10 February 2020

A study, published in Cell Reports, investigating when and how human stem cells develop into egg and sperm cells could one day help generate lab-grown gametes to treat infertility.

Human pluripotent stem cells can evolve into germ cells, which are the precursor cells for gamete development. By growing these human germ cells in vitro, the theory is that gametes engineered in a laboratory setting could someday be used, instead of natural eggs and sperm, in IVF treatment.

The research conducted within the Eli and Edythe Broad Centre of Regenerative Medicine and Stem Cell Research at University of California, Los Angeles (UCLA) provides great hope for those who are unable to produce gametes naturally,including thosewhose fertility has been affected by injury, illness or medical treatment.

'With donated eggs and sperm, the child is not genetically related to one or both parents. To treat patients who want a child who is genetically related, we need to understand how to make germ cells from stem cells, and then how to coax those germ cells into eggs or sperm'Dr Amander Clark, lead author of the study at UCLA, explained.

'Right now, if your body doesn't make germ cells, then there's no option for having a child that's biologically related to you. What we want to do is use stem cells to be able to generate germ cells outside the human body so that this kind of infertility can be overcome.'

In previous studies, scientists have been able to grow similarinduced pluripotent stem calls (iPS cells), and develop them into human skin cells and blood cells. The researchers, in collaboration with Massachusetts Institute of Technology, analysed the hundreds of thousands of genes active when both human embryonic stem cells and iPS cells transition to germ cells.

The data obtained allowed the researchers to firstly formulate when the germ cells are likely to form, which was between 24-48 hours after starting differentiation, and secondly which lineages of the differentiating stem cells give rise to the germ cells.

They also found that the activation and manifestation of germ cells was identical when developed from embryonic stem cells and iPS cells. This information was essential as they needed to ensure that the in vitro environment they had created was mimicking the molecular signals of the testis and ovaries to give hope for successful sperm and egg cell development.

Dr Clark stated: 'This tells us that the approach we're using to begin the process of making germ cells is on the right track. Now we're poised to take the next step of combining these cells with ovary or testis cells.'

Although current research is far from generating gametes, the end goal is that one day scientists are able to use a patient's skin cells to form stem cells, which can be programmed into egg or sperm cells to be used in fertility treatment.

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Lab-grown eggs and sperm a step closer - BioNews