Mice produce rat sperm with technique that could help conservation

Alex Wilkins is a writer.

Rat sperm cells have grown inside sterile mice and the technique could lead to human-rat hybrid

Stem cells can be differentiated into other types. A chimera can be formed when these cells are taken from one individual and injected into a blastocyst.

If the blastocyst is genetically modified to lack genes that code for certain features, the PSCs will step in and form these features in a process called blastocyst complementation.

Ori Bar-Nur at the Swiss Federal Institute of Technology wanted to see if he could use the same method to grow rat sperm in mice.

Bar-Nur and his team injected rat PSCs into modified mice blastocysts that lack a genes to produce sperm. There is an empty area in the testes that can be colonised by rats. It gives them the space and the ability to give rise to germ cells because of the lack of mouse counterparts.

The mice only produced rat sperm cells that could be used to fertilise female rat eggs, which is less successful than regular rat sperm.

The researchers failed to get the fertilised eggs to develop normally or produce live offspring, but they hope to adapt methods from the work on growing mouse sperm in rats, which succeeded in fertilising mouse eggs that resulted in adult mice.

According to Bar-Nur, the technique could be used to produce sperm or eggs of extinct species. If we had cells from an extinct species, you could use them to make germ cells.

Harry Leitch at the London Institute of Medical Sciences says that the work is very difficult and they have done a good job. The low success rate of producing fertile rat sperm and failure to develop fertilised eggs into adult rats means that any potential applications, such as producing human sperm in interspecies chimeras, are probably a while off.

The poor viability of the sperm and lack of live offspring suggests that the development of these cells is compromised in this cross-species environment, according to Ramiro Alberio. He suggests that this might be an alternative for the rescue of species that are related to domestic species.

Stem cell reports is a journal.