Using human embryos produced from in vitro fertilization laboratories is always a major ethical concern. There is a great resource neglected in this field, which is the eggs containing two sperms. This type of egg, called tripronuclear zygotes, will be routinely discarded in the in vitro fertilization laboratory. Approximately 7% of fertilized eggs contain more than one sperm, with tripronuclear zygotes as a most common phenomenon.
There is some evidence that tripronuclear zygotes could develop into normal embryos. Recently, a normal, live human birth was achieved by removing the extra male pronucleus in the zygote. Previously, in pigs, the normal piglets were delivered by transferring the polyspermic eggs confirmed by microscope. The principal investigator for this proposal also reported in 2001 that polyspermy in pigs could be a physiological phenomenon if extra sperm did not affect the embryonic genome.
Therefore, in this proposal, the extra male pronucleus from the tripronuclear zygotes will be removed by a microsurgical procedure and the resulting zygotes will be cultured to the blastocyst stage when the inner cell mass can be used for establishing human embryonic stem cell lines.
Once the technique is established, the scientists will have a valuable resource in using the ESC lines for therapeutic applications and regenerative medicine. The most important aspect of this work is to further study the biology and differentiation of human embryonic stem cells.
To date, none of the fertility clinics in the Northern California reserves or freezes these tripronuclear zygotes for research studies. Hence, there is an urgent need to bring attention to this unique resource in the field of human embryonic stem cells.
Summary of benefit to California
Obtaining human embryonic stem cell lines is the prerequisite for developing therapeutic approaches. The proposed research is to use the eggs with two sperm inside that are routinely discarded in the in vitro fertilization laboratory. There is evidence that these eggs could develop normally after removing the extra sperm. It is a valuable resource to generate human embryonic stem cell lines without ethical concern of using human embryos.