Wednesday January 4 2012
The sperm appeared normal, but could not be fully tested
Infertile men may soon be able to father children with their own sperm grown outside their bodies, the Daily Mirror has today reported. The article explained that researchers have successfully created mouse sperm in the lab, raising the possibility of couples no longer having to rely on sperm donors.
The story is based on a laboratory experiment in which scientists were able to take cells obtained from the testes of young mice and grow them into mouse sperm in the laboratory. They grew the sperm using a special nutrient-rich jelly in a 3D environment, which they say more closely resembles the environment found in the testes than the systems used in previous, unsuccessful experiments.
Although the research is of interest, there is a long way to go before scientists can know if the same techniques could be used to grow human sperm in the laboratory. In particular, it is unknown whether appropriate cells could be obtained from humans, and whether they would behave in the same way as testicular cells taken from immature mice when grown in the laboratory. It should also be noted that the scientists were unable to isolate live mouse sperm in this experiment or test if they were capable of fertilising mouse eggs.
Where did the story come from?
The study was carried out by researchers from Ben-Gurion University, Israel and the University of Muenster, Germany. It received external funding from the German-Israel Foundation and was published in the peer-reviewed Asian Journal of Andrology.
The research findings were over-interpreted by some newspapers. In particular, it is unlikely that this research will soon allow infertile men to father children with their own sperm grown outside their bodies, as suggested in the papers. Much more research will be needed before this could become a reality.
What kind of research was this?
This was a laboratory experiment in which scientists tested whether they could extract immature cells from the testicles of baby mice and use a special culture system to make them successfully develop into sperm cells.
In mammals, testicular germ cells normally develop into sperm cells capable of fertilising an egg. The researchers pointed out that several unsuccessful attempts had already been made to grow sperm cells from testicular germ cells in the laboratory.
The researchers said that most attempts to culture mammalian sperm have been made using what they call “two-dimensional” cell culture systems, where the cells are essentially grown on a flat surface. In this experiment they used a “three-dimensional” culture system using a soft agar jelly, called SACS. They said that this is more representative of the natural environment which germ cells are exposed to within the testes.
This type of laboratory study is appropriate for developing techniques in which to grow cells. Once they have been perfected using animal cells, researchers may then try to determine whether they could be used for human cells. If this technique is successful, it might allow researchers to grow sperm in the laboratory from men who are infertile.
What did the research involve?
Using specialised laboratory techniques, the researchers took seven-day-old mice and isolated immature cells that would normally develop into sperm. These were then cultured in the SACS. The SACS included two layers of agar: a more solid lower layer and a softer upper layer.
The immature cells were cultured in the upper layer and both layers contained nutrients for the cells. The cells were then grown in standard cell culture incubators for up to four weeks. Over a period of 30 days, the researchers continually carried out various analyses of the cells to evaluate whether they had developed into sperm cells and how far this development had progressed. They did this by looking at which genes the cells had switched on, what proteins they were producing and what the cells looked like.
What were the basic results?
The researchers found that they could grow the immature testicular cells from the seven-day-old mice in the SACS in the laboratory. After 30 days of growing these cells in the laboratory, the cells had switched on the relevant genes and started producing proteins which indicated that they were undergoing the process by which sperm normally develop (meiosis).
Microscopic analysis revealed “normal-looking” sperm in 11 out of the 16 samples grown for 30 days in the culture. The researchers found only a few normal-looking sperm developed in each sample. From each sample of 10 million testicular cells, only an average of around 16 normal-looking sperm developed.
How did the researchers interpret the results?
They researchers said the results reveal for the first time that it is possible to induce immature testicular cells taken from mice to grow into specialised sperm cells, using the SACS culture. They hope that this unique system could lead to new strategies for the study of sperm development and to new therapies for male infertility.
This study has shown that, under the right environmental conditions, it is possible to grow normal-looking mouse sperm from immature testes cells in the lab. There are some limitations to note; in particular, the researchers point out that they were unable to isolate the live sperm produced using this method and therefore could not test whether they were able to fertilise eggs. In addition, although these sperm cells looked normal, the researchers could not assess their movement and did not carry out an in-depth assessment of whether the cells were genetically normal.
Although this development is of interest, a lot more research will be needed to determine whether this method provides a viable way of producing functioning, normal sperm in the laboratory. It will need to be perfected on mice first before being tested using human cells. Scientists do not yet know whether adult human testicular cells isolated and cultured in the laboratory would behave in the same way as testicular cells taken from immature mice.
Therefore, there is still a long way to go before this method could potentially grow human sperm and be used as a treatment for male infertility.