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Subzonal transfer of multiple sperm (MIST) into early human embryos
S C Ng1, A H Sathananthan, T A Bongso
1Department of Obstetrics and Gynaecology, National University of Singapore.
Molecular Reproduction and Development
|July 1, 1990
Summary
Microinsemination sperm transfer (MIST) into early human embryos does not lead to sperm chromatin decondensation or male pronuclei formation. This study investigated sperm-blastomere fusion, finding it does not occur after MIST.
Area of Science:
- Reproductive Biology
- Embryology
- Cell Biology
Background:
- Microinsemination sperm transfer (MIST) involves transferring sperm into the perivitelline space (PVS) using micromanipulation.
- MIST is employed to explore sperm-blastomere membrane fusion capabilities in early human embryos, analogous to metaphase II oocytes.
Purpose of the Study:
- To investigate whether sperm can fuse with blastomere membranes in early human embryos after microinsemination sperm transfer (MIST).
- To determine if sperm chromatin decondensation and male pronuclei formation occur following MIST into early human embryos.
Main Methods:
- Sperm were transferred into 11 donated human embryos (pronuclear to 16-cell stage) via MIST.
- Embryos were cultured for 6-24 hours in vitro and then prepared for transmission electron microscopy (TEM).
Main Results:
- Sperm were observed in the PVS and between blastomeres; some penetrated the zona pellucida.
- Sperm-blastomere membrane fusion was not observed; occasional phagocytosis of sperm tails by blastomeres occurred.
- Incorporated sperm heads were found in vesicles or vacuoles, showing no chromatin decondensation or male pronuclei formation.
Conclusions:
- Sperm heads are incapable of chromatin expansion to form male pronuclei after MIST into early human embryos.
- The study demonstrates a lack of sperm-oocyte fusion-like events at the blastomere membrane level post-MIST.