Ear cells from Japanese bull produces clones after prolonged freezing.

Ear cells from a prize Japanese bull that were frozen and cultured in a lab over several months have successfully produced clones, challenging the notion that cells become too stale to duplicate.

Cells used in cloning generally are either fresh or have had fewer that 10 "passages," or periods in a culture medium. But in the current study, ear cells from 17-year-old bull Kamitakafuku went through up to 15 passages over 3 months before they were used to create calves, according to a report in the January issue of the Proceedings of the National Academy of Sciences. The experiments, performed at the University of Connecticut in Storrs and the Kogashima Prefectural Cattle Breeding Development Institute in Tokyo, Japan, suggest that a library of cells could eventually be used to create clones at any time, even long after the original animals are dead. It also means clones could be produced from cells kept in the laboratory long enough to complete the slow and meticulous process of gene manipulation.

"This is very powerful stuff," said Thomas Wagner, MD, head of cancer research at Clemson University in South Carolina.

The researchers collected Kamitakafuku's ear cells and cultured them for 2 to 3 months. The cells' genetic material then was placed in cow embryos and implanted in surrogate mothers. Four calves were born from cells cultured for 2 months, 2 of which later died--one at birth, the other from a viral infection. Two more clones were born from cells cultured for 3 months.