CALLS for more proof greeted claims that human sperm have been created in the lab for the first time. If further tests show that the lab-grown sperm are identical to the natural kind, they might be helpful in understanding male infertility.
Karim Nayernia of the University of Newcastle, UK, and his colleagues treated male embryonic stem cells (ESCs) with a range of substances, which converted them first into germline stem cells and then into spermatogonial stem cells. These divided to produce “haploid” spermatocytes with just 23 chromosomes, which went on to mature into sperm (Stem Cells and Development, DOI: 10.1089/scd.2009.0063…
