Extends Reproductive Life Of Male Mice
Living with a female mouse can extend the reproductive life of a male mouse by as much as 20 percent, according to a study conducted by Ralph Brinster and a team of other researchers at the University of Pennsylvania School of Veterinary Medicine. The study was reported online January 22 in the journal Biology of Reproduction.
The researchers hypothesize that the females’ effect on the environment of the spermatogonial stem cells likely occurs through the male’s endocrine and nervous systems, but other systems are likely involved. The change amounts to a reduction of fertility six months earlier in “lonely” mice as opposed to those who have female companionship.
The results have significant implications for the maintenance of male fertility in wildlife, livestock and even human populations.
Brinster and his team housed male mice with and without female companions for 16-32 months. Each male was placed with two novel females at two-month intervals to test its ability to impregnate the females. The results indicated that males housed with females did not show a drop in fertility until 32 months of age, a six-month increase in fertility over males housed alone.
The study also indicated, however, that once male fertility began to decrease, the rate of decrease was the same for both those that lived with females and those that did not. The decline in fertility appeared to be due in part to defects in the sperm-production process.
“It appears that housing females with a male mouse delays the decline of reproductive processes at the cellular level by somehow affecting the cells surrounding the stem cells that produce spermatozoa in the testes,” said Brinster, professor of physiology at Penn Vet. “Whether this female influence occurs in other species is not known.”
While it is commonly known that reproductive aging of males includes decreased fertility, the factors that delay aging are largely unknown. Histological analysis indicated that abnormal spermatogenesis occurred sooner in isolated males, suggesting that defects in spermatogenesis may play a role in the greater decrease in fertility in isolated males.
“If it turns out that this reproductive effect is mimicked in other species, for example, livestock animals that affect food production, then a 20 percent increase in male fertility could mean an extension of the male reproductive life span of years,” Brinster said. “This finding may also have relevance for the protection of some large endangered species.”