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Identikit for new life

May 16th, 2008

Monash researchers are the first to use DNA fingerprinting to identify viable embryos

Monash researchers have used DNA fingerprinting for the first time to identify which embryos have implanted after in vitro fertilisation (IVF) and developed successfully to result in the births of healthy babies.

The technique, combined with sampling cells from blastocysts (the very early embryo) before implantation in the womb, opens the way to pin-pointing a handful of genes that could be used to identify those blastocysts most likely to result in a successful pregnancy.

Researchers Drs David Cram and Gayle Jones, senior research scientists at Monash Immunology and Stem Cell Laboratories (MISCL) believe that their findings will revolutionise IVF by improving pregnancy rates and eliminating multiple pregnancies.

"DNA fingerprinting is the ultimate form of biological identification, but until now it has not been used to identify the embryonic origin of resultant babies born following embryo transfer nor has it been used for gene expression studies," Dr Cram said.

"We have developed a novel strategy of utilising a combination of blastocyst biopsy, DNA fingerprinting and microarray analysis to identify viable blastocysts among the cohorts transferred to patients. Our ultimate aim is to find out which genes are expressed by viable blastocysts."

When couples attend fertility clinics for IVF, eggs from the woman are fertilised with sperm from the man and then the fertilised eggs are allowed to develop in the laboratory until they reach the blastocyst stage after about five days . Before the blastocysts are implanted into the woman’s womb, a decision has to be made about how many should be implanted and which ones look most likely to develop successfully. Currently there is no reliable way of differentiating between viable and non-viable blastocysts, and clinic staff tend to decide on the basis of some fairly crude tests, which include looking at the form (morphology) of the blastocyst. The result is that couples often opt to have more than one blastocyst implanted in order to increase their chances of a successful pregnancy; but this runs the risk of multiple pregnancies with all the associated dangers to both the mothers and babies.

When multiple embryos are transferred, it then becomes impossible to work out which are the ones that developed into a successful pregnancy, making it difficult to develop criteria for identifying viable blastocysts.

Although more work needs to be undertaken before these findings become applicable in the clinic, the researchers say that their work will also be useful for testing different treatments of embryos without the need to recruit large numbers of women to clinical trials, and DNA fingerprinting could be used to refine existing criteria for selecting embryos for implantation.

"Major improvements in IVF practice in the last decade have seen the introduction of better laboratory techniques that allow complete pre-implantation development to the blastocyst stage in vitro," Dr Jones said;

"One of the major stumbling blocks to worldwide acceptance of a single embryo transfer policy is the lack of highly predictive criteria to select the single most viable embryo within a cohort."

This research was first published in Human Reproduction - A monthly journal of the European Society of Human Reproduction and Embryology (ESHRE).

Copies of the paper are available at :
http://humrep.oxfordjournals.org/cgi/content/abstract/den123

DNA Code