Researchers were able to revert human cells back to primordial germ cells, which give rise to sperm in the ova.
These are the first human cells to ever be changed back into this early form, the Weizmann Institute of Science reported. The findings could help find solutions to fertility problems and even lead to new reproductive technologies.
"Researchers have been attempting to create human primordial germ cells (PGCs) in the petri dish for years," said Dr. Jacob Hanna of the Weizmann Institute's Department of Molecular Genetics.
These types of cells are born within the first few weeks after conception. Once these cells are "specified" they begin to develop towards precursor sperm cells or "ova."
To accomplish the feat the researchers used induced pluripotent stem (iPS) cells, which are "reprogrammed" act like embryonic cells through a method that involved the insertion of four genes. The researchers created a new method for turning down the genetic pathway for differentiation, creating a new type of cell called "naïve cells," which are closer to the embryonic state.
Using techniques that had been successful in past mouse experiments that successfully reverted cells back to the embryonic state, the researchers produced cells that appeared to be identical to human PGCs. The team determined about 40 percent of the sample cells had become PGCs.
Through this study the team also determined the existence of a master gene, dubbed Sox17, that regulates stem cell differentiation in humans.
"Having the ability to create human PGCs in the petri dish will enable us to investigate the process of differentiation on the molecular level. For example, we found that only 'fresh' naïve cells can become PGCs; but after a week in conventional growth conditions they lose this capability once again," Hanna said.
We want to know why this is. What is it about human stem cell states that makes them more or less competent? And what exactly drives the process of differentiation once a cell has been reprogrammed to its more naïve state? It is the answers to these basic questions that will, ultimately, advance iPS cell technology to the point of medical use," he concluded.
The findings were published Dec. 24 in the journal Cell.
