What's New -the Latest Advances in IVF | What's New at New Hope Fertility | What's Next -the Future of IVF
WHAT'S NEXT - THE FUTURE OF IVF
Cytoplasmic Transfer and Oocyte Reconstruction
Couples faced with egg infertility almost invariably resist the most effective option available: egg donation. Many find the financial and emotional burden of egg donation too great, and long hold out hope of somehow transmitting the genetic legacy of the infertile woman. Now, a promising experimental procedure is bringing that hope closer to becoming a reality. Oocyte (egg) Reconstruction (also called Human Nuclear Transfer or Cytoplasmic Nuclear Transfer) involves transferring part of one woman's egg into another's. In this case, scientists use the healthy portion of a donor egg to supplement the defective portion of the infertile recipient's egg and to help it survive, hence making one good egg. The infertile woman's genetic legacy is preserved because 99% of the genetic material that determines physical traits in the embryo is from her; the donor cytoplasm (which simply contains mitochondrial DNA that gives the egg energy to survive) contributes only 1% of the embryo's genetic makeup. Once the egg is fertilized, the embryo is implanted in the infertile woman's uterus.
Unfortunately, after many babies were born in the US using Human Cytoplasmic Transfer (HCT), ethical and medical complications spurred the U.S. government to curtail the procedure in 2001. Today, fertility scientists must file an investigational clinical trial application to continue research in this area, and New Hope Fertility intends to obtain approvals and continue our research. It is likely that with continued research this technique may prove its efficacy and safety in the future.
New Hope Fertility Center's Founder & Medical Director Dr. John Zhang was one of the few of scientists whose research resulted in a human pregnancy from HCT. Dr. Zhang led a team of Human Nuclear Cytoplasmic Transfer scientists at Sun Yat-Sen University of Medical Science in Guangzhou, China, and in 2003 a Chinese woman became pregnant with triplets. The fetuses terminated in the 24th and 29th weeks, but their work remains unprecedented in advancing this important science.
"Scientists Create Three Parent Embryos"On February 5, 2008 Reuters reported the groundbreaking achievements of a group of reproductive researchers from New Castle University, England that created a three-parent embryo. The idea behind the creation of the human embryo is to prevent the inheritance of defective mitochondria from mother to child, and thereby protect the child from the fatal diseases resulting from this genetic defect.
Dr. John Zhang is a pioneer in the field of nuclear transfer and he successfully studied the progress of the fetus up to 29 weeks after nuclear transfer. He presented this innovative research in 2003 at the annual meeting of American Society for Reproductive Medicine (ASRM) and was met with acclaim from scientists around the globe.
Dr. Zhang's original work was published in the journal Fertility and Sterility (80: supplement 3, S56, 2003) as an article entitled "Pregnancy Derived from Human Nuclear Transfer," of which he was the primary author.
What is Nuclear Transfer?In higher organisms including humans, both nucleus and mitochondria (an organelle responsible for energy synthesis located outside the nucleus in the cytoplasm) contain DNA. In normal sexual reproduction, the offspring inherits its mitochondrial DNA from the mother. This type of inheritance pattern is generally known as maternal inheritance. But, when the mother passes defective mitochondria to the child, fatal heart, liver, brain or muscular disorders can result. The only possible method to overcome this situation is through nuclear transfer, which allows the mother to provide her nuclear DNA to the child, but not her (defective) mitochondrial DNA. Nuclear transfer is an invasive procedure where an in-vitro fertilized egg's nucleus (from two parents) is transferred into an enucleated ovum (egg cell with the nucleus removed, provided by a third donor). The purpose of the donation of an enucleated cell is to provide the child with non-defective mitochondria, from a woman other than the mother. This results in a three-parent embryo. Its nucleus is formed by the fusion of sperm and mother's oocyte nucleus, and its cytoplasm is provided by the enucleated donor cell. This results in the inheritance of DNA from three different sources, the nuclear DNA is from sperm and recipient oocyte, and the mitochondrial DNA is mainly through the donor. See the Reuters link.