A new technique for freezing sperm-producing tissues can provide "biological immortality" for males, a finding that researchers say could have major impact on conserving endangered species, protecting research animals and preserving the reproduction ability of males who undergo intensive chemotherapy for cancer.
The technique might even make it possible for men with abnormally low sperm production to reproduce.
Fertility specialists now routinely freeze sperm itself, but the freezing process is tricky and unique for each species. In addition, frozen sperm lasts a relatively short time and researchers are limited to the amount of sperm originally frozen.
Veterinarian Ralph L. Brinster, a pioneer in genetic engineering of animals, and his colleagues at the University of Pennsylvania report in today's editions of the journals Nature and Nature Medicine that spermatogonia -- the tissues that produce sperm -- can be easily frozen and stored for long periods.
When the tissue is thawed, it can be transplanted into the original donor or a host, where it begins making unlimited quantities of fresh sperm. Although Brinster has not tried to fertilize eggs with the sperm, he has every confidence that it can be done.
"This is a brilliant piece of work," said Dr. Geoffrey Sher of the Pacific Fertility Center in San Francisco.
Sperm are frozen routinely today for a variety of purposes, including breeding of cattle and artificial insemination of humans, but results can be variable. Bull sperm freezes easily, for example. But human sperm varies in its ability to survive the process.
Brinster has circumvented those problems by focusing on spermatogonia, the cells that serve as the source for all sperm. "Every time a human male's heart beats, he produces 1,000 sperm, from puberty to old age," Brinster said.
Once mouse cells were thawed, the team reports in Nature Medicine, they could be easily transplanted back into the original donor or into so-called nude mice. Because nude mice have no immune system, they do not reject such transplants.
Pub Date: 5/30/96