Researchers at Northwestern University (NU) are exploring the potential of using "sparks" produced by egg cells when they come in contact with sperm enzyme as a way to determine whether it is fit for in vitro fertilization (IVF).

In a study featured in the journal Scientific Reports, obstetrics and gynecology professor Teresa Woodruff led a team of scientists in studying zinc fireworks that typically occur whenever a human egg cell is activated by sperm enzyme.

Woodruff explained that examining these zinc sparks can help researchers find out whether a particular set of eggs are ideal candidates for transfer in an IVF. It can serve as a way for them to identify the quality of these cells in a way that scientists have never been able to do before.

The NU researchers activated egg cells by injecting them with a sperm enzyme that triggers the calcium in the eggs to increase, and causes zinc to be discharged. Woodruff and her colleagues were not able to use actual sperm to fertilize the egg cells they studied because federal law strictly prohibits such action.

The team first observed the zinc spark while examining a mouse model. Woodruff said seeing the spark occur in each of the human egg cells was a breathtaking experience.

Whenever an egg releases its zinc content, the substance tends to bind itself to small molecule probes. These probes are what produce the light researchers typically see during experiments using fluorescence microscopy. Releasing zinc at such a fast manner is what produces the flash of light that the team considers as a spark.

With the help of previous fluorescence microscopy experiments, study co-author Tom O'Halloran said that they were able to confirm that the zinc sparks do happen in human eggs, and that scientists can view these sparks from outside of cells.

Egg cells are known to arrange themselves into compartments and release zinc to help regulate the growth of healthy embryos. Woodruff and her team have identified that the decision of an egg to develop into a new genetic organism is influenced by the zinc it releases.

"This is an important discovery because it may give us a non-invasive and easily visible way to assess the health of an egg and eventually an embryo before implantation," study co-author Eve Feinberg said.

Feinberg pointed out that researchers do not have any available tool that could allow them to find out if an egg cell or embryo is a viable candidate for fertilization. This is why identifying the zinc sparks can help them determine whether an egg is of good quality or if an embryo can be transferred in IVF procedures.

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