Nuclear-Cytoplasmic Exchange: Can it Rejuvenate the Eggs of Older Women?

It is well established that as a woman ages, so do her eggs. Upon undergoing luteinizing hormone (LH) or human chorionic gonadotropin (hCG)-induced maturational reduction in chromosomal number (i.e. meiosis) older eggs are les likely to end up being chromosomally normal (euploid), “competent eggs” that upon fertilization with normal sperm, are able to propagate embryos that develop into healthy babies. It is also well recognized that the ability of the egg to end up euploid, is at least in part influenced by developmental events that take place in its cytoplasm.

Nuclear cytoplasmic exchange (NCE) is a procedure involves removing the nucleus from the extracted eggs of older women and transplanting it into the eggs of a younger woman from which the nucleus had been removed. The method which was first introduced in the 90’s was designed to try and enhance (rejuvenate) the eggs of older women in the hope that the cytoplasm of a younger woman’s eggs would improve post-fertilization embryo “competence”. Proponents of this approach failed to take into account the fact that by the time an egg is harvested it has already undergone meiosis and its chromosomal “competence” has already been decreed. Thus performing NCE at this time is like “closing the door after the horse has already left the stable

Over the years, many NCE procedures have been performed. As might be expected, results have been very disappointing. In fact in my opinion, the handful of pregnancies hitherto reported worldwide following NCE p4robably occurred or in spite of rather than due to the performance of the procedure.

Since neither the premise nor the promise has been fulfilled NCE should now be relegated to the history books.