Fertility experts called the work a "crucial experimental advance" towards the use of lab-grown sperm in the clinic and a stepping stone to the routine creation of human sperm for men who cannot make the cells normally.
Though the procedure would be illegal in Britain under current legislation, sperm grown in the laboratory, if proven safe, could be used to help infertile men have children through standard IVF treatments.
The procedure could also benefit boys with cancer who are too young to produce sperm but are at risk of being made infertile by radio- or chemotherapy.
While men can have their sperm frozen before cancer treatment, the latest research suggests boys could have testicular tissue removed and kept in cold storage for use in later life.
Japanese researchers cultivated small pieces of tissue from the testes of baby mice on a gel bathed in nutrients. After several weeks they collected viable sperm from the tissue. (read more)