Washington: Scientists have found a promising way to preserve sperm stem cells that could enable boys to undergo cancer treatment without risking their
fertility.
Adult men can have their sperm frozen before undergoing radiation or chemotherapy, both of which can render sperm infertile. However, boys who have not been through puberty can only have sperm stem cells removed and frozen in anticipation of technology that could culture the cells and place them back in the testes, where they produce sperm after puberty.
Now, Jon Oatley, associate professor at Washington State University (WSU) in the US and colleagues are well on their way to developing such a technology. "I think it is going to become the standard by which everybody cultures their cells, including trying to develop conditions for human cells," said Oatley.
"After the cancer is controlled, the quality of life, which often includes the ability to have a normal child, becomes a major issue," said Marvin Meistrich, oncologist at University of Texas in the US. With each heartbeat, mature, fertile men produce some 1,300 sperm cells. They come from a pool of self-renewing
spermatogonial stem cells that are present at birth. As each stem cell differentiates, it can produce some 5,000 sperm.
Working with prepubescent mouse pups, Oatley and his colleagues put a fluorescent tag on a gene specific to stem cells. This let them in effect watch the process of a stem cell differentiating to create the progenitors that eventually
become sperm. Early in the process, they saw the stem cells creating energy through one method, called glycolysis, then switching to another method.
The second method, called oxidative phosphorylation, produces free radicals, reactive forms of oxygen that can be particularly harmful to a cell's DNA. "If you are a stem cell that is going to give rise to sperm essentially through the whole lifetime of an individual, you want to have a pristine genome," said Oatley. "You do not want it damaged by reactive oxygen species. That is why we think glycolysis is important for the stem cell. So we tried to change the culture environment to favour glycolysis," he said.
By lowering the oxygen in the culture adding nitrogen to cut it by more than half the researchers found they could dramatically improve the percentage of stem cells capable of making normal sperm when put back into the testes. Where before only 5 per cent of the cells remained viable after six months, now 40 per cent were viable. "We are getting an eight-fold improvement," Oatley said.
