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Stem Cells Capable of Regenerating Lung Tissue
April 2018

Over the last several months, studies and trials from around the world have found new and groundbreaking ways to repair lung functions in both humans and mice. In the latest study, researchers from the Perelman School of Medicine at the University of Pennsylvania report identifying a lung stem cell that repairs the organ’s gas exchange compartment.

The findings will be essential in repairing slow to regenerate lung tissue that has been damaged by respiratory ailments like severe influenza, pneumonia, cystic fibrosis and bronchitis to name a few. The European Respiratory Society reports that an estimated one billion people are currently suffering from chronic respiratory conditions.

The team – led by Edward E. Morrisey, PhD, a professor of Cell and Developmental Biology, director of the Penn Center for Pulmonary Biology and scientific director of the Institute for Regenerative Medicine – published their findings in February in Nature.

The lung is often considered one of the most complex organs and in order to find treatments, the team first had to seek to understand its function and complex structure.

“One of the most important places to better understand lung regeneration is in the alveoli, the tiny niches within the lung where oxygen is taken up by the blood and carbon dioxide is exhaled,” Morrisey said. “To better understand these delicate structures, we have been mapping the different types of cells within the alveoli. Understanding cell-cell interactions should help us discover new players and molecular pathways to target for future therapies.”

One of the cell types that line the alveoli is called epithelial cells which are vital in regenerating damaged tissue and restoring gas exchange (breathing) after an injury or illness. Organs like the intestine turn over the entire epithelial lining every five days. But, like we’ve said, lung tissue is slow to regenerate.

In studying epithelial cells in general, the team found and studied an alveolar epithelial progenitor (AEP) lineage which acts as a wetting agent and keeps the lungs from collapsing.

By studying mouse AEPs, the team was able to identify a conserved cell surface protein called TM4SF1. TM4SF1 was used to isolate AEPs from human lungs which were then used to generate three-dimensional lung organoids.

“From our organoid culture system, we were able to show that AEPs are an evolutionarily conserved alveolar progenitor that represents a new target for human lung regeneration strategies,” Morrisey said.

These studies, while in their beginning stages, provide much-needed insight into how the lung regenerates. By exploring molecular pathways, they may be able to promote AEP function, design drugs that activate signaling within the lung, and promote lung regeneration.

“We are very excited at this novel finding,” said James P. Kiley, PhD, director of the Division of Lung Diseases at the National Heart, Lung, and Blood Institute, which supported the study.

“Basic studies are fundamental stepping stones to advance our understanding of lung regeneration. Furthermore, the NHLBI support of investigators from basic to translational science helps promote collaborations that bring the field closer to regenerative strategies for both acute and chronic lung diseases.”

With access to more than 300 lungs through the lung transplant program, the team plans to dive deeper into their understanding of influenza-damaged lung tissue in particular. Such research naturally lends itself to the understanding of other respiratory ailments and has the potential to save the lives of thousands around the world.

 

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