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March 29, 2012

Mitochondria and Embryos

Simplistically, think of mitochondria as an embryo’s battery.  Embryos require energy to develop and divide.  Mitochondria are intracellular organelles inside the oocyte (egg).  The energy produced from the mitochondria is known as ATP, which serves an embryo’s source of fuel for growth and development.

Male mitochondria derived from sperm do not survive after fertilization.  Therefore we know the entire mitochondrial content of the developing embryo is maternal.  It is estimated that mature oocytes contain between 20,000 and 800,000 mitochondria.  Oocytes deficient in mitochondria may account for the variable quality seen in IVF embryos.  The mitochondrial activity may also influence oocyte quality.  Oxygen consumption has been one way to measure mitochondrial metabolism and we know that the rate of oxygen consumption increases in the peri-ovulatory period.  One of Dr. Hardy’s patents used NADH fluorescence to measure embryo metabolism.

So why the current interest in mitochondria?  OvaScience, a Boston-based life science company, will soon begin a clinical trial to determine if oocytes may be improved by adding mitochondria to the retrieved oocyte.  The mitochondria will be obtained from the female patient through a laparoscopic biopsy of the ovarian tissue.  Mitochondria will be extracted from the patient’s oocyte stem cells and then injected into the oocyte at time of fertilization.  This will be the first use of autologous (from the same patient) mitochondrial transfer; prior use of mitochondrial transfer from non-autologous (from one woman to another) was banned by the FDA in 2001 after concern with the early data.  The medical community will be looking with interest at the outcomes of this initial small trial to determine if further studies are warranted.  Eventually this may provide a tool for optimizing oocyte quality in IVF patients.

 

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Medical Director,
Fertility Centers of New England