Severe cases of the flu can trash lungs, leaving patients gasping for breath.

In a first, researchers used regenerative stem cells to repair fragile damaged lungs in mice previously infected by a nasty strain of H1N1 influenza. The results could lead to new therapies for asthma, chronic bronchitis and emphysema in humans.

The research will appear in the journal Cell on Friday.

 This virus is as close as you can get to the one responsible for the 1918 influenza pandemic, said Frank McKeon of the Genome Institute of Singapore and the Harvard Medical School, who led the study. The 1918 influenza virus killed nearly eight million people, according historic reports. You get massive lung damage, infiltration of white cells, and loss of lung tissues. Two months out, the lungs miraculously look normal again.

The team of U.S., Singapore and French researchers captured stem cells that not only regenerated lung tissues inside mice, but also generated lung-like tissue in petri dishes.

Whether the research will lead to better lung therapies has detractors, McKeon among them.

The problem in the case of a pandemic is that people die quickly, McKeon said. It is hard to imagine how a cell-based treatment will play in those time constraints.

Stem cell-based therapies or secreted factors identified by this study as important for lung regeneration have the potential to enhance the speed of lung regeneration. It is also possible that such regenerative therapies could aid in those with hard-to-treat condition pulmonary fibrosis, in which lung tissue becomes scarred.

Pulmonary fibrosis is a bad disease, McKeon said. The question is: could you get rid of the fibrosis and replace it with real lung tissue?