Telomeres, the body's own cellular clocks, may be a crucial factor underlying the development of emphysema, according to research from Johns Hopkins University.

"We found that in mice that have short telomeres, there was a significant increased risk of developing emphysema after exposure to cigarette smoke," said Mary Armanios, MD, assistant professor of oncology at the Johns Hopkins School of Medicine.

The study appears online ahead of the print edition of the American Journal of Respiratory and Critical Care Medicine.

Telomeres are DNA protein structures that protect chromosome ends from degradation. Their length is genetically determined, but they also shorten progressively with cell division. Short telomeres are considered one marker of ageing in cells.

"With age, short telomeres accumulate and cause cells to stop dividing. Telomeres can be thought of as 'biological clocks,'" Dr. Armanios explained. "We wanted to determine whether telomere length itself was why susceptibility to emphysema increases with age."

Dr. Armanios and her colleagues examined the role of telomeres in lung disease by studying mice that have shortened telomeres. The mice were exposed to cigarette smoke for six hours a day, five days a week for six months.

The researchers then analyzed the lung tissue and pulmonary function of the mice. "Although the mice had no lung disease at baseline, after exposure to cigarette smoke, they surprisingly developed emphysema. In contrast, mice with long telomeres did not develop lung disease during our experiments," said Dr. Armanios.

In emphysema, alveoli, the small air sacs where oxygen exchange occurs, are permanently lost. Emphysema changes are normally found in older individuals, and occasionally even in those who have never smoked. But they are most commonly found in smokers.