro-insemination is indicated in spermatozoa with no or very poor motility, very low density, multiple defects, or inability to penetrate oocyte vestments. There is a 10% incidence of chromosomal abnormalities in spermatozoa from fertile and normal men. However, there is no increase in sperm chromosomal abnormalities in men with normal peripheral karyotypes and highly abnormal sperm parameters. Preliminary results of karyotypes of human oocytes that failed to become fertilized after MIST and mouse morulae and blastocysts produced after MIST reveal that there was no significant increase in aneuploidy or polyploidy. There is evidence that MIMIC may result in increased abnormal sperm karyotypes. Polyspermy is low in the mouse and human after transfer of multiple spermatozoa into the perivitelline space, thus suggesting an oolemmal block. However, blastomere membranes do not fuse with spermatozoa, as observed in a study of MIST into human embryos. Zona drilling with acid is not advised because of disturbances to chromosomal kinetics. The conclusion of this review is that MIST does not result in an increased risk of chromosomal abnormalities, while caution must be exercised with MIMIC.
Insights
Micro-insemination Sperm Transfer (MIST) does not increase chromosomal abnormality risks. However, Micro-Insemination Micro-Injection into Cytoplasm (MIMIC) requires caution due to potential increases in abnormal sperm karyotypes.
Area of Science:
- Reproductive biology
- Assisted reproductive technologies
- Human genetics
Background:
- Micro-insemination techniques like MIST and MIMIC are used for male infertility.
- Indications include poor sperm motility, low density, and defects.
- Sperm chromosomal abnormalities exist even in fertile men.
Purpose of the Study:
- To evaluate the risk of chromosomal abnormalities associated with MIST and MIMIC.
- To assess the safety of micro-insemination techniques in assisted reproduction.
Main Methods:
- Review of existing literature on MIST and MIMIC.
- Analysis of karyotype data from oocytes and embryos post-MIST.
- Examination of polyspermy rates and membrane fusion in MIST and MIMIC.
Main Results:
- MIST showed no significant increase in aneuploidy or polyploidy in human oocytes or mouse embryos.
- MIMIC may be associated with an increased risk of abnormal sperm karyotypes.
- Polyspermy was low, indicating an oolemmal block, and blastomere fusion did not occur in MIST.
Conclusions:
- Micro-insemination Sperm Transfer (MIST) is a safe technique with no increased risk of chromosomal abnormalities.
- Caution is advised with Micro-Insemination Micro-Injection into Cytoplasm (MIMIC) due to potential karyotype risks.
- Zona drilling with acid is not recommended due to interference with chromosomal kinetics.