Researchers Found Lung Stem Cells

A group of researchers have demonstrated that adult lung stem cells may play a key role in the SARS epidemics.

Published in the recent issue of the Proceedings of the National Academy of Sciences (103 9530-9535, 2006), the study shows the lung stem cells, while not easily spotted, was an important target of SARS viruses in a "Decapitation Strike" like attack toward against lungs.

During the SARS epidemics back in 2003, Dr. John Yu, the leader of the Stem Cell Program in Genomics Research Center of Academia Sinica in Taiwan, had witnessed first hand the SARS outbreak and noticed a lag time between the peak virus load of SARS patients and development of acute respiratory distress syndrome (ARDS).

He speculated that the lag time may reflect the duration of a stem cell's regenerative cycle to repair lung damage.

It has been known that 90 percent of the lung cells contribute to lung tissues as bubbles for gas exchange, referred to as "type I pneumocytes" which are derived from "type II pneumocytes."

Scientists have long speculated that there are adult stem cells in the lung which are responsible for making both type I & II lung cells in order to maintain the smooth running of the respiratory system.

Supporting proof was finally made by Yu's team in the in vitro study of SARS infected lung tissues.

The team had grown lung cells in vitro, and in a P4 lab, they have noticed only one unique cell population was infected by SARS viruses.

Through various steps of verification, they found that this specific group of cells bears the Oct-4 and SSEA-1 markers which are also markers for embryonic stem cells.

Therefore, it is very likely these cells that are aimed specifically by SARS viruses are the pulmonary stem progenitor cells. "They could also be the left over "embryonic" stem cells hidden in lungs", said Yu.

The study has implicated a possible involvement of lung stem cells in SARS-CoV infection, accounting for the continued deterioration of lung tissues and apparent loss of capacity for lung repair in the later stage of infection.

This discovery has opened a door for future manipulation of lung stem cells in cellular therapy of ARDS. A patent application is currently in process.

The work is a joint group effort made by the stem cell program of Genomics Research Center and Institute of Cellular and Organismic Biology of Academia Sinica, National Defense Medical Center, and Taipei Medical University.