The successful development of micromanipulation techniques for ICSI and PGD has stimulated research into further potential clinical applications. Putative beneficial uses of this technology have included the use of empty ZPs for the cryopreservation of spermatozoa (Cohen et al., 1997a), the transfer of ooplasm from one oocyte to another (Cohen et al., 1997b), the transfer of a GV from one oocyte to an enucleated oocyte (Zhang et al., 1999), ploidy reduction by removal of pronuclei from polyploid zygotes (Rawlins et al., 1988), and the removal of fragments of cytoplasm from fragmented embryos (Alikani et al., 1999). Almost all of these techniques are still at an early research stage and have yet to be proven unequivocally to have beneficial clinical application. Indeed, some of these techniques have become controversial due to concern over their safety, such as the possible inheritance of defective mitochondrial DNA, which could lead to disease in later life. It is not within the scope of this book to review exhaustively all of the new applications currently being researched. However, some of these techniques merit further description by virtue of their perceived benefit to the enhancement of reproductive and therapeutic potential. Consequently, these will be discussed briefly in this chapter.

CRYOPRESERVATION OF SPERMATOZOA WITHIN THE ZP

Some patients have sparingly few spermatozoa, such as those presenting with cryptozoospermia and those requiring surgical sperm recovery, particularly patients with non-obstructive azoospermia.