Earliest stages of sex determination explored in stem cell-derived models

Sertoli cells, which are crucial to sperm formation, have been recreated in the lab using pluripotent stem cells, to help study the earliest stages of sex determination.

A recent study published in the journal Science Advances outlined a method developed by researchers to differentiate mouse embryonic stem cells into Sertoli-like cells, similar to those found in the testes. Scientists from the Bar-Ilan University in Ramat Gan, Israel, alongside collaborators from the Francis Crick Institute, London, and the Université de Paris and Pasteur Institute, Paris, France also used human induced pluripotent stem cells (iPSCs) from a patient with a disorder of sex development to study the mechanism of their disease in vitro using this method.

'Being able to understand the reasons behind differences in sex development is often very valuable to the individual affected and to their family. Additionally, it is often important when deciding on possible clinical treatments. For example, to potentially preserve, maintain or restore fertility,' said Professor Robin Lovell-Badge, head of the Stem Cell Biology and Developmental Genetics Laboratory at the Francis Crick Institute and Progress Educational Trust chair of trustees.

Disorders of sexual development occur when an individual's gonads and/or genitalia do not develop in line with their chromosomal sex. The lack of an in vitro model to study the different variants of these disorders has meant it is difficult to understand how they develop. It is expected that these disorders occur during differentiation of gonads during embryonic and fetal development. Using an affected individual's cells to create iPSC-derived models, could provide unique insight into a patient's condition.

First, researchers developed a protocol to differentiate mouse embryonic stem cells into Sertoli-like cells. Transcriptome analysis via RNA sequencing showed the differentiated cells were equivalent to sperm progenitor cells found in mouse embryos at day 11.5 of gestation. Using this same protocol with induced pluripotent stem cells from a healthy human male led to the creation of Sertoli-like cells which expressed testis-specific genes, secreted anti-Müllerian hormone, and formed tubular structures similar to those found in the testes for sperm production.

When this same protocol was used with induced pluripotent stem cells derived from a patient with XY sex chromosomes and a variant on a gene known to cause a disorder of sexual development, the resulting differentiated cells showed non-typical gene expression and no tubule formation. CRISPR/Cas9–mediated correction reversed this.

Lead author, Dr Nitzan Gonen said: 'Combining somatic supporting cells with germ cells will enable us to create a "mini testis in a dish" to better understand cases of disorders of sexual development and infertility. Hopefully, we may be able to use that in the future to generate functional sperm in the lab to allow infertile men to have a biological child.'