Using human embryos produced from in vitro fertilization laboratories for generating embryonic stem cell lines is always a major ethical concern. There is a valuable resource neglected in this field, which is the eggs containing two sperms (polyspermy). This type of fertilized eggs, called tripronuclear zygotes, is routinely discarded in the in vitro fertilization laboratories. Approximately 7% of fertilized eggs contain more than one sperm, with tripronuclear zygotes being the most common polyspermic phenomenon.
There is some evidence that tripronuclear zygotes could develop into normal embryos. More recently, a live birth was achieved by removing extra male pronucleus in a zygote. 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. Although there is a recent accomplishment of reprogramming adult cells into pluripotent stem cells by transfecting them with controlling genes, their pluripotency and safety remain concerns. Until the safety of reprogrammed cells is proven, it is important to continue to develop new lines of human embryonic stem cells from embryos.
In this proposal, the extra male pronucleus from the tripronuclear zygotes will be removed by micromanipulation procedure and 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, scientists will have many more options and numbers of embryonic stem cell lines for therapeutic applications and regenerative medicine. Future progress in using these cell lines for transplantation into humans will require many lines so that cells can be matched to recipients. Another important fact is that the abnormally fertilized polyspermic eggs are from large amount of diversity in our region, which will make the clinical applications more feasible in using newly established embryonic stem cell lines.
To date, there is no report on utilizing these tripronuclear zygotes for generating new embryonic stem cell lines. Hence, there is an urgent need to preserve these tripronuclear eggs that are now being discarded. It is a valuable resource for generating human embryonic stem cell lines.
Statement 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 fertilized in vitro by two sperm . These eggs are routinely discarded in the in vitro fertilization laboratories. There is evidence that these eggs could develop normally after removing the extra sperm. These eggs are a valuable resource to generate human embryonic stem cell lines without the usual ethical concern of using normal human embryos.
Although there is a recent accomplishment of reprogramming adult cells into pluripotent stem cells by transfecting them with four genes, their pluripotency and safety have not been proven and many researchers have concerns in this regard. Future progress in using human embryonic stem cell lines for transplantation into humans will require many lines so that cells can be HLA matched to recipients. The large amount of diversity in our region also makes the clinical applications more feasible. Therefore, the proposed project has a great potential of generating many new embryonic stem cell lines for clinical therapeutic applications.