July 17 (UPI) -- A larger presence of a lung-healing protein called amphiregulin may be the reason why men recover from the flu more quickly than women, according to a study of mice and human cells.
Scientists at Johns Hopkins Bloomberg School of Public Health believe new treatments can be developed to boost amphiregulin production. Their findings were published Tuesday in the journal Biology of Sex Differences.
Researchers for years have thought the slower recovery by women from flu was linked only to their greater levels of lung inflammation during flu infections.
"The novel finding here is that females also have slower tissue-repair during recovery, due to relatively low production of amphiregulin," study author Dr. Sabra Klein, an associate professor at Hopkins, said in a press release.
The Johns Hopkins researchers infected mice with a non-lethal dose of H1N1, which is an Influenza A strain that caused more than 18,000 deaths worldwide in 2009 and 2010.
Male and female mice had similar virus levels and cleared it in about the same amount of time. But the female mice had greater loss of body mass and more lung inflammation during the acute phase of infection, and were slower to recover normal lung function.
They found amphiregulin was the key factor, which has been known known to promoteepithelial cells in the skin, lung and other surfaces in the body while wounds heal, including during recovery from lung infections. Male mice produced significantly more amphiregulin than females during the recovery phase of their infections.
In addition, male mice genetically engineered to lack amphiregulin had the same flu results as females. Females without amphiregulin had unchanged infection severity. Researchers believe that the lung-healing protein makes a difference primarily for males.
Also in a study of flu infections of mice and human lung epithelial cells in culture dishes, they found significant increases in the production of amphiregulin only when the cells were from males.
In 2016, Johns Hopkins researchers found the sex hormone progesterone stimulates amphiregulin production in female mice.
The researchers theorize that males evolved with greater wound-healing ability because of they took part in more battles for territories, mates and resources.
The researchers originally thought amphiregulin production rose in males during flu infection because of testosterone. But they found it does not seem to be the case in controlling amphiregulin levels and want to conduct future research on the reasons.